noises following pinion seal replacement

4773 Views 6 Replies 6 Participants Last post by Feterbush, Apr 22, 2020

pgilland

Discussion Starter · Aug 7, 2011

Hello all, many thanks in advance for taking the time to read this post.

1) I replaced the pinion seal, tightened the pinion nut good and tight with a 1/2" socket wrench and topped off the differential oil.

2) While under the I noticed the drive shaft support was old and there was a bit of free play. The transmission mount appeared to have been recently replaced by PO.

The car now makes a horrible bearing noise not while driving down the road, but only while coasting in neutral. It almost sounds like something is dragging on the ground as well (I originally thought maybe I left a tool up while working). I put the car on jack stands and ran the motor in gear and could not replicate the noise. The differential makes some noise, as heard through a stethoscope, however I am not sure what I differential is supposed to sound like so it may or may not be normal.

So, it makes a noise while coasting in neutral - which is strange to me. Any ideas?

thank you,
Paul

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Alfajay

· #2 · Aug 8, 2011 (Edited)

pgilland said:
1) I replaced the pinion seal, tightened the pinion nut good and tight with a 1/2" socket

Paul:

I'm not sure exactly what's wrong. But, if something changed after doing the pinion seal, then that job, and not the drive shaft support, is probably the cause.

The thing that jumped out at me in your description was "I ... tightened the pinion nut good and tight with a 1/2" socket". My manual lists the pinion nut torque as 58 to 101 foot lbs - I'm a little puzzled by so wide a spec., and suspect that some tightening procedure is called for. Can anyone expand on this? I'd suggest getting a torque wrench, and determining if the nut is tight enough.

On my Alfas, that nut is an odd castle-style. I'm surprised you just refer to a 1/2 inch socket. Is the pinion nut on your car just a regular 6-sided hex?

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rogerspeed

· #3 · Aug 8, 2011

what happens when you depress the clutch and hold while coasting in neutral?

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Geoman

· #4 · Aug 8, 2011

When I reinstalled my drive shaft, I had a very metallic sounding groan coming from the rear end. When I jacked it up, and ran it, no noise. I found out that the small cupped spacer (?) that fits directly behind the connection between the drive shaft and the differential flange was out of place. I had moved it forward to give me more room to get at the flange nuts, but forgot to move it back. While jacked up, the drive shaft is at a different angle and the spacer doesn't rub, but when the car is down, it's in contact with the spinning flange and makes the sound. Not sure if that's it, because why would it not make a sound only some of the time, but easy to check.

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pgilland

Discussion Starter · #5 · Aug 8, 2011

The pinion nut on my 82 alfa is the castle nut, requiring the special 1/2" drive socket sold on e-Bay and sometimes at IAP and other venders.

Turns out the pinion nut gave me a false torque reading, and after disassembling and retightening the nut, all is well! Another learning experience with the Alfa...

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papajam

· #6 · Aug 8, 2011

Alfajay said:
The thing that jumped out at me in your description was "I ... tightened the pinion nut good and tight with a 1/2" socket".

That jumped out at me too.

Pinion bearing pre-load is adjusted with shims, not pinion nut torque or a crush collar. If the pre-load is correct, the torque on the nut will not change the pre-load. What happens over time as the bearings and races wear, the torque on the nut gradually gets less and less. If one now retorques the nut, or tightens it good and tight, the bearing pre-load can be so high as to prevent the pinion from even spinning!
The trick to replacing the pinion seal is to first note the torque on the nut before removing the nut. After seal replacement, torque the nut to the previous value (disregarding the torque spec in the book).

I'd wager the noise is excessive pinion bearing pre-load. To remedy this, remove the driveshaft and loosen the nut. Then tighten the nut by hand until there is zero horizontal, vertical and axial play in the pinion. Now note the resistance required to turn the pinion. Gradually tighten the nut until the resistance starts to increase and stop there. Then lock down the nut.

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Feterbush

· #7 · Apr 22, 2020

papajam said:
That jumped out at me too.

Pinion bearing pre-load is adjusted with shims, not pinion nut torque or a crush collar. If the pre-load is correct, the torque on the nut will not change the pre-load. What happens over time as the bearings and races wear, the torque on the nut gradually gets less and less. If one now retorques the nut, or tightens it good and tight, the bearing pre-load can be so high as to prevent the pinion from even spinning!
The trick to replacing the pinion seal is to first note the torque on the nut before removing the nut. After seal replacement, torque the nut to the previous value (disregarding the torque spec in the book).

I'd wager the noise is excessive pinion bearing pre-load. To remedy this, remove the driveshaft and loosen the nut. Then tighten the nut by hand until there is zero horizontal, vertical and axial play in the pinion. Now note the resistance required to turn the pinion. Gradually tighten the nut until the resistance starts to increase and stop there. Then lock down the nut.

As usual, Jim is right about this. I replaced the seal in my ‘79 Veloce but unfortunately didn’t read Jim’s posts before I’d already loosened the pinion nut and lost any chance to tell what torque it was at. But following his advice, I hand tightened the nut until the pinion wouldn’t wobble around any more when I yanked on it, then just a tad more with the wrench. It wound up being 3/4 of a turn tighter than than the mark I made before I first loosened the nut. My car had no locknut, so I ground off the punch marks from the nut and used blue Loctite to set the nut in place. The noisy diff went away.

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