New Old Truck Woes

[PossumJr]

So I'm new to the world of FSJs and hoping people with more experience mechanically/FSJ wise can help me out here.

I recently acquired my J10 and have been trying to work out the gremlins as I find them. So far I've had no indications of drivetrain issues other than U-joints that need to be replaced; today I decided to try it out for an extended highway jog to work. After about 15 minutes of 65-70 mph (no idea how far off my speedo is) I hear a single loud *clink* followed a few seconds later by another, I was loosing speed and giving it gas only revved the engine. After pulling over I noticed a slight whif of something that smelled hot that wasn't the usual smell of exhaust that surrounds my truck and a subtle ticking noise. After a few minutes it subsided and I was able to drive off without issue and made it through 30 miles of back road driving just fine. (Probably shouldn't have pushed my luck but at that point I didn't care)

Anyone have any ideas what caused this? TH400 need attention? Quadratrac?

[tedlovesjeeps71]

What year J truck is it?

[tedlovesjeeps71]

What year J truck is it?

[PossumJr]

1979.

[tedlovesjeeps71]

What's the fluid in the quadratac look like? Just a guess (as that's all I can do on the interwebs) but maybe the fluid is low/old and not letting the coupler work/was sticking? Maybe flush and fill with proper q-trac fluid?

[PossumJr]

Wouldn't be surprised if the QT fluid is gnarly, my next to-do has been to tear into it and replace chain, fluid, etc so I've put off looking at it and the low-range box. I'm likely not putting off too much longer after today.

[derf]

I'd probably look at the transmission as well. Especially if you're going to pull the transfer case. A 40 year old tranny is probably not in pristine working order.

[candymancan]

When i got my 90 GW i never checked the transfercase fluid right away because the bolt to remove it was like a huge 1 1.2 inch socket i didnt have. 2 months later i got the socket and checked.. and it was completetly empty. Like nothing in it.

I filled it up and ive put 25k miles on it since oddly being dry didnt hurt it at least from what ive seen which is lucky lol.

I know off top and i cant help your ussue but i felt like posting this lol

[rocklaurence]

My guess would be tranny--fluid or shifter.

[letank]

After about 15 minutes of 65-70 mph (no idea how far off my speedo is) I hear a single loud *clink* followed a few seconds later by another, I was loosing speed and giving it gas only revved the engine. After pulling over I noticed a slight whif of something that smelled hot that wasn't the usual smell of exhaust that surrounds my truck and a subtle ticking noise. After a few minutes it subsided and I was able to drive off without issue and made it through 30 miles of back road driving just fine. (Probably shouldn't have pushed my luck but at that point I didn't care)

Anyone have any ideas what caused this? TH400 need attention? Quadratrac?

a clink can be a part that abruptly separated and bounced over such as a front brake dust shield, explaining the slow down,... otherwise, exhaust heat shield, exhaust hanger, the ticking may not be related, but a sudden observation due to the clink. Ticking noise can be anything anywhere, time to check for exhaust leaks, the quality of any drivetrain oil.

Do you have a QT with part time kit?

Use a gps to have an idea of your speedo