The Stovebolt Site Forums The Parking Lot Big Bolts 37 1.5 ton SD transmission ID?

I'm trying to determine if I can swap this 4speed for a newer SM420 with backup switch, or if I already have one installed. I'd like to either add syncs to this transmission or swap for a SM420. I believe the 37 4spd is the precursor to the SM420 and parts might be interchangeable. Here's some pics.
It is an H pattern. Granny 1st left/up, 2nd down, 3rd right/up , 4th down , reverse is little lever up and stick all the way left and down.

Hy prubah, that transmission is a sliding gear transmission that has nothing in common with the SM420. The bellhousing bolt pattern is not correct to allow bolting the SM420 in place. There is no factory bellhousing which allows the SM420 to bolt up to it and provide the mounts for the clutch and brake pedal shaft. While there are SM420s for torque tube driveshafts the SM420 is a longer transmission than the earlier sliding gear transmission and will not fit in place of the sliding gear transmission. I'm not saying the swap is impossible but it is not a drop in proposition, hope that helps.

Thank you 3B,

This is the kind of information I've been looking for. I've been on the search for 235s and 261s as well as full synchro trans that may work in place of the original 216 and 4spd. I appreciate the response. I feel now I'm left with what I have, as this truck is way too nice to start hacking rivits, drilling or welding the frame and moving crossmembers.
This is a driver in its current condition aside from needing radiator repair. I really don't want a barn queen and may sell it at some point this Summer.
If I can't get a fair price for it then I'll have to rethink totally modernizing the drivetrain for next Summer over Winter.(235/261:SM420:Custom driveshaft:Dana 80 3.73 w/disks)

Best regards and thank you,
-Scott

Thinking of doing a similar switch in order to get the luxury of a synchro box. I have worked mainly with 4 speed 1940 to 45 non-synchro...... I have a spare tranny which I think is a sm420.....came off a 59 fuel delivery truck......salvaged/rebuilt the 261 but mated the engine to a 1940 216 bellhousing...all is fine with that set up. Now planning the next truck..... how do you identify the SM420 from others...is there a web site I can tap into and visually ID that box of mine........

Thanks

Bob C.

Hy RAC1812, try typing Novak SM420 into your search engine, that should bring up lots of information, hope that helps.

Scott,

You will get the hang of double clutching your non-synchronized transmission. It is really mentally "automatic" once you figure out the process. The only problem I have is once in a while I catch myself double clutching synchronized transmissions.

Paul

Thanks 3B....exactly what I was looking for....... will be using the info to ID my tranny...... was on a 1959 fuel truck with a 261 engine.......

Scott...... I can double clutch....in fact I can shift 3 to 4th if I pay attention to the revs/sound and speed with out using the clutch....just unloading the gear via the gas pedal.

My problem is a back issue that is robbing strength from my left leg .....plus the fact that my 1940 Chev Canadian military was designed using British standards so the brake pedal is on the right..... throttle button in the middle and clutch on the left...... add to this the extremely tight foot well...... very difficult to drive with size 11 work boots.....much easier to use light running shoes........ usually wind up driving with the right toes on the gas and my left shoe tucked under near my seat........ a very hellish design!!!!! .....ooh forgot to mention the truck is right handdrive and shifting with a clumsy left hand is no fun either.........Now planning to work on another Chev truck with more conventional pedals and foot space but would like the ease of a fully synchro while retaining a similar shift pattern and gear ratio. Chev truck base will be a model 1533 circa 1940-45 1 1/2 ton 133 inch wheelbase running a stock 235.

Thanks for your help.