Differential issue...

[| 1990 ZR-1 |]

Well Gentlemen, here I am again seeking help with the beast. I've had a great time for the past 3 months with the car since I repalced all the injectors, brakes, and replaced/fixed the FX3 system. Now I have an issue with the rear diff. The car is MY 90 with 34k original miles.

Two weeks ago, I noticed the driver rear wheel visually looked out of allignment. Upon closer inspection, it had a pretty big negative camber, and the toe was pointing in. A couple of days prior, I hauled about 300lbs in the trunk area, which I didn't think was a big deal, but it sure enough caused some kind of damage. The car drove fine with the exception of very slight vibration at about 40 mph. At first I thought maybe one of the busings wore off or expolded, or some suspenssion part either broke or bent, but after jacking the car up and inspecting all the components underneath, I didn't see anything out of ordinary. I dropped the car off with my local mecahnic, and he said that something in the differential broke and is causing the wheel to get out of allighment. He said he would not take it apart and suggested we replace the whole rear diff, which looks like an expensive option.

My questions are:
Has anyone else experienced anythign like this and could tell me which part would be a suspect? I searched the tech forum, but didnt' see anything.

Should I take the car from my macahnic and take the diff appart to see if i can fix it?

I've never removed diffs before, but am pretty handy. How complicated is it, and would I need any special tools? I do have the service manual that I will reference to, but if anyone has step by step instructions they could reference, I'd appreciate it.

Last but not least, I keep reading about the 4.10 gear upgrade. How envolved and costly is this upgrade? If it's too much money, I'd rather just replace the broken part, and put her back together.

As always, thanks in advance!


-Gary

[Ccmano]

Hold on.....I think the camber adjusting cam moved on you. Loosen the nut (center of photo) and rotate the cam to get the camber you desire :cheers:

If something let loose in differential, you would hear it and that has nothing to do with camber. You have a short shaft between differential and wheel bearing as you can see on differential side in photo.

http://www.zr1.net/forum/picture.php?albumid=108&pictureid=907


:iamwithst No way that's internal to the differential! Either a suspension issue or a wheel bearing (even that would be a stretch). Your mechanic is either clueless, doesn't communicate well, or is flat trying to rip you off.
H
:cheers:

[| 1990 ZR-1 |]

Thanks guys. I'm really hoping this is the case. This guy came highly recomended by my neighbor who's a car enthusiast, but is not a technical at all.

Here's another thing. This mecahnic installed my new tires and did a 4 wheel alignment about a month ago. I bet they didn't tighten somethign up properly, and with the additional weight I had in the trunk, somehtign gave and shifted. It just sounds wierd that a diff would go on a 34k mi car. I don't drag race it, or abuse it, or launch it severaly. Just spirited driving on weekends. I'll call him tomorrow. I just wish there was a knowlagble corvette mechanic around here.

[PhillipsLT5]

Try VBP align recomendations, works for me
http://www.vbandp.com/
Dynomite your info is GREAT!!!!!!!
4.10's are the way to go, really push you back in seat, instant improvement

[ZR1Vette]

Sound like the boys have the issue ID'd, but just 'to cover' everything inspect the leaf spring and make sure is was not fractured etc. with the additional weight.

[Z51JEFF]

For starters Id find a new mechanic.Id go with the camber adjustment moving.

[| 1990 ZR-1 |]

Quick update. I had a chance to pick up the car from the mechanic this week, and jack it up and inspect it myself. I did not see any bent parts, and I also do not see anything visibly wrong with the diff. The mechanic claimed that the half shaft where it connects to the the diff was loose, but I pulled on it in every which direction by hand and also with a crowbar and it didn't budge. I did notice, however, that the yoke is presssed into the diff about an 1/8 of an inchwhen compared to the passanger side and caused the big spacer with rounded edges rub against the diff housing. I also noticed a little bit of diff fluid on that side, but not enough where it dripped on the floor. I started to inspect the trailing rod bushigs, and noticed that the all have small cracks on them and one on the lower rod connecting to the spidle had a huge crack in it. I removed the lower dog bone and noticecd that the bushing is not centered and looks severily deformed. I ordered a new set of 8 bushings and will repalce them on both sides. I just hope this has not caused any issues with the seal in the diff since the half shaft is pushing into the diff.

