Muncie Transmission Countershaft to Case leak

[Tom D.]

Re: Muncie Transmission Countershaft to Case leak

The casting number for all the '65 Corvette Muncies I've seen ends with 325. (3851325) Was this main case used in any 1966 Corvettes, or other Chevrolets with factory installed four speeds? Thanks.

[Richard M.]

Re: Muncie Transmission Countershaft to Case leak

The casting number for all the '65 Corvette Muncies I've seen ends with 325. (3851325) Was this main case used in any 1966 Corvettes, or other Chevrolets with factory installed four speeds? Thanks.

Okay I misunderstood. I thought you meant quantity 325. I missed that.

Thanks

[Patrick B.]

Re: Muncie Transmission Countershaft to Case leak

Patrick, Thanks for that information. So the "01" is January, and the "20" is the 20th day?

How did you deduce that it was 1966? Was it the "G" prefix in the number on the other side?

Is the "01056" the vin derivative for the Chevelle?

I have a hard time understanding the Spec Guide for Transmissions.



I don't really follow what you're saying Tom. Can you expand?


===============
Thanks all for your ideas. On rebuild or whatever is decided, I like the O-Ring idea.

I used the Loctite and this morning I applied the RTV. I'll test it for leaks later.

Thanks,
Rich

The pre-67 Muncie dating system was simply the month expressed in numbers rather than letters and the day of the month. Since your case was an 010, used only in 66 and 67, it had to be a 66. The G101056 is the VIN dirivative of a car built in the Framington plant where Chevelles were assembled.

[Richard M.]

Re: Muncie Transmission Countershaft to Case leak

Thanks Patrick.

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Update. Leak is fixed. I used the Locktite, waited overnight, then the RTV, waited overnight. I then tilted it forward as a test for another night, and all day today.

Not a drip anywhere.
PC220039.jpgPC220040.jpg

Tomorrow I'll add more RTV to fill the cavity, wax paper over the area and remount to the engine. We will decide later what to do longer term.

Thanks to all for the ideas,

Rich

[Edward J.]

Re: Muncie Transmission Countershaft to Case leak

Rich. Don't be afraid to add some more RTV, when the transmission bolts up to the bell housing you'll note it compresses between the two. I my self just finished pulling a 64 Muncie and this is what I did and It works, I generally use a RTV on the counter shaft when rebuilding a transmission they always tend to leak.

[Frank D.]

Re: Muncie Transmission Countershaft to Case leak

I cut a very thin piece of rubber (can't remember what is was from) and slathered RTV on both sides of it.
I put this RTV sandwich over the countershaft hole and bolted the tranny back up. That was 18 months ago.
No more leaks.

[Tom P.]

Re: Muncie Transmission Countershaft to Case leak

I totally, completely, 100% agree that multiple things can be done to stop the leak (example: as Frank mentioned above). BUT THAT DOES NOT FIX THE CAUSE OF THE LEAK----------------WHICH IS NOT GOOD!!!!!!!!!!!!!!!!!!
The front end of the cluster gear shaft is (or SHOULD BE) a very tight interference fit in the hole. Consequently, this tight fit keeps the cluster gear stabilized and in proper alignment and mesh with the gears on the main shaft.

IF THERE IS A LEAK AT THE CLUSTER GEAR SHAFT/HOLE, THEN THAT MEANS THE HOLE IN THE CASE HAS BECOME ENLARGED----------------thus allowing the shaft to move around in the hole. Not only does a leak occur-------and in time becomes progressively worse because the hole gets bigger as the shaft moves around. Also, irregular and accelerated wear occurs to the gear teeth.

Solution: FIX THE CAUSE OF THE PROBLEM-----------DON'T PUT A BAND AID ON IT!!!!!!!!!!!!!!!!!!!!

[Richard M.]

Re: Muncie Transmission Countershaft to Case leak

Tom,

Yes I agree, this is only a band-aid. But it's a temporary fix until we either find a correct 1967 Muncie or decide to do a proper repair on this unit. I am planning to pull the transmission at a later time when we find a more applicable replacement. I'm on a time schedule right now. I'm sure you know what I mean.

Since I now understand that the shaft leaks due to a slightly egg shaped hole in the case, what you and others are saying makes sense to me. I have never rebuilt a manual transmission, nor even opened one up to work on one, but I can see that if that shaft has any side play, it will ultimately become worse over time and cause more internal issues.

