You're supposed to do a quick 30 minute drive at first, then let them cool completely. They get VERY hot on the first drive of break in.

LOL that is a big no no, driving them with no cooling off period. Like stated above they need heat cycles the first time you break them in. Oh and your also supposed to keep it under 50 mph for the first 200 miles or so.

Please read this article about proper break in procedure.

New Gear Break In

heres what the paper work says for AAM gears pretty much.

"No burnouts, wheel stands, gas, nitro, drag radials or fun period.
Our paperwork says 200 `easy' miles. Do not pull a trailer or load
the truck for the first 500 miles"

The first heat cycle is the most critical.

I did a 30 min drive, about 15 miles with some stop and go, babied it and stayed under 55, then let it cool over night. Then did a 15 min drive got up to 65, let it cool over night. Then ~150 miles staying under 65 with approx 10 heat cycles. Then got up to 500 miles staying under 75. Need to change the break in oil this week and inspect the gears, but no strange noises so far. The gears are dead silent. I used Valvoline 75W-90 conventional.

Break in seems to be as important as setup.

subbed

I just had a set of 4.56 USA standard gears and valuetrac put in my truck Wednesday. Me and a buddy did them. .040 pinion shim, .005 backlash. They are dead silent. Did the proper break in. I'm just shy of 400 miles. I highly doubt it's the gears either. I say bad install. We've put atleast 5-7 front and read sets in trucks in the 4.56 and 4.88 ratio. And all have been dead quiet. I use valvoline oil also fwiw.

Yeah I did do the 20 min first drive around period and let it sit for almost 3-4 hours after then the next day drove it around the city for a good bit

A friend of mine almost took his gears out after an install. The bearing set just past the diff body but he pressed them on, on a flat surface. So after a bit of driving the bearing settle all the way on and he lost the back lash.ucky for him he heard them soon enough and reshimmed. They have been good to go since.

gear swap head to track make quite a few passes load on trailer head home, no gear issues ;)


theyll break in and cool down during run time hahaha!


always ran USA standard gears!! setup my buddy up with my used gears no issues !


go figure