When I rebuilt my rear-end I must have over tightened the front mount bolt, because the bushing has recently split. Anyone know the torque specs for that not? Also, would a poly bushing hold up better than rubber in this circumstance? Thanks

 

Front differential bushing is 55-75 ft/lbs Use rubber.
Gary

 

 

It seems as though i didnt have the bolt that tight (75 ft/lbs), could anything else cause the split besides a defective bushing?

 

Usually they are pretty good for a long time. If oil gets to them then they'll go bad over time. The bolt is mounted so the head is up in the top and the nut is exposed. You replaced both bushing halves correct?
Gary

 

There is suppose to be a metal insert in the center if the bushing. When you tighten this down the insert keep the bushing from being crushed. It should not matter even if you overtightened it. I suppose you could break the bolt.

The torque is suppose to be 65 ft-lbs. I used a poly and I had to go to almost 65 before it pulled tight.

I had the infamaous rear end clunk. The replacement fixed most of it.

 

I really don’t understand how it split I replaced both halves and it did have the metal sleeve. I have only put maybe 150 miles on the car since it was replaced. I do however have a slight differential leak from the front yoke seal but I wouldn’t think it wouldn’t eat a bushing up like that. I can change it just by removing the drive shaft right?

 

I think you're asking about changing the front pinion seal? If so take a good look at the procedure first. the 80-82 have an aluminum housing with an intergrated forn bracket. This is different then the 63-79 iron housings with a removalble front bracket. It may be tricky to get to it. The driveshaft will have to be removed. The thing you have to do is mark the position of the pinion nut to the pinion shaft end. It is very important to maintain this relationship to keep the bearing preload as close to original as possible. I haven't replaced a seal on the car on a 80-82 so I don't know just how tight it is. I was under an 82 last week that had both pinion and yoke seal leaks. It looked very close and that was with the car on a lift. The oil should not have caused the damage you spoke of over 150 miles. Is it possibel that there is a burr near the bushing?
Gary

 

I replaced mine (Diff brace/bracket bushings) a few months ago with a poly bushing. It totally stopped the "bump" I was feeling, but my orig rubber bushing was totally shot. I can understand the difference between rubber and poly suspention bushings, but I see no reason not to go polyurethane with this bushing.

I was able to replace mine without taking the driveshaft, or anything else out. It was a little tricky getting the new bushings/bolt correctly in place, but not hard if you take your time.

 

I have ordered a new bushing and have removed the old one which was completely trashed. I have the build manual but its not to clear on which bushing goes on top and then in between the frame. can someone give me the right order? thanks

 

Just did this three days ago.
Thinner bushing with the metal sleeve insert at the top (over the crosmember) with the sleeve protruding through the crossmember bracket hole. Thick bushing goes between the crossmember and the diff. bracket with the molded metal washer down (touching the diff. bracket). Large flat washer goes on the underside of the diff. bracket to support the smaller lock washer.

 

An acquaintance with a lot of Corvette drag racing experience advised not to use the poly bushings. I didn't follow too closely as to his reasons why because I now have a poly bushing so I just made a mental note that I may have trouble with poly. I know the orthdox bushing to use is the rubber one.

My question: What about the solid aluminum bushing? Does anyone have experience with this bushing? If the only disadvantage is that it adds differential noise to the frame, that's not going to be a concern to me because my engine exhaust sound will mask out everything else.

If I have to replace my poly bushing, I'd prefer not to do it more than once. With the differential support bracket, the differential, and the drive shaft/yoke all in place it's pretty hard get wrench and socket on both ends of the attaching bolt.

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Another interesting bit advice from the same person. He said he never had a fiberglass monospring that he didn't break. He advised me to use my steel spring. Anyhow I really am glad to get rid of the 40 plus pounds in that steel spring. I don't plan to drag race my 68 or abuse it on acceleration so I'll stick to the monospring. It's so light - you can easily hold it with one finger.

 

I don't know of anyone who makes an aluminum bushing. Did "this guy" tell you why not to run poly?
As for the fiberglass rear springs, don't worry about breaking it. I know lots of guys that use them and they drag race a lot. Maybe he's using to soft of a spring and it's flexing to much. I don't know. I do know that serveral people locally have the fiberglass spring and they don't break. The most HP that one guy has is 700HP and he's now putting nitrous in the car to bump it up to 1000HP

 

An aluminum "bushing" to replace the rubber/poly bushings can be had by ordering Tom's Differential Part #10V-LK. It costs $70. It includes the aluminum disks to bolt over the underneath of the crossmember bushings and then it includes an aluminum "front tongue bushing eliminator." This kit is intended to, quote "eliminate that horrible bang noise that occurs on initial launch and between shifts." I think I've seen this kit in other catalogs. My acquaintance I referred to in my original post did not say to not to use poly bushings, he said they hadn't worked for him. He told me why, but unfortunately I didn't really pay too much attention because I wasn't going to replace the poly's I had just installed. I believe he told me he had trouble keeping them torqued in tight. Anyhow, I just made a mental note to check the tightness of the bushing mounting bolt when I finally start driving my car. He said that as of to date he has broke every part in a Corvette IRS at the drag strip, including several mono springs. He said that his mono springs tended to fail at the spring to trailing arm bolt hole.....anyhow just repeating what I thought I heard someone say. As I said before, I really like my mono spring.

I still have the question: is using an aluminum "bushing" a reasonable substitute for the rubber/poly bushing? If it's noisy that's not a problem since I assume l'll never hear it. I wouldn't be surprised though if for normal driving, the pinion shaft/differrential housing needs a little dampening from a rubber/poly bushing.

 

I never had a problem with the diff clunking when i shifted until the bushing completely failed. I would think that an alum. bushing would not give and cause the possibility of the diff. cracking or completely breaking