66ragtop owner

How much play is normal in the input shaft on my M-21? Can I remove the input shaft without completely disassembling the trans. Can I remove it by taking the front bearing cover and bearing out? Then I could check the bearing inside the input shaft.
Thanks for any help
Brian

TheOman

The front cover is just that a cover. You can't just remove it and then remove the input shaft. You remove the pilot shaft by sliding it to the rear of the case and then taking it out via the inside of the case. Obviously to do that ya gotta remove the main shaft from the case. These transmissions are really easy to work on but if you don't have much experience likely best to let a pro fo it. If I recall right the gears on the pilot shaft wont pass thru the hole in the case which houses the input bearing. Over the years I have worked on T-10's Muncies and Richmond 5 Speeds and I cannot remember ever pulling the input shaft of a Muncie out from the fornt of the case unless there was a catastrophic failure.


[Modified by TheOman, 9:11 AM 2/20/2003]

TheOman

Dupe....


[Modified by TheOman, 9:13 AM 2/20/2003]

66ragtop owner

Thanks for the input. I think I could handle the dissassembly if it is needed, but how can I tell if the input shaft has too much play? I'm going to pull the front cover off and check to see that the bearing retainer nut is tight. other than that do I have to dissassemble the trans to tell if the input bearings are bad.
Thanks
Brian

TheOman

I don't know if there is some kind of specification someplace describing movement of the input shaft tip. If there is I never saw it. Ya gotta get a good idea of the condition of the ball bearings and the races that is where your answer as to wear will be found. The following is really a crude answer. I hate to post it here but I sure have seen worse "I heard" and " A buddy says" kinda answers to other questions so here goes.

If that input shaft can be manipulated to the point where it hits the throwout bearing cover your front bearing is dead. That would be extreme and I doubt even a bad bearing would be that bad before a real failure would happen. There should (even with a new bearing) be some amount of movement of the tip of the input shaft. I have seen transmissions with good, even brand new, bearings that had a fair amount of play discernable at the tip of the input shaft. Loaded the used ones from that little sample study into the car and they were OK.

Remember though if (hypothetically) you entended the tip if the input two feet the tip would move further with a given bearing just due to the geometry of the longer shaft. The bearing would be no more warn but the movement of the tip would be exaggerated. That is why I wonder if there is any measuremant criteria based on movement of the tip.

My 66 Muncie had lots of slop visible at the input shaft tip and honestly I just set it on the floor under the bench and forgot about it. It did not hit the bearing collar but it was really warn...read on. My pilot bushing was also shot which can't have helped the front bearing eather. Take off the front cover. See if the shaft turns smoothly and concentrically. Mine was so warn that I could move the input shaft and the inner race up and down (as in perpendicular to the mainshaft centerline). That was when I said if the rest of this thing is as worn as this bearing is I aint pouring money into this gearbox. When rotating my input shaft there were noticable areas of higher "drag" at certain points in the 360 degree rotation. Likely that was when the most worn points on the bearing ***** were on the most worn parts of the races.

Also look at the bore in the front of the case. If that is scared up well then you are into even deeper trouble but I honestly doubt it. I really think that to diagnose this correctly ya gotta disassemble the box. At least ya gotta take out the mainshaft. Might be OK to leave the counter shaft in but even then if the rollers on the counter shaft are shot you might get a false indication that the input bearing is warn due to incorrect (non concentric) rotation of the counter shaft.

Go over to the transmission section of the Chevelle Forum at http://www.chevelles.com. The moderator is a guy named Wally. He has a cottage industry building Muncies and selling parts. Might be he can help. You can join that Forum for free. Like this forum you can get a fair amount of good info. just for the asking. There are some "Speed Racers" types over there and sometimes their lack of experience is very clear. Like any Forum you gotta know who to trust and who to avoid as far as takin advice. Wally has been around a lot of years and has a lot of experience from the school of hard knocks. He knows his stuff on the transmissions. I would follow his advice.


[Modified by TheOman, 10:14 AM 2/23/2003]

Denney

You know, Oman, I agree with what you say and only wanted to add that the Munice trans is one tough cookie (all things considered). I had an M-20 in my coupe that had a siezed bearing and it STILL worked (can't imagine how long it would ultimately have lasted since the shaft was pretty galled) but it was a real mess inside and still performed. Go figure... :smash: :thumbs:

66ragtop owner

Thanks Oman,
I pulled the front bearing cover off and the beaing looks ok. It feels fine when turning. I also had the side cover off and looked at the front inside of the trans case and didn't see any wear. I'm going to replace the gaskets, put it in the car and take my chances.
It' been about 20 years since I played with Muncie's and I just didn't remember how much play they had.
Thansk again for the help.

chewy

How many miles on the front bearing? They aren't expensive and it sure is easier to change it now.

66ragtop owner

5,000 miles since a rebuild, according to the guy I bought it from. I had the front bearing and side covers off and it looks in good condition. The condition of the trans supports his story of a recent rebuild. I guess I'll take my chances, besides the way the weather is here in Pa. I'll have plenty of time to do it over before driving weather gets here.
Thanks
Brian