I'm getting the truck regeared from a 3.55 to 4.10 rear diff gears in a couple of weeks and I want some advice on how to properly break them in.

Any advice appreciated.

 

Usually its drive roughtly 20 miles then stop and let them "cool down" for a while. Then drive 60 miles and let them cool down. Don't go excessevly fast and don't hammer on the throttle or tow for about 500 miles.

Not to complicated, also run synthetic in it!

 

should I change out the diff fluid at 500 miles to get out the gear chafing?

 

run 15 miles cool it down.. drive 100 miles cool it down// at 500 miles change it... i put royal purple in mined.. then again at 1000 miles i changed it.. now i plan on doing it every 3000... so it depends hhow you treat the truck

 

Okay so next question,

The owners manual says 75w90 and the service manual says 80w90. Which is the safer one to go with? I always run synthetics BTW.

 

75w90 is better if you have harsh winters.
75w140 synthetic is factory fill is equipped with the towing package. I run the 140 all year in both diffs.

 

There is disaggreement about whether diff gears need a special break in proceedure, but doing this couldn't hurt:

quote
"All new gear sets require a break-in period to prevent damage from overheating. After driving the first 15 or 20 miles you must let the differential cool for 30-40 minutes before proceeding. Drive 500 easy miles before towing. Tow for very short distances (less than 15 miles) and let the differential cool before continuing during the first 45 towing miles. Change the gear oil after the first 500 miles. This will remove any metal particles or phosphorus coating that has come from the new gear set." end quote

from

http://www.offroaders.com/tech/differentials.htm

I have also read about gently driving the truck in large circles, both clockwise and then counter-clockwise, in a large parking lot before doing the oil change at 500 miles.

 

when I had mine done (up to 4.11's) the shop wanted me to initially drive it for 30 minutes, then let it cool all the way down, then every 20 minutes or so of driving, let it cool down for 20~30 minutes for the 1st 500 miles. kinda pita but better to do it right. Ask the shop when you get the truck back.

 

Pretty good advice so far. Don't forget you have a front R&P to break in too. Some people do not bother to really break them in since they will typically be driving at low speeds when 4 wheeling. But, I'm overly cautious and would consider doing the front as well.

I have seen an R&P that was not properly broken in - and it was UGLY! The ring gear was excessively worn and rounded, and it had less than 200 miles on it. I wish I had a picture of it with me. Might have to stop by the local off road shop to snap a picture of it...

Take a look here: http://www.4crawler.com/4x4/CheapTri...ml#GearBreakin

I know this is geared (hahaha) more towards Toyota's, but it is generally good advice.

Good luck!
Cartman

 

I don't have a front R&P, just a 2wd.

But here'shopefully the last question: How to you recalibrate the speedo in our trucks for new gears; is it gear drivenor a sensor? I thought programmersdidn't work to change the gearing, but shouldyou figure out a tire size that'll put the ratio as close to stock as possible and just lie to the programmer about the tire size?

I'm about to order from PORCand I know I need the R&P andthe master install kit, but is there anything else I'm forgetting?

Thanks everybody!