Our ultimate solution will be to find a properly dated P7xxx case, and I will CERTAINLY look very closely at that countershaft hole to ensure there will be NO leaks next time.

IMO, it seems to me that the Muncie designers never anticipated that leaks would occur there due to egg-shaped case holes. I think they should have incorporated a more rigid/fixed shaft fit into a bushing or sleeve and possibly even a o-ring on the shaft in the first place.

Thanks again to all that helped the "Tranny Rookie"......
Rich

[Peter M.]

Re: Muncie Transmission Countershaft to Case leak

Hi Rich,
Tom Is absolutely correct, he has probably forgotten more than most of us will ever know about transmissions. Don't feel bad about doing the temporary patch I suspect you want the car together for Lakeland. You can practice your removal skills on that fun job after the show. I have always felt that case wear was a contributing factor to catastrophic failures. I think a lot of people don't remove the cluster when they overhaul their transmissions, it looks fine so they just leave it be, but wear on the countershaft, countershaft rollers and countershaft to case increase the clearance between the teeth on the main drive gear and the cluster, shifting the tooth load further outward. You are "MORE" than capable of overhauling a Muncie.
Kind regards and Merry Christmas.

[Frank D.]

Re: Muncie Transmission Countershaft to Case leak

A bushing is what some have done for a permanent fix....there is also a company that makes an upgraded Muncie tranny case to deal with the problem...of course then you might lose matching numbers...

[Edward B.]

Re: Muncie Transmission Countershaft to Case leak

BUT THAT DOES NOT FIX THE CAUSE OF THE LEAK----------------WHICH IS NOT GOOD!!!!!!!!!!!!!!!!!!
The front end of the cluster gear shaft is (or SHOULD BE) a very tight interference fit in the hole. Consequently, this tight fit keeps the cluster gear stabilized and in proper alignment and mesh with the gears on the main shaft.

I 100% agree, and this is what can happen if you DON'T fix the problem (see below). Third gear was totally trashed as was the cluster. Second is also unusable. All this was caused because of the exact same issue your Muncie is having. I didn't think it was a big deal until my son was driving the car one day and downshifted from 4th to 3rd. That was all she wrote! Luckily for us it wasn't the "original" transmission for the car.

Ed

[Tom P.]

Re: Muncie Transmission Countershaft to Case leak

I fully understand a person not wanting to remove the cluster when rebuilding a Muncie (or T-10), even if it APPEARS to be just fine. It is a NO fun and tedious task to get all those roller bearings, washers, thrust washers installed and then getting the shaft shoved through all that mess without some of the rollers dropping out of place. I've been building 4spds (mostly Muncies) for over 45 years, and I cuss those rollers EVERY time!!!!! But as mentioned, the rollers, shaft and even the inside surface of the cluster gear can be, and often is, pitted. The ONLY way to know is to remove the cluster and see what you have. The rebuild kits now include new rollers as well as a new shaft------------USE THEM! Why?, because over time, the diameter of the rollers themselves as well as the diameter of the shaft where the rollers ride, can be (and usually is) worn down. By installing new rollers and a new shaft, this will contribute to tightening up the cluster on the shaft as well as returning it to the correct alignment inside the case.
When the cluster is removed, and the shaft CLOSELY examined in the surfaces where the rollers make contact, it is common for the heavy thrust surface of the shaft to be worn down more than on the other side. That means the cluster gear is not rotating in its designed circle.

[Patrick H.]

Re: Muncie Transmission Countershaft to Case leak

I found rebuilding the Muncie in my 71 to be very enjoyable. With a rebuild kit and a VHS tape (its now available DVD) and a clean, empty workbench it was easy to do. The rollers didn't bother me at all, but maybe I used too much grease to hold them in place.

I wish the transmission in my Austin-Healey had instructions and parts that were as easy to find!

[Eric D.]

Re: Muncie Transmission Countershaft to Case leak

Tom, What date 1967 Muncie case are you looking for, I have a large selection of 010 cases, some with out VIN, some without VIN or build date...

Thanks... Eric

[Richard M.]

Re: Muncie Transmission Countershaft to Case leak

Eric, I'll send you a PM.......Rich (not Tom)