The Stovebolt Site Forums The Shop Area Engine Shop Trans question

I bought my truck a couple of months ago. It was not running when I bought it. It is a 53 1/2 ton with a stick on the floor. The place I bought it from told me it was a four speed. I am not sure they knew what they were taking about, they never drove the truck. If it is a 4 speed, I assumed it would be SM420. Since the truck was never running, I have not been able to check it out. The truck does not have any information on it about the trans. Some great people on this site helped me identify the motor as a 235(it was changed before I bought it) and so I am back for more expertise info.

Can anyone tell me how to determine what trans it is, how to identify (numbers and location ect.)?

Can anyone tell me where reverse would be, and would that help confirm if its trully a 4 speed or 3 speed.

Thanks for your help!

An SM420 has a rectangular plate held on by a handful of bolts on the driver's side of the transmission for a pto (power take off).

Reverse is all the way to the left, and then back. The stick should move easily between the 1-2 and 3-4 slots, and require a bit more force to come further left for reverse.

Post a picture. They aren't hard to recognize.

If the tranny is original, or same as original, it would have to be the 4-speed, being a floor shift (with the shifter coming right out of the top of the tranny). The 3-speeds were column-shifted, and the shift levers are on the side of the case, connected to the shifter with linkages. If the tranny is not original, having been swapped with the engine, it could be either.

If you can find the serial number on the tranny, it may tell you if it is the original to the truck (or at least the original year). Assuming an SM420, the serial number is stamped on the rear of the case, toward the right side, just below the top edge. Casting numbers can be found on the side of the case (I forget which side), along with casting date codes (a letter followed by 2 or 3 numbers). Check here for a picture and a listing of possible casting numbers.

Did you ever get any numbers off your engine?

The trans comes through the floorboard. It does not appear that it was ever mounted on the steering column.

OldSub, thanks for the info on the reverse. I will take a photo Sat. 28th and get back to you.

Xram53, I hope to get the numbers off of the motor and trans on Sat. the 28th. The next available time to go where the truck is stored.
I will get with you when I get them.

Once again you guys have a great wealth of information for me. I can't believe how nice everybody is and you all never make me feel stupid. This dream truck (aka rust bucket basket case) is my first restoration of this scope, not counting a VW Thing (very simple) I restored. I am 39 years old and I love all the learning that I am doing at this site through all the helpful people. Like a kid in a candy store.

Check this site for pictures of an SM420

http://www.jeeptech.com/convtrans/gm/gmsm420id.html

LT

Lt,

Thanks, that will really help me know what I am looking at.

One of those pictures shows a part on the rear, I purchased on ebay from a memeber of stovebolt, which will convert it to an open driveline and get rid of the tourque tube. I bought it believing my trans to be the SM420. I knew if it wasn't I would re-sell it.

I don't know if I can wait until next Sat. to look at it! I have to know sooner.