Been having loads of fun with my Excursion. I've completely gone through the rear axle, new Yukon 4.30 ring and pinion and "ALL" new Timken bearings. I set the pinion at 30 inch pounds preload. Back lash is 13 thousands. But now I have a gear whine during acceleration. Slight at first but more noticeable near 50mph. Coasting or decel is quite. But just barely touch the gas pedal and it starts to whine.

I know that the backlash spec is published as 6-10 but other sources state 12-15 thousands. So that's why it's set at 13. Gear pattern looked great to me. In fact most changes I tried had little effect.

So is it just normal for a gear set to whine until broken in?? Should I reset the backlash down. I only have about 40 miles on it. But would like to fix before it's wrecks something.
Thanks

 

Gears shouldn't whine while broken in. Find out what kind of cut the gears are from Yukon and you'll know which lash spec to use. Put up a pic of your pattern if possible.

 

I reset the backlash to 7-8 thousands. Sounds a little better but still a whine at 55 mph. Under very lite acceleration, like when trying to hold speed over small hills. But nearly quite under moderate accel.

I'm going to run it for 500 miles and see what happens. Seems like it's getting better but I could just be getting used to it. I'll pull the cover and change oil and take pictures then. Gear pattern looked nice after 40 miles. Centered in the pinion and ring gear teeth. Not running on the edges.

Thanks

 

That's good it's seems better. A centered pattern is a good thing but what's more important is the contact pattern. It needs to be oval shaped. Anything in a triangular shape is too deep or shallow on pinion depth depending whether that shape is on the heel or toe of the ring gear. Backlash will also play a part in the pattern but you want to be sweeping a pattern with the correct backlash anyway.

 

Ok I need to quit kidding myself and get this right. I just popped the cover a took a couple pictures of the gear wear over the last 50 miles. About 160 total so far. I will certainly put some marking compound and take more pictures if needed. Would be Monday morning after the gear lube has a chance to drip off.

Thank you.

 

Can't make a good call without compound. But from what I can see on your coast side the pinion looks too close to the ring gear. You have one real shiny spot on the toe of the drive side. Get it marked up and we'll see what you got.

 

Got a little carried away with the compound. Hope they are OK.

 

Hold some pressure on the gears and run them back and forth. That will get you a better pattern

 

Here's a few more. Wiped the old pattern off and held a little pressure on the ring gear with my fingers while turning the pinion.

What I'm guessing is take the "last" 10 thousands shim off the pinion. To pull it more onto the drive side, off the toe of the ring gear?? Reset the backlash to about 7 thousands or as close as I can get. What do you think, I'm obviously not an expert??

10 thousands is all that's left on the pinion.

 

How much pinion shim are you using. About 25 thou is a good starting point.

 

I'm pretty sure it's at 10 thousands right now, maybe 15. I had it written down but can't find the paper now. I had tried 20 during setup but the pattern was even closer to the toe of the ring gear, as I remember.

Factory was 30 thousands but with the new Yukon gears that doesn't really mean much.

 

Looking at that pattern something is way off. To me its looking as the pinion is too close to the ring gear but your shim thickness is saying different. Are you shimming under the pinion bearing or under the race? Not that it really matters but if you had the races out there's a chance of the housing getting dings in it from driving the race out. Then you new race won't be seated. Are you using a new matched set of bearings and races? Mixing bearings and races can cause trouble being different brands can use a different cone taper. If that were mine I'd pull it all and check everything. Races fit bearings correctly, bearings seated, races seated and so on. You might get a little bit of variation between gearset but not that much.

 

I've had it apart enough times to know it's right. Pinion races are seated tight and can't be mixed up with carrier bearing races, different sizes. I've done enough bearings and races to know not to wreck or nick up the housing. Checked with feeler gauge to make sure, between race and housing. Bearings are all new with matching races, Timken.

I noticed when I got the bearing kit from NAPA the REAR pinion bearing was different from what was in there. I did call the parts guy who checked and said that the different bearing was right to use in the axle. BUT now I think he was wrong after measuring the inner bearing races.

Timken NP504493. The original bearing. INNER bearing race measures 1.213 thick.
Timken NP761271. The bearing in my rebuild kit from NAPA. Inner bearing race measures 1.315 thick.

You can see the difference in the picture. I wonder how badly this is throwing off everything??? Guess it's another new bearing time. I wouldn't want to be in the NAPA store in a half hour.

 

I wasn't implying you were doing anything wrong, just something to get the wheels turning in you head. Sounds like you found it. Definitely explains the pinion being so close. I had a very similar problem with an 8.8 the inner pinion bearing was matched to the wrong race in a kit. It looked like it was correct but not quite, it was a good head scratcher.

 

Just wanted to thank you for the help. I'm sure my frustration and anger at NAPA came through a little. It wasn't meant to be directed at you in anyway.