76 Cj5 Transmission Help

I have a 76 CJ5 with the 304 and a 3 speed transmission. I've only had it for a few months, and only really drive it on the weekends. It's the first Jeep I've owned, and I'm learning a lot about it right now.

I haven't had any issues with it in the few months I've owned it, and today I was driving to work, maybe 10 minutes into my commute, had just jumped on the interstate, and was probably going 65-70. All of the sudden, the back tires locked up and there was a crazy high-pitched squealing noise. I pulled over, turned the Jeep off, and started looking for something, anything, and there was no signs of damage from the outside. I got in, started it up, and it slipped into first and drove to the next exit. Couldn't find anything, figured screw it, and drove the remaining 15 minutes to work on the interstate, no more issues.

I was just on my way to lunch, and in second gear, mid-range in the RPMs, going up a decent incline, it did it again.

I have absolutely no clue where to even begin troubleshooting or what to even Google for. It's somewhat intermittent and isn't obviously catastrophic, but I know I probably have a big problem on my hands.

Please help!

 

I'd get it home. Don't drive it until you figure out what is wrong because it's going to leave you stranded and maybe damage things more. First thing, drain the trans (3spd manual?) and look for clues in your oil (metal). You may have seized a bushing or bearing?

 

I did end up getting it trailered home. Thanks for the suggestion, I'll drain the oil and take a look.

Yes, 3 speed manual, sorry, I didn't specify.