The Stovebolt Site Forums The Shop Area Driveline Parts source for rebuilding a 3 speed tranny

Looking to see if anyone has a source for parts to rebuild a 3 speed transmission. I have a 53 3100 with a 3 speed tranny I wanted to rebuild while I had it removed from the truck. Jim Carter and the Filling Station have various gaskets and needle bearings listed as a rebuild kit but those are somewhat lacking. I did not want to take the transmission apart until I knew I had somewhere to obtain parts. A fellow Bolter already told me he thought I needed the 2nd gear cluster based on our conversation. Any info would be appreciated.
Here are the numbers on my transmission.
Just below the shifter levers on that cover is 3686832
Same side but lower is a large 7 then under the seven is the letters GM then under that 591615
On the fwd cover by the shaft is 581620

Deegs

1953 was the transition year for the SM318 from the two lug synchronizer to the four lug synchronizer. They also made some change to the gears. The casting numbers are the same for the early and the late but the internals are different. You really need to disassemble your transmission to see what you have.

It is possible you may find what you need through Wade Transmission & Gear here in Dallas. Some of the stuff is no longer available but these guys are known to keep old inventory. I've dealt with them for 50 years.

https://www.wadetransmission.com/manual-transmissions/

Good luck.

You've got the standard 3-speed transmission use from 48-54. It's called an SM-318. Some parts are unobtanium like the 2nd gear synchros, but eBay has various parts from time to time.

Unless the gears are pitted, they're likely OK. A common rebuild is to replace bearings. The ball bearings would have numbers on them that can be crossed to modern numbers, and should be obtainable at any bearing shop. There's no "2nd gear cluster" but there is a slider that has 2nd and 3rd synchros and that the 1st gear slides on.

HERE's an illustration of your transmission. If you browse thru section of the Service Manual (select previous or next page on the link) you'll get a better understanding of what's in there.

[on edit] Do a google search for "sm318 transmission parts" and pick your poison.

Looks like the other guys have gotten their licks in before me. Good info.

Please look closely at the first/reverse gear. There's one on eBay now at a decent price (new, old stock) eBay item number 405149399064. If a prior owner used first gear as a downhill brake, that gear can suffer...please look for broken teeth edges/corners or simply over worn parts. You'll know if it is worn if you hear a lot of whining or if it wants to jump out of gear frequently.

Thanks Guys I appreciate your information and links to possible resources. It helps when you can get info from others who have prior experience.

Deegs

I just saw this, but earlier this year I got the 2nd/3rd gear synchronizer from All American classics in Vancouver. You will have to call them 1-800-955-4999 the website will not show their stock. They will physically go check and call you back. If the have another it won’t be cheap. 💵

Thanks I will give them a call.
Deegs

Deegs, Just to follow up with what "crenwelge" posted, The two different 2nd to 3rd gear synchro hubs are identified as GM# 605020 (1940-53 3 speed - two lug - 24 external spline) and GM# 37051122 (1953-54 3 speed - four lug - 24 external spline). Doing a little web surfing this morning I found this listing with both parts potentially being available. You would need to call the number at the top of the page for availability and price, but a possible option if needed.

Once you get into your transmission and figure out what your needs are, let us know and we can continue to offer help and leads.

If that first/reverse gear is chipped, take a close look at the countershaft gear that it meshes with. Also look closely at the splines on the input shaft that mesh with the synchronizer drum. Check that they are still straight and true with no bevel or wear on one side. That is one of the main causes of jumping out of 3rd.
They're not hard to work on, just need a lot of patience and two homemade tools... a thin wrench to remove the input bearing retainer and the tang end of a large file to open the retainer holding the center bearing in place.
Ask questions... We're here to help.