jimkari

I switched my '73 L48 from an auto to 4 speed. I've been having some shifting issues. when we pulled the trans for him to inspect, trans guy said I should use a step pilot bushing in my crank versus the standard bushing. He said my input shaft is only being supported about halfway down the shaft where it rides on the bushing. He also said I pounded in the pilot bushing too far. I simply bottomed it out on the crank. I did find a pilot bushing on Summit Racing's site that appears to extend out into the larger bore found on the automatic cranks. Should I be using one of these stepped bushing?

https://www.summitracing.com/parts/m...FdgPgQod22YE2w

Thanks,

Jim

jnb5101

What kind of shifting issues? I never knew an auto crank to be different than a manual-especially since autos don't need a pilot bushing.

gkull

Just a question. Did you center the bell housing using a dial indicator and off set down pins

lvmyvt76

maybe you put the bushings into the crank too far?

jimkari

The shifting issue is going into 3rd. Sometimes when I shift and then let the clutch out the trans is in neutral instead of 3rd. I think there may be an issue with the trans, but I am trying to cover every base before I put it all back together.

I did not dial indicate the bell housing because I heard the GM bell housing were pretty accurate, but I do plan to check that as well.

The bushing is flush with the crank bore. Not sure if I installed it too deep. I think I pounded it in until it bottomed out. Should I have left a gap and had the bushing sticking out a bit?

When we pulled the trans there was a wear mark about midway down the input shaft where the shaft rides on the bushing. I trans guy said the mark should be much closer to to the transition where the input shaft increases in diameter.

Jim

LT-1 kid

no differance in cranks, PB are installed flush to the crank end, like gkull said
you might have aliglment issues.

jimkari

Thanks guys, I'll check the alignment.

Jim

jnb5101

It sounds like the shift linkage is out of adjustment, or the transmission's shift forks are worn.
In any case, I think you're getting questionable advice from your trans guy. The nose on the input shaft should not bottom out in the bushing, and there is a certain amount of run-out engineered into the input shaft assembly.

0Willcox Corvette

The pilot bushing is hard to screw up.. I don't think that is your issue. The nose shouldn't bottom out either.

This system is way to simple to be having the issues you are having and I too would suspect it's a linkage or Trans issue vs the pilot bushing.

I'd put the lock adjustment tool in the shifter at neutral.. then re-adjust the linkage looking for something that is loose or not properly adjusted. If you don't find something that way then I'd look at the tranny.

A quick story for us.. We yanked a driving (blown) engine from a 65 last month, replaced the engine with another one, bolted the pressure plate and clutch up to the car, installed the engine.... And when we went finally got the car fired back up the clutch had a horrible noise and wouldn't shift worth a hoot. We pull the tranny back out of the car only to discover that the pressure plate was defective... One of the fingers was not compressing when the plate was bolted down.

So things can go wrong but the I'd highly doubt the issues you are looking at are the cause.

IMHO,

Willcox

jimkari

Thanks guys, I really appreciate the advice. Now that I have the pressure plate off the car, I do plan to test it by bolting it back on to the flywheel while off the car and use my press to compress the pressure plate .500" and confirm the disk is releasing. I also plan to see if I can determine the amount of force needed to release the pressure plate. My fork and pivot ball look like they are both in good shape. Based on my pedal movement and the geometry of the fork, I think I am getting about .57" of travel at the clutch which should be plenty to release the disk.

Jim