I really think that my issue lies in those 21 year old, blown trailing rod bushings. I belive when i had the additional 400lbs loaded in the trunk that day, the extra weight did it. If this is the case, I'm going to take those old busings to my mechanic and will put him to shame, since he's suppose to be the pro, but I, a none mechanic just a handy person, used my brian and figured this out within the 15 minutes I had the wheel off.

I'll keep you guys posted once the poly bushings are installed.

[lbszr]

Quick update. I had a chance to pick up the car from the mechanic this week, and jack it up and inspect it myself. I did not see any bent parts, and I also do not see anything visibly wrong with the diff. The mechanic claimed that the half shaft where it connects to the the diff was loose, but I pulled on it in every which direction by hand and also with a crowbar and it didn't budge. I did notice, however, that the yoke is presssed into the diff about an 1/8 of an inchwhen compared to the passanger side and caused the big spacer with rounded edges rub against the diff housing. I also noticed a little bit of diff fluid on that side, but not enough where it dripped on the floor. I started to inspect the trailing rod bushigs, and noticed that the all have small cracks on them and one on the lower rod connecting to the spidle had a huge crack in it. I removed the lower dog bone and noticecd that the bushing is not centered and looks severily deformed. I ordered a new set of 8 bushings and will repalce them on both sides. I just hope this has not caused any issues with the seal in the diff since the half shaft is pushing into the diff.

I really think that my issue lies in those 21 year old, blown trailing rod bushings. I belive when i had the additional 400lbs loaded in the trunk that day, the extra weight did it. If this is the case, I'm going to take those old busings to my mechanic and will put him to shame, since he's suppose to be the pro, but I, a none mechanic just a handy person, used my brian and figured this out within the 15 minutes I had the wheel off.

I'll keep you guys posted once the poly bushings are installed.

From your description, I would investgate the diff more, as the mechanic described the problem. Because the half shaft does more than just transfer torque. It acts as a fixed link that controls camber, the lower camber rod is the adjustable one. If the halfshaft could be shortened, it would make negative camber, which is what would happen also if the yoke was pushed in the diff. What you found actually backs up the mechanics findings. If the halfshaft has trully pushed in the diff, then that would affect camber and also toe. A lot of force is pushing inward or outward on the halfshaft normally, depends on what type of driving is taking place and if something broke at the halfshaft yoke while in a hard turn....it could be an exciting ride!

If the yoke is pushed in the diff, there might not be enough adjustment in the camber rod to make for it.

The yoke should have .0045 in. +- .004 in. end play. It seems like if part of the yoke is wearing into the housing, the clearance would be a lot more, unless it was set wrong at the factory.

[| 1990 ZR-1 |]

From your description, I would investgate the diff more, as the mechanic described the problem. Because the half shaft does more than just transfer torque. It acts as a fixed link that controls camber, the lower camber rod is the adjustable one. If the halfshaft could be shortened, it would make negative camber, which is what would happen also if the yoke was pushed in the diff. What you found actually backs up the mechanics findings. If the halfshaft has trully pushed in the diff, then that would affect camber and also toe. A lot of force is pushing inward or outward on the halfshaft normally, depends on what type of driving is taking place and if something broke at the halfshaft yoke while in a hard turn....it could be an exciting ride!

If the yoke is pushed in the diff, there might not be enough adjustment in the camber rod to make for it.

The yoke should have .0045 in. +- .004 in. end play. It seems like if part of the yoke is wearing into the housing, the clearance would be a lot more, unless it was set wrong at the factory.


Thanks for this. It makes perfect sense, and it was the answer I was afraid of getting.

How hard is it to remove the diff without a porper lift?

Once the diff is off, is it posible to just replace broken ande worn out parts? Or would you suggest replacing the whole diff with a new one?

Last but not least. What is the best source for diff parts?


Thanks!

[lbszr]

Thanks for this. It makes perfect sense, and it was the answer I was afraid of getting.

How hard is it to remove the diff without a porper lift?

Once the diff is off, is it posible to just replace broken and worn out parts? Or would you suggest replacing the whole diff with a new one?

Last but not least. What is the best source for diff parts?


Thanks!

