Trans rebuild

[RTHarvey]

I have a 67 c10 that is making some noise, like a loudish whine. Sounds to me like a differential, but my main mechanic thinks the noise is coming from the transmission. It is an SM420 GM/Muncie 4 speed, compound low. Option code M20. If it is the transmission, I think it is gears rather than bearings. I have been doing a little research, and the gears for this transmission are not plentiful, at least at anywhere that I can find. I don't know what I need yet, but I would like to have a few sources for gears for this transmission lined up before it is scattered on the floor. Most of the normal wear-and-tear parts seem to be available from multiple sources. Anyone have any ideas for a source for the gears for this trans?

[Ironhorse]

Google " A and Reds" Transmission. They are located on west 29th street south in Wichita. They have been THE place to go for hard and soft transmission parts in the Wichita area since the early 70's. Bought from them to rebuild my BIL's car Muncie 4 speed when he trashed it, parts for the rebuild on my Chevelle when had a 700R4 installed. Most all the mechs I know use them. Hope that helps, good luck with the rebuild.

[Shaky]

I don't have any personal experience with these guys. They are primarily a Jeep adapter place, but they've been around for a while and have a lot of info/parts:

http://www.novak-adapt.com/knowledge...s/manual/sm420

They note in their rebuild parts list which parts are difficult or impossible to find. I imagine the gears are on that list...

[demian5]

Id change the fluid and see:
1. If metal comes out.
2. If it helps with new fluid.

[zosoppp]

Does the whine change/go away in top gear?

My Saginaw three speed whines in second but gets much quieter in third.

[cleszkie]

Does the noise change with clutch pedal in or out? If so, could just be a throw out bearing going out.

[Wrenchbender Ret]

A trans noise (like Zoso says) usually is much quitter in the high gear. I rear end noise will change will change with throttle position. Usually louder on acceleration but often on deceleration. Sometimes it will be a high pitched wine at real light throttle. Grinding noises may be wheel brgs. or drive shaft carrier brg.
George

[s10mk]

Originally Posted by RTHarvey

I have a 67 c10 that is making some noise, like a loudish whine. Sounds to me like a differential, but my main mechanic thinks the noise is coming from the transmission. It is an SM420 GM/Muncie 4 speed, compound low. Option code M20. If it is the transmission, I think it is gears rather than bearings. I have been doing a little research, and the gears for this transmission are not plentiful, at least at anywhere that I can find. I don't know what I need yet, but I would like to have a few sources for gears for this transmission lined up before it is scattered on the floor. Most of the normal wear-and-tear parts seem to be available from multiple sources. Anyone have any ideas for a source for the gears for this trans?

Hey bud, my 2 cents
Just keep in mind that the sm420 is a very good transmission. they are known to make a lot of noise, almost like the sound of marbles bouncing around in a glass jar....my point being, as long as it has good fluid, (did you check it?) I would not worry about a noise from that trans. How long ago did it start making the noise? There is a lot of trouble shooting you can do. Does it make the noise with the clutch in or out? Clutch engaged trans in neutral?

[RTHarvey]

Thanks for the ideas and tips. I did contact A and reds, and they thought they would probably be able to help. Novak is a good site too--lots of info. The noise is worse with speed, and seems to be just as bad in fourth as any other gear. Actually it is worse, because it gets worse with speed, and to get to 60 mph, you pretty much have to be in 4th. The noise changes with acceleration, or deceleration, and almost goes away on a no-load coast. ? We did take the differential apart, and it is a disaster. I did a separate post on that, with a few pics of the ring and pinion. Virtually everything is awful--gears, bearings, spider gears, even the axles. Lots of rust and mud inside too. Looks like it has had water in it at some point. All we are going to reuse is the housing and carrier. (ouch!) When I got the truck, I pulled the fill plug on trans and diff. Both were up to level with what looked like as-new gear oil. My hope is that the noise is all from the rear end, and I won't have to fool with the trans. I had a good SM420 in a 64 PU, so I know they are not completely quiet even when good.

[RTHarvey]

Good news--turned out to be the rear axle after all. Rebuilt that and it sounds like the trans will be fine. The rear end was a real mess. The only parts I could re-use were the axle housing and the carrier. Everything else new.