Car maintenance question

edbert

Alright, I'm pretty savvy when it comes to auto maintenance but something has me a little confused. My in-laws are headed to Colorado for the majority of the summer and so I offered to get everything up-to-date maintenance wise on their jeep so everything would be running well for them. I inquired about changing the fluid in the differentials and he told me that he had it done a few years ago and that they put synthetic fluid in and that it would be good for 100K miles! In searching around I have found nothing that suggests any type of gear oil that would last this long.

For those that will request it, 2001 Jeep Wrangler Sport, 4.0L, 5spd, Dana 44 in the rear and Dana 30 up front, no traklok in the rear.

I had to use synthetic fluid in my wife's Grand Cherokee and it was scheduled to be changed every 25K at the longest intervals. I think the guy at Express Lube was just trying to sell him something(although I don't know what since he prolonged the interval until the next service) he thought he didn't necessarily need.

This should have been a havoline product since it was done at an Express Lube.

Does this sound screwy to anyone else? If you have actually heard this to be true then by all means fill me in on the details. Otherwise I'm gonna have to call my father-in-law and tell him the guy lied to him 4 years ago. It's not that big of a deal since he should be running synthetic since it has been flat-towed back and forth for about 20K miles and fills every bullet point on the severe driving schedule.

Thanks for any help you can provide!

apc

It has been my experience that these folks can answer almost all your questions.

http://www.jeepforum.com/forum/forumdisplay.php?f=9

edbert

I have asked on my local club forum as well, but thanks for the tip apc. I know there are some pretty big gearheads on here so I would just post up and dip into their brains a little.

jcaut

I'm not an expert on this, but I believe there's very little in car maintenance that's "lifetime". Most of that is just marketing.

I'm a believer in synthetic lubricants and I believe that they have particular advantages in high-shear, gear oil type applications, BUT I still wouldn't go longer than 50K on a hypoid differential lube. And certainly not if it sees anything that amounts to "severe" service. That said, I think the most critical change is the first one, to remove the break-in wear products.

Assuming they did indeed put a good quality synthetic 75W-90 in there, if it's got 20K since the change it's probably fine. If it's got 50K, I'd change it.