The Stovebolt Site Forums The Parking Lot Big Bolts 4 speed muncie jumping in 2nd gear

I have a 54 chevrolet 1 ton truck with a 235 engine and Muncie 4 speed transmission. Transmission casting number is 591953.

In process of rebuilding 235 so everything is out. Transmission has been 'jumping out' of second when you hit a bump in road, let off gas, etc. Not every time, but often enough. All other gears, including reverse, are fine.

What is wrong/worn and how do I fix?

Maybe the 2nd gear synchronizer went out?

Robert
Perhaps. We were wondering the same and also wondering what/how much to rebuild. I note that rebuild kits are available which include synchros. Best probably to do the whole thing while it is apart. Won't be a better time.
Thanks.
Jones

Yep, rebuilding the whole thing while it's apart would be your best bet. That way you know nothing should go wrong with it since it's been rebuilt.

Uhhhhhhh think thats a sm420 isnt it..??? uhhhhhhh thats typical of those xmissions... and sycronizer wont fix it... the 1st second shift collar and second gear on main shaft need replaced...and theyrer dang hard to find... i looked last month,,and did finally find them at someplace in PA...but they wanted 180 bucks for the collar,,,and 190 for second gear... If ya can find a used one that works...might be cheaper...ive got three here that i dont know if theyre any good but the guy wants 250 for them... ive got two used ones...LOL..thats jump outta second...hehehe soooooo if we can find someone that its jumpin outta Hi...then we can fixem up.... course it could be a bent fork...or rail... or detent on rail gone...but i really doubt it... its hard to see too...but if ya pull the top off...ya can see second gear...and if there is any taper then they will jump out....sorry.....

Jones,
Does it jump out of second gear with "vigor". Sometimes the clutch gear, or more commonly known as the input shaft if worn out. I had this happen and couldn't see the malfunction, but a replacement cured it. Be sure to put a new pilot bearing in the crank when you re-do the motor. The detents in the tower for
the shift collars aren't suppose to keep the
gears engaged they just position them where they are suppose to be. Like fatweed said, the collars can be bad and cause problems too.

Stuart.

I have seen a snap ring keeper that let go & caused the same symptoms. Brian

yeah, what they said..... (or maybe a syncro). at any rate, if yer gonna crack the case, then why not rebuild it?

check with a company called power train service in indy. they usually carry some hard to find stuff.

maybe time for a 5 speed with overdrive?????

Thanks for the help. I will check things out
with an eye toward these problems.

Anyone bolted up a 5 spd with OD to a 1954 235?
Which trannie? Any adaptor plate needed?

What is cost of this setup?

Many thanks, again.

The 5 speed swap is very popular. See the tech tips part of this websight & search the posts. There have been a lot of info about it.