I still would want to verify play in the yoke before tearing into it. Did you check with the wheel on at the 12 and 6 position, with the spring connected to the knuckle it might be hard to move and it might take another person to watch the yoke.

If you still don't feel any play, could try disconnecting the spring from that knuckle and try again, if you haven't already.

Not for this rearend, but gm 12 and 10 bolt, I've bought parts from http://www.drivetrainspecialists.com/

[| 1990 ZR-1 |]

I still would want to verify play in the yoke before tearing into it. Did you check with the wheel on at the 12 and 6 position, with the spring connected to the knuckle it might be hard to move and it might take another person to watch the yoke.

If you still don't feel any play, could try disconnecting the spring from that knuckle and try again, if you haven't already.

Not for this rearend, but gm 12 and 10 bolt, I've bought parts from http://www.drivetrainspecialists.com/


I could not get any play at the yoke at all. The car is already jacked up with the wheel removed so I'll disconnect the spring tonight and see if there is any play in the yoke. I'll let you know.


On a side note, I thought that Dana 44's and the ZR1 drive trains in general are bullit proof. I don't drag race the car or drop the clutch of the lights, only some spirited dirivng on the weekends. It only has 34k miles, adn the only mods are headers, high flow cats with cat abck exhaust, and SLP intake. At the same time, I've only had the car for about 7 months, and don't know much if it's history. I think the extra weight i was hauling and the worn out bushings strained the suspenssion compenents too much and allowed the drive shaft push into the diff and damage somethign in there. Just a word of causion I guess.


Does anyone have a write up on step by step diff removal? I'll also check in our tech section.

[lbszr]

I could not get any play at the yoke at all. The car is already jacked up with the wheel removed so I'll disconnect the spring tonight and see if there is any play in the yoke. I'll let you know.


On a side note, I thought that Dana 44's and the ZR1 drive trains in general are bullit proof. I don't drag race the car or drop the clutch of the lights, only some spirited dirivng on the weekends. It only has 34k miles, adn the only mods are headers, high flow cats with cat abck exhaust, and SLP intake. At the same time, I've only had the car for about 7 months, and don't know much if it's history. I think the extra weight i was hauling and the worn out bushings strained the suspenssion compenents too much and allowed the drive shaft push into the diff and damage somethign in there. Just a word of causion I guess.


Does anyone have a write up on step by step diff removal? I'll also check in our tech section.

With the wheel removed, it's hard to get the leverage needed to find play.

If you still don't feel the play, it's a tough call, the yoke rubbing into the housing would probably cause me to tear it apart anyway. But it would be a lot of work. I do remember a write up of somebody taking theres out and doing all the bushings on this site.

[| 1990 ZR-1 |]

I was finally able to pull the diff out this weekend and take it apart. Sure enough one of the side yokes is worn out all the way to the C clip. I'm having a real hard time finding those side yokes for sale any where. Do you guys have any suggestions?

Also, does anyone know what would cause only one of the side yokes to wear? I'm planning to repalace the side berrings and seals, everything else seems to be okay.

[Ccmano]

I was finally able to pull the diff out this weekend and take it apart. Sure enough one of the side yokes is worn out all the way to the C clip. I'm having a real hard time finding those side yokes for sale any where. Do you guys have any suggestions?

Also, does anyone know what would cause only one of the side yokes to wear? I'm planning to repalace the side berrings and seals, everything else seems to be okay.

Can you take a photo of this and post it? This still sounds really weird. How does the old bearing look?
H

[a1991zr1]

There is no way in h$ll you damaged the Diff. Take your car down to the local firestone as they tend to have the best alinement machines out there, and get the alignment checked. I would say 95% chance the rear camber got knocked out. I have had way more than 300 lbs in the back of mine and never had an issue. you can check this yourself with a barnyard alignment the service manual give you all the measurements take two levels and hold them on the outside of each rim and measure the distance from the level right to left front of tire and rear of tire and let me know what you get.

[lbszr]

I was finally able to pull the diff out this weekend and take it apart. Sure enough one of the side yokes is worn out all the way to the C clip. I'm having a real hard time finding those side yokes for sale any where. Do you guys have any suggestions?

Also, does anyone know what would cause only one of the side yokes to wear? I'm planning to repalace the side berrings and seals, everything else seems to be okay.

