Originally

1. Originally the 1969 ‘Cuda came with two extremely rugged rear differentials an Open 8 3/4" Rear Differential, 3.23 gears. 657 case or a 2.76 7 1/4 rear. Very few ever broke.
   

2. 
   

3. Originally the 1967 ‘Cuda S convertible had the 7.25 and came that way according to the build sheet.
   

4. 
   

5. Originally with the 273 S cars had 904s.
   

6. 
   

7. Originally with the 273 4bbl autos the 7.25 was standard.
   

8. 
   

9. Originally with the 8.75 was optional with automatics, standard with 4 speeds or 383 cars.
   

10. 
    

11. Originally with the Formula S package, came with the limited-slip Sure Grip differential.
    

12. 
    

13. Originally with the ‘68 Hurst Hemi-powered 'Cuda, it used the indestructible Dana 60 differential.
    

14. 
    

15. Four-speed equipped 'Cudas could be ordered with one of a wide array of ratios. Final drive ratios depended upon which transmission was installed.
    

16. 
    

17. Originally automatics came with a final drive ratio of 3.23:1 or 3.55:1 .
    

18. 
    

19. Originally factory Mopar axles had non-sealed axle bearings.
    

1. Originally ‘69m factory Mopars on a 440 6 barrel it came with the option of Dana 60 rear axle It was mandatory on all 440 4 barrels, 440 6 packs (Plymouth) and 426 Hemi engine options. It came with 2 axle groups:
   

2.     A-33   with a 3 54 gear or
   

3.     A-34   with a 4 - 10 axle
   

1. Originally the 318’s with a tow package came most of the time also with an 8 3/4 rear.
   

1. Originally the lug nuts on left hand side of car came with a reverse thread.
   

During Restoration What do People Do:

1. They replace the Differential with Sure Grip 8 3/4", 3.55 gears, 742 case.
   

2. 
   

3. They replace the Differential with an A-Body 8 3/4 with 3.23 posi.
   

4. OEM 8-3/4 rear end with 3.91 gears.
   

5. 
   

6. They replace the Differential with Sure Grip Detroit Locker Differential, and Richmond 4.30 gears.
   

7. 
   

8. They replace the Differential with Richmond 4.88 gears.
   

9. 
   

10. They replace the Differential with National Drivetrain-equipped 831/44 rear end.
    

11. 
    

12. They replace 3.23 rear axle gears with 3.91 gears for more torque multiplication.
    

13. They replace the driveshaft with a Victory 3" driveshaft, that was bought through Mancini Racing.
    

14. 
    

15. They replace the driveshaft with a custom one by Denny's Driveshafts.
    

16. 
    

17. They replace the factory axle with new forged axles.
    

18. They replace the factory axle with Billet Dutchman Axles.
    

19. They replace the factory axle with Moser Axles.
    

20. 
    

21. They replace the factory axle bearings with Strange Engineering sealed units that eliminate the adjustor.
    

22. 
    

23. They replace the eliminate all reverse thread lug nuts with regular thread.
    

General Information

Rear Differential

Rear Differential Types

1. The differences between rear differentials, in most cases, is the bolt pattern. Its about an inch difference. Seriously, this should help....
   

2. http://www.moparts.org/Tech/Archive/axle/6.html
   

3. Jonathan Lockhart
   

7 1/4

1. You could get a 7-1/4 or an 8-3/4 in 1967.
   

2. 
   

3. The 7-1/4 will be a 4" bolt pattern.
   

4. Phil Saran
   

8 1/4

1. The 8-1/4 was not available in 1967. The 8.25" wasn't available until ‘71 or’ 72. The 8-1/4 will be a 4-1/2" bolt pattern.
   

2. Jim Lusk
   

1. If you are upgrading from a 7 1/4, you will need 3" u-bolts, shock plates from the 8 1/4 or 8 3/4 and a shorter driveshaft. E-brake cables will work with the new rear.
   

8 3/4

1. You could get an 8-3/4 in 1967. The 8 3/4 rear end has a sure grip clutch system in it. And has a 10 bolt pattern.
   

2. 
   

3. 8 3/4 mopar rear axle is so simple to work on. The 8.75 (8 3/4) rear end LOADS FROM THE FRONT and IS THE ONLY REAR END THAT DOESN’T HAVE A REAR COVER.
   

