Hello,

I have some 4 spd transmissions that need to be rebuilt. They've been sitting around for years and have a little surface rust on the input shafts. The rust is quickly and easily removed with a wire wheel but there is very light pitting left behind.

I don't have a good way of posting a picture, but can anyone give me an idea of how much pitting is too much? Or, said another way, is there even such a thing as an acceptable amount of pitting?

Also, which is better able to accommodate input shaft flaws: a pilot bushing or a pilot bearing (the MP bearing that seats in the crank register)?

I understand that this is a bit nebulous, so thanks in advance for any input.

I've run lots of pitted gears and such. I'm more concerned with high spots than low spots.

I always run a bushing and not a bearing.

Use a bushing and polish it with emery cloth. Liberty gear can replace the input stub if you are really worried, I would not.

Is this input shaft pitted inside or outside of the trans case?
If its outside the case, on the splines, as long as the clutch disc can slide on and off the shaft without hanging up, it will be OK. Inside the bearing retainer, the shaft only has to clear the bearing retainer. If your referring to the bearing retainer, the throw out bearing needs to slide smoothly across it and it will be OK.
If the pitting is inside the case, as long as it doesn't interfere with the gear operation it will be OK.
It would have to be pretty serious pits before I was concerned.

Bushings are a little more forgiving if everything istn't lined up exactly, but I've used both bearings and bushings. Gene

The area of pitting I was concerned about is at the end of the input shaft where the bushing rides.

I've already wire wheeled the surface rust and polished with wet/dry sandpaper. So long as the pilot bushing/bearing doesn't require a perfect polished surface, i think I'm in good shape.

Thanks for the input!

I'll probably get slammed for saying this, but the pits will probably help lubricate the mating surfaces by pocketing material. I have an old friend who is a racing engine builder. Owned a big shop that turned cranks for big machinery. Said the same thing about crank shaft bearing surfaces.

Agreed. You're thinking too much.

Find something worthwhile to worry about. The ONLY time the bearing or bushing has relative motion is when you're shifting and the synchros are speeding up or slowing down the disk, or when you have it in gear with the clutch pedal depressed. When it's not in gear with clutch pedal depressed it may or may not be spinning.

In other word all this angst about bearings or bushings is just wasted energy.

R.