Rear Differential Help
Thread Starter
Heel & Toe
Joined: Aug 2008
Posts: 15
Likes: 0
From: Woodbury MN
Rear Differential Help
I recently bought a 71 corvette (my first), but the rear diff seams to be leaking, I'm 90% sure its the gasket. So, I figured I'd pull the cover and replace the gasket, however my service manual doesn't really have specific instructions for doing this (or at least I couldn't find it). Looking under the car, looks like I need to remove the spring, but it looks like there are bolts connecting the suspension crossmember to the differential cover (bolt heads are on the top side of the crossmember). How do I deal with these bolts? Do I have to remove the crossmember too, if so how? If so, how do I reinstall the crossmember and diff. cover without messing up my gasket material? Any help you can give me is greatly appreciated! Thanks!
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
I would do it in this order.
Remove the rear spare tire assembly, remove the outer spring to trailing arm bolts, remove the four center spring bolts and the spring is free.
Then remove the front suspension snubber cushion bolt, nut and upper and lower cushions. Once you have this done, you can attempt to remove the two large cross member bolts. This is the end you described above. Doing it this way will drop the cross member and the rear end at the same time.
You can remove the top cover bolts without removing this cross member but it’s not easy. You have to drop a socket in the hole and then work a strong arm in to place and on the socket. There is enough room but it’s tight.
Should you attempt to remove the cross member, you will probably have fits getting it to release once the bolts are removed. They can be very difficult to pry loose.
When you re-assemble the car, be sure not to tighten the four spring center bolts until you have the car under load. Snug the bolts up and then drop the car down on the ground to tighten up. If you tighten them up before you drop the car down there is a good chance you’ll crack your cover.
Willcox Inc.
Remove the rear spare tire assembly, remove the outer spring to trailing arm bolts, remove the four center spring bolts and the spring is free.
Then remove the front suspension snubber cushion bolt, nut and upper and lower cushions. Once you have this done, you can attempt to remove the two large cross member bolts. This is the end you described above. Doing it this way will drop the cross member and the rear end at the same time.
You can remove the top cover bolts without removing this cross member but it’s not easy. You have to drop a socket in the hole and then work a strong arm in to place and on the socket. There is enough room but it’s tight.
Should you attempt to remove the cross member, you will probably have fits getting it to release once the bolts are removed. They can be very difficult to pry loose.
When you re-assemble the car, be sure not to tighten the four spring center bolts until you have the car under load. Snug the bolts up and then drop the car down on the ground to tighten up. If you tighten them up before you drop the car down there is a good chance you’ll crack your cover.
Willcox Inc.
Drifting
Joined: Jul 2002
Posts: 1,697
Likes: 3
From: Woodinville WA
I just did mine about a week ago and did it similar to what Willcox is saying, with a few exceptions. I loosened the pinion bolt without taking it all the way off and put my half shafts on to steady things. I loosened my crossmember bolts about 1/2" and then used a 2-jaw puller ($15.99 from Harbor Freight) to free each end. The bolts left in were there to catch the crossmember once it was free. Once the crossmember is free, you can put a jack under the differential to lower everything down after taking off the two crossmember bolts, half shafts and pinion bolt. The whole thing wieghs around 120lbs.
Advanced
Joined: Jan 2002
Posts: 77
Likes: 1
From: Stillman Valey Illinois
I recently bought a 71 corvette (my first), but the rear diff seams to be leaking, I'm 90% sure its the gasket. So, I figured I'd pull the cover and replace the gasket, however my service manual doesn't really have specific instructions for doing this (or at least I couldn't find it). Looking under the car, looks like I need to remove the spring, but it looks like there are bolts connecting the suspension crossmember to the differential cover (bolt heads are on the top side of the crossmember). How do I deal with these bolts? Do I have to remove the crossmember too, if so how? If so, how do I reinstall the crossmember and diff. cover without messing up my gasket material? Any help you can give me is greatly appreciated! Thanks!
Team Owner
Joined: Sep 2006
Posts: 31,164
Likes: 4,242
From: Westminster Maryland
Hi Red71,
You've gotten some good info and advice.
