Popping/banging under load/acceleration

[hafner]

Hi all,

If I'm accelerating uphill or giving it more than partial throttle, my 1978 Wagoneer Quadratrac seems to give a couple of short pops or bangs - mechanical, not backfiring. It happens only when going straight, and under load/acceleration. On the freeway or in gradual driving, it's fine.

My shop seems to think its a problem in the rear diff, possibly a spider gear problem, and wants to pull and tear down the rear axle. I'm less convinced; I would think that problems with the diff would surface mostly when turning.

I'm inclined to wonder if it's the Quadra-trac chain jumping under load and if it's time for a bright shiny new BJ's chain, but the shop insists it's coming from the back of the Jeep.

I understand nobody here has x-ray vision, but is this painfully clear to anybody who has dealt with this before? I'm being quoted a lot of money to pull the rear axle and tear into the rear diff even to diagnose.

[ZiRiu]

It's getting close to winter so you could always inspect the diffs and xfer case while doing a fluid change. Should be easy to see if something has gone wrong in there.

[babywag]

Sounds like a QT chain to me, inspect it for stretch. If it(chain) breaks the case will explode like a grenade. I've had it happen twice, and it isn't pretty.

There is a plug on the bottom of the case to check the chain for slack/stretch.
You'll need new QT fluid.

[FSJunkie]

I'd probably pop the cover off the rear diff before I tore into the Q-trac.

There is an inspection hole on the bottom of the Q-trac for checking chain tension. I'm sure some other guys on this forum know more about it than I, so I'll let them explain how it's done.

[fulsizjeep]

Jeep QuadraTrac TSM:

http://www.jubileejeeps.org/quadratrac/77jeep_qt_tsm.pdf

I would check the chain tension first. If that looks OK, drive it around the block a couple times with fresh fluid then do a torque test. I think you'll find the chain is loose. Once the chain starts popping/clunking you are on your way to detonation. Popping can also be torn spline in one or both brake cones.

[mokurt]

Hi all,
My shop seems to think it's a problem in the rear diff, possibly a spider gear problem, and wants to pull and tear down the rear axle. I'm less convinced; I would think that problems with the diff would surface mostly when turning.

Not necessarily.
I had the spider gears go out once and it popped going straight.Had to drive in front wheel drive.

Should be able to just pull the cover and check for chunks of metal.If it's an open diff.,you can see some of the gears.

[tgreese]

Chain tension. Worn out QT chain. See Flint's post.

[Schlagger]

Could be wicked bad ujoints. Ask me how I know. Easy enough to check and eliminate it as the problem.

[hafner]

Thanks, everybody, for all the great advice and resources. I'll update once we figure out what's going on.

[azmtn04]

It helps to update threads for those looking for answers.

[tgreese]

It helps to update threads for those looking for answers.

You could send a PM to the author. He visited the forum last on 10/30/17. Sometimes life interferes, and he may have nothing to report yet.