4. Graveyard Cars
   

5. 
   

6. If you are upgrading from a 7 1/4, you will need 3" u-bolts, shock plates from the 8 1/4 or 8 3/4 and a shorter driveshaft. E-brake cables will work with the new rear.
   

9 1/4

1. The 9 1/4 rear end came with 12 bolts.
   

Dana 60

1. The Dana 60 rear end was basically a 3/4 ton truck rear end. It had 10 bolts with a 9 3/4” ring gear.
   

Rear Differential Axle Tubes

1. The axle tubes on a 7 1/4 are 2 1/2", the 8 1/4 and 8 3/4 are 3" diameter.
   

2. Jim O’Conner
   

Sure Grip vs Positraction

1. Chrysler calls its rear end Sure Grip rear end. You have a Sure Grip, with the car is off the ground, when you turn one rear wheel the opposite wheel will turn the same way.
   

2. Graveyard Cars
   

Rear Differential Identification

1. Mopar Rear Axles are Identified by casting number & number of cover bolts.
   

2. 
   

3. Year        Body            Size    Casting Number     Notes
   

4. 1967          A               7.25         2070051        9 bolt cover      
   

5. 1967          ABCD        8.75        1634985       10 studs, no rear cover
   

6. 1969          ABCE         8.75        2881489     
   

7. 1967-69     ABCE         8.75        2070741     
   

Measurements

1. The quick and short of it: measure the center to center distance on the spring perch, should be 43".  Outside drum to drum is 57-1/8". 
   

2. Michael Mosley - ’68 Coupe
   

Reference

1. Below is a link to the moparts page for reference.
   

2. http://www.moparts.org/Tech/Archive/axle/17.html
   

3. http://www.bigblockmopar.nl/tech/mopar-rearaxle-dimensions/
   

4. Eric Valentin  - ‘69 FB
   

Rear Differential Disassembly

1. Make sure you take pictures of brake lines before disassembly.
   

Restoring Rear Differential Order

1. After painting the differential, be sure to put on new brake lines and flex lines on rear differential before reattaching to car. Use mild steel versus stainless steel brake lines. Also add white tape on threads. Make sure you don't cross thread the lines.
   

2. 
   

Rear Differential Assembly

1. Housing, differential, cover, backing cover, brakes stuff then brake lines.
   

2. Rear end, then springs, add third member, bolt it on to carrier, it has sure grip and carriers in it.
   

3. 
   

4. When assembly, now is time to tighten everything down.
   

5. New lines tend to want to leak pretty easy.
   

1. Press on bearings to axle, slide left axle in, then right axle, bolt it in and you have rear end assembly. Put on leaf springs, detail it and it's ready to bolt on car. Then get brakes done.
   

Part Number Labels

1. Axle part number tag goes on the differential near rear brakes. It can be on different sides per car.
   

2. Paint mark white (X) goes on cover.
   

3. 
   

Rear Differential Gears

1. Be very careful with used gears. The drive side of the ring gear teeth will have a wear step. You *must* set them up with more backlash than their prior installation. If you set them with less backlash, the edge of the pinion tooth will be riding on top of the ridge, which will lead to breakage.
   

1. Get a Mopar FSM for most any rwd car and it will detail the gear set-up procedure.
   

2. Ken Mayer
   

Rear Differential Repair Shops

1. The name of the company is "The Gear Man", located in Garden Grove on the Southwest corner of Stanford and Flower. Cross streets are Garden Grove Blvd and Brookhurst Ave.
   

2. 
   

3.     "The Gear Man"
   

4.     10382 Stanford Ave, Ste I,
   

5.     Garden Grove, CA 92840
   

6.     (714) 537-9495
   

7. 
   

8.     Sutton Engineering
   

9.     Imperial Blvd. (just west of Harbor Blvd.)
   

10.     La Habra, CA
    

11. 
    

12. The Gear Man in Garden Grove takes his problem jobs to Ed Sutton. They are both good, and their pricing is about the same. I heard Sutton was or could be very slow on getting the work done.
    

13. Phil Saran
    

14. 
    

Rear Axle Housing

1. Get familiar with the rear axle, so you know what parts to buy, what work needs to be done by a shop, what you can do yourself, etc. Removing the carrier from the housing while it is on the car isn't much fun.
   

1. 4 speed car, you can choose between 2 axle packages:
   

2. 
   

