Grinding During Engine Braking
 

Hey folks,
My 84 TA is making a grinding sound when I take my foot OFF the gas in gear; noise happens in all gears. As soon as I give it the slightest bit of throttle, it goes away. I also get the same grinding at all times in reverse. Noise seems to be coming from the transmission, am I looking at a worn clutch or stripped gearbox? I suppose it could also be a wheel bearing, but that doesn't explain why it disappears so suddenly.

Thanks for any suggestions!

Re: Grinding During Engine Braking
 

Could be a throwout bearing. What about if you press the clutch in while coasting, does it go away?

Re: Grinding During Engine Braking
 

Yep, it goes away when I press the clutch in.

Re: Grinding During Engine Braking
 

Narrowing it down.... What does it do in neutral while coasting, and clutch out?

Re: Grinding During Engine Braking
 

It could also be a rear end noise they tend to transmit through the torque arm.

Re: Grinding During Engine Braking
 

That's where I was heading...pinion bearing

Re: Grinding During Engine Braking
 

Just drove around for a bit. I get grinding while coasting in neutral with the clutch OUT. Once again, noise goes away when the clutch is IN. Throw-out bearing?

Re: Grinding During Engine Braking
 

Throwout bearing

Re: Grinding During Engine Braking
 

Thanks everyone for the help, I'm floored by how fast you all responded!

Re: Grinding During Engine Braking
 

It's a good knowledgable group.

Re: Grinding During Engine Braking
 

Hold on, guys.
Throwout bearing typically makes the noise with clutch pushed in.
I'm going with Bob's original statement: pinion bearing.
Symptons are classic.

Re: Grinding During Engine Braking
 

Thanks for the reply. I'll probably have to replace all the bearings, the car was neglected for a time and they're all in questionable shape, but cheap. What I was really worried about was stripped gears, which it sounds like it isn't.

Re: Grinding During Engine Braking
 

A friend of mine had an issue once where the thrust bearing of the crankshaft was worn out. This allowed the crankshaft to move forward and backwards in the main journal area.
​ You can observe this by watching the crank pulley or harmonic balancer while someone revs up the car or engages/disengages the clutch. If the crank moves too far forward, then the flywheel could be rubbing up against the back of the block.

Re: Grinding During Engine Braking
 

Sounds like the rear gearset, on the coast side since it goes away when he gives it any throttle, my car does the same thing

Re: Grinding During Engine Braking
 

When i busted a tooth off my pinion gear I had 3 people swear the sound was coming from the trans area. That tq arm is tricky

Re: Grinding During Engine Braking
 

UPDATE for you guys:
Pinion bearing was the winner! Bought a rebuild kit, had a shop replace all bearings in the diff, grinding sound is gone. Interestingly, they said that there was no preload on the pinion when they opened it up, so that bearing was set up to destroy everything. Glad I didn't have to learn that one the hard way. Thanks again everyone for your help in diagnosing the issue!

Re: Grinding During Engine Braking
 

There never is, if it has more than 20k miles or so on it.

I kinda wish there was a way to reset it periodically, like we do with front wheel bearings. The comparison is actually fairly comparable. Problem is, especially with a crush sleeve, it's REAL hard to measure pinion bearing preload properly, let alone SET it, whereas it's pretty easy w front wheel brgs; but in reality, only a VERY TINY amount of bearing wear, affects it DRAMATICALLY. Again, just like front wheel brgs.

Once it goes away, the bearings start failing MUCH faster, since they are no longer held in proper contact. The small "tail" bearing, the one behind the yoke, usually shows it up first; but sometimes the larger "head" bearing does. Most rear ends that whine under ONLY either acceleration or coast need bearings, not gears.

If there was a way to restore it occasionally, there'd be AHELLUVALOT less wasted rear axles in the world. Unfortunately I have no solution I can offer. I can only state the problem clearly, but not the solution.

What's this? "Shop" is something women do for handbags and shoes; are you saying some of those will actually mess with your rear end? (well, your car's, that is)

Re: Grinding During Engine Braking
 

Wouldn't a solid pinion spacer solve the problem? Since you put it in with shims, you can just remove shim to tighten it back up.

Re: Grinding During Engine Braking
 

I us solid pinion spacers in all my rearend rebuilds.

Re: Grinding During Engine Braking
 

I use those too; but the bearings still wear, and the preload goes away as a result. But since I can tighten the nut MUCH tighter that way than with a crush sleeve, at least it doesn't back off.