Rear end gear break-in

[Texas97]

blew the rear end gears on my Charger because whoever set it up, did it terribly with mismatched parts, wrong thickness and pinion gear, etc. thing got so hot it was causing pressure in the gas tank and was pushing grease through the end seals before it actually let go...

got it rebuilt with 3.55 gears and now will be better all around... question is, y'all have a good break-in procedure?

when i went to 4.56 in my Ram truck, it was a couple of sessions of mind driving, 20-30 minutes a peice, let it cool completely after each time, change the gear oil after that and send it. is that what i need to do here?

carnage for those interested

 

[pnora]

Its a good question that will get lots of opinions. The one that stands out in my mind is that what do all the millions of new cars and trucks do for break in? Nothing.

 

[R413]

That break in you describe is for the lower ratio aftermarket racing gears.

It won't hurt to do that with your 3.55. I doubt it is necessary.

 

[451Mopar]

I think my S60 Axle just said 500 street miles with the regular gear oil, then change the gear oil using regular or synthetic stuff.
If your racing, after break-in you might want to try the Red Line Shock Proof Gear Oil.
Lightweight ShockProof®

 

[Texas97]

Its a good question that will get lots of opinions. The one that stands out in my mind is that what do all the millions of new cars and trucks do for break in? Nothing.

yes, i have heard that question asked before, but its not nothing. basically, its the same break-in procedure, just without the oil change. New cars get test drove by folks and that is the heat up and cool down cycle. im not saying its exactly the same but it kinda is.

 

[Texas97]

I think my S60 Axle just said 500 street miles with the regular gear oil, then change the gear oil using regular or synthetic stuff.
If your racing, after break-in you might want to try the Red Line Shock Proof Gear Oil.
Lightweight ShockProof®

thats interesting.

was just going to use the 80-90w non-synthetic with the limited slip modified in it.

Does the redline need modifier for the sure-grip?

 

[R413]

thats interesting.

was just going to use the 80-90w non-synthetic with the limited slip modified in it.

Does the redline need modifier for the sure-grip?

That's more for race cars, not street driven stuff. Read the page, for manual trans also.
Yes it needs the additive.

 

[snakeoil24]

Get the ford whale oil additive and use non synthetic gear oil run it a few weeks and change it out your done needs to be hi in moly and zinc

 

[roadrunnerh]

Years ago I was advised by McCandless Shop to start the car with wheels off ground, shift into Drive and allow the idle to rotate the rear wheels for 10 minutes or so. Then, again in reverse.

 

[Runner 68]

Like the tag on my last new Strange 60 said "NO SPIRETED DRIVING FOR THE FIRST 500 MILES".
Good advice. At 501 miles I torched the tires for a solid 100 feet.

 

[Diodedog]

Whoever set that up should be smacked.

 

[old guys rule]

Years ago I was advised by McCandless Shop to start the car with wheels off ground, shift into Drive and allow the idle to rotate the rear wheels for 10 minutes or so. Then, again in reverse.

That is the one I've heard of. Run it at about 30 mph, I forget how long they advised.

 

[john-9]

here are the break in instructions i give out with every differential i build ,, and i stress strongly to the customer before they leave to follow the instructions to the letter. new bearings and gears build a lot of heat on initial run in and you have to give them a chance to run in properly. n

 

[john-9]

new rear wheel drive cars/trucks are broken in well before it arrives at a dealer ,, when the car/truck comes off the final car line ,,where fluids are topped up and other items checked they are driven to the Rollers where each vehicle is run to check transmission function etc. if it passes then it is driven out to the yard and parked ,, now it may have to come back in for maybe electrical work ,paint touch up , interior work etc. once the car is processed and passes inspection it is out to the shipping yard where again it gets jockeyed around till loaded for delivery to some dealer. all this is done at 5 mph or less over the course of several days/weeks .
for the diffs i build i recommend a gear oil in the heavier weight such as 75w140 , 80w140 etc. i like the Royal Purple gear oil ,,, no rear drive vehicle built since the late 80's uses a 90 weight oil ,,, save the 90 weight stuff for your tractor.

 

[451Mopar]

I have run the Amsoil and Red Line gear oil in limited slip diffs without any friction modifier, even the shock proof stuff.
I have only run the Blue light weight shock proof in the 3.91:1 geared 8-3/4" (741 case) with limited-slip diff and didn't have any issues running mid 12s.
When I was running 11.80's the old stock limited slip diff did start to make popping noises at launch in the 4200 pound Charger.
I also ran the light weigh shock proof in a stock 2004 Ram 1500 with no issues for around 40,000 miles when I traded it in because it was a 4.7L
Normally, I just run the regular synthetic gear oil in everything except a race car that takes heave shock loads at launch.
Originally started using synthetic gear oil (Amsoil) in the 1980's to get a bit better fuel mileage. In my 4 wheel drive trucks, I think it might have been worth an extra 1 MPG?

For Manual transmissions, they make Manual Transmission Lube (MTL) with the correct friction modifiers.