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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