3. A33 - Track Pak, 3.54:1 Gear Ratio
   

4. Sure Grip (aka Powr-Lok or Trac-Loc) Dana Axle
   

5. 
   

6. A34 - Super Track Pak, 4.10:1 Gear Ratio
   

7. 
   

8. ’69 Mopar with 440 engine, or 426 Hemi engine you would receive Hemi 4 speed which is a:
   

9. HD 4-speed 18 spline input shaft (Hemi 4-speed), you also would receive a mandatory Dana rear axle
   

10. 
    

11. Dana Axle = 9 3/4” Ring Gear (Removable Cover)
    

12. Sure Grip (aka Powr-Lok or Trac-Loc) Dana Axle
    

13. Dana has 10 bolts cover to remove,
    

14. Bigger differential means drive shaft is shorter than on other cars
    

15. 
    

16. 8 3/4” Ring Gear (Drop out carrier) has no removable cover, no bolts. You remove the carrier (pumpkin out the front)
    

17. 
    

18. ’69-71 A33 or A34 = 26” Max Radiator Cooling package
    

19. 7 - blade torque drive fan and H.D. Suspension
    

20. 
    

21. ’69 clutch diameter 11”     ’70 clutch diameter 10.5”
    

22. ’69 cast iron bell housing  ’70 aluminum bell housing
    

23. 
    

Restoring Rear Axle Housing

1. After sandblasting use a garden hose to clean the sand out of the axle housing.
   

2. Jeff Ramin - ’67 Coupe
   

Mating the Carrier with the Axle Housing

1. It will be easier to do this before the axle housing is bolted on the car. It is wise to put the new axle oil seals in the axle tubes before installing the carrier. Use a piece of PVC pipe to drive them in. Try not to bend them. Scrape the old gasket off the carrier. Using a little lithium grease, place the new gasket on the axle housing, and then set the carrier down over the studs. Do this with the axle housing sitting in a milk crate. The axle housing will be nice and stable, as opposed to rolling around on the ground.
   

2. 
   

3. After securing the carrier with the nuts, you’ll have a really nice setup for detailing the carrier. Make another pass over the carrier with simple green, and then put a coat of POR15 on it. After that dries, a top coat of chassis black must be applied. 
   

4. Jeff Ramin - ’67 Coupe
   

Reinstalling the Axle Housing

1. To get the axle housing back in the car, place it on a crawler, and wheel it under the car. By rotating the housing, you will be able to lift once end at a time up and on top of the springs. Using a floor jack and several trips from side to side, you will be able to get it located properly.
   

2. 
   

3. Get the U-bolts / shock plates in place and torqued down. This is a two man job. Now mount the shocks using the torque wrench and lying on the crawler under the car! Move the jack stands from the frame rails in front of the rear end to the axle housing. Greater distance between front and rear jack stands = greater stability. Properly torque the nuts on the spring shackles and the front eye bolts. The Factory Service Manual says not to do that until the weight of the car was on the springs.
   

4. Jeff Ramin - ’67 Coupe
   

Rear Axles

Reinstalling Rear Axles

1. You can't install the axles if you don't have the foam gaskets that go between the axle flange and the backing plate.
   

1. Now put the axles back in the car. Reuse the metal gaskets that sit between the axle housing and the backing plates. They might be a little rusty around the edges, but they should do. Just followed the instructions in the Factory Service Manual. A little nerve wracking involves setting the axle end play. You may have to set it quite a bit deeper than what it was originally on the car. For a while I thought something was wrong, because I kept turning the adjuster and turning it, and the play of the left axle wasn't diminishing! But eventually it did tighten up.
   

2. Jeff Ramin - ’67 Coupe
   

Rear Axles Adjustment

1. Adjust end play on the axle. Adjust with nut behind axle. You want a little play because when metal heats it expands. So you want a little room in between them. Use a dial indicator at home.
   

Axle Bearings

1. Axle bearings are inside the housing once you pull the axles out. The axle bearings are held in place by a pressed-on sleeve. They must be repacked with grease at regular intervals to perform properly. To achieve proper axle endplay, Chrysler added an adjustor to one of the axles. This adjustor can be a problem, especially if you perform frequent gear changes. Factory axles and axle bearings still perform just fine in stock applications.
   

