8.25 noise

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supertruck

supertruck

Unretired Old Fart stock car racer
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73 Dart Sport, 340, fresh 8.25 rear with Motive 3.91 gears and a Sure Grip. Part of a 4 year restoration. When driving I get a steady whine from the rear. Whine speeds up and slows down with vehicle speed. Did not hear anything with a stethoscope on the housing and the car in gear. Pulled the rear cover and checked backlash - the same all around and the wear pattern on the ring gear is near perfect. I can turn the pinion by hand and for about 3/4 of the ring gear travel it spins freely. At one spot, for about a 1/4 of the ring gear travel, it binds up. Doesn't spin freely but can be turned by hand. Any thoughts? Could it be a problem with axle bearings? Looking for things to check before I drop the rear end and pull everything apart.
 
axle bearings are a concern on the 8-1/4", so it's worth looking into. Unlike the venerable 8-3/4", the rollers for the axle/wheel bearings ride DIRECTLY on a machined journal on the axle shaft. So if you have a damaged roller bearing, it will likely damage the axle shaft, too.
 
Thanks! I thought that could be the issue. Figured I'd pull the axles enough to get them out of the carrier and see if that frees up the full rotation of the ring gear with no binding. At the least, a bad axle is a bit easier to replace than pulling the entire rear end out.
 
Pulled both axles today. Bearings look to be OK. Spinning the pinion after axle removal and the tight spot is gone, turns easily for the full rotation of the ring gear. Still thinking there's an issue with the axles / bearings. Gonna reinstall one axle at a time and check for the binding on the ring gear travel. Maybe that will show which one is the problem. Don't really know what else to try at this point.
 
are you positive the whl brgs are ok? It's pretty hard to examine them thoroughly, what with the lube and having to stand on your head. You may have to slide hammer the bearings out of the tube, and clean them to get a thorough assessment of the rollers, and outer race.
A very remote possibility is the housing may be bent.
 
Here's a pic of the ring gear pattern.
Ring gear 10-21-20.jpg
 
I used to use (artist)painter's oil out of a tube. I liked cadmium yellow. take a dollop, and mix/thin it with oil, and paint it on with an acid brush.
 
here's the best I have right now. I'll get some marking paste tomorrow and get a better pic.
Gear 2.jpg
 
Guessing your pinion depth needs to be deeper. Seems to me that whining gears changing with the speed is the pinion not deep enough in the ring gear.

Will have to see what your wear pattern looks like with the new colored paste.

20201021_200926.jpg


20201021_200057.jpg


Good Pattern
Screenshot_20201021-194736_YouTube.jpg


Screenshot_20201021-222321_Gallery.jpg
 
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Checked both axles today - not bent. Maximum .0035 out of round. I'll be checking the ring gear with some good paste again later.
 
Most of your gear contact patterns look like they still need to be stretched out a little wider yet, like the good pattern pictures. Suggesting the pinion still needs to go a little deeper into the ring gear yet spreading out that wear pattern with out getting to the point where it binds.

Are you running .010 ths on the backlash too after you have set the pinion preload and depth, that can make a difference on the pattern too.

20201023_112642.jpg


Screenshot_20201023-111920_Gallery.jpg


Did a little photo enhancement to help bring out the contact pattern better. You can use a small prybar on the backside of the ring gear to create some drag while turning the pinion to put more pressure on the wear pattern and help it show up better.

Have to work though the steps of your setup again and see if you can get those wear patterns too look a little better, without getting things too tight.

Good Luck, kind of fussy to get it right.
 
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Took some readings ahead of disassembly. The ring gear has a chamfer on the back edge. With a dial indicator on that chamfer I got a deviation of 0.0125. I checked the back lash at 6 locations. I got 0.009 @ one location, 0.013 @ one location, and 0.012 @ 4 locations. Now I'm wondering if maybe the carrier is not true. Gonna pull the ring gear, reassemble the carrier, and check it with the dial indicator.
 
supertruck said:
Took some readings ahead of disassembly. The ring gear has a chamfer on the back edge. With a dial indicator on that chamfer I got a deviation of 0.0125. I checked the back lash at 6 locations. I got 0.009 @ one location, 0.013 @ one location, and 0.012 @ 4 locations. Now I'm wondering if maybe the carrier is not true. Gonna pull the ring gear, reassemble the carrier, and check it with the dial indicator.
Click to expand...

That is what I was wondering about that 1/4 turn tight spot you were talking about.

Getting those ring gears down evenly on the differential carrier is usually a real tight fit. Cross tightening the ring gear bolts to draw it down, but still is quite tight.

You may have to inspect that carrier hub where the ring gear slides on to and check for burs, and on the inner diameter of the ring gear too. May have to relieve it with a little emry cloth so that it goes down properly.

Any luck uploading the pinion gear wear pattern pictures so we can see where that has been running too ?
 
Checked the carrier and the ring gear, no deviations more than 0.001. Talked to the guys at Motive and sent them some pics of the pattern. The drive side appears to be a little high towards the heel of the tooth according to them, suggested I add another 0.003 pinion shim. I'll give that a try.
 
supertruck said:
Checked the carrier and the ring gear, no deviations more than 0.001. Talked to the guys at Motive and sent them some pics of the pattern. The drive side appears to be a little high towards the heel of the tooth according to them, suggested I add another 0.003 pinion shim. I'll give that a try.
Click to expand...

Yes, add some pinion shim. Wish you were closer, I would let you borrow my pinion depth gauge. It never fails me but I suspect you have something to get the measurement anyways....


Something else to check is make sure the bearing races for the Pinion are seated even and properly. I have went behind atleast one setup in a friends car and that was a problem in that the pinion didn't feel smooth when turning..... Just a thought....

JW

JW
 
Why is it so fn hard to get u to post a pick of the pattern on the pinion? R u just being stubborn or don’t understand the question? Kim
 
oldkimmer said:
Why is it so fn hard to get u to post a pick of the pattern on the pinion? R u just being stubborn or don’t understand the question? Kim
Click to expand...
Not stubborn at all. Just trying to figure out how to get a good pic of the pinion with the unit assembled. Don't want to waste everyone's time with a pic that doesn't show much.
BTW, thanks slopar72
 
OK, for oldkimmer and to prove I'm not stubborn, and anyone else interested - 2 pics of the pinion, best I could get.
pinion gear.jpg
Pinion gear2.jpg
 
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