Rear end clunk
Thread Starter
Cruising
Joined: May 2005
Posts: 10
Likes: 0
Rear end clunk
I have been reading about people changing out half shaft and redoing the diff. I am new to IRS and not sure where to start in removal. Where is a write up that I can read to get familiar with what I am about to do?
Racer
Joined: Apr 2007
Posts: 492
Likes: 3
From: Temecula CA
Look up forum member gtr1999's posts. He's a diffy guru! The rear end on Vettes is a can of worms. Lots of pitfalls, but there is alot of knowledge on this forum to get you through it! First, get an assembly manual for your year. This will be invaluable. The hardest part of the rear end drop for me was all the rust. Nuts, bolts, shims, washers will all be rusty and difficult to remove. Penetrating oil and/or heat is your friend! Plus a big-a** breaker bar!
I removed and replaced the trailing arms, rear end, spring, bushings, etc. by myself in my garage with just basic hand tools. I'm no mechanical genius, so I think anybody can do it with the proper motivation and advice. Try searching for posts on trailing arms, differential crossmember, camber rods, and rear springs to get you started. Good Luck!
Temvette72
I removed and replaced the trailing arms, rear end, spring, bushings, etc. by myself in my garage with just basic hand tools. I'm no mechanical genius, so I think anybody can do it with the proper motivation and advice. Try searching for posts on trailing arms, differential crossmember, camber rods, and rear springs to get you started. Good Luck!
Temvette72
Le Mans Master
Joined: Aug 2006
Posts: 7,411
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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Welcome to the forum!
Rear end clunk could just be a worn bushing in front of the differential, you might check that before you panic!
Your Vette is 75? Stick or auto and when do you hear the "Clunk"? PG.
Your Vette is 75? Stick or auto and when do you hear the "Clunk"? PG.
Thread Starter
Cruising
Joined: May 2005
Posts: 10
Likes: 0
75 Auto. Most of the time we can hear/feel it when going into reverse sitting in my driveway.
We lifted the rear of the car and when the car is put in REV the right rear tire really moves a lot. I am feeling that it is in the control arm bearings and a little in the halfshaft on that side. With engine off and car in park, no parking brake, it is almost impossible to rotate the wheels around. Lots of noise coming from the right side. I have been looking at Zip and they have a complete ready to go assembled control arm assly ready for install. I am thinking to replace with that and a half shaft at the same time. Question now is do I do both side at teh same time?
We lifted the rear of the car and when the car is put in REV the right rear tire really moves a lot. I am feeling that it is in the control arm bearings and a little in the halfshaft on that side. With engine off and car in park, no parking brake, it is almost impossible to rotate the wheels around. Lots of noise coming from the right side. I have been looking at Zip and they have a complete ready to go assembled control arm assly ready for install. I am thinking to replace with that and a half shaft at the same time. Question now is do I do both side at teh same time?
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
75 Auto. Most of the time we can hear/feel it when going into reverse sitting in my driveway. We lifted the rear of the car and when the car is put in REV the right rear tire really moves a lot.
.......With engine off and car in park, no parking brake, it is almost impossible to rotate the wheels around........
.......With engine off and car in park, no parking brake, it is almost impossible to rotate the wheels around........
The reason you cannot rotate the wheels manually is that your differential has a positraction unit. It's just doing it's job.
Best read up on how the suspension works and should be maintained before you tear into it or hurt yourself.
Thread Starter
Cruising
Joined: May 2005
Posts: 10
Likes: 0
I do know a little about cars and can appreciate your warnings. I did not think about the IRS being maxed out though, good pointer, thanks.
Even with a posi traction the opposite wheel should turn. Only with a spool or a locked rear end locker would it be impossible to turn. For reference we jacked up and put on stands my Grand National with a posi trac and the opposite rear spun backwards just like it should. Yes the GN does have posi that works correctly. I leave parallel signatures with it all the time
Even with a posi traction the opposite wheel should turn. Only with a spool or a locked rear end locker would it be impossible to turn. For reference we jacked up and put on stands my Grand National with a posi trac and the opposite rear spun backwards just like it should. Yes the GN does have posi that works correctly. I leave parallel signatures with it all the time
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
A properly working posi unit should have the opposite wheel turning in the same direction and the input drive shaft turn if the transmission is in neuatral. If the transmission is in gear (park) then either wheel will be difficult to turn meaning that the posi clutches are grabbing as per design. Normal breakaway torque is 50-75 ft/lbs I think, possibly more on older cars. Gary would know.
Drifting
Joined: Jul 2002
Posts: 1,697
Likes: 3
From: Woodinville WA
I believe that this is the sign of an open diff or heavily worn posi unit.
A properly working posi unit should have the opposite wheel turning in the same direction and the input drive shaft turn if the transmission is in neuatral. If the transmission is in gear (park) then either wheel will be difficult to turn meaning that the posi clutches are grabbing as per design. Normal breakaway torque is 50-75 ft/lbs I think, possibly more on older cars. Gary would know.
A properly working posi unit should have the opposite wheel turning in the same direction and the input drive shaft turn if the transmission is in neuatral. If the transmission is in gear (park) then either wheel will be difficult to turn meaning that the posi clutches are grabbing as per design. Normal breakaway torque is 50-75 ft/lbs I think, possibly more on older cars. Gary would know.
I haven't heard of a posi that doesn't turn both wheels in the same direction when rotated freely Sounds like an open rear.
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