If you don't have the GM CHASSIS SERVICE MANUAL for your 71 I'd suggest you think about getting it. It'll be a help on projects like this and others that may come along.
How about a couple of pictures of your 71?
Regards,
Alan
You've gotten some good info and advice.
If you don't have the GM CHASSIS SERVICE MANUAL for your 71 I'd suggest you think about getting it. It'll be a help on projects like this and others that may come along.
How about a couple of pictures of your 71?
Regards,
Alan
Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
I just did mine about a week ago and did it similar to what Willcox is saying, with a few exceptions. I loosened the pinion bolt without taking it all the way off and put my half shafts on to steady things. I loosened my crossmember bolts about 1/2" and then used a 2-jaw puller ($15.99 from Harbor Freight) to free each end. The bolts left in were there to catch the crossmember once it was free. Once the crossmember is free, you can put a jack under the differential to lower everything down after taking off the two crossmember bolts, half shafts and pinion bolt. The whole thing wieghs around 120lbs.
1. Can you leave the half-shafts and drive shaft connected?
2. How did you manage fluid once you pulled the cover with the diff lowered?
I thought I would pull a couple of bolts and let it drain but that was too easy...didn't drain a drop. I've got a pump that I've used before but than there will still be some residual. I was hoping I could leave it on the jack but realized I would have a mess once cover was removed.
Next step is to remove the front support bolt which will than permit the differential to drop once the crossmember is loosened.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
You have to remove the drive shaft and half shafts.
I'm not much help on the fluid, I have a pump we use to remove the fluid before the rear is pulled down. If the rear is full, and you crack the bolts you'll have it all over the place.
You could just remove the plug and turn it on the side for a more controlled drain. (If you are un-bolting it from the crossmember).
Willcox
I'm not much help on the fluid, I have a pump we use to remove the fluid before the rear is pulled down. If the rear is full, and you crack the bolts you'll have it all over the place.
You could just remove the plug and turn it on the side for a more controlled drain. (If you are un-bolting it from the crossmember).
Willcox
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
Drifting
Joined: Jul 2002
Posts: 1,697
Likes: 3
From: Woodinville WA
Originally Posted by Willcox Corvette
You have to remove the drive shaft and half shafts.
Originally Posted by hunt4cleanair
1. Can you leave the half-shafts and drive shaft connected?
2. How did you manage fluid once you pulled the cover with the diff lowered?
I thought I would pull a couple of bolts and let it drain but that was too easy...didn't drain a drop. I've got a pump that I've used before but than there will still be some residual. I was hoping I could leave it on the jack but realized I would have a mess once cover was removed.
2. How did you manage fluid once you pulled the cover with the diff lowered?
I thought I would pull a couple of bolts and let it drain but that was too easy...didn't drain a drop. I've got a pump that I've used before but than there will still be some residual. I was hoping I could leave it on the jack but realized I would have a mess once cover was removed.
Safety Car
Joined: Sep 2007
Posts: 4,454
Likes: 328
From: Indy Indiana
absolutely, whle you are in there, replace your 3 seals, 1 front pinion seal , and both side yoke seals along with your gasket, give your rear crossmember a good bath and painting, and new u-joints.. check your side yoke play and replace if necessary.... dont' start playing with the gears and their clearances unless you have to but while you are all apart, spend a couple hundred and get it all refreshed and painted up.. it will really look good..
Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
If you are just doing this to replace the gasket, you can leave the diff supported by the jack with half shafts and drive shaft attached. Remove the 4 bolts that are connecting the crossmember to the diff cover and remove the crossmember. The jack should be supporting the diff below the strut rod bracket if you are changing the gasket and not removing the diff. As you loosen up the bolts holding the diff cover it will start to leak the fluid, so have a bowl positioned under to catch it as it drains.
No pinion leaks, 35k miles, an NCRS Bowtie car not sure I want to get into pinion seal replacement and U joints. Your thoughts?
Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
got it! I't's draining but found an interesting label on the top of the housing. This label has a printed code for the 3.08 L48 M38 gear...or OK. this reconciles with the code on the build sheet
Any suggested inspections of gear...no unusual wear or sediment.
