Another differential whine post

[Trevian26]

I know its been discussed before but I cant seem to find the specific forum that I saw months ago, sorry in advance.

Context: 1 shop install gears wrong, rear end went boom. 2nd shop replace whole rear end and I have 4.10 with the FRPP traction lok and FRPP cover (the non finned one) Only thing repurposed was my axles.

I had a minor whine during my break in period, the shop did accidentally over fill it cause the fill hole on the cover is higher than the actual fill hole on the other side of the diff (a lot of diff spewing everywhere) Anyways did my 500 miles, replaced the fluid. I had RoyalP in it so the fluid was still relatively purple still but had a decent bit of sparkle, however i didnt notice any extra wear on the gear/pinion. Now I put in probably about 2.6 bottles of Royal purple 75-140 in it (using the right hole) along with 4oz of FRPP friction modifier but now it whines a lot louder. I did figure 8s for about 10 minutes (no change) and the loudness/speed of the whine is correlated with wheel speed. Acceleration, deceleration, coasting, braking, anything involving the wheels moving.
Should I throw another bottle of friction modifier in it or cause of the royal purple there is too much?

Once again sorry for the post, thanks in advance.

 

[whitmanink]

Welp I installed 4.10 in my car ( Ford gears) I also rebuild the trac loc .. and installed new Axle bearings and seals as well as axles..

I have zero whine at all .. even breaking in the gears it has a very very very quiet whine the first 50 miles .. then was quiet .. and still is..

If the gears are installed correctly... You should have zero whine ....
Other than normal tolerance whine .. but that's very quiet or should be

 

[mustanger]

The friction modifier isn't going to help with gear whine. It's purpose is to allow the trac lock clutches to not bind and grab when cornering. I wonder if the fact the diff was overfilled just helped mask the whine.

 

[Trevian26]

So I did some tighter figure 8s and drove around shortly and noticed that the whine is actually quieter with the windows down than with them up. Now its not silent but youd have to be listening for it to notice. With the windows up though, its a very noticeable noise. Assuming the gears was installed properly (I only say this cause it was a performance gear/trans shop with plenty pro street and other drag cars in there) could it potentially be a bearing? Ive also installed bmr LCA but that was installed way prior to the flush.

 

[Midlife Crises]

You said you had some sparkles in the break-in fluid. That should not be the case. Those sparkles circulating in the oil have left marks on the pinion and carrier bearing races. The bearings will never run quiet now. You will have to thoroughly clean all the metal flake out of the housing and out of the carrier, then install new carrier and pinion bearings. Set up correctly there should be no visible metal floating around in the oil.

 

[GriffX]

backlash and/or pinion shim wrong. The metal slime is quite normal with a new gear set, they are really rough from factory (at least my Ford 3.73 was)

 

[TexasBlownV8]

Whine from improper backlash is usually related to certain speed ranges. If it's there, always, you have some other bearing/race issue. Could be pinion inner or outer, differential, or wheel bearings.
A properly-installed set of gears will be quiet.

 

[GriffX]

If it's there, always, you have some other bearing/race issue. Could be pinion inner or outer, differential, or wheel bearings.

I had a failed pinion bearing and a grinding noise at low speed range up to 30 mph no whine at all (?)

 

[TexasBlownV8]

Pinion is usually growling/grinding, whine is usually backlash (differential)..from installation variances.

 

[JC SSP]

Can you take it back to the shop that did the gears? Did you get any warranty?