Rear End Howl on Decelleration

I'm starting to road test my Healey. When it is at speed or accelerating the rear end is quiet. When the car is decelerating I am hearing a howl from the rear end. The rear end has new bearings in it. Any thoughts on the cause?

Thanks,
Larry

When the bearings were replaced,was the backlash re-checked? Generally, a howl or whine on coast indicates insufficient backlash, or the ring gear engaging the pinion too deeply. I don't know the correct setting, but would guess it's in the book.
Bugeye58

I think that Bugeye is sort of on the right track except - everything that I have read & personal experience lead me to believe that he has stated it backward. I think that a whine on coast is usually caused by too much ring to pinion backlash or insufficient preload on the pinion bearings. The other possibility is loose pinion bearings which I doubt since you said that the bearings are new. If the whine happened during acceleration, then Bugeye would be correct.

In any event - It would be better to get it fixed now before it causes abnormal ring & pinion gear wear. The problem is not likely to get better with time. Don't buy the "it just has to wear in a bit" story that some repair shops try to give.

The correct ring to pinion backlash setting is marked on the end of the pinion gear & I believe it is in the range of .008 to .014 as measured at the ring gear. The most likely cause of this problem as Bug says is that the incorrect thickness of pinion bearing depth shims is installed. The other possibility is that the carrier bearing spacer collars were incorrectly installed.(side to side)

All of the above assumes that the gears were not noisy before the new bearings were installed. If they were, it is possible that excess ring & pinion gear wear due to improper previous adjustment is causing the problem. Sometimes one of the pinion bearing spacers/shims breaks up in a well used differential & changes the setting of it's own accord. This would normally be detected at the time of bearing replacement.
D
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Bugeye58:
When the bearings were replaced,was the backlash re-checked? Generally, a howl or whine on coast indicates insufficient backlash, or the ring gear engaging the pinion too deeply. I don't know the correct setting, but would guess it's in the book.
Bugeye58<hr></blockquote>

Dave, I'll stick by my original statement regarding diff whine on "coast", but with limited experience on big Healeys, I could be entirely wrong. I did go back and read the diagnostic sheet in a rear axle textbook I have, and it said the same thing I did.
The numbers etched on the head of the pinion are the variations from "nominal", and are used for selecting the correct shims to establish the pinion depth. Provided you have the zoomie little special tool. I don't know about the Big cars, but on the Spridgets, the correct backlash numbers are etched on the back of the ring gear, and, as the ring and pinion are matched sets, are only applicable for that particular combination.
If I'm way off base here, let me know. I've eaten crow before.
Bugeye58

Bugeye
Far be it for me to question your book.
The information that I gave is from the big Healey shop manual & from my personal experience. Others may differ.
D

Dave, I bow to your greater experience concerning the big cars. So, Larry, consult your shop manual, and see what it says.
Now, Dave, may I have Hollandaise sauce with that crow?
Bugeye58 (Jeff Dahn)

Jeff,
I'll bet that I have been wrong more than you have. With greater experience comes more chances to screw up.

Dave, I'm having lunch Tuesday with a bunch of GM engineers, and I will ask them the question regarding Larry's problem. I mean, after all, gearsets are gearsets, regardless of who makes them, right?
I'll post their response tomorrow afternoon.
Keep the Hollandaise from curdling, will you please!
Jeff

Update to Larrys'noise problem. We have formed an Engineering Analysis Group to evaluate the complaint. Results to follow shortly.
Bugeye58

Guys,

Thanks for all the help. It looks like I'll be
getting into the rear end to do some shim adjusting.


Larry

OK, It took two lunches to hash this out, but the consensus was that the pinion is engaged too deeply into the ring gear. Decrease the thickness of the shim under the head of the pinion gear. You could probably also use less shim on each side of the carrier bearing to achieve the same result, and it may be easier to do.
Bugeye58