1. Factory axles were held in by five nuts and studs on the axle end tubes. With the brake drum removed, you can access the nuts through a hole in the axle flange. Note the factory adjustor on this axle.
   

1. Replacing factory axle bearings is a good upgrade.
   

Axle Bearings Problems

1. In 1992, I was driving my Barracuda and the left axle came out and the car came to an abrupt stop as the tire rubbed up against the fender wall. I was told that the old bearings on the axle were probably heated off and new ones were pressed on. The axle in some way was compromised.
   

2. Angel Garrido - ’69 Fastback
   

3. 
   

4. The wheel bearing probably burned up due to water contamination. A fresh pair of wheel bearings should solve the problem if your housing end did not get ruined.
   

5. Cass Eslick  (Dr. Diff)
   

Replacement Axle Bearings

1. Make sure they use a good American brand bearing. National part number is something like A7, but the axle shop should know these by heart. Chinese bearings are crap. The cheap bearings I got from Currie made noise from day one until they came apart 30k miles later.
   

2. Nathan Nuttall - ‘67 Fastback
   

DIY Axle Bearing Removal

1. It is very difficult to replace the rear bearings yourself. You need a proper tool to avoid scoring the axle. You will need a slide hammer with outside fingers to get the old seal out. Never use heat to remove bearings. Now might be a good time to put in a limited slip if you feel inclined to do so, but it isn't real easy or cheap to do.
   

2. Nathan Nuttall - ‘67 Fastback
   

Shop Removal

1. I recommend taking the axles out of the housing and taking them to a competent shop to have them do the R&R of the bearings on the axles.
   

2. 
   

3. A hydraulic press should be used to remove the old bearings, and is a necessity to install the new ones. Most of the less-competent shops will cut the old bearing off instead of pressing it off. Don't let them do it as it will mar up your axle and you can only do that 2 times at most before the axle is junk. Also, don't let them talk you into unnecessary "green" bearings. Just use the original tapered bearings and adjust them properly.
   

4. Nathan Nutthall
   

5. 
   

6. My advice....don't do it. I have seen them come off and it is quite dangerous. Most rear end shops now refuse to press them off and will cut them off instead. I don't like that idea either because it destroys the axle after the 2nd time. So I always take them to a shop that has the setup to press them. Best way to get it done in my opinion. I have a 20 ton press too, but I don't mess with them.
   

7. Nathan
   

8. 
   

9. Make sure you check your housing as well for any gouging or wear. If it is worn badly, you will have to replace (weld) a new end on the housing. This can be expensive & many shops will do the repair poorly so hope that isn't the case.
   

1. Cutting off the bearing may mar the bearing surface on the axle at the location of the cut. Since it is only in 2-3 places on the axle, the new bearing can still seat OK. But after the second time, you start to run out of good surface for it to hold properly.
   

2. Nathan
   

3. 
   

4. I would agree. I always press on and off. Harbor Freight does the job easily!
   

5. Same for the center section! I have a couple bearing separators for use with my press and just got through with new carrier bearings on the carrier.
   

6. Gerald Drury
   

DIY Reinstall

1. Install it with a large socket & hammer or a seal installer. A hydraulic press should be used to install the new ones.
   

Alternative

1. As an alternative to changing the bearings on your axles is to replace the factory axles. New axles will save the hassle of pressing bearings on and off, and you won't have to wonder about them if your car is equipped with a powerful engine.
   

2. 
   

3. New axle kits can also be ordered from Strange. These axles are far tougher than factory units, and meet the aftermarket axle requirement of racing sanctioning bodies. They're available for all common Mopar rear ends, and can be made for custom narrowed applications as well. The axle bearing kit from Strange comes with new, non-adjustable, fully sealed bearings (commonly called "green" bearings), new axle retainers (to hold the axles in the housing), new press-on sleeves, and gaskets. These bearings are already pressed into place and never requiring maintenance. They also eliminate the factory adjustor.
   

4. 
   

5. Unlike factory axles which have pressed in wheel studs, the Strange axles utilize stronger, screw-in style wheel studs. These should be installed using Lock-Tite, and will take far more abuse than the factory studs. Once bolted in, you should never need to worry about the axles for the life of your car!
   

6. 
   

7.     Strange Engineering 
   

8.     www.Strangeengineering.net
   

9. 
   

