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2002 TJ. 4.0 ltr. 5.5 RE long arm lift, 35" tires, 4.56 gears, Teraflex S/T disconnect,
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Discussion Starter · #1 ·
I just had new ring and pinion gears and bearings put in the rear of a Dana 44. I picked it up after the shop closed and when I drove it I noticed a slight noise coming from the rear end.
My question is is it normal for there to be a little noise until the gears wear in. They gave me instructions on how to break them in and I've been careful to follow them

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There should be no unusual sounds from your new gears, even during the break in. Hopefully they filled your axle with a conventional gear lube for the break in to help the gears run cooler.
 

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2002 TJ. 4.0 ltr. 5.5 RE long arm lift, 35" tires, 4.56 gears, Teraflex S/T disconnect,
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Discussion Starter · #3 ·
The shop told me they used 85 140 synthetic oil.

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The shop told me they used 85 140 synthetic oil.
Those in the know like Revolution Gear and Currie specify conventional gear lubes, especially during the critical gear break in period.

For example, this from Revolution Gear at https://www.revolutiongear.com/ring_and_pinion_break_procedure

"Recommended gear oil is an 85-140W, Non-Synthetic, GL5 grade or Higher, Name Brand Oil."

Currie specifies conventional gear lubes for their axles too. They conducted their own tests after new gears they installed into their custom axles started having a higher than expected failure rate. After difficult tests they were totally surprised to determine it was caused by some customers running synthetic gear lubes. They later changed their warranty to require only conventional gear lubes.

It's proven that gears run hotter when lubed with a synthetic. Really.

It doesn't really matter if you run a synthetic for light duty uses but the harder the gears are used the more important the use of conventional gear lubes becomes.

This totally surprised almost everyone in the industry.
 

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It doesn't really matter if you run a synthetic for light duty uses but the harder the gears are used the more important the use of conventional gear lubes becomes.
Which is strange since it is the opposite of what the manual states as far as heavy use
 

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Which is strange since it is the opposite of what the manual states as far as heavy use
Jeep just goes by what their petroleum vendor reps tell them. The problem with synthetic gear lube doesn't show up with typical uses, it's only in hard uses when it makes a difference. The problem happened to me after doing a break in with synthetic last year. The gear guru who replaced the rear gears immediately blamed synthetic gear lube for the problem after seeing the gears had gotten too hot even though I had been gentle during the break in. He scolded me for having used synthetic gear lube. I knew better too but let myself get talked into it before my last regear to 5.38. The guy who fixed the problem, who does nothing but gear installations, did comment they had been set up properly.
 

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Jeep just goes by what their petroleum vendor reps tell them.
Or they go by what makes the vehicle last long enough to get out of the factory warranty
 

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2002 TJ. 4.0 ltr. 5.5 RE long arm lift, 35" tires, 4.56 gears, Teraflex S/T disconnect,
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Discussion Starter · #8 ·
Thanks to everyone for all the information.
What do they consider "too hot" and how would this be determined? After my first 20 minute drive, the diff cover was hot enough that I couldn't keep my hand on it more than a couple seconds.

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Normal differential temps would be too hot to hold your hand on the cover more than a couple seconds.
 

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Something is not right. Take it back and let the shop check it out. Many years ago, I had a shop redo my gears and I also had a noise, which they tried to tell me was "normal" I insisted and they took it apart and found a problem.

I just did a 5.13 swap myself in my project jeep and the new gears run nice and quiet.

Using synthetic for the first time is a waste of money, you'll need to do a oil change after about 300 easy miles anyway.
 

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Revolution has their REM gears now which do not require a break in. I dont know enough about it other than it is achieved thru a finishing process before being put in the box.
 
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