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- - Transmission ID? (https://67-72chevytrucks.com/vboard/showthread.php?t=700857)

Transmission ID?

I'm not familiar with these two models, can anyone ID them?

Re: Transmission ID?

Pretty sure that the first one is an SM 465 by the reinforcing ribs in the case casting and the second is an SM 420 by the lack of the reinforcing ribs. Not 100% as Im not totally familiar with either of these.

Re: Transmission ID?

The first is an SM420. SM465's have two PTO ports, SM420's have one.
I don't know what the second is.

Re: Transmission ID?

X2 dieseldude ... looks like the 420 had the add-on back-up light kit ( found it )second one is a New Process 435....limited distribution in GM & Chevrolet trucks from 1968-1972

Re: Transmission ID?

Neither one looks like the other SM420's that I have, with the telltale bulge on the right side. Unless the design changed over the years? I have probably half a dozen 420's and none have that ribbing.

Re: Transmission ID?

Late model 420's IE '67 have the ribs.

Re: Transmission ID?

This will help

The SM-420 4-speed transmission was produced by General Motors between the years of 1947 & 1967.
It was the standard transmission for GMC 2500, 3000, 3500 & 4000 series Trucks, & an option for 1000 &
1500 series trucks. There was no option for any other transmission in GMC 2500 & 3000 Series Trucks.
Starting in 1966 General Motors offered the NP-435GA for its light truck applications as an option.
The NP-435-GA became the standard 4-speed some time in the late 1960s. The cast iron case with large
bulge on the passenger side makes the SM-420 easy to identify. Ribbing was added to the bulge on
later cases, my 1965 GMC 2500 has this feature. The ribbed SM-420 case should not be confused with
the later SM-465 transmission. How can you tell which 4-speed your 1966 has, if reverse is to the
driver & down, it's the SM-420, if to the passenger & down, it's the NP-435-GA. The SM-465 Replced the
SM-420 in GMC truck in 1967. The General Motors Transmissions are also called Muncie by many folks.
SM = Synchro-Mesh, NP = New Process.

http://6066gmcguy.com/SM420.html