New true-trac differential whine

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jcolman

jcolman

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I got my car back from the shop that replaced the rear end with all new components including axles. There is a "whine" that happens on light acceleration and goes away when off the throttle. I've followed the break in procedures and have about 200 miles on the car since the install. The break in oil was replaced (to see if that helped the noise) and I've put another 20 or so miles on the car since then with no change in the sound. I know that the manufacture says to break in the gears properly, I need to put 500 miles on the car.

I know that the whine can be caused by improper pinion gear depth, improper shims or simply new gears. I asked the shop about it and they claim that they did the installation correctly. My question is: Should I put more miles on the car and see if the noise goes away after 500 miles, or take it back and tell them to fix the problem. I don't want to ruin my new gears if they are not properly installed.
 
jcolman said:
I got my car back from the shop that replaced the rear end with all new components including axles. There is a "whine" that happens on light acceleration and goes away when off the throttle. I've followed the break in procedures and have about 200 miles on the car since the install. The break in oil was replaced (to see if that helped the noise) and I've put another 20 or so miles on the car since then with no change in the sound. I know that the manufacture says to break in the gears properly, I need to put 500 miles on the car.

I know that the whine can be caused by improper pinion gear depth, improper shims or simply new gears. I asked the shop about it and they claim that they did the installation correctly. My question is: Should I put more miles on the car and see if the noise goes away after 500 miles, or take it back and tell them to fix the problem. I don't want to ruin my new gears if they are not properly installed.
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I think I would take it back to them and let them drive it and re-evaluate it. In the end, I would hope if the gears get damaged it would be on them to replace and if I was them I would want to correct it now before my reputation gets stained. Most things don't fix themselves as you know.
 
ACME SS said:
I think I would take it back to them and let them drive it and re-evaluate it. In the end, I would hope if the gears get damaged it would be on them to replace and if I was them I would want to correct it now before my reputation gets stained. Most things don't fix themselves as you know.
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I've already taken the shop owner for a ride and he's aware of the problem. He's the one who told me to drive it some more and see if the noise quiets down.
 
Pinion Depth
Pull it out and check the pinion depth.

Get a picture of the wear pattern on the ring gear with the yellow marking grease.

Don't want them running near the toe or the heal of the ring gear.

Screenshot_20220629-080146_Gallery.jpg


Have to find out if they used the crushed sleeve eliminator kit. If it is a crush sleeve and they crushed it too deep, time for a redo. If it is eliminator sleeve just add another shim or take one out as needed.

Good Luck
 
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It is set up too tight. I also have a tru-trac. No whine at all.
 
I do my own differential work and always file away photos of the final gear imprint. If I was having a shop do a ring and pinion set up for me I would have them take photos of the final gear imprint and provide them to me. I am surprised they did not do that anyway, about everyone has a cell phone these days. That would save a lot of second guessing if a problem did arise.
To your current issue, thinking that you have an 8.75, pulling the differential and rechecking the gear mesh is not a big deal. Try working with the shop.
Maybe you pay for the lube and gaskets and they provide the labor to pull the diff and re check the gear mesh.
And this time get photos.
 
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Check You Tube. You will see that many have the same problem.Some do, some don't. I understand it is blamed on the helical cut differential gears.At one time Dr Diff stopped selling them because of complaints. Mine did too at slow speed and Most at slow speed turns.Yes as stated above do not use friction modifier gear oil. 70-90 was too thin for me (Desert car) and 140 straight gear oil was recommended.I use 140 and you can hardly hear any noise.Unless you are looking for it.
This is just my experience. Nothing more.
 
dartindanno said:
If it's an Eaton True-Trac it does not require friction modifier. Ask the shop if they added it with the gear lube
Mopar 8 3/4" (8.75) Eaton Truetrac Differential (doctordiff.com)
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Never had a limited slip additive make any difference in gear whine or not.

jcolman said:
I've already taken the shop owner for a ride and he's aware of the problem. He's the one who told me to drive it some more and see if the noise quiets down.
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The type of diff you're running shouldn't have any bearing on gear whine unless it has more run out than allowed. Do you know what brand of gears you have in it....and how loud is the whine on a scale of 1-10? Gear noise on accel usually points to the pinion being too shallow. If you pull it out and clean the oil off the gears, paint it with the yellow or white marker grease then rotate it through. I like to paint the pinion gear only and then rotate it. The pinion will leave a nice footprint on the ring gear. If the pattern says the pinion is shallow, you can ad .005 and see how it looks. The easy way to do this would be to add the shim under the bearing race in the case instead of under the pinion. Unless they honed the pinion bearing to make it go on of off easier, you will probably ruin it trying to get it off. I use 'dummy' bearings that have been honed for an easy slip fit then when I get my settings, I install the permanent bearings.
 
