Transmission swap

[Guest Larry wagner]

I have a 38 special coupe that has a 40 special eng in it, the 38 trans is shot so i purchased a 37 trans that was available thinking it would be a simple swap only to find that upon after removing the 38 trans and inspecting the two side by side that the 37 unit has a larger tooth diameter input shaft plus a support collar that is bolted to the front of the case witch means it wont mate up to the 40 eng bell housing because the hole in the 40 is smaller then the collar thats bolted to the 37 case. Dose anyone know if a 37 special clutch and bell housing will solve this problem or did i get taken by the clown that sold this thing to me and has since left town.

[1939_Buick]

Is the 37 transmission from a 40 (248ci) or 60-80-90 series (320ci) ?

Your bell housing may the 1938. just bolted to the 1940 engine

[Guest Larry wagner]

Allan, yes the 37 trans is supposed to be out of a 40 series 248 ci special coupe ,as was told to me by the old gent who sold it to me. He was a retired engineer that worked his whole life for CHRY, GM, and FORD at verious times and i suspect its the real thing because i have a master parts catalog that matches a number that is on the rear housing. As far as i know the bell housing is the origonial 38, i say this because it is also the rear eng support that is bolted through each side of the frame with shims where as in 1940 i beleive the rear of the eng was supported by a cross member with a rubber mount.

[bobj49f2]

Have you been able to figure out a way to use the transmission you have?

I am trying to use the available parts I have to assemble my '37 Special. I have a '36 tranny, which looks to be the same as the '37, and a '40 engine with a '40 tranny. I also have the original '37 bellhousing, junk cluch and pressure plate. I think I have it figured out but I might be wrong.

[jeff]

My '38 Special is also running with a '37 gear box. The only reason I figured this out is that I salvaged a transmission from a '38 parts car, intending to make one good transmission out of two. Only when I had them side by side did I notice the differences.

Clutch shaft - your clutch disc is expecting the size shaft used in '38. If you want to use the '37, you will need a '37 clutch disc (slightly different size, and it's gotta be right!). On my car, someone before me had made this change.

Front of case - here you have a choice. Someone before me had taken off the '37's bolt-on nose piece, then cut the heads off of the bolts and threaded them back in. Then, he used the '38's slip-on nose piece instead. Works ok, however I do have a slight and persistent oil leak. When I look at the modification, and the return path for the oil, it looks like it should work ok.

So, in making one gearbox out of two, my choices were a bit limited. Everything interchanged (if I recall) except the clutch gear. That sucker has to stay with the right case. (and be accompanied by the right clutch disc) Since my '38 clutch gear was rough, I had to reuse my '37 case. I did swap out a better idler gear, rear torque ball components, and shifter plates, so I guess I did alright. I hope to go back someday and use the '38 setup.

[bobj49f2]

They sure made this stuff difficult.

I think I'll to use the bellhousing from the '37 and the flywheel from the '40 to make sure it matches the '40 crankshaft. I don't know if I can do this yet, I haven't taken the bellhousing off of the '40 engine yet.

[The Old Guy]

Do not forget that the bell housing hole for the trans was bored after the housing was mounted on the engine to make sure that it was properly aligned, If you use another bell housing , chack to make sure that hole is concentric with the crank . if it is not ,you will have a trans that will kick out of gear when you decellerate.

[bobj49f2]

I saw the procedure to make sure the opening was true in the shop manual. Did they bore out the hole at the factory during assembly for each car? Or are you just referring to if we use a different year bellhousing?

One thing I am learning about these old Buick is nothing is simple.:mad:

[F&J]

Front of case - here you have a choice. Someone before me had taken off the '37's bolt-on nose piece, then cut the heads off of the bolts and threaded them back in. Then, he used the '38's slip-on nose piece instead. Works ok, however I do have a slight and persistent oil leak. When I look at the modification, and the return path for the oil, it looks like it should work ok.

QUOTE]

On GM transmissions that had the non-bolted front bearing retainer...those cars had a full gasket covering the entire face of the transmission (between the trans and bell). If you don't use the gasket, or if the gasket is too thin, it will leak from the bearing retainer.

[Ben Bruce aka First Born]

F&J. does that apply to the 1950s as well?

Thanks

Ben

[F&J]

Yes in the 50s because the GM selector type trans were still being used...and those had the slip-on bearing retainer. My 55 olds has that. Selectors were used by Buick Olds and Pontiac from what I have read. I do not know what was the last year...may be later 50s or maybe even very early 60s.

Another trans like that was Cad/ LaSalle, (as far as a slip=on retainer)...which needs a gasket

[The Old Guy]

The hole was bored after the bell housing was mounted to the block. You can use another bell housing if you pull the dowels and readjust the bell housing to ZERO on an indicator. Then use a tapered dowel pin reamer and reset the housing.