Gear noise-New Gears

I've always wanted to give gear work a go and I did... I know, leave it to the professionals, but its something I want to know how to do and ya gotta start somewhere.

Installed new Nitro 4.10 gears, koyo bearings (jeep had timken originally) and a detroit TT in the 8.25 axle. I wouldve used timken bearings but the nitro install kits came with koyo and I didnt know what the Jeep had till I had it apart. This Jeep has always had a slight gear whine when coasting under very light throttle, done this since new and Ive changed the gear oil 3 times in the Jeeps life, the Jeep only has 116k miles on it. Otherwise the stock gears were 100% silent. I checked the pattern and backlash before taking it apart and I thought the pattern was terrible, the backlash was 0.010".

I followed the FSM to a T and felt like everything was perfect. I emailed my contact pattern to nitro gears before driving it and they said they thought the pattern looked perfect. Drove the Jeep less than 20 miles the first 3 trips taking it very easy. The issue is, Im getting gear whine at ~65-75mph. It started as only whining when coasting at 65-75mph under light throttle (think going down a slight incline and you dont want to slow down), but now its doing it when just cruising along and is loudest at 75mph. Under 65 its quiet, ~80 and above its quiet, off throttle its quiet, and when under load it seems to quieten down. I've already done the 500 mile oil change, checked the pattern and back lash (0.008") again, all is well. I took photos of the contact pattern again and sent them to Nitro, they say it still looks good but the coast side could be a little deeper, but I have zero noise when off the throttle at any speed so idk if thats worth messing with.

Any ideas? Its pretty dang loud... Nitro said sometimes you just have gear noise and their gears are the quietest you can buy, but this is too much to live with. Ive not been able to find anything that mentions what causes gear noise at a certain speed range. If it were bearing issues I imagine it would do it at lower speeds.. Maybe Im wrong, which is why Im asking. The first two photos show the new gear pattern, 3rd and 4th show the factory pattern.

Original





This is the pattern on the new gears after 500 miles

In the first two pictures it looks to me that on the drive side, you have top heel and on the coast side you have top toe.

Looking at the pattern table I reckon that means you need a thicker pinion shim.

There is no harm in painting a lot more teeth to get more patterns to check.

Vince said:

In the first two pictures it looks to me that on the drive side, you have top heel and on the coast side you have top toe.

Looking at the pattern table I reckon that means you need a thicker pinion shim.

There is no harm in painting a lot more teeth to get more patterns to check.

Click to expand...

Thanks for the reply. Just to check, are you looking at what the pattern was when it was stock? B/C its certainly what youre describing.

Jeepster04 said:

The first two photos show the new gear pattern, 3rd and 4th show the factory pattern.

Click to expand...

I have just looked at the text between the photos, they were the wrong way around.


The pattern in the third and fourth photos looks bang on the mark to me.


I had a gear noise issue with my Ford 8.8 about a year after doing the gears. I had fitted an after market diff cover that had a higher fill hole than stock. I had also put a different lube in than usual. I had filled it to the new fill hole height with a mineral 75w-140. When I returned home a few weeks later I switched back to the synthetic 75w-90 and filled it to a measured 3 Litres instead of to the fill hole and it was fine.

Dang, thats my bad... If I could edit it I would fix it.