Incorrect pinion gear depth. Period.
 
George Jets said:
Pinion Depth
Pull it out and check the pinion depth.

Get a picture of the wear pattern on the ring gear with the yellow marking grease.

Don't want them running near the toe or the heal of the ring gear.

View attachment 1715949084

Have to find out if they used the crushed sleeve eliminator kit. If it is a crush sleeve and they crushed it too deep, time for a redo. If it is eliminator sleeve just add another shim or take one out as needed.

Good Luck
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I believe they used a crushed sleeve
 
RustyRatRod said:
Incorrect pinion gear depth. Period.
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Can ya tell me about this one? Can hear a faint whine in a Dana 70 in a pickup starting at 55 and can't hear it anymore once above 65. Let off the throttle and it's not as loud but still there. If the radio is on just enough to hear the announcer talking, you can't hear the whine. That's how low the whine is. No noise on accel or decel, just cruise and between 55 and 65. Gear brand is Motive.
 
Cranky said:
Can ya tell me about this one? Can hear a faint whine in a Dana 70 in a pickup starting at 55 and can't hear it anymore once above 65. Let off the throttle and it's not as loud but still there. If the radio is on just enough to hear the announcer talking, you can't hear the whine. That's how low the whine is. No noise on accel or decel, just cruise and between 55 and 65. Gear brand is Motive.
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Gear brand makes no difference. Gear ratio makes no difference. If there's a whine getting on or off the gas, the pinion gear depth is incorrect. I can never remember which way is which. One way is too much gear depth, the other is not enough. First thing I would check in either case is the pinion nut. They are problematic sometimes about backing off.
 
RustyRatRod said:
Gear brand makes no difference. Gear ratio makes no difference. If there's a whine getting on or off the gas, the pinion gear depth is incorrect. I can never remember which way is which. One way is too much gear depth, the other is not enough. First thing I would check in either case is the pinion nut. They are problematic sometimes about backing off.
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If the pinion is too deep, gears are noisy on the coast down....pinion too shallow (not deep enough), noise on accel. This doesn't do either one....it's just a faint whine at steady throttle between 55 and 65. Step on the throttle just little at 55 to push it up to 60 and it goes away until you let up a bit for steady cruise speed and then you can hear it whine again. Doing the same thing to get to 65 makes the same results but once it's cruising at 70, nice and quiet again. As far as name brand....was just for reference but I remember a time when everyone was bitchin about Richmond gears being junk. I never had any problems with Richmond gears. Pinion nut is fine. Loc-tite was also used on it.
 
Cranky said:
If the pinion is too deep, gears are noisy on the coast down....pinion too shallow (not deep enough), noise on accel. This doesn't do either one....it's just a faint whine at steady throttle between 55 and 65. Step on the throttle just little at 55 to push it up to 60 and it goes away until you let up a bit for steady cruise speed and then you can hear it whine again. Doing the same thing to get to 65 makes the same results but once it's cruising at 70, nice and quiet again. As far as name brand....was just for reference but I remember a time when everyone was bitchin about Richmond gears being junk. I never had any problems with Richmond gears. Pinion nut is fine. Loc-tite was also used on it.
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That would define at coast.
 
Cranky said:
Cruise is define as coast? Heck, let off the throttle at any speed and it's quiet. On the throttle at any speed and it's quiet.....
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To prevent the argument, the pinion angle is incorrect. How's that?
 
RustyRatRod said:
To prevent the argument, the pinion angle is incorrect. How's that?
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Not good enough imo......you act like the 'man in the know' but can't seem to tell me anything I don't already know. Saying that cruise is the same as coast is what I gathered and to me, it's not the same. If you can't say to adjust the pinion in deeper or out more then why say anything?
 
Cranky said:
Not good enough imo......you act like the 'man in the know' but can't seem to tell me anything I don't already know. Saying that cruise is the same as coast is what I gathered and to me, it's not the same. If you can't say to adjust the pinion in deeper or out more then why say anything?
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You can cram it up your *** for all I care. I won't try to help you anymore.
 
Personally, my experience, any time there is gear whine, it typically the pinion is set up too tight (deep). Also could be little to no backlash. 0.008-0.012" is what I set mine at.
 
Cranky said:
Not good enough imo......you act like the 'man in the know' but can't seem to tell me anything I don't already know. Saying that cruise is the same as coast is what I gathered and to me, it's not the same. If you can't say to adjust the pinion in deeper or out more then why say anything?
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I believe Rusty @RustyRatRod meant "cruise and coast" in a not accelerating nor decelerating. This would make them the same. Cruise, maintaining speed, is the in between. On and off the gas but generally very light throttle to maintain. A decelerating coast to slow down is the opposite side of the ring gear.

No backlash will be tight always also, which can easily whine.
 
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