The Stovebolt Site Forums The Shop Area Engine Shop Is there a 4-speed transmission ...........

Is there a 4-speed trans that fits between a 235 and a 1936 1.5 ton torque tube rear? I know all the swaps are from 1937 and up, but is there any hope for us 36' and under guys? 207's suck!..Rick

Doesn't the 1.5 ton have a short torque tube shaft followed by an open driveline? If so, either get an SM420 out of a 3/4 ton '49-54 truck, or get an open driveline GM tranny and re-work the driveshaft.

Mines a 131" wheel base , all torque tube all the way to the trans. I've since found out from Baldy that a '38-'47 bellhousing will give me what I need, a 235, a later bellhousing, with my double clutching '36 trans. connected to my original torque tube. All I need now is a '38-'47 bellhousing. Gotta be one laying around someones shop in Western Washinton. Thanks 4ontheFloor for your time, this site and it's people are the best!!......

Put an add in the classified section, I bet Ken or one of the other early truck guys has one he'll part with.

Just out of curiousity, why do the 207's suck? I am actually being serious, because I've never heard anybody talk about them much one way or the other. Is it that different from the 216 / early 235?

Actually,I have to apologise for that comment, I've heard them run and any old stovebolt is cool.What I need to do is appreciate the old school engines more, it's where our new breed of engines came from. I was a teen in the 60's so the bigger is better attitude is engrained in my brain and sometimes I can't control it.Sorry. Actually my original intention was to try to wake up the ol' 206.8 but alas, It expired some time ago on a farm in Washington state. I have another '35 207, but if I'm going to go through the exercise of removing the engine any way I might as well put a more modern power plant in it. One of the drawbacks of the 207 is the dipper oiler system. I have every intention of driving this truck alot and I personally am not comfortable with the old motor. It seems they get about 50,000 on them and die. Sorry about my rambling on but I've thought alot about this project and I really want a driver. I'm familiar with the full pressure 235's and they have a awesome reputation for a work horse. Plus my brother is a ex-California Hi-Po engine builder who highly reccomends the 235 over any early inliner. He has Torque plates and knows them well, so guess why I'm prejudice?..thanks for the ear,39az3/4ton......Rick

Rick,

Thanks for the reply. No problem on the rambling. I was just curious. I don't disagree with you at all, the 235 high pressure is a great swap for a serious driver truck. I've contemplated the same as a swap out for my 235 low pressure. Since I have no cash for such a project, I continue to work on my babbit beater. I haven't driven it nearly as much as I'd like, but I finally have to put some work into it for the first time in 13 years. Decent engine, but again, the high pressure is a great swap.

Good luck!

I know what you mean AZ, I'm as low buck as it gets believe me, thats why I only want to do it once. I just want to double clutch a rig one more time and keep it this time without selling it to pay the mortgage payment or some other God dang thing, nope this is a keeper and who knows i'd love to drive it on down to AZ someday I sure miss the sun up here in WA state. take care ..Rick

I have two questions, I see the term "SM420" transmission used a lot here. What is it? There are charts and silowets of the later three, four and five speed transmissions abut these arn't mentioned. Are they GM, Muncie, etc., and do all the 3/4 and bigger AD trucks use this tranmission? I have the original four speed in my 3/4 ton 1950 but never knew what it was called.
The other thing was the dipper engines. I think it is a testament to this engine that there are so many still running 60 or 70 and more years after they were built. Most of them were worked to death on farms and hauling commercialy. Of course if your going to try driving them on the freeway at 75mph everyday or hot rodding them to compete at the drag strip then they certainly won't hold up. So whats REALLY wrong with the early inliners???
Denny Graham
Sandwich, IL

207's and the earlier 194's only have 3 main bearings which is the real weak point, also the rod and main bearing oiling was improved with the 37 and up 216 engine. But I have 2 vehicles with the 194 and they do well, but I don't over rev them.

Denny,
the SM420 came out in late 47 I believe. They were a redesign of the old four speed with a synchro design. First is really low and second is lower than the first on the three speeds. The offroad rock climbers really love them because they have such low gearing and they are tough. I don't know how far up in the truck size they were used but certainly they were used on the 3/4s and 1 Tons. I believe that they were built by Muncie.

I know that the 4 speeds in the 39's were built by both Saginaw and Muncie. I believe the four speed was referred to as a SM-22? It is the non-snycro and was used for a long time. It is the same size as the 37-46 3 speed and is a fairly simple drop in for those year trucks. I would think the same might be true for some of the pre 37 trucks.

Don't know if that helps or not, but just a few thoughts. For the late thirties, standard equipment was the three speed for 1/2 and 3/4 tons. Big bolts got the four speed. However, it was an option to get the 4 speed in either the 1/2 or 3/4 ton's and lot appear to have been equiped that way.

Gearing on the 4 is meant for hauling. First is 7.23 to 1. 2-4 nearly approximate the three speed with 1:1 at the high gear. Not exactly the kind of gear to spin the tires with. Since I'm doing mostly improved road driving, I rarely use it. Since you've got the big bolt, you probably would use it more that I do!

I would have added these thoughts earlier, but it really just came into my mind now.

Let us know how the swap out goes.

If you are looking for a more modern 4 speed I would get a 3-groove Saginaw from a '60's-70's GM. They bolt right up to the 235 bellhousing, you just need a driveshaft and shifter. They aren't granny-geared.

Not to hip here guys, but what do you mean by a "3-groove Saginaw"? And then you would need a Hurst shifter or something similar or is it a top shifter?
I have a '97 GMC Sierra and was told here that the 5-speed that it uses wouldn't work in my ’50 AD. I Love that 5-speed transmission by the way. I taint been under the GMC but I think the issue was that it had the bell housing cast into the case like an automatic?
Denny Graham
Sandwich, IL

Denny, whoever told you the 5 speed wouldn't work is wrong. The 5 speed in my 1992 GMC has an integral bellhousing (i.e. part of the case of the trans. that bolts directly to the block of a smallblock V-8 or 6 cyl. from 1962 and later. If you are bolting to a 235, get an adapter from Langdon's. 3 groove Saginaw refers to the number of grooves on the front shaft of the trans, there are no groove, 1 groove, 2 groove and 3 groove styles. The Saginaw is a good trans. and will bolt up to the truck bellhousing, making the easiest adaption ever.

Thanks I'll look into that an keep it on file.
Something new to me, never heard of groovey clutch shafts before, I've only seen splined shafts.
Denny Graham
Sandwich, IL

Denny, here's the groovey info on ID\'s of GM 4 speeds

Bill

Thanks Bill, down loading it right now.
Denny G

Denny here is another helpful link about the "Synchro-Mesh" 420 URL . And yes that's what's in your 50.

Wow Frank...that's mine. Can the backup light thingy be added?

I guess mine is grandfathered for the safety inspection, but for my own safety it may be interesting to add.

Dave

I have seen a couple of articles on the web about installing the back-up light switch. Try over on oldgmctrucks.com.

Jolly Goodfellow's site 6066GMCGUY may have something on the back-up light switch. Good luck