What is the break-in procedure for gears?

[caverman]

I'm probably going to get a set of LPE gears pretty soon. I know I need to break them in before really getting on it hard. I've seen/heard of a couple different procedures to do so I wanted to get the steps others have heard or done. Last thing I want to do is break some gears. These things aren't cheap at all.

Also, is it recommended to change the rear end oil after a short time in order to get any metal out?

[GEEo]

[Russell James]

All the gears I've ever bought come with break in instructions from the supplier. It's also on the gear companies websites.

Most say something like... several short drives, light accel and decel loads, cooling off time between each drive. You go through some drive cycles like that for xxx miles, then change the gear lube. Any noise after that break in and the pattern needs to be rechecked. No noise, change the fluid and have at it.

What you don't want to do, is take a long drive for the first couple drives or put heavy loads to it on those first few drives. It will be getting quite hot inside the diff on those first few drives. Short easy drive, cool off, repeat.... repeat.... repeat....

[toml_pa]

Originally Posted by caverman

I'm probably going to get a set of LPE gears pretty soon. I know I need to break them in before really getting on it hard. I've seen/heard of a couple different procedures to do so I wanted to get the steps others have heard or done. Last thing I want to do is break some gears. These things aren't cheap at all.

Also, is it recommended to change the rear end oil after a short time in order to get any metal out?

This is what my installer gave me. Also said to change oil after 500 miles.

AAM 3.91 Gear Break In Procedure

The break in is VERY specific.
-Drive 30-35 MPH for 20-30 minutes.
-Drive 55-60 MPH for 20-30 minutes.
-Come to a complete stop and let the diff cool (15 minutes minimum)
This is one cycle. Repeat this cycle 4-5 times.
If you don't do this EXACTLY, the diff WILL whine.
500 miles will be needed for a full break in.

[caverman]

Originally Posted by toml_pa

This is what my installer gave me. Also said to change oil after 500 miles.

AAM 3.91 Gear Break In Procedure

The break in is VERY specific.
-Drive 30-35 MPH for 20-30 minutes.
-Drive 55-60 MPH for 20-30 minutes.
-Come to a complete stop and let the diff cool (15 minutes minimum)
This is one cycle. Repeat this cycle 4-5 times.
If you don't do this EXACTLY, the diff WILL whine.
500 miles will be needed for a full break in.

Thanks. Those are the gears I'll be getting and this is one of the procedures I've heard as well. It will be a little tuff to do exactly but I guess I need to mark off 1/2 a day to devote to just breaking them in.

[BullF-16]

I just had a Gforce 9" conversion installed with 35 Spline S-trac posi unit and new 3.50 gears. The break in recommended driving at normal speeds for up to 50 miles, stopping for 30 minutes then continuing for another 50 miles.
Then repeat till 500 miles is accumulated.

I drove back from FtWorth but did not exactly follow the first part of this. I drove for about 65 miles, stopped for some food for about 12 minutes then continued on home. the rest of the breakin was driving around town at normal speeds for about 10 to 20 miles at a time the parking it for the day.

From my research, the big thing is not to let the lube get too hot. This is alot more critical for the higher rations 4.33 and up. I am at 3.50 and the drive home my RPMs were only at 1700. So i think its ok. I notice no noise or abnormalities. Only a very slight whine when coasting or not under load.

[inferno camaro]

If these gears are made by the same company as stock, why is break in required on these but not factory gears?

[Big Daddy Kane]

Originally Posted by inferno camaro

If these gears are made by the same company as stock, why is break in required on these but not factory gears?

Same thing I was thinking.

[rick john]

Good reading and good advise.... My car is in the shop now getting the 3.91's installed I should be picking it up tomorrow, however I have a 50 mile ride home on the freeway, I'm wondering if I should stop halfway and sit for 20 mins??

[caverman]

Originally Posted by rick john

Good reading and good advise.... My car is in the shop now getting the 3.91's installed I should be picking it up tomorrow, however I have a 50 mile ride home on the freeway, I'm wondering if I should stop halfway and sit for 20 mins??

My guess is you'll be fine going all the way home. But get it heated up then cooled down a few more times before hammering them. I will probably put at least the 500 miles then new oil before I hammer or race them.

Like someone mentioned, AAM mfg as the same as stock gears. I can tell you that I drove my car hard right off the bat and the gears haven't been any issue at all.

Please post up your initial thoughts once you get them.

[allmotor]

I'm having 3:91 gears installed next week and JRE is 142 miles away. Considering the AAM break in routine above, should only take me a week to get home...

[inferno camaro]

You guys running 3.91s, are you running any 1/4 mile stuff? lingenfelter says you will top out at115 at 6700 rpm in 4th gear with a6

[Merc]

Originally Posted by inferno camaro

You guys running 3.91s, are you running any 1/4 mile stuff? lingenfelter says you will top out at115 at 6700 rpm in 4th gear with a6

Pumpkin has run 12.35 @ 113 up against the rev limiter in 3rd gear with the stock gears. Hoping the LPE/JRE/LPW 3:91 set up will make the difference. My diff builder wants four or five heat and cool cycles before I romp on it.

[rick john]

Thanks Caver.... I should be getting the call to come pick up my car today or tomorrow. And i will take it easy driving home and do a couple of the heated and cool off runs before I let it rip.

And double fatty, I am an ls3 6 speed w/ cam, c.a.i., Lt's, 3 inch, high flo-cats, dyno tune 6 months ago @ 440whp. But my gear installer is going to re-run the car on his dyno-jet before and after he puts the gears in, so I too am anxious to see what if any diference there will be... Running the 1/4 mile last year i was 12.7 w/ 3rd gear against the limiter @110. So it's gonna be a whole different ball of wax this year, I think.