The Stovebolt Site Forums The Shop Area Driveline Saginaw 3 speed OD into 1942 3/4 ton

I'm looking at putting a Saginaw 3 spd. OD into my 1942 AD 3/4 ton (BL). Everything looks like I will fit fine except, I'd like to avoid changing the bell housing (rear motor mounts, pedals, etc.). Does anyone know if a 1957 Saginaw 3 speed OD trans will bolt up to the OE 42 bell housing without the mods? If I have to go to the 57 bell housing to install the Saginaw, I'll have to fabricate rear motor mounts, pedals, and probably some other stuff as well. The truck is running a 1962 235, with dual carters, Offy intake, Fenton headers, and dual exhaust. I'd really appreciate hearing from anyone that has experience with using the Saginaw OD in these older trucks. Thanks for any advice you can offer.

Tom,
A 57 overdrive transmission is actually a Muncie SM319. It would have a 4 bolt side cover and a Borg Warner R10H overdrive unit.
The Saganaw/BW overdrive came out in 66 and was a full syncro unit with a 7 bolt side cover. The bellhousing to transmission mounting pattern would be different on the early models vs 48 up trucks. You could use a 54-66 rear crossmember and the 57 (55-59 6 cyl) truck bellhousing.
You would likely have to modify the crossmember to fit the frame on your truck.
There are no rear mount provisions on the 57 transmisson.
I can't advise you on the pedal issue, but someone here has information on that.
You will also have to engineer some type of shifter set up. A standard 3 speed floor shifter generally will not work with an overdrive as there is interference with the solenoid.
Fred

Fred:
Thanks for your help. OD unit on my trans is BW R10H. I was told it was a Saginaw. The casting numbers come back as 1957. Guess that's my error. However, when I searched for a shifter mounting kit for the 57 OD trans, the only thing that came up was for the Saginaw. Regarding the shifter, I've been told that the only shifter that will work properly on the 3 speed OD trans is the Hurst Syncro-Loc. All of the images I have seen for a 57 Saginaw OD match the trans I have here. However, what I'm going to do (before spending money on a rebuild) is test fit the OD trans to see of it mounts to the OE 42 bell housing, without interference issues. Being a 3/4 ton, there are many differences from the 1/2 ton trucks, so most information I find does not apply. Another issue is that the 3/4 ton clutch was a slightly wider diameter than the 1/2 ton. Another reason I want to keep the original bell housing if at all possible. Thanks again for your help. It is really appreciated. All The best.

A 1957 transmission will not bolt to a 1942 bell housing. The bolt pattern changed when in mid 1947. I have been playing with overdrives for over 50 years and my preference has always been the Hurst Mystery shifter that has been obsolete for 50 years. They made kits for Ford T86 overdrives because they were so common. I'm not sure if Hurst ever made a shift kit for a SM319. If they did, they are very scarce because I have never seen one. Overdrive was not near as popular with GM as with Ford. The mounting kit has to be for an overdrive in order to clear the shift solenoid. And another consideration is that the shifter sets pretty far back on a SM319 and may well wind up under the seat in front of it. You are going to have a lot of hurdles trying to install a SM319 in a vehicle that wasn't built for a column shift and doesn't fit the bell housing.

Thanks for you input. The more I look at this OD trans, the more problems arise. I suppose, at this point, it's best to select a different transmission to replace my OE Muncie 4 speed. I do also have a Saginaw 4 speed trans sitting in my garage. It's dated 73. I'd be interested in your thoughts on the potential for that swap. It does look like that would also require a bell housing change.

I have never seen it done, but the insides of the Muncie 3 speeds are pretty much interchangeable except the main shaft is different in direct and OD. A passenger transmission through 1954 will fit your bell housing. It might be interesting to see if your Sm 319 gears might build in a 1954 or earlier case.

Many people call it a Saganaw but it doesn't really matter if it makes them happy. I'll go with my parts supplier, Anaheim Gear, their books call it a Muncie.
There were three 3 speed transmissions available in 57 for cars, the standard SM318, the OD SM319, and the close ratio Corvette version. Trucks had the first two plus a heavy duty Warner non OD unit which has a 9 bolt side cover.
None of the late transmissions will fit your early bellhousing. The Saganaw 4 speed is still 1:1 in 4th gear, so would be no improvement for highway speeds. OD's work great in older trucks, I have installed many of them. None that old, however.
Fred

I agree that the shift kit is VERY rare for this 3 speed. However, I found one, and it's on the way. Unfortunately, if I do not use this transmission, I'll have to return it or sell it on. After much measuring, figuring, photographing, and research on the internet, I've basically decided to abandon the SM319 swap, and just go with an 1984-92 S10 T5. It's more supportable, and I can buy a simple adapter plate to mount it to my 42 bell housing, with no mods. Because I was building something that was "period correct", I wanted to try to stay with a trans available between the 50s and 70s. However, it's becoming obvious that doing so will actually require more modifications to the truck than going with the T5. The T5 allows me to use a "bolt in" solution, and put every OE drivetrain component on the shelf, for a future restoration to factory configuration, if that ever becomes desirable down the road. I never did like cutting on these old vehicles.

I think the T5 is a good choice. They evolved from the Borg Warner T89 that was used in the Ford police interceptor and GMC used it as a heavy duty option over the Muncie. They are not for a muscle car application, but will work well in your application. However, they come in different ratios. Overdrive can be anywhere from .72 to .86. I would look for the .72 or .73 ratio.