[SS4speed]

Hi Wally,

I have a 1969 M-20 Tranny, in which the Case plug was welding in. (On this tranny's tailhousing, the speedo cable is on the Passager side (I think). It was removed and tapped, but I don't like the job that was done. Anyway, I have a 1965 Case from a M-20 and would like to swap. (On this 65 tranny's tailhousing, the speedo cable is on the driver's side (I think). Can it be done, does the tail housing have to go with it? The 69 is not the original tranny, it's just a spare, do I don't care what I do to it.

Thanks,
Fred.

 

[DZAUTO]

Fred,
How about a little background first.
The 66-74 Muncie MAIN cases are interchangeable with one another (they use a 1inch cluster gear shaft).
The 63-65 MAIN cases use a 7/8inch cluster gear shaft. So, even though all the parts will physically bolt together, you cannot install a 66-74 cluster gear and shaft into a 63-65 main case, unless you have the 65 case bored out to accept the 66-74 cluster gear shaft--------------------THIS REQUIRES AN EXPERIENCED PRO WHO KNOWS EXACTLY HOW TO DO THIS TO AN EARLY MUNCIE CASE!!!

The Muncie case is aluminum and the plug was steel----------------you can't weld them together. So, just how was the hole welded? Did someone just weld the hole closed, or what? If it is just welded closed, possibly it could be drilled and new threads tapped (1/2in pipe threads).

ALL Muncie tail housings will physically bolt up to any Muncie main case (there is a mid plate between). The 63-70 tail housings are totally interchangeable. For example, if you have a Muncie with a pass side speedo fitting, and you need the speedo fitting on the driver side (for whatever reason), then you just swap the tail housing. The 71-74 tail housing will bolt up to a 63-70 main case, BUUUUUUUUUUUUUUUUUT, 71-74 Muncies got the bigger tail shaft and tail housing (which is also 3/4in longer). Thus, if you want to bolt up a 74 tail housing to a 66 main case-----------------you also have to swap the longer 71-74 tail shaft plus the speedo gear (which has a bigger hole).
Let us know if you need more info.

 

[SS4speed]

Tom,

Thanks, as always your a wealth of info, your brain has to be working overtime. Sorry about the jumbled message, I was thinking at work and wrote a quick note. I should have known better than to think at work, anyway.
I checked it out when I got home, the one case is a 3885010 and the second is a 3925660, both 1 inch bores. Your right, the plug wasn't welded, it was just in the hole so long (around 30 years or more), I couldn't get it out. I had a local shop remove it, but I don't like the job they did. Having the extra case started me thinking (at work), and knowing they looked close to being the same, hence the lacking note.

Thanks,
Fred.

 

[DZAUTO]

Fred,
Two of the most common areas of damage, wear, problems are the front hole in the case (for the cluster shaft) and the gussets between the case and the ears where the case bolts to the bell housing. Cases with lots of miles, abuse and have been disassembled a few times will frequently have that front hole enlarged. When the cluster shaft is inserted through the case, the front end of the shaft MUST NOT protrude beyond the front face of the case. It SHOULD fit tight enough (the nose of the shaft and the hole are a taper fit) that it is recessed in the case a little.
Also, it is not uncommon (once you get the case thoroughly cleaned up) to discover cracks in the gussets (especially at the left ears) between the main part of the case and the ears that bolt to the bell housing. I have had a ton of these cracks welded up. The crack first needs to be V'ed with a die grinder all the way to the bottom of the crack before welding. ANYONE who is good at welding aluminum can do this. After welding, I use a die grinder and rotary file to grind down the welded area. These are just some things to inspect the main case for before rebuilding a Muncie.
As I mentioned, the 66-74 main cases are totally interchangeable. The differences between the 010-660-661 cases are VERY minimal and have no bearing on their interchangeability. The 660-661 cases are cast with a wider flat stamp pad at the right rear of the case for stampong the date code/VIN.

 

[SS4speed]

Tom,

Thanks for the help, I'll be starting to tear it apart in a few minutes. I'll check it inside and out for cracks, wasn't even thinking about that. If I have any problems, hope you don't mind me giving you a few more questions.

Thanks,
Fred.

 

[Guest]

Fred,
Two of the most common areas of damage, wear, problems are the front hole in the case (for the cluster shaft) and the gussets between the case and the ears where the case bolts to the bell housing. Cases with lots of miles, abuse and have been disassembled a few times will frequently have that front hole enlarged. When the cluster shaft is inserted through the case, the front end of the shaft MUST NOT protrude beyond the front face of the case. It SHOULD fit tight enough (the nose of the shaft and the hole are a taper fit) that it is recessed in the case a little.
Also, it is not uncommon (once you get the case thoroughly cleaned up) to discover cracks in the gussets (especially at the left ears) between the main part of the case and the ears that bolt to the bell housing. I have had a ton of these cracks welded up. The crack first needs to be V'ed with a die grinder all the way to the bottom of the crack before welding. ANYONE who is good at welding aluminum can do this. After welding, I use a die grinder and rotary file to grind down the welded area. These are just some things to inspect the main case for before rebuilding a Muncie.
As I mentioned, the 66-74 main cases are totally interchangeable. The differences between the 010-660-661 cases are VERY minimal and have no bearing on their interchangeability. The 660-661 cases are cast with a wider flat stamp pad at the right rear of the case for stampong the date code/VIN.

The only thing I would add to what Tom said is check the face of the case after welding and make sure it's flat. The intense heat generated when welding aluminum can warp the face of the case.

I just have Mr Bill mill the face just enough to correct, don't get nuts whacking on the case.