10. Most people eliminate all reverse thread lug nuts with regular thread.
    

Drive Shaft

U-Joint

U-Joint Removal

1. The original U-joint may have to be pressed out of the drive shaft.
   

Checking Drivetrain Geometry

1. Build a homemade tool as described in "Chrysler Performance Upgrades" to measure your u-joint angles. It works very well. If your out of wack, shim the tranny mount. Hopefully that will take care of the rear angle also.
   

2. Jeff Ramin - ’67 Coupe
   

1. Unbolt the tranny from the mount and jack up the tranny with the floor jack. Slide 3 washers between the mount and tranny on each side, which amounts to about 3/8". Lower the tranny back down, and check the angles again. You should have only .5 degrees difference at the tranny, and around 2->3 degrees at the rear end. Note: It’s probably better to use a plate of steel that runs the entire width of the tranny mount than using washers for shims.
   

2. Jeff Ramin - ’67 Coupe
   

Installing Drive Shaft

1. There is a rubber seal called the Output Drive shaft seal that is between the drive shaft and transmission. It needs to be wet not dry or seal will leak transmission fluid. Grease that before you put it in.
   

2. 
   

Bolt & Pinion Shaft

1. You need to remove the shaft in the middle of the carrier too so that you can push the axles inward and get the clips out. The clips are sunken into the inside of the spider gears and that is what is keeping them in place. And the shaft keeps the axles from moving. Once you remove that shaft it should be clear. Only thing is, don't rotate the axles afterward unless you do them both at the same rate, or else you will have spider gears falling out.
   

2. 
   

3. I am a little concerned about your statement that you can turn the pinion without either axle turning. If you turn the pinion, there is a large gear on the inside of it that will turn the ring gear. Turning the ring gear should turn at least one axle.
   

4. Nathan Nuttall - ‘67 Fastback
   

5. 
   

6. Almost all the c-clip axles are the same. Whoever took the picture put the bolt back in the pin after they slid it out of the carrier. Just like the picture, you do not have to take it all the way out, better if you leave it slightly in the "bottom" spider gear to keep the gears from turning and coming out. Once the pin is clear of the axles shaft you push the axle in a little and the clip will all but fall out. 
   

7. http://www.nastyz28.com/2gcog/tech/c-clip.jpg
   

8. Michael Mosley - ’68 Cuda
   

9. 
   

10. Remove the bolt for the pinion shaft (spider gear shaft) and then push in on the axle slightly and you will then be able to remove the c clip.
    

11. 
    

12. Concerning the pinion and gears, put a clamp on one side to block the wheel drum from turning. The pinion will definitely turn the other wheel then. 
    

13. 
    

14. Let me get this straight. Turn the carrier so that the bolt is toward the diff opening (for easy access). Loosen the bolt and slide the pinion shaft out. Push the axle in toward the center to clear the spider gear. Then remove the clip.  Don't turn the axles in the process, or if I do, make sure that they are turned equal amount. Is this right?
    

15. 
    

16. Is there anything else I should do while I have easy access to everything? For gear oil, I saw 85w90 recommended. I'm replacing brake shoes, hardware, springs and wheel cylinders. Do the outer axle bearings have seals? Guess I should go ahead and replace those if they are there.
    

17. Jim Conner - ’68 Cuda
    

18. 
    

19. You have it. Just if you keep the shaft inside one of the spiders, then you can rotate it a little without worrying about them coming apart.
    

20. 
    

21. If you are going to weld on the perches, you should do it now without the axles installed. If you weld with the axles in place, the axles will prevent the housing from moving, and as it cools, it will warp. By welding without the axles, the housing can move as it needs to when hot and move back to where it was as it cools.
    

22. Nathan Nuttall - ‘67 Fastback
    

23. 
    

24. I would like to put in a SG and taller gears. This is a 3.55 and I would like to go higher for the gas mileage. I don't think there would be any way to find any used parts in this area for a Chrysler rear end. Possibly at pick-a-part, but I doubt it. I guess it would be much better to do the welding before installing new seals?
    

25. Jim Conner - ’68 Cuda
    

1. In '67 and '68 the only ratio from the factory was the 3.23. The rest had to be installed by the dealer or somewhere else.
   

2. Mike Jarvie - ’68 Fastback
   

3. 
   

4. 3.55 and 3.91 were optional, at least in ‘68, but I'm sure in ‘67 too. You could also get a 2.94 (might have been 7-1/4 only in the A-body, though). I have also seen a 2.76 8-3/4 in other cars.
   

