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Another gear pattern critique, please...

mopurist

NAXJA Forum User
Location
NE
Chryco 8.25. So how do these look? Would you say the pinion is too deep (need to reduce pinion shims)?

drive_side.jpg

coast_side.jpg

My impatience and the heat got the best of me, and I buttoned it up with this pattern.:doh:

They whine rather loudly from ~38mph to ~48mph, accel more than decel, FWIW.

TIA.
 
That's kinda what I was thinking.

Looking at the Yukon install instructions, it sorta matches one of the patterns they have for "Pinion is too close". Centered, but kinda triangular, with the wide base near the root and tapering towards the crown.

They are USA Standard Gears, and the box even says "May be noisy." I ordered Yukons, but was shipped these. Like an idiot, I took a partial refund instead of an exchange after reading mostly positive reviews of the USA Std. Now I can't be sure if its the gears or the setup.

I gotta try something. Its way too loud as is.
 
Did you replace all the bearings? That pattern looks acceptable. I would take out only a couple thousandths if any. What was the backlash? Are you sure the pinion preload was good?
 
Did you replace all the bearings?
Carrier and pinion.

That pattern looks acceptable. I would take out only a couple thousandths if any.
I took 0.003" out (smallest decrease I could get from the shims I have), and this is the result:
drive-36_7.jpg

coast-36_7.jpg


What was the backlash?
0.007" on both sets of pics.

Are you sure the pinion preload was good?
20in-lb (I went by the FSM that says 15-35 for new bearings. I see now that the Yukon manual says 12-15 for new.) taken with a beam-style torque wrench

I dunno. Alot of images on the net have much more definitive patterns (cleaner edges, more complete wipe). Could just be the consistency of the marking compound, but would a rougher finish on the teeth cause the whine? I was applying as much resistance on the ring gear as I could by hand.
 
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I'd say your pattern looks good. If you still have the whine after 500 miles then it could be the brand. Make sure you put a very strong magnet on the inside of the diff cover to catch wear particles.
 
Post #5, firts picture, lowest tooth on the ring in the picture
 
Good eye. Though I don't think that's enough to cause the noise problem
 
As far as the tooth, I'm pretty sure that's one of the two teeth I had to grind. 4.56s in the 8.25. Had to take just a little bit off that tooth and the one next to it for the cross shaft to fit.

Properly broken in (per their instructions) and 500 miles on them, and I don't think the whine is better. It still really whines from ~40-50mph. Loudest when cruising at that speed. Quieter under decel and even more quiet under moderate to heavy acceleration.

I guess I'll live with it until I get around to getting a locker for the rear, then out they go.

Thanks.
 
Sometimes if you don't get the pinion bearing fully seated against the head of the pinion it will result in a loose preload on the pinion and that wuill cause it to eat the bearings. It's worth pulling the carrier to check that.
 
My Yukon 4.88s in my 8.25 are dead silent as well as my USA stander 4.88s in my 30. I'm 99.9% sure that USA is a sub division of Yukon, I would keep playing with your pattern. I'm just not sure how much you can change it now though since you've broken them in already and probly have a wear pattern set on the ring gear.
 
My Yukon 4.88s in my 8.25 are dead silent as well as my USA stander 4.88s in my 30. I'm 99.9% sure that USA is a sub division of Yukon, I would keep playing with your pattern. I'm just not sure how much you can change it now though since you've broken them in already and probly have a wear pattern set on the ring gear.
The pattern is dialed in. Either there is some kind of bearing problem or the gears are not a matched set.
 
I have 4:56's in my Chryco 8.25. Mine have a whine to them also, although not teribbly bad I can here it when I am on the free way.
Unfortunately I bought the xj with the gears already installed so I don't know the setup. I have been driving it and wheeling it for a while like this with no problems.
 
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