- Hey Scotty, love your videos! I know you've done several on classic cars. Buying a 1974 AMC Javelin AMX 360 4-speed. Want to upgrade to a 6-speed to reduce stress on the engine and also save on gas, especially on the highway. Any advice on making the swap a successful one?
You might want to ask in an AMC forum such as the following:
https://theamcforum.com/forum/forums.html
A 6 speed is probably longer than a 4-speed, to accommodate the additional gears. In that case the driveshaft will have to be shortened and rebalanced or replaced
Here's a 5 speed: https://www.shiftsst.com/tremec-tkx-5-speed-kit-for-amx-hurst-sc-rambler-and-javelin/p162
I would hope you aren't intending on driving that as a daily driver. Next to nobody knows how to work on AMCs in a run-of-the-mill mechanic's shop anymore, nor are parts readily available for them. AMC was taken over by Chrysler in the mid '80s, in a very hostile manner and Lee Iaccoca only wanted the Jeep name. He forced as many dealerships as he could to destroy any AMC-specific parts, leaving only very limited number of AMC-specific parts that are still OEM (not the Chinese company). My father-in-law has a 1960 AMC Rambler and he knows firsthand.
I'm not sure of the specs on the "new" transmission, but you can't just willy-nilly swap out transmissions without doing a lot of homework first. The engine must mate to the transmission, and then you need to make sure the tail shaft is compatible. That car also has a carburetor, not fuel injection. It's still going to drink gas like no tomorrow.
@justin-shepherd The situation isn't quite as dire as that. At the AMC Forum that I referenced there are a lot of greasy fingers who know how to do custom modifications and restomod updates on these cars. I think 5-speed swaps are more common that six-speed but it should be possible, though of course a certain amount of custom fabrication will be necessary.
I just hope that OP is really using his head. I love classic cars too, and I had issues with replacing that rear main seal. A professional mechanic could barely figure it out.
@justin-shepherd The post-1966 newer series AMC V8s (290 through 401) don't use a rope rear main seal. The old 1950s Nash V8 engines (250/287/327) had that "feature". Pontiac was a bit of an outlier continuing to use a rope seal as long as they did.
Interesting. My mechanic couldn't figure out how to install that rope seal without taking the engine apart. Apparently, GM retrofitted a one-piece rubber rear main seal right before they discontinued the Pontiac V8. He ordered a new rubber rear main seal and he put that in, instead. It was still a pain in the rear end, apparently.
I've also never seen an AMC Javelin in person. Granted, I live in Ohio where everything rusts that's not protected. Even my Pontiac's right rear floorboard is starting to rot, and it was pretty babied.
@justin-shepherd There's really nothing exotic about the engineering in a Javelin or most other AMC cars though there are some differences one needs to take into account when working on them. For the most part they're bog-standard mainstream practice for the time they were built.
It's mostly some of the pre-1970s models that have wacky stuff in them like trunnion front suspension and torque-tube drive that will get your head scratching if you have to work on them.