Chev 4 speed rebuild

[Perry Kitson]

Does anyone have any information on allowable tolerances on shafts and bearings in the Chev 4 speed from a C15A?
Things seem rather loose to me, but I am used to working to four decimal places.

thanks, Perry

[rob love]

Originally Posted by Perry Kitson

Things seem rather loose to me, but I am used to working to four decimal places.

4 decimals...on a chev??

[Phil Waterman]

Hi Perry

Can you be more specific about which bearings. I've been playing with these for forty years, and they are very tolerate of play that would kill a modern transmission. But they are also vocal about the amount of accumulated play inside.

The main and secondary ball bearing are the most critical also the easiest to get and replace. The needle bearings seem to most likely to get unnervingly noisy as they will rumble, chatter and vibrate as the clearances get to large.

I've posted some photos and information I've experienced driving and working on these transmissions over the years:

https://www.canadianmilitarypattern....ansmission.htm

https://www.canadianmilitarypattern....nchevrolet.pdf Manual Section

http://www.canadianmilitarypattern.c...ansmission.htm

Unfortunately some of the sources for parts I've mentioned and used over the years are no longer in business. I got lucky the last time I had a transmission problem, broken tooth, and found a complete NOS transmission, also found the repacement gear need. Cleaned and installed the NOS transmission which still after several thousand miles shift much stiffer than the other 3 transmissions. Rebuilt the other transmission filled with gear lube and sealed it up and put it on the shelf as a spare. Hope it will guarantee I'll never have transmission problem with any of the trucks.

Take pictures as you disassemble and share the photos of what you find.

All three of my CMPs share the same transmission, each of them sounds different, shifts differently and has different vibration pattern as felt through the gear shift.

Cheers Phil

[Mike K]

Originally Posted by rob love

4 decimals...on a chev??

Yes more like 2 decimal places .

[Perry Kitson]

Rob/Mike,
Surely you can't be poking fun at the pinnacle of automotive engineering? I have always understood that all that was needed during a Ford rebuild was a tape measure and a rather large hammer.
Phil,
I currently just have the rear cover off exposing the rear countershaft and output shaft bearings. The countershaft roller bearing has .003" play between the shaft and bearing. I am replacing the rear output shaft bearing as it is easy to do now. I am on a bit of a tight schedule as I want the truck ready for June 2 D-Day parade here in London, and may pull the transmission apart this fall instead of now.

[Perry Kitson]

Phil,
Did you measure clearance between bearing 4.422 and the shaft on disassembly? If they were replaced, did you get tighter fits?
It is the roller bearings wear on the shafts I am thinking of.

Perry

[Phil Waterman]

Hi Perry

Did I measure the play as with dial indicator? No, did I feel for play yes and there was not movement that you could feel, in that lower cluster (where the two 4.422 bearings are use) . But what I can remember spending more time feeling for roughness while turning.

When I got the NOS transmission all of the preservative inside had dried out so the whole transmission had to be cleaned in particular the bearings, lots of hot water and degreaser. But at one point I had the new transmission and the original transmission apart on the bench so I got a real chance to feel for difference in play. (Yes I was very careful not to mix any parts.)

Where I did find play was around 4.352 needle/cage bearing, earlier with C60S, that bearing and shaft had to be replaced (see http://www.canadianmilitarypattern.c...ansmission.htm ) because it started to chatter. The top couple of photos show how I pull the transmission, with a bar for and aft in the cab and lower it out the bottom, I've found this easier than trying to support/lift it from the bottom.

I will go back through my notes and photos to see if I have anything that might be of more help.

Cheers Phil