The Stovebolt Site Forums The Parking Lot Big Bolts 1966 C60: Rebuild Trans or find O/D?

I recently picked up a 1966 C60 and it seems like the syncros in third gear are pretty far gone. The truck has the 327 and a four speed trans. Have to be pretty patient and sometimes double clutch it to get it to go into gear. With a load on the back those extra seconds of fighting the trans equate to a lot of momentum loss! The truck will go ~50 mph if pushed, but in an ideal world I'd like to get 60 mph out of it.

The question is, is it worth rebuilding the transmission or should I be looking around for another transmission with overdrive? I've done a little searching and it seems like the O/D transmissions do exist that would bolt right up, but aren't readily available? The part I haven't looked into is how hard it is to rebuild the trans and/or how readily available parts are going to be for it.

Any suggestions or insight would be welcome!

I'm not too familiar with a newer type trans swap, but the old way would be to install a 2-Speed or 3-Speed Aux Trans with an Overdrive behind what you have now.

Do you feel like your Trans now is about to give up or is it just hard to shift into 3rd?

I had a 5-Speed in a '62 that had trouble getting into 3rd, but Double-Clutching it every time cured it. I would actually Double-Clutch every gear anyway and after a while, you would actually forget it had an issue, lol.

You need to establish what trans you have before the question of who can supply parts can be answered.

Your truck would have the SM-420 4-speed as standard issue or it could have been ordered with a NP-435 4-speed.

The SM-420 has the PTO on the drivers side and has this shift pattern;

...1..3
R..2..4

The NP-435 has the PTO on the passenger side and has this shift pattern;

1..3
2..4..R

Mike B

Most 2 speed rears have slow and slower ratios. Figure out what your existing ratio is to start with. NV-4500 is an OD thanks that would work. SM-420's are easy to rebuild.

Ed

Overall, the trans feels ok it's just third gear that has issues. The shift pattern matches the SM-420.

What was the NV-4500 available in originally?

Isn't there a 5 speed trans that came in 90's pickups that was fairly heavy duty? I haven't looked for years but I think it is a big ugly aluminum thing .I suppose all the bolt patterns are wrong though.

4500's were installed in GM and Dodges from the factory. Dodge bolt pattern have longer input shaft, 1"(approx.) spacer with old GM bolt pattern fits GM, or drill and tap GM case with old GM pattern.

Early 6 speeds(forgot the model desig.) with an integral oil pump were in GM(only a few years) and Fords. Lots of parts support for 4500's.

ZF in modern Dodge and Ford.

Ed