OK broadcast code
Not a bad job at all...probably the dread was more overbearing than pulling everything done. But than air tools make it sweet.
BTW...what 75/90 do you use? I was looking for some Redline but no luck
Any suggested inspections of gear...no unusual wear or sediment.
OK broadcast code
Not a bad job at all...probably the dread was more overbearing than pulling everything done. But than air tools make it sweet.
BTW...what 75/90 do you use? I was looking for some Redline but no luck
Last edited by hunt4cleanair; Mar 8, 2009 at 04:47 PM. Reason: add
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Tom,
I would replace the outer shaft seals and if you want to be a little more brave the front pinion.
Check the condition of the half shafts, there is a page on our site that shows what they should look like. Pay extra attention to the passenger side since it wears quicker than the driver side.
As far as the lube, I only use the GM lube and additive. 2.5 lube and 1 additive. I only deviate from this if I have a car with the posi clutches sticking and then I will run two bottles of the GM additive.
Willcox Inc.
I would replace the outer shaft seals and if you want to be a little more brave the front pinion.
Check the condition of the half shafts, there is a page on our site that shows what they should look like. Pay extra attention to the passenger side since it wears quicker than the driver side.
As far as the lube, I only use the GM lube and additive. 2.5 lube and 1 additive. I only deviate from this if I have a car with the posi clutches sticking and then I will run two bottles of the GM additive.
Willcox Inc.
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Remove the half-shaft and put a dial indicator on the stub axle end (where the half shaft u-joint goes). Pull the stub axle in-out and measure how much it moves. Perfect is 0-0.015". Up to 0.040" is OK. Much more than 0.040" and you should start planning to refresh the diff.
BTW, 35K miles is no guarantee that the stub axles are still good. Later C3's had very poor hardening of the stub axle ends and they can wear out very quickly.
BTW, 35K miles is no guarantee that the stub axles are still good. Later C3's had very poor hardening of the stub axle ends and they can wear out very quickly.
Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
Tom,
I would replace the outer shaft seals and if you want to be a little more brave the front pinion.
Check the condition of the half shafts, there is a page on our site that shows what they should look like. Pay extra attention to the passenger side since it wears quicker than the driver side.
I would replace the outer shaft seals and if you want to be a little more brave the front pinion.
Check the condition of the half shafts, there is a page on our site that shows what they should look like. Pay extra attention to the passenger side since it wears quicker than the driver side.
Looked under rear suspension, all 219 parts but could not locate the half shaft reference page...can you direct me to it?
Pro
Joined: Jun 2008
Posts: 680
Likes: 3
From: charlotte N.C
here is what i did but i had the body off making it a lot less dificult.
http://corvetterestoration.webs.com/framedisasemble.htm
http://corvetterestoration.webs.com/framedisasemble.htm
Burning Brakes
Joined: Sep 2008
Posts: 805
Likes: 5
From: Naperville Illinois
Tom,
I would replace the outer shaft seals and if you want to be a little more brave the front pinion.
Check the condition of the half shafts, there is a page on our site that shows what they should look like. Pay extra attention to the passenger side since it wears quicker than the driver side.
...
Willcox Inc.
I would replace the outer shaft seals and if you want to be a little more brave the front pinion.
Check the condition of the half shafts, there is a page on our site that shows what they should look like. Pay extra attention to the passenger side since it wears quicker than the driver side.
...
Willcox Inc.
Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
For those still tuned in for this thread, I've completed gasket replacement, reinstalling crossmember and leafspring but two issues:
1. The new rubber for the spring mounts aren't sitting nicely in their respective link bolt cups...will this straighten out once its under weight? And if not, what's the fix?
2. I removed the front snub bracket (I think that's the name) but its the last install item. The front bolt hole is not aligning up. Once underweight will it shift or do I put a crow above it to ease it down into place?
1. The new rubber for the spring mounts aren't sitting nicely in their respective link bolt cups...will this straighten out once its under weight? And if not, what's the fix?
2. I removed the front snub bracket (I think that's the name) but its the last install item. The front bolt hole is not aligning up. Once underweight will it shift or do I put a crow above it to ease it down into place?
