1989 C4 Functional Restoration

[SirReal63]

I should explain the need for UHMWP, the shifter on the ZF S6-40 transmission uses ultra high molecular weight plastic as bushings for the pins on the shifter. They are sort of a wear item but tend to last many decades. Unfortunately on mine they were completely missing. When I opened up the shifter this is what I saw...



I "fixed" it initially with some 3/4 UHMWP round stock that I had. I had to drill it off center to get the height as close as I could, I undersized the hole and drove them on. It was a temporary fix that I hoped would last, it has lasted but needs to be done correctly.



This is what the original shape was like, though this one is incorrect, it came from a Ford F350 ZF 5 speed. The outer dimensions are correct but the pin is smaller on the Ford.


The original part is no longer made and next to impossible to find and if you find them, they are over 3 decades old. This is a part I can make, the plastic is cheap and machines easily.

 

[tom3]

Looking at your rpo sticker I see the 8.5 ring gear and 3.33 ratio, but no positraction code. That car have an open differential? Lots of good work in the car!

 

[SirReal63]

Looking at your rpo sticker I see the 8.5 ring gear and 3.33 ratio, but no positraction code. That car have an open differential? Lots of good work in the car!

Thanks, it has been a labor of madness.

I believe all of the C4's had limited slip, both the Dana 36 (auto) and the Dana 44 (manual) as standard equipment, I don't know what flavor of LSD GM used in them but could probably find out. Both tires do spin the same direction when lifted, I just checked since it is on jack stands while I clean power steering fluid off the front of the engine. I hope it continues to function correctly, I dread the day I have take that down and open it up. This car is about as base model as it gets, the only unusual option was the TPMS.