Dana 70 shudder

[Smokin 90]

Hi everyone,



I was wondering if anyone could help me with a problem I am having with the Dana 70 rear diff in my 90 3/4 ton? Frist of all the rear diff was rebuilt by my local dealer about 1 1/2 years ago and I have only put about 7,000 miles on it since then. The problem I am having is that the rear end shudders and feels like it wants to wheel hop real bad when accelerating from a stop and after each shift of my 727 auto. It seems to be worse at lower engine rpms and goes away at higher rpms but then the transmission shifts upshifts and the rpms drop and the shudder comes back and the rear of the truck feels like a bouncing basketball.



I checked the u-joints and they seem tight and they were replaced the same time as the rear diff was rebuilt. but I noticed that i could move the yoke on the diff around a little so I removed the driveshaft and yoke to see what the problem was. I noticed the yoke had been rubbing on the rear seal hard enough to put a groove in the surface of the yoke so I assumed the pinion bearings were shot so I replaced them by the book and now everything is tight again and the ring and pinion looked very good but my problem is still there if not worse than before. I should also tell you that the transmission was rebuilt about 5,000 miles ago by the same dealer and it seems to work fine.



This is a problem that started out slowly but quickly has gotten worse and I will not drive my truck until I can fix it. I know that the community on this site is VERY sharp so I would be very grateful for any insight you guys can provide.



Thank You,

Kurt.

 

[Philip]

If you truck has the 6" lift blocks on it from the factory. You need to install a 1/2" spacer between the carrier bearing and the frame it mounts to. The was a TSB out on this problem.

 

[Smokin 90]

Thanks Philip,



Are the spacers for the carrier bearing available from the dealer? and will the TSB tell me how to install them?



Thanks,

Kurt.

 

[Philip]

You can make it your self. You would need a section of 1/2" flat stock. Then measure the bolt centers on the carrier bearing mount. Then drill and install. 1" wide flat stock should work.

 

[Smokin 90]

Thanks again Philip,



My truck has a 1 piece driveshaft so I am not sure that that TSB applies unless there is something I do not understand but thanks for your help.

 

[Philip]

Ok your a reg cab. I didn't see that in your sig. Forget what I posted then.



Let me set back and think now.

 

[Philip]

Here are a few things to check on.



Check spring eye bushings. See if they have fallen apart and are letting the springs move around.



Look the driveshaft over real good. See if it might have tosed a weight off of it.





Have you rotated the tires lately? Gotta ask on this one.



You replaced the pinion bearings! What was the setting you used on the backlash?



Have you checked the bearings in the hub's?

 

[Smokin 90]

Philip

To answer your questions I havn't looked at the spring eye bushings and the driveshaft does not look like it has thrown any wheights. I just had new tire installed after I noticed the shudder and they did not seem to effect it one way or another.

as for the backlash I used the method of putting some white grease on the ring and pinion and inspected the wear pattern as the Hayes service manual I have does not go into servicing the diff's except for the pinion nut torque and carrier cap bolts. I have a service manual on order from Dodge but it will not come in for about two more weeks.

I have not checked the bearing in the hubs. but I will.



I may replace the u-joints on the rear driveshaft and see if that helps, they feel tight but you never know after the way the yoke was moving around. Thanks for your help and if you or anyone else can think of anything else I may be missing please let me know.

 

[Philip]

The back lash is the amount of movement you have in the pinion before it touches the ring gear. It is normaly a small measurement. Of the top of my head it should fall in the . 010 to . 020 range. If this measurement is to tight. You will get rear end vibration. It will also lead to premature gear wear and failure sometimes.



Using the white grease just gives you a wear pattern.



The u-joints feel tight. Now are you talking in a twisting motion or when you move it threw the full range of its movement?



Right now I am leaning towards to tight of backlash.



Just for a test. Take the rear shaft out. Lock in the hubs and put it into 4x4. Then go for a drive. Do you still have the vibration?

 

[Smokin 90]

Hey Philip



I thought I would let you know that I checked the backlash on my rear diff and it was way too loose. It looks like I have got some shimming to do. While I am at it I am going to check all of the other spec's while I am adjusting the backlash now that I have them thanks to Paychk, He posted a link to Chiltons web site to Dodge drivetrain service specs and procedures.



Thanks for all of your help.

I hope this does the trick.

 

[Paychk]

Glad to help out