Does that mean there is not much of a groove left for the C clip to be in?

How much metal from the end of yoke shaft appears to be gone, compared to the other side?

Does the inward end of the yoke push against the pinion shaft surface, and also the wear point? Just making sure I understand where it is worn.

I doubt if a heavy load or anything you did caused this. A one wheel burn out for a really long time is the only way I can think to really cause friction on the end of the yoke. Maybe a loose yoke bearing could set up some kind of movement causing wear. Maybe the yoke was just inferior with a soft spot on the end. The end play might of been set up wrong, there is suppose to be 8 different thickness C clips for adjustment. Sorry just thinking out loud.

http://www.drivetrainspecialists.com/categories/dana/ Might have something. Corvette Central, or White Racing. Guess you already tried the dealer?

[Jagdpanzer]

Try Tom's Differentials, catalog page 32
http://www.tomsdifferentials.com/catalog.asp?pg=32

or Ikerds
http://www.ikerds.com/catalog/group13/group13.html

Please post a photos so we can get a better idea of your problem.

[| 1990 ZR-1 |]

Thanks for all the replies gents. I'll try to answer all questions from today, and provide more info. Please bear with me since it's my first time opening and seeing inside of a diff. Also here are some pics. Please note that C clip is already removed at the time of taking the pictures.

After removing the diff and before even opening the cover, the driver side yoke had an approximate 1/4" in and out movement, while the passenger side yoke did not have any play at all, as it should not. After removing the cover, the problem was apparent. The inner part of the driver side yoke that butts against the spider gear cross shaft is worn out by about 3/16th of an inch, just enough where the C clip was almost resting against the cross shaft. You can see from the pictures that yoke is worn. I guess I lucked out that C clip did not fall off the yoke and cause more damage. Now this could have been an ongoing issue that maybe even started before I got the car. The side bearing does have a little bit of play in it, but I’m no expert. I will replace both side bearings and seals as a precaution. I believe that the worn out bushings in the spindle rods along with the extra weight in the trunk and me going over a dip at a higher speed than I should have with the extra weight somehow put too much strain on yoke or the bearing or both and caused this issue. I'm going to replace the yoke and the bearings and I think I should be okay. Please tell me if I'm missing something here. Thanks!


http://img26.imageshack.us/img26/1867/img00831201109272035.jpg (http://imageshack.us/photo/my-images/26/img00831201109272035.jpg/)


http://img833.imageshack.us/img833/2976/img00829201109272032.jpg (http://imageshack.us/photo/my-images/833/img00829201109272032.jpg/)

[a1991zr1]

good catch at least it is not to costly as a repair. Glad to see you figured it out

[Ccmano]

Looks like bearing failure, faulty installation or side impact on the wheel caused the yoke to push in against the pinion shaft. I would also inspect the bearing seat in the case for damage. I'm thinking accident damage somewhere in the past that was not picked up. (or ignored)
H
:cheers:

[a1991zr1]

any curb rash on rim what does car fax say

[| 1990 ZR-1 |]

Looks like bearing failure, faulty installation or side impact on the wheel caused the yoke to push in against the pinion shaft. I would also inspect the bearing seat in the case for damage. I'm thinking accident damage somewhere in the past that was not picked up. (or ignored)
H
:cheers:

I agree that it's most likely a bearing failure, but not due to an accident since there are zero signs of any damage or repairs to the suspenssion or body. Also, the carfax was clean. I distinctly remember going over a deep in the road where the car almost buttomed out, and I strogly belive that the extra weight inthe trunk strained/stretched the bearing to a point that the yoke started to wear. I'll try to get all the parts this week and put her back together this weekend. I"m reaplacing all rear bushings while I"m under there. Need to get here ready for a corvette show next weekend!! :)

Quick question. What diff fluid should I use?

[Ccmano]

I use Mobile 1 75-90 synthetic gear lube, no additive required.

http://www.zr1.net/forum/showthread.php?p=79124

H
:cheers:

[vinsZR-1]

Amsoil 75W-90 synthetic lubricant and friction modifier additive.

Vince
90 #1966
Corsa, 410's, Haibeck chip

[a1991zr1]

I use Mobile 1 75-90 synthetic gear lube or lucas makes a great product