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BlackDiamondBound
01-06-2005, 02:29 AM
i got gears installed a little over 500 miles ago. i have been breaking them in like everyone here has told me to do. after 45 mins on the freeway i pull over to give it a rest and check the diffs. and they (front and rear have the 249) are always realy hot. i am changing the oil on fri, right now i have 75w up front and 90w in the rear. is there anyother type of dif oil i could put in that will keep it from getting so hot?

thanks

LouisianaZJ
01-06-2005, 02:51 AM
its the gears not the oil

synthetic will be a tad cooler than dino

BlackDiamondBound
01-06-2005, 03:06 AM
thanks. the gears will cool down eventualy though right? i just though after 500 miles it would not be this bad

RufftyTuffty
01-06-2005, 11:12 AM
They will cool down....but diffs run warm anywayz.

Make sure that your breathers are clean...maybe even get some new (larger) tubing.

~Mike

ATL ZJ
01-06-2005, 12:03 PM
Second what Mike said. And be careful with synthetic. My gear guy warns me that synthetic breaks down quicker under heat. So I use non-synthetic 80/90 with my 4.88s.

OverkillZJ
01-06-2005, 01:38 PM
Second what Mike said. And be careful with synthetic. My gear guy warns me that synthetic breaks down quicker under heat. So I use non-synthetic 80/90 with my 4.88s.

Your gear guys an idiot, IMHO!

ATL ZJ
01-06-2005, 02:25 PM
Your gear guys an idiot, IMHO!

Haha, he might be... He's pretty redneck. I had to tell him about pinion angles with CV-type driveshafts as opposed to the stock kind since he deals with racing applications mostly.

What is the real deal on synthetic? I run the partial synthetic or whatever it's called up front since it doesn't see much daily use and never gets that hot, even on the trail.

Jim311
01-06-2005, 11:51 PM
I thought synthetic oils offered INCREASED protection to thermal breakdown.


:?:

OverkillZJ
01-07-2005, 12:33 AM
I thought synthetic oils offered INCREASED protection to thermal breakdown.


:?:


They do, but I'm not going to pretent to be smart enough to understand why.

My buddy Mark (Karstman on the boards) explained it to me once, and I think I understood for a brief moment... but now, whatever. I blame the bottle of Jacks in my left hand.

His explenation, as well as others I've read here and there, are enough for me to spend 3 times as much and run it in my diffs.

JpRngr
01-07-2005, 01:53 AM
Synthetics are specifically DESIGNED for the application. One of the things they take into effect is thermal breakdown. Convential oils HAPPEN to have a lubricating property and that is why they are used. Not saying convential oils don't do the job, just that they weren't specifically created to do it as well as possible.


Corey

LouisianaZJ
01-07-2005, 02:01 AM
the easiest way to describe it would be like iron vs steel. steel is iron with all the impurities all meted out and all the molecules all uniform and lined up nice
synth is kinda like that where the dino is purified so it is more uniform and less likely to break down

when it "breaks down" say you start with like 75W-90 it will break down to like 70W-80 or something. it will shear down to a lighter duty oil

ATL ZJ
01-07-2005, 10:02 AM
the easiest way to describe it would be like iron vs steel. steel is iron with all the impurities all meted out and all the molecules all uniform and lined up nice
synth is kinda like that where the dino is purified so it is more uniform and less likely to break down

when it "breaks down" say you start with like 75W-90 it will break down to like 70W-80 or something. it will shear down to a lighter duty oil

That helps a lot. So would that mean that it's best to run the thickest gear oil that you can get away with in order for it to provide protection as long as possible, since it will eventually break down to lighter duty oil? I can't exactly accept the OE manufacturer's recommendations completely since their gears aren't in the axle anymore. I admit I don't know a whole lot about this lubrication stuff. :lol:

Alaska ZJ
01-07-2005, 11:11 AM
Second what Mike said. And be careful with synthetic. My gear guy warns me that synthetic breaks down quicker under heat. So I use non-synthetic 80/90 with my 4.88s.

Your gear guys an idiot, IMHO!

Werd

Mtn WJ
01-08-2005, 03:21 PM
The hottest Diff I have seen in awhile is Alaska's Avator.



About a year after I bought my WJ new Jeep replaced the rear diff gears under warranty. During the break in the diff got so hot that the paint burned on the cover. Jeep said it was normal to get hot during break in but I was not convinced. I put in new gear lube after 500 miles and the problem went away.

I later had new 4.10's put in when I had an ARB installed. No extreme heat this time during break in. Same type of gear lube. I replaced the lube after 500 miles and it looked much better than the previous break in. Same brand of Gears DANA.

If you plan to change your diff lube every 10-20k miles I suggest staying with a standard type gear lube. If you want to go longer between changes then I suggest going to a synthetic.

ATL ZJ
01-08-2005, 06:38 PM
Well as it is now, I am changing my conventional about every 6k miles. I just really don't want to burn up my gears... Maybe I'll try synthetic if it'll do a better job.

nate
01-12-2005, 11:21 AM
How hot is hot? Can you keep your hand on the diff?


i got gears installed a little over 500 miles ago. i have been breaking them in like everyone here has told me to do. after 45 mins on the freeway i pull over to give it a rest and check the diffs. and they (front and rear have the 249) are always realy hot. i am changing the oil on fri, right now i have 75w up front and 90w in the rear. is there anyother type of dif oil i could put in that will keep it from getting so hot?

thanks

BlackDiamondBound
01-16-2005, 02:49 PM
i can keep my hand on the difs. its hot, but not hot enough to burn me

nate
01-18-2005, 12:20 PM
Yeah if its hot enough to burn you that would be BAD. If you can hold your hand on the pumpkin and it's not uncomfortable, it should be ok.