Bobchad

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.

I had planned on replacing the bushing with a poly bushing but was warned for two reasons. Most of the poly bushings supposedly aren't thick enough and they don't have the internal spacer sleeve. This supposed to change the geometry of the rear U-joint.

The Vette Brake Products bushing came with the internal spacer but is half as thick.

Does anyone have any thoughts on this? I was told that this would raise the angle of the nose of the differential (I think this was primarily related to the spacer) but in fact appears to drop the nose because the smaller spacer would appear to actually drop the front of 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.

Bob




[Modified by Bobchad, 8:11 PM 9/28/2003]

1979toy

How odd. I used an Energy Suspension bushing that came in the total car kit. It looked to be the same thickness as the stock rubber bushing.

In John Greenwood's articles on how to improve the handling of the C2 and C3 he mentions removing the rubber bushings that mount the crossmember to the frame. I wonder if your bushing was designed for that type of modificantion.

ManFromEagle

I just replaced mine also and the poly lower bushing was thinner than the old rubber one.
When installed the thickness was about the same. The rubber one just plain compresses more. The Poly is stiffer. There is a metal spacer that needs to be installed in the top smaller dia spacer. It actually sticks down through the bracket on the front of the differential and will go through the center of the larger bushing. When you torque the bolt holding it all togeather this spacer will be pulled down until it contacts the frame crossmember.

Let me know if you have any questions. :thumbs:

Bobchad

Thanks. What did you torque your bushing down to?

jerryp58

I had mine replaced with poly when I had the differential rebuilt.

I can't say that I noticed any difference between it & rubber, but I'm glad the poly is there.

FWIW, the '77 AIM calls for 55-75 ft-lbs on the bushing nut.

Bobchad

Thanks Jerry.

Were in general in the AIM is the torque specs. I've been looking through mine as well as other manuals I have and either can't find any or the ones that I am looking for.

Bob

Scooter70

Usually there's a little triangle with a number in it pointing to the bolt in the AIM diagram. If you look in the bottom corner of the page, there should be a chart with the triangle numbers and the recommended torque range.

Bobchad

So that is what those numbers mean. Thanks.

I discussed the issue of bushing size with VBP this morning. As the Man from Eagle pointed out 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


[Modified by Bobchad, 10:39 AM 9/29/2003]

Van Steel

I' ve sold and installed many of the poly pinion bushings. You won't have a problem at all with it. It's a good piece.

Bobchad

Thanks. Since buying it from VBP I found out about you guys. Next time.

Bob