5. Jim Lusk - ’67 Cuda
   

Pinion Stubber

1. The pinion stubber is a piece of rubber that prevents rear end from hitting undercarriage with torque of rear end. It wants to move up. It sits on end of rear end by u-joint.
   

Pinion Seal

1. The pinion seal holds all the gear oil in the the rear end. If the seal is bad, it can rupture causing damage to bearings and the rear end itself.
   

Pinion Angle

1. Pinion angles can be referred to angles oriented from front to back. As an example, an engine centerline angle is 4* down. That is, negative four degrees going from front of engine to rear. You can determine this by placing a small piece of wood vertically against the front pulley and measuring with a dial protractor. Now, the simple solution says to orient the pinion 4* down. That's negative 4* starting at the front of the pinion and measuring going down. Refer to the first diagram on the Moparts link, parallel centerlines. The front of the yoke is higher than the back.
   

2. Jim Conner - ’68 Cuda
   

3. 
   

4. http://www.moparts.org/Tech/Archive/axle/8.html
   

5. 
   

6. Don’t measure the pinion angle at the front pulley. Do it at the output shaft of the transmission. That is where the angle matters most. It is probably the same. If the angle measures 4 degrees down at the output shaft of the tranny, then you need the yoke to measure 4 degrees up. You want the output shaft of the tranny and the yoke to be parallel with each other (if you were to extend straight out from each).
   

7. Jonathan Lockhart
   

8. 
   

9. If you measure everything front to back, then both angles should be the same. As an example, if the tranny output shaft is 4 degrees down (measured front to rear), then the angle from the front of the pinion to the rear should also be 4 degrees down. But, that is NOT how they are typically measured. The angle should be measured towards the driveshaft - not front to rear.
   

10. 
    

11. Look at the VERY last picture on that URL posted from Moparts - called Driveshaft Phasing. It is exactly right on how to set them up. It is the simplest way to look at it. That pic has the tranny level and the pinion level. They have an angle of 0. If you drop the trail of the tranny down (say to 4 degrees), then you need to pick the nose of the pinion up to offset.
    

12. Jonathan Lockhart
    

13. 
    

14. Make the centerlines parallel to each other. And it is that simple. 4 degrees angled down toward the back is pretty standard. However, keep in mind that the pinion will angle up (more negative as you call it) under load, and will angle down under braking. If you have serious power in your drivetrain, you may want to offset the angle a little to account for the shift in pinion angle under load. The reason to do this is to make the centerlines more parallel under high load when you launch the car off the line. This will help race cars to prevent them from breaking U-joints and such. But most street cars don't need to worry about such things.
    

15. Nathan Nuttall - ‘67 Fastback
    

16. 
    

17. When you finished putting a 8 1/4 trac loc into the rear leave just a tiny bit of "slop" in it. Torque the side adjusters so can just barely hear a click when moving the pinion back and forth. Use a dial indicator with magnetic base to see how close you are. Put it on the gear. Put heavy grease on the threads. Put anti-seize on the adjuster threads and retainer bolt threads and it should work like a charm! Preload is 75 ft-lbs, backlash is .008". Perfect!
    

18. 
    

19. As far as axle play, if it goes tink tink with no real movement you’re fine, as long as it's not jammed tight and as long as it's not really loose it should be OK.
    

20. Daty Rogers - ’67 Conv.
    

Lithium Grease

1. Put white lithium grease on the ring and pinion and check the contact pattern.
   

Backing Plates

1. The 10" backing plates will fit anything with small bolt brakes (assuming this is from a small bolt 7-1/4). Some of them did not have the lower stud hole, but it can be drilled. 
   

2. Jim Lusk
   

Lubrication

Differential Oil

1. You’ll need a gear oil with limited slip additive. Look at the OEM lube recommendation for the vehicle it came from. It be synthetic limited-slip lube. Just about everything uses 85w90, and anything built in the last 15 years uses synthetic. Just have the right lube for the limited slip component, whether it's in the oil or a small tube of goose grease.
   

2. Max Heim - ’67 Fastback
   

3. 
   

