The Stovebolt Site Forums The Shop Area Driveline SM 420 vs SM 465 transmissions

I have a 54 Chev 3100 with a SM420 and would like to know if a SM 465 will swap in. They appear to be the same at the back. I have an enclosed driveline and need to have the output side compatable. Any help would be appreciated.

Hy Rainierman, welcome, as far as I'm aware there are no parts made to convert an SM465 into an enclosed driveline transmission. If I am wrong someone will be along with better information.

The SM 465 front bearing retainer is a bit larger and will not fit your bell housing. Also, the SM 465 is a bit longer. And, as mentioned before, will not work with enclosed driveline. Should work if you machine out the bell housing and convert to open drive shaft. I doubt that it would be worth the trouble and expense.

Thanks for the info! To add to that I have now found an SM420 for the truck. It's been 40 years since I removed a transmission with a torque tube. My question is does one need to move the tube down and remove the 4 sp from the top or vice versa? And when rotating the tube should I loosen all the u-bolts on the differential so I don't bend the tube. Any guidance will be appreciated.

Hy Rainierman, to ask a question of us and then not comment on whatever answers come in for five weeks seems rude to me. As far as the "U" bolts are concerned it is not necessary to loosen them the rear axle is designed to pivot up and down with rear spring compression, hope that helps.

I found it easier to remove the SM420 from the bottom but I also removed the floor cover to make the whole process easier. I was working by myself and strapped the trans to a platform jack. No way could I have man-handled from below like I used to do with 3 speeds a few decades ago. Have the back of the truck on jackstands so the rear end will rotate easier as 3B described.

I used guide rods the first time I replaced the trans but found it easier without them the second time. I got to do this twice because since I struggled getting everything lined up it looked Like I could get the throwout bearing arm in place after the trans was in. I couldn't.

I agree with Hookalatch (remove downwards/below using a floor jack), although I foolishly once somehow removed/installed an SM420 "by hands" from underneath. Here are some additions to Hookalatch's nice instructions.

- Disconnect the torque-tube cover, and slide it back as far as possible.

- Support-up the torque-tube with a jack, and disconnect and remove the u-joint.

- Remove the u-joint and slightly lower the torque tube to allow you to push/knock the rear u-joint yoke rearwards.

- Jack up the torque-tube and hold it up, out-of-your-way, using the a 2x4 under it, supported/braced side-to-side inside the two frame rails.

To assist in installing the SM420, cut off the heads of two transmission mounting/support bolts, (guide pins referenced here, and, shown here ), to allow safe/correct alignment of the transmission to the clutch-housing cover (bell housing).

Thanks for all the advice. I just want to mention to Master Gabster that I don't access my laptop regularly because of retiement plans. I will make a point of returning thanks as soon as I can. You folks are a great source of information. Thanks again!

Another option is to put an 8 foot long 4X4 wooden post across the window openings of the cab and use a cable come-along to remove/install the transmission. Open the doors first, so you don't have to climb in and out of the cab through the windows!
Jerry

Any reasons to Run a SM420 Low Fill on Trans Oil - I checked it when I got this Truck -and it was Down a good 3 inches , Darn . .

What's Up
1 Ton Dual with PTO . .

???

How/where did you measure it was down three inches?

I was using the search function, found the info I needed in this thread. You guys are simply magnificent . Kudos again to the Stovebolt forum