The Stovebolt Site Forums The Parking Lot Big Bolts 41 1.5 ton trans, or 62 SM420 hydrolic?

Hello, I have a 1962 SM420 complete with bellhousinging that I could put into my 41 1.5 ton. From what I understand the 420 is a superior transmission that is fully syncronized between 2nd and 4th. But, converting to the hydrolic clutch my be over my head. I could enlist some help. The bell housing will match my 1962 261 with very few mods. I'm only gonna drive the big bolt around town. maybe help some friends move some stuff. No real hi-way driving. I would like to do the truck right the first time. Any input would be appreciated. Thanx, Marc

The advantage will be in the shifting. Other than that the original transmission will take anything you throw at it.

If you want to go with the sm420 then use a bell housing from a 47-52. Make sure the motor mounts are horizontal and not at an angle.

Send it over to Buffalo http://www.inliners.org/buffalo/index.htm, they will weld on mount points for the clutch and brake.

Re- use your original fly wheel, pressure plate, starter, etc.

You probably know the SM420 is longer that the original so you will need to shorten your driveshaft.

Bolt it all on and enjoy!

I thought I could use the Bell housing that came with my 41 chevy, that it would bolt up to any bell housing made up until 1962. Don't they use the same motor mounts? I knew i was gonna have to shorten the drive shaft, that's acceptable. Why is it necessary to change to a 57 to 52 Bell housing? After i send it to buffalo chips, will i have a hydrolic clutch and brake? Thanks for your help. I guess this would be a good time to admit that i'm a hacker. : )

Hy 1fletch, unfortunately there is no stock bellhousing that I'm aware of that has the bolt pattern for mounting the SM420, and the mounting points for the brake and clutch pedal shaft. The mounts on the 62 bellhousing are not compatible with your 41 chassis, that is why InMy40s suggested using a 48 - 53 bellhousing, that bellhousing would be compatible with your chassis and allow you to bolt the SM420 to your engine, the only thing this bellhousing lacks is the mount for the clutch/brake pedal shaft. InMy40s suggested that "Buffalo" could modify the bellhousing to install the clutch/brake pedal mounting holes. Your 1941 bellhousing does not have the correct mounting pattern for the SM420, the pattern it has is too small, hope that helps.

fletch,

You do not need to set up a hydraulic clutch. I do not when when the hydraulic clutch with an SM420 started being used, but one was not needed in many earlier years of use of the SM420.

1960

It is easy enough to drill and tap a 420 pattern, depending on trans mounting holes, just get the retainer dia. matched up, put the bellhousing face down, install the 420, make the trans, level, mark hole locations w/ transfer punch, drill holes.

An optional method, is to drill and tap '41 bolt pattern in the front of the 420, same method.

Hey Fletch,

I may be able to shed some light on this issue. I have a 42 1 1/2 ton that someone in the past put in a 1959 235 with an SM420 tranny. In order to get the clutch and brake pedal to work they welded on a segment of an earlier bellhousing that had the boss for the pedal shaft. I've had the truck for over 30 years but just last year I noticed how poorly the weld was done. Looked dangerous to me and was trying to figure out what to do. Here is a picture of it. http://s1293.photobucket.com/user/M...ellhousing/DSCN7360_zps8dbb68e9.jpg.html

Well it just so happened as I perusing the parts at Jim Carter Truck Parts I saw where they sold a modified bellhousing with the pedal shaft for the owners of the early 40's trucks so they could use the more modern trannies such as the SM420. Voila !! I believe the change in the bellhousing in these rigs occured in 1948. That's when they went to the later tranny bolt pattern. Either one will bolt to the inline six block. So I went ahead and purchased the modified bellhousing from Jim Carters. Here's a picture of the bellhousing I installed with much better welding for the pedal shaft. http://s1293.photobucket.com/user/M...ellhousing/DSCN7356_zpsd0204952.jpg.html

Here's a link to the part if you are interested. http://www.oldchevytrucks.com/cart/index.asp?sdes=bellhousing

Check it out. And check out the rest of my photos on this subject in my photobucket album.

Tony