Differential Fluids

1. Valvoline /Full synthetic gear oil SAE 75W-140 is for limited slip differentials.
   

2. The Valvoline tech line [800-832-6825] sell a "high performance gear oil" that says on the label it's suitable for limited slip differentials. It has 4% frictions additive. If want to add some more frictions additive, it won't hurt up to about 2oz per 2 quarts (which is 1/32 or about 3% by volume) in addition to the 4% additive already in the product. Modern LSDs use the same modifiers as the older LSDs. Synthetic oils offer more protection but aren't compatible with any RTV and will cause leaks to develop.
   

3. Ed
   

4. 
   

5. I found a Quaker State 90 W product that says it has the additive for posi traction/sure grip.  
   

6. Wiff
   

7. 
   

8. All of my research said that there's not quite enough friction modifier in any of the blends. I added a little bottle of the Chrysler sure-grip modifier. If you use the blend, you can always add modifier later if needed. The friction modifier is to actually lessen the friction in a sure grip rear so that it won't bind and "pop" going around corners.
   

9. Jim Conner
   

10. 
    

11. I’d be concerned it is for modern limited slip diffs, not vintage ones. I might use it with the factory-recommended additive.
    

12. Max
    

13. 
    

14. You can buy the additive at a dealer that sells to the drag racing or circle track racing crowds or try eBay.
    

15. 
    

16. Jeep Dodge Limited Slip Additive Friction Modifier Mopar  #4318060AB $10
    

17. http://www.ebay.com/itm/Jeep-Dodge-Limited-Slip-Additive-Friction-Modifier-MOPAR-4318060AB-/161898183385?hash=item25b1e23ad9:g:gT8AAOSwc0FUqo5b&vxp=mtr
    

18. Steve Toth
    

19. 

    
    

20. 
    

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22. The 2 shops I've go to both use exactly the same thing: Lucas 85-140 with GM additive. One of those shops, Performance 4 Wheel Drive in Bellflower, is used by many of the local Mopar "hobby racers". The other shop is J&S Gear in Huntington Beach. J&S does a lot of hot rod work, but they are more expensive.
    

23. Ron Evans
    

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25. Synthetics may have other properties that aren’t compatible with older cars. But’s getting hard to even find non-synthetic gear oil at this point.
    

26. Max
    

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28. Synthetic tends to be more slippery than traditional. That allows it to find a way out easier. As such, synthetics are much more prone to leak.
    

29. Jonathan Reck
    

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31. Just add this to you favorite gear oil and  Mopar-On!
    

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33. http://www.ebay.com/itm/Mopar-limited-slip-additive-friction-modifier-4318060AB-trac-lock-posi-trac-OEM/311480123772?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3D34afb665e80f4b63a72a7284e98b3004%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D320949080974
    

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35. Luke - ’69 FB
    

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Differential Additives

1. As far as additives, some of them are pre-blended with the gear oil. Use an 85w-90 or such. Lean toward Valvoline synthetics - power steering, brake fluid, etc. Valvoline blended synthetic has about 3% friction modifier, equating to about 2 ounces of additive. Go with Valvoline with 2 ounces of Mopar additive. If you get the non-blended Valvoline use 4 ounces of Mopar additive. Chrysler had recommended NOT to use friction modifiers on cone style limited slip differentials. They had an old copy of a tech supplement to back it up. Seems the modifier is only for the clutches.
   

1. 8 3/4 SG:  I use Sta-lube limited-slip Hypoid SAE 80w90 gear oil API/GL-5.
   

2. Some articles and such talk about staying away from the synthetic for posi rears (SG). The right synthetic is probably ok, but I'm perfectly happy with either Sta-Lube or Amsoil (75W-90, not the synthetic). Another used by a lot of garages around the area: Valvoline High-Performance 80W-90 Gear Oil.
   

3. Tim Moller -’69 Cuda Conv.
   

1. Kendall Limited Slip Additive, or their gear oil with it already in there. It's the best stuff I've ever used.
   

2. Rob McCall - '68 Fastback
   

Changing Differential Oil

1. Changing the diff oil is messy and stinky, but it will go pretty smoothly. Use a suction gun to remove as much of the old oil as possible.
   

2. Jeff Ramin - ’67 Coupe
   

Parts

1. You might want to contact Dr. Diff over on http://www.moparts.com/ he builds rear ends and suspensions out of his shop in Montana and is a wealth of information. Ron Evens on the BOG recently got his new Dana with disc brakes from him.
   

2. Phil Saran
   

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