The Stovebolt Site Forums The Shop Area Engine Shop Need help identifying a tranne

I need some help identifying this trannie that I recently bought. I bought it under the assumption that it was an SM420. I took it apart and noticed that ALL the gears were straight cut and there is no synchro! :confused: Here are a few pictures:

http://www.pirate4x4.com/forum/attachment.php?s=&postid=461967

http://home.off-road.com/~md11fr8dog/Graphics/SM420GearSet.jpg

http://www.pirate4x4.com/forum/attachment.php?s=&postid=459978

http://www.pirate4x4.com/forum/attachment.php?s=&postid=459464

Its by diganosed as a 1940-47 GM truck trannie, part #185 by someone else. The seller still insists that its an SM420, stating he got it out of a '50 GM 1 1/2 ton truck. Any advice? Anyone ever seen an SM420 with ALL straight cut gears and no synchro?

Thanks

only one of your links worked, MD11Fr8Dog. I think you got screwed, man. is there a shift pattern on the shifter knob? heres what the sm420's shift pattern is.

[img]http://community.webshots.com/rz/r1/0/18/26/29701826YcXmvnLmyb_ph.jpg[/img]

The sm420 had syncros on 2nd, and third gear. Reverse and first were straight cut, and 4th is direct drive.

Get back to us soon.

Sean , what you have is identical to the original box in my '40.

The gear lever has a wee lever to lift to get it into reverse. Definately no syncro.
A good tough box , but not an SM 420.

These were common in all the bigger '40 - '47 trucks , and optioned in the smaller ones

What are you planning on fitting it into ? .

Yep, I have manual pages for the SM420, just trying to figure out with this thing is. The PO still thinks its anSM420 since it came out of a '50 truck! I asked how he was sure "its the originally trannie, after all, isn't that what we're doing??"

Thanks

I was planning on using it in my 75 FJ-40 Land Cruiser with an early 3spd t-case and rebuilt original 2F inline 6. The grannie gear in the SM420, at 7.05:1 is about the lowest out there! [img]http://www.pirate4x4.com/forum/images/smilies/smokin.gif[/img]

Your observation confirms my friends research about it coming from a '40-47 truck!

Thanks

Yup, it's not a 420, I have one in my truck, it's original, and it's a '50. 1st gear isn't synchro'd in the SM420, but the rest are, as you probably know. If you don't mind double clutching the crashbox you have is ok and probably stronger than the 420 but it will be a pain to drive on the street, loud, and is hardly worth anything- A real SM420 is probably worth 3 times as much. The pre-SM420 chevy 4speeds had the same ratios I think as the 420s but were not sychronised in 2nd-4th gears. The cases look almost the same in both of them but the shifter on the crashbox has a reverse lockout lever and the shifter on the SM420 doesn't. I suggest you either get your money back or use the tranny you have if you are not going to drive on the road and are good at double clutching. Have fun with your cruiser.

Yep, sending it back to the seller, unless someone on this board wants it!!

Thanks