Rear Transmission Bushing Replacement - 2 ?'s

[Bob Chadwick]

I just finished taking out the drive shaft and painting it and pulling the front differential bushing and POR15ing the area. The drive shaft goes in tomorrow for new u-joints and balancing. The differential mount area gets another top coat over the POR15 and a poly bushing.

I'm going to replace the rear trans bushing while I have it this far apart and have two questions. Should I go with poly on the bushing, $10 v. $30, and how do I support the rear of the trans as I remove the small section of frame that appears to be held in place by about 6 bolts that the trans bolts to? The only available area that you could get a jack with a board on it appears to be the pan and that can't be good. Or is static support not needed?

Bob

 

[JohnZ]

Compare the poly front diff mount bushings with the originals - most of the poly mounts I've seen aren't thick enough and don't have the internal spacer sleeve either, which raises the nose of the diff and puts the rear U-joint pretty close to the floor pan (also changes the operating angle of the rear U-joint, not a good thing).

 

[Bob Chadwick]

Thanks John. I'll went and took a look.

The Vette Brake Products bushing came with the internal spacer...

 

[Bob Chadwick]

but is half as thick.

Because this kit does have the spacer, it would appear to actually drop the differential down by about 1/2 inch. The bracket the diff attaches to is below the differential with the thinner bushing going between the bracker and diff.

John, do you have the same opinion?

Also, do you agree C5D's recommendation to support the rear of the trans with blocking spanning the oil pan? Seems to make sense in that the motor mounts would still bear the brunt of the weight and the block on the pans would simply stop it from dropping. I appreciate C5D's input but whenever I do something I have never done before I appreciate as much help as I can get.

Bob

 

[Vettehead Mikey]

Here's a guy having exactly the same problem as you:

http://forums.corvetteforum.com/zerothread?id=660826

 

[Bob Chadwick]

Mikey,

That is me. :s

I discussed with VBP this morning. They claim that by the time that you finish applying 50 pounds of torque to the bushing that the rubber would compress where the poly won't and the difference is negligible.

Bob

 

[JohnZ]

The extension on the spacer just aligns the upper and lower cushions so the bolt will go through. The poly cushion in your second photo looks just like the ones I've seen before - it's half the thickness of the original, which raises the nose of the diff (it goes between the diff nose bracket and the frame bracket). In each compaint case where I've advised owners to replace the poly kit with the correct OEM parts, it has solved the problem; I don't know why they keep selling this stuff when it would be so simple to make the lower cushion the right thickness.

Supporting the trans under the pan with a square of plywood or a piece of 1x8 at least the width of the pan should work fine.

 

[Bob Chadwick]

John,

Your right on this. I forgot the diff bracket is on the bottom and is being pulled up.

Thanks for the advise.

Bob

 

[Vettehead Mikey]

I discussed with VBP this morning. They claim that by the time that you finish applying 50 pounds of torque to the bushing that the rubber would compress where the poly won't and the difference is negligible.

Bob

So now you can join the club of people that will learn to hate poly bushings. Just think, now you've introduced a NEW way of transmitting vibration to the frame! The very thing the rubber bushing was designed to eliminate..............