Muncie rebuild question

[Jerome T.]

Hello everyone, this is my first time on the discussion board. I hope I don't bore everyone.

The second gear syncro in my 65 muncie needs to be replaced. I've looked at the master rebuild kits available which include new front and rear bearings and the countershaft. Do these items really need to be replaced? Or should I just replace all the sycros and small parts, new gastkets and seals of course. My main concern is replacing bearings and shafts that are perfectly fine with items that may be of a lower quality, and certainly not the original parts.

Thanks for the advice, Jerry

[Ridge K.]

Re: Muncie rebuild question

Hello everyone, this is my first time on the discussion board. I hope I don't bore everyone.

The second gear syncro in my 65 muncie needs to be replaced. I've looked at the master rebuild kits available which include new front and rear bearings and the countershaft. Do these items really need to be replaced? Or should I just replace all the sycros and small parts, new gastkets and seals of course. My main concern is replacing bearings and shafts that are perfectly fine with items that may be of a lower quality, and certainly not the original parts.

Thanks for the advice, Jerry

Jerry, welcome to the world of posting!
First let me give this qualifier, I am not a four speed trasmission mechanic. I can tell you this, however. I worked at an auto dealership from about 1971 to 1985. That was somewhat the "heyday" of the musclecar era winding down.
At the dealership, for "in house" units, which are us, cars the dealership owns, thru trade-ins or purchases,..... when the four speeds would need minor overhauls, they had their side covers removed, and if the gears looked good, they only received syncros, and gaskets unless they had obvious gear face issues). I didn't rebuild the four speeds, but was assigned the task of road testing the car after this minor syncro rebuild.
I can tell you, that in about 98% of the cases, new syncros, along with rear seal, and gaskets, put the four speed back into an excellent, working condition. In maybe 2% of cases, I would be able to hear bearing noise, or other gear mesh issues.
Just my observations. Hopefully, the four speed mechanics will come forward to enhance, or discount this observation.
Once again, welcome to posting. Ridge.

[Jerome T.]

Re: Muncie rebuild question

Thanks Ridge - that makes a lot of sense and confirms my gut feeling. I'll obviously check everything once I get it open.
Jerry

[William C.]

Re: Muncie rebuild question

Just remember that the '65 design brass "blocking" rings and associated hubs are not the same as the 66-up units, so make sure you get the correct parts for the early design muncie. Not sure what symptoms you are seeing as you didn't elaborate, generally a small parts kit will include all the thrust washers and new needle bearings for the countergear, no reason to not replace those while the box is apart. Good time to check the condition of the pilot bushing also.

[Joe L.]

Re: Muncie rebuild question

Hello everyone, this is my first time on the discussion board. I hope I don't bore everyone.

The second gear syncro in my 65 muncie needs to be replaced. I've looked at the master rebuild kits available which include new front and rear bearings and the countershaft. Do these items really need to be replaced? Or should I just replace all the sycros and small parts, new gastkets and seals of course. My main concern is replacing bearings and shafts that are perfectly fine with items that may be of a lower quality, and certainly not the original parts.

Thanks for the advice, Jerry

Jerry-----


It's very hard to assess the condition of the transmission's main ball bearings unless they're really bad. However, if you're not experiencing any bearing noise or other obvious bearing problems and considering the kind of mileage you probably put on the car, you could very likely get by without replacing the current bearings.

The countergear shaft can be inspected and measured for wear. ANY wear, AT ALL, is reason to replace it.

As far as gears go, you can purchase replacement Muncie gears as manufactured in Italy by Masiero SA. Masiero SA is the largest manufacturer of gears in the world. They make various gears used on Ferraris and also some used in jet engines. Since these new gears are available, I would NOT recommend the use of any USED gear.

[Ridge K.]

Re: Muncie rebuild question

Jerry-----


It's very hard to assess the condition of the transmission's main ball bearings unless they're really bad. However, if you're not experiencing any bearing noise or other obvious bearing problems and considering the kind of mileage you probably put on the car, you could very likely get by without replacing the current bearings.

The countergear shaft can be inspected and measured for wear. ANY wear, AT ALL, is reason to replace it.

As far as gears go, you can purchase replacement Muncie gears as manufactured in Italy by Masiero SA. Masiero SA is the largest manufacturer of gears in the world. They make various gears used on Ferraris and also some used in jet engines. Since these new gears are available, I would NOT recommend the use of any USED gear.

