sm 420 is a muncie and were in light duty gm trucks from 47 to 67.
10.43 in length
7.05 1st, non-synchronized
3.57 - 2nd
1.70 - third
1 - forth
4.686 retainer
i looked for a 420 for my jeep cause of the length but i ended up using a
sm465 which replaced the 420 but is 12.00 in length and has a low of 6.54
after the jeeps drivetrain was done i did find a couple of 420's one was in
a 2 ton 47 chev. another that i kept, came out of a 64 gmc 1 ton (canadian
version used chev drivetrains)and had the hand brake on the ass end.
steve 55TF gmc w/ 283
78 CJ7 (levi special)- 70 LT1 350/sm465/205 transfer case/dana 44 rear w
lockers
varanus@phoenix.net
Reply-To: varanus@phoenix.net
To: oletrucks@autox.team.net
Subject: [oletrucks] sm420 history/data/discussion needed
Date: Sun, 16 Feb 2003 11:48:06 -0600
I am tired of being in the dark on these sm420 trannies used in our
(47-54?) 55-59 (and up to 67?) gm trucks.
as with everything in my life, i want to know everything there is to
know about them. such as:
1.) EXACTLY what years were they used?
2.)How many configurations are there? (i've noticed what I think
were slight differences on housing castings - different ridges on top
plate or whatnot). Also, a list member says he has sm420s with
handbrakes. EXACTLY what trucks were they offered in and was
there a difference between a 1.5 ton 420 and a 1/2ton 420?
3.)I know the 420 to be a Muncie. What exactly does this mean?
Muncie manufactured this tranny for GM? Is that what the M in
sM420 means. If so, what does the S mean? What is the Muncie
part number for this trans?
4.)the 420 seems to be popular with offroad applications. i think the
ratio was 7.05:1. Is this correct?
5.)Where can I get parts list and detailed diagrams on this trans?
6.)my local trans shop quoted me $700-$800 to rebuild my 57 420.
I spoke with 2 obsolete trans parts suppliers and the parts I needed
came out to about the same as the trans shop quote. have ya'll
had similar prices quoted to rebuild your 420 4 speeds?
I think that about takes care of my immediate questions - lol.
I'd appreciate any and all data anyone can provide on this trans.
Thanks a lot ya'll.
Charles
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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