trans input shaft wobble

cuzncletus

cuzncletus

Senior Member
I'm changing the clutch on my 59a/39 trans just because while I have it apart I want to go back up with new parts. The combo ran and shifted fine. However, when reassembling it I discovered that it had been running without a pilot bearing.

When pushing sideways on the end of the input shaft the shaft "wiggles" back and forth. I also have a 37 and a 49 truck trans in the shop that both have the same wobble but not as much. From this I'm guessing that some run out is normal as I know the truck trans ran fine, also. My question is how much of this slop, if any, is acceptable?
 
Everyone of the manual transmissions I've ever removed or repaired had some side play in the input shaft. If the bearing doesn't feel rough when spinning it by hand it should be OK. How does the end of the input shaft look where the bearing or bushing rides? I had to replace a input shaft once because the pilot bearing locked up and damaged the shaft, this however was found after damaging other parts from hot rodding. If the outer race of the bearing is still in the crankshaft pack the crank end with grease and use a dowel or rod that fits snug in the race and hit the dowel with a hammer to use hydraulic pressure to remove it, I did this once and it worked.
 
There is no spec. published but running without a pilot may have caused the front bearing 7025, the bearing at the rear of the input shaft 7118, excessive wear. Even the transmission case could crack around the front bearing. The transmission should be inspected. and the front end disassembled for inspection. It's always a good idea to a visual inspection and check the end plays of the intermediate gear and other spec.before installing a used transmission. It will save you a LOT of time! A good inspection of the pressure plate and clutch before reassembly is also a good idea.
 
I have disassembled this trans and found it was in excellent condition, possibly even rebuilt and then had very few miles put on it. I've replaced some bearings, clutch shaft, and a reverse idler gear on the other two but the 39 seemed fine.

I may have to do some work on the end of the input shaft or the pilot bushing. The bushing does not turn freely on the input shaft.
 
If the pilot shaft bushing in the flywheel is the old bronze type, it should be replaced with the ball bearing type. Most input shafts have some side play. The shaft is held in place by the pilot. It compensates for any slight mismatch between the engine and transmission.
 
Something that often gets overlooked is the rear end of the "input " shaft (main drive gear) where the roller bearing O D rides . (inside the end of the shaft). I have seen a number of main drive gears that look great, good teeth, good splines, good syncho teeth, good pilot surface only to find the inside of the rear to feel like a washboard. Check them out before using them. Bad ones are out there, they look good on the swap meet table.
Just my opinion
 
ALSO, pay attention to the fit of the circlips on the front and rear bearings in there retainers.
Most of the trans I have worked on they are loose,that is,the circlip is not clamped up tight.
Tales a bit of machining on the retainers to get them tight.
Lawrie
 
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