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Diff whine

clhiller

Silver Level Sponsor
During my refresh this winter, I was able to replace the existing 4:55 Rapier rearend with a 4:22. All the bearings seemed in good shape, I was concerned about the amount of backlash. A mechanic buddy checked it out with the Mark I eyeball and pronounced it "good enough". Now when I drive, in 3rd, 4th and OD, there is a loudish whine from the rear area of the car. It stops when I let off the gas and coast, and is quieter when I am hard on the gas. It is loudest when just cruising.

Is that indeed the sound of a sloppy differential? I am prepared to live with it until the winter when I can remove and dial it in correctly. Or could it be the wheel bearings, or the transmission? I did not replace the wheel bearings when I had it apart (dumb), but I did use the two that were smoothest and quietest and were acceptable in my opinion.

I did have the transmission rebuilt by a reputable British car shop and it was run on their test bench with no issues. There is no vibration coming through the gear shift and no vibration in general when cruising at 65 mph. Just the whine (and not the good kind!).

What is everyones' opinion?
 

alpine_64

Donation Time
When you pull it the ring gear bolts have washers that compress amd go loose. This keads the bolts to loosen and causes bad sound and also increses wear.. Worse they can lead to failure of they come out.

Replace with new bolts and locktite them in
 

clhiller

Silver Level Sponsor
I checked all the bolts when I swapped the diff into my S1 rearend, ( the diff is out of a S3). All the bolts were Nice and tight.
 

alpine_64

Donation Time
I checked all the bolts when I swapped the diff into my S1 rearend, ( the diff is out of a S3). All the bolts were Nice and tight.
If the diff was from a series 3 you should check the ratio again. S3 was the only series where both 4 speed and OD cars ran the 3.889 diff.

If the one tou swapped into your car has a 4.22 ratio it was changed at some point
 

alpine_64

Donation Time
Also i would say if you have OD and the 3.889 thats a great combination for cruising.. I run that with 195/65/14s on the back and the car eats miles beautifully
 

clhiller

Silver Level Sponsor
It is definitely a 4:22. I went from a non-OD with a 4:55 rearend to an OD with a 4:22. It is like night and day. I’ll keep my eyes open for a 3.89, but for now I’m happy with what I have. (Once I get rid of the whine!)
 

alpine_64

Donation Time
Yes the OD and 4.22 was used on all series I/II and IV/V .. Gives a goosld balance of acceleration and cruise. With a 4.55 it would have been howling at 60mph.

Interesting someone had swapped the diff in the donor s3.

Good luck with sorting the whine... If you can get a decent 3.889 from any non OD car ( Barring stateside SV) that would be an even nicer upgrade
 

RootesRooter

Donation Time
I checked all the bolts when I swapped the diff into my S1 rearend, ( the diff is out of a S3). All the bolts were Nice and tight.

"All the bolts were nice and tight"? That makes you part of the lucky 1%. Did you bend the washer tabs down before you tried to check the torque? Did the washers look like someone else had previously bent them down and then back into place?

Once the gears start to whine, has anyone been able to get rid of the whine by adjusting the backlash? I'm not aware of any success stories offhand.

One other thought: its been a while since I had a bad u-joint in my Alpines. I can't remember if it howled under under acceleration, off-throttle, or both. U-joint whine isn't as 'grindy' as a bad diff, but it is loud.
 
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Shannon Boal

Platinum Level Sponsor
I just replace the ring gear bolts and washers on my 1968 series V. Rafe Selfridge (my step-dad) bought it new, and never ran it hard....neither did I. So, I bent back the tabs, broke each bolt in turn, and measured to torque at the point of original install. The bolts were tight, ranging from thirty-five to forty ft-lbs torque. I replaced the bolts (torqued to 48-50 ft-lbs) with AN6H6A aircraft bolts, drilled for safety wire. I used ARP washers, 3/8" ID, 7/8 " OD, P/N 200-8678. I cleaned it with brakeclean, used plenty of lok-tite red and then safety-wired all of them. Bill Blue says I tend to over-think things.....
 

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Bill Blue

Platinum Level Sponsor
Not so much overthink as insisting on using belt and suspenders, even at times it wont matter if the pants fall down. Holding the ring gear in place is not one of the "wont matter" situations.
Bill
 

Shannon Boal

Platinum Level Sponsor
What I learned; yes the fasteners lost some tightness. I guess that if you heated that unit when new, in cycles from 15F to 250F over and over, the soft tab washers would yield to the hard bolt, gear, and housing. Then the gear can move a little under shock loading. This car never saw shock loading, but lost 10-20 ft-lbs of tightness. Have not measured thickness of tab washers, but they are certainly soft.
 

Bill Blue

Platinum Level Sponsor
Yes, I was shocked at how soft the washers are. By comparison, cheap hardware store washers would be called "Half Hard". My dif had two broken bolts, the rest I removed by finger pressure.

Bill
 

Shannon Boal

Platinum Level Sponsor
Now, to install propeller shaft, and rear brakes. Is there a special thread for self-adjusting Series V brakes? I think I got them straightened out.....
 
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