Joe, if one pulls the side cover off a 1967 M21 muncie with confirmed 43,000 total road miles, and there is no visible gear face damage, in your opinion, would you still replace the gears? Thanks in advance, Ridge.

[Joe L.]

Re: Muncie rebuild question

Joe, if one pulls the side cover off a 1967 M21 muncie with confirmed 43,000 total road miles, and there is no visible gear face damage, in your opinion, would you still replace the gears? Thanks in advance, Ridge.

Ridge------


No, not at all. I didn't mean to say that the gears in this transmission should be replaced. I believe the poster originally said that he needed to replace the 2nd gear, so that's all I was referring to here. In fact, I have the original Muncie out of my 1969 sitting here and I'm going to go through it (as soon as I finish the project with my 69 and have it on the road). That transmission has 200,000 miles on it and I don't plan to replace any gears, at all. I don't think I'll find that I'll need to, either. Of course, I know the guy that's been virtually the exclusive driver of the car since it was knew.

[Ridge K.]

Re: Muncie rebuild question

Thanks Joe.
My plan was to keep my original gears also.
Thanks for clearing that up for me.

[Thomas H.]

Re: Muncie rebuild question

Hello everyone, this is my first time on the discussion board. I hope I don't bore everyone.

The second gear syncro in my 65 muncie needs to be replaced. I've looked at the master rebuild kits available which include new front and rear bearings and the countershaft. Do these items really need to be replaced? Or should I just replace all the sycros and small parts, new gastkets and seals of course. My main concern is replacing bearings and shafts that are perfectly fine with items that may be of a lower quality, and certainly not the original parts.

Thanks for the advice, Jerry

Jerry,

I recently rebuilt the M21 in my 71 LS5. The car had 119k miles on it and I did not need to replace the gears, they were in great shape. I bought a master rebuild kit from a very helpful trans shop in NY (http://www.dandltransmission.com/). The kit included the bearings, synchros (the good ones...) plus all of the small parts. Since the trans had such high mileage on it, I did replace the bearings. It was a very easy rebuild except my 12 ton press had some difficulty pressing one of the gears off of the main shaft. I took it to a shop that used to build the automatics for my racecar and he had it off in no time.

It went back together easily and works just fine, no more popping out of gear..

Good luck,
Tom

[Bob S.]

Re: Muncie rebuild question

Jerry,

I recently rebuilt the M21 in my 71 LS5. The car had 119k miles on it and I did not need to replace the gears, they were in great shape. I bought a master rebuild kit from a very helpful trans shop in NY (http://www.dandltransmission.com/). The kit included the bearings, synchros (the good ones...) plus all of the small parts. Since the trans had such high mileage on it, I did replace the bearings. It was a very easy rebuild except my 12 ton press had some difficulty pressing one of the gears off of the main shaft. I took it to a shop that used to build the automatics for my racecar and he had it off in no time.

It went back together easily and works just fine, no more popping out of gear..

Good luck,
Tom

Tom, could you please elaborate how to distinguish between the "good" synchros and others....? (Brand, material, design, or??)

Thanks,
Bob S.

[Thomas H.]

Re: Muncie rebuild question

Bob,

I am no expert, but in doing my research before I dug into the rebuild, I was told (probably from some of the more experienced folks here) to make sure that the overhaul kit included "bronze" synchros. I do believe that some of the imported or less expensive overhaul kits use a different alloy for the synchros, maybe brass?

I spoke with Larry (I think?) at D&L and he assured me that they only use high quality bronze alloy synchros in their kits.

Joe L. had posted some GM part numbers in a post I found in the archives by doing a search on Muncie and synchro. This is the link (I hope it works...) https://www.forums.ncrs.org/showthre...nchro&uid=7089

Hope this helps....
Tom

[Bob S.]

Re: Muncie rebuild question

Bob,

I am no expert, but in doing my research before I dug into the rebuild, I was told (probably from some of the more experienced folks here) to make sure that the overhaul kit included "bronze" synchros. I do believe that some of the imported or less expensive overhaul kits use a different alloy for the synchros, maybe brass?

I spoke with Larry (I think?) at D&L and he assured me that they only use high quality bronze alloy synchros in their kits.

Joe L. had posted some GM part numbers in a post I found in the archives by doing a search on Muncie and synchro. This is the link (I hope it works...) https://www.forums.ncrs.org/showthre...nchro&uid=7089

Hope this helps....
Tom

Thanks Tom.....very helpful!

Regards,
Bob S.