Rear Diff Whine

[bkasl]

When I decelerate there is a whine from the rear differential, of course always sounds worse with hardtop on vs convertible, but without sacrificing correct lubrication would a different weight oil help quiet the noise? Currently using 75w/90 gear oil, would rather try this alternative first than dismantling

 

[bernd_st]

You may try thicker diff oil, but doubt it will help. Would assume either wear and/or loose gear bolts. The latter problem happens quite often on Alpines due to soft washers. Better to dismantle & check instantly rather than letting it become worse...

 

[bkasl]

I did have the original tab washers and bolts replaced when the 3.89 was installed around the Big Sky SUNI event date maybe 20-25 years ago

 

[hdar5702]

My 66 seriesV had the whine while decelerating.I removed the driveshaft from the differential pinion flange and found the flange nut loose.Should be 110ft.lbs....the differential is now in pieces on my workbench.Just checking everything and converting the rear brakes to manually adjusted.

 

[bernd_st]

My 66 seriesV had the whine while decelerating.I removed the driveshaft from the differential pinion flange and found the flange nut loose.Should be 110ft.lbs....the differential is now in pieces on my workbench.Just checking everything and converting the rear brakes to manually adjusted.

That could well be the root cause too. Easy to check....

I did have the original tab washers and bolts replaced when the 3.89 was installed around the Big Sky SUNI event date maybe 20-25 years ago

On my SV the whole diff was checked back in the nineties, but the screws worked loose after 20+ years. Perhaps because I didn't use Loctite back in the day...

 

[alpine_64]

I would hope it's not the bolts if you replaced.. it worth a check if the sound is when lifting off then likely it's the faces starting to wear.

Check the bolts for safety first.. you could try a friction modifier like the LSD fluid to try and see if it can coat the faces of the gears

 

[volvoguys]

My 66 seriesV had the whine while decelerating.I removed the driveshaft from the differential pinion flange and found the flange nut loose.Should be 110ft.lbs....the differential is now in pieces on my workbench.Just checking everything and converting the rear brakes to manually adjusted.

You likely already know this but, if not, if you're converting the Series V self-adjusting brakes to the early manual type, you'll need different backing plates.

 

[hdar5702]

Thanks.Fortunately I have a couple of parts cars and one had the manual type brakes.
I spent so much time failing to get the self adjusting brakes to work I ended up disabling the emergency brakes.
Then I heard the differential whine...so now I will fix the diff and the brakes

 

[Tim R]

When I had a diff that was whining there was a four month waiting time at the local differential repair shop and I wanted to run the car through the summer without the noise. They advised me to drop the oil out and refill it with EP140 instead. I did this and the noise almost totally disappeared.
Tim R

 

[jumpinjan]

refill it with EP140

And mix in some sawdust, that will quiet it....LoL
Jan

 

[bernd_st]

Would regard both " fixes" just temporary improvements which will not cure the root cause(s)...

 

[jumpinjan]

I suspect it lost pre-load on the pinion bearings, maybe due to failed pre-load shims. Those are the ones in the front and they are small & narrow.
Jan

 

[bernd_st]

Could well be. Found a couple of those worn preload shims on my recent diff rebuilds too (especially with the very thin ones). Interesting to detect the root cause for this. Perhaps not enough torque on the pinion nut, creating some unwanted & destructive tumble under changing load conditions...

 

[Jay Laifman]

You may be interested in this thread: https://forum.sunbeamalpine.org/index.php?threads/how-to-shim-rear-end.33210/