The Stovebolt Site Forums The Shop Area Driveline What tranny and year?

Wondering what tranny this is and what year it is from.

Brendan - It's an MKT-134 "Crash Box" 4 speed used in Chevy and GMC trucks from 1931-47. Non synchronized and the predecessor to the SM420.

From the casting date code on the main case "K309" decodes as November 30th, 1939 for the casting date. The shift tower casting date code "L 19 9" decodes as December 19th, 1939.

If you can find the serial stamped onto the rear of the main case, we can decode that info to figure out what model truck it was originally installed in.

Thanks Dan. I will look for the serial.

I reached down to feel the corner of my trans, but didn't feel any numbers. But using a mirror I could see the numbers were a little more towards the center.

Dan - is it possible it is a 1949? I ask because I was told the motor and tranny came from the same truck and the 235 I believe is a 1949. Distributor deck #GEA 854 bb
I am going to look for the serial # of the tranny today. Maybe that will help confirm. I am a bit ahead of myself in this search for info but those numbers were staring me in the face the other day so I got sidetracked from my brake bleeding.

Brendan - Unlikely to have been a '49 as the "Crash Box" which we confirmed by the casting codes was replaced by the SM420 by then. I did some digging in the GM Heritage Archives and found the "PM" serial number prefix Utah John posted above is actually associated with 1946 Chevy 1/2 and 3/4 ton truck as RPO 318 (4 speed option) for that year. Looks like he has an original to his truck transmission.

Best SWAG considering the casting date codes on the case and top cover on your 4 speed is it make me think your transmission is a very late '39 or early '40. The serial number will be the tell all I think.

BTW - The "GEA" engine prefix was used on 1949 6000 series trucks according to the 1949 Chevrolet Truck Data PDF, but "PM" prefix not used on an transmissions that year so very likely from two completely unrelated trucks.

Let me know what you find on your serial number and we'll hunt more details down.

Good to know. Thanks Dan!

Tranny serial number 7037606

Here you go Brendan!

1940 Chevrolet Truck Data PDF (extract below) shows your serial number sequence beginning with 7000001 was used to identify 1940 MKT-134 Crash Box 4 speeds which where optional in 1/2 thru 3/4 ton trucks and standard equipment in Conventional Heavy Duty trucks, School Bus Chassis and COEs.

Perfect original year correct optional 4 speed for your 1940 1/2 ton if that's what you want to use.

Wow. Thanks Dan. This puzzle is starting to come together and make sense. My brother thought dad swapped the motor and tranny but he was pretty sure it was always a 4 speed. So it is possible that is the tranny the pickup left the factory with?

Brendan - I'd venture that it probably is in fact the original transmission for the truck. But either way, that serial number puts it in the "close enough" category to say it is IMHO.

Have you ever posted the truck serial number/data plate info? I peeked through your previous posts and couldn't find anything on that. If you can share that info, we can do a little further decoding to better ID where it was built and other related details.

I don't believe I have Dan. I think I had deciphered most of the info but here it is. Please correct me.
21KC037241
21 = Janesville Wisconsin
KC = Light Delivery
0 = 1940
3 = March
7241 = production number

Brendan - You have the decoding dialed in.

Of note is the fairly low production number. They actually started at 1001 at each plant, so yours would have been the 6241st truck (that's of all trucks, not just 1/2 tons) produced on the Janesville line. That equates to a fairly early in the model year build and pretty much coincides with the casting dates on your transmission too.

FYI - Last fall I came across and acquired a Chevrolet Dealers "Confidential Price Book Cars, Trucks & Equipment" for 1940 which now resides in my Stovebolt Library. It came from a dealership in Oregon, MO and has a ton of original documentation, letters, order sheets and sales flyers for Chevrolet and aftermarket accessories. If you are interested, perhaps I can take pictures or scans and share them when I have an opportunity. Since this is kinda swinging off-topic, send me a PM and we can chat further on this topic.