Gear experts, where did I go wrong? Differential noise

[sonicblue232]

Long time lurker first time poster here. So I just finished swapping an IRS from an 03 Cobra into my car and I'm getting some noise from the differential which I rebuilt with new Ford Racing gears and bearings and a Torsen T2 differential. The noise I'm getting is rotational growling/clunking that matches the speed of the car when coasting or decelerating at low speeds. It doesn't matter if I'm in gear with the clutch in or out or in neutral. It doesn't happen when accelerating or at speeds over about 35 MPH, but it makes it at low speed right up until the car is stopped and I can hear it between shifts when accelerating. One interesting thing I noticed is that it doesn't do it at all when rolling in reverse, where it would be clunking up a storm going forward. Also, turning in either direction doesn't make it louder, if anything, turning makes it quieter. So I don't think it is hub or wheel bearings or cv joints, I'm also positive it is not my u-joints or driveshaft as it happens with both my old driveshaft and my new aluminum one. I have checked the pinion for play up and down and back and forth, and there is none. I can't recreate the noise with it up on jack stands, so it seems to need to have a load on the drivetrain to make it. I'm thinking maybe too much backlash? I set it to .010, which should be right in the middle of the suggested range, so I'm having a hard time believing it could be off by enough to make this much noise, but it's the only thing I can think of that makes sense. The gears don't seem to make any other whining or howling noises like I would expect if they were not meshing well. I'm going to pull the differential out and have a look, is there any other mistake I could have made in setting this up that could cause these symptoms?

 

[Goindeafonmtx]

Factory rubber bushings or FTBR/MM bushings?


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[sonicblue232]

Factory rubber bushings or FTBR/MM bushings?


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Full MM bushings all around (poly bushings on differential mounts and subframe, delrin everywhere else).

 

[MG0h3]

Got any pictures of the pattern you ended up with?

 

[sonicblue232]

Got any pictures of the pattern you ended up with?

Unfortunately I didn't take a lot of pictures, but I've got these. I thought the pattern looked a bit high on the tooth, but before that the pattern was way too deep on the tooth, so I settled on this. Maybe I should have tried to get some finer adjustment. I ended up with I think a .040 pinion shim, which is more than the typical .030, but from what I read is normal for the timken pinion bearing I used.

 

[me32]

Op is does look like its on the high side. Were you not able to get a .08? What was the orginal shim on the pinion? Alot of times the original shim on the pinion will be the correct setting if using ford oem or ford racing gears.

 

[MG0h3]

Thats odd marking compound. I'd almost venture to say the pinion is too deep. If you look at the coast side, its buried all the way into the ring. I also feel like it may be too deep (thicker part of pinion hitting ring) because you can't see a rounded area on either side of the contact patch.

No expert but I've set up 4 or 5 sets now over the years.

 

[me32]

Thats odd marking compound. I'd almost venture to say the pinion is too deep. If you look at the coast side, its buried all the way into the ring. I also feel like it may be too deep (thicker part of pinion hitting ring) because you can't see a rounded area on either side of the contact patch.

No expert but I've set up 4 or 5 sets now over the years.

This right here. I think he has the wrong size pinion shim in there.

 

[sonicblue232]

Thats odd marking compound. I'd almost venture to say the pinion is too deep. If you look at the coast side, its buried all the way into the ring. I also feel like it may be too deep (thicker part of pinion hitting ring) because you can't see a rounded area on either side of the contact patch.

No expert but I've set up 4 or 5 sets now over the years.

Thanks for the input, so what you're saying is the opposite of what I was thinking, the pinion gear is too deep into the ring gear, so I need a thinner shim?

 

[MG0h3]

That’s what I’m thinking. I’ve never had one look like that but it’s a little hard to tell with that compound. I like the yellow better. More contrast


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[MG0h3]

I took my old pinion bearing and ground the inside out a bit so I could just slip it on and off to change shims. Then verified with the new bearing on final install


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[hotcobra03]

seeing you noticed a noise going forward and not backwards.

I would think pinion is off..

there is a thread floating..on rear pinion..where you use a template to get pinion depth..

I just winged it and set gears as even as I could see.

I still have gear whine.but not half as bad as the last time paying to have it done.

 

[1wild-horse]

Too deep, the patch where it's wiped clean is too close to the inside. Pinion shim too thick (or pattern too deep) will whine on acceleration. Too thin of a shim or too shallow of depth will whine on coast.