Gear break in

[KH96XJ]

I know for the 1st 100 miles I need to heat cycle and drive lightly. Then easy driving for the next 400 miles.

My question is what is an approximate time for the diff to cool down after the 15-20 miles during the heat cycle for the 1st 100 miles?

[XJ4IV]

basically the run errands kinda deal like the mall or groceries...:sad0147:
(we never can get away from the stereotype) so an hour between should give cool down time!

[Mudderoy]

I know for the 1st 100 miles I need to heat cycle and drive lightly. Then easy driving for the next 400 miles.

My question is what is an approximate time for the diff to cool down after the 15-20 miles during the heat cycle for the 1st 100 miles?

Seems like it was 45 mph or less for 30 minutes then cool 12 hours. Let me find it.

[Mudderoy]

Even with synthetic oils, I still recommend the following procedure for breaking in a new gear set: After driving the first 15 to 20 miles it is best to stop and let the differential cool before proceeding. Keep the vehicle at speeds below 60 mph for the first 100 miles. I also recommend putting at least 500 miles on the new gear set before heavy use or towing. During the first 45 miles of towing it helps to go about 15 miles at a time before stopping to let the differential cool for 15 minutes before continuing. This is necessary because not all of the gear tooth is making contact until it is heavily loaded. When towing, the teeth flex to contact completely, and cause the previously unloaded portion of the teeth to touch and work harden. All of this may seem like paranoia, but it is very easy to damage the ring & pinion by overloading before the teeth are broken in. If you take it easy on a new ring & pinion and keep it full of high quality oil, it should last a lot longer.

:link: (http://www.4x4now.com/gt0999.htm)

[KH96XJ]

Thanks, that helps a lot. I'm on a time crunch since the shop didn't get my jeep done till this afternoon and I'm trying to get the break in done before Sat. When the shop was doing the test drive the jeep started overheating on them. :bang:

So, according to the shop, the aux fan is shot. The radiator overflow hose came loose and got hung up in the fan, burned the fan up and trashed the hose. They also think the clutch fan is worn out also. Guess its time to do the Grand Cherokee fan clutch upgrade. I hope the aux fan I ordered from 1A Auto gets here by Friday. Also need to put some holes in the hood for the Z-28 vents I bough. So much to do and so little time.

[Outlaw]

...So much to do and so little time.

That is like the nightly prayer of XJ owners :pray::bang::pray::D

[KH96XJ]

That is like the nightly prayer of XJ owners :pray::bang::pray::D


How true. :pray: