A family member recently gave my son a very clean 1992 4x4 V6. It's a solid truck, but it has high mileage (260K miles). The engine has either been rebuit or swapped at one point. He's planning to drive the truck about 1,200 miles to another state to work for a few months.

I'm not sure when the transmission and diff were last serviced and I was planning to help him do so before he left. Based on several recommendations that I found on this and other boards in the past, I've used Redline trans and gear oils in the 4x2 Toyota pickup that I drive, and it has performed very well for many years in that application. I'm a little concerned, however, about running a synthetic gear oil in such a high mileage truck primarily because of seal seepage. I've heard that some people have had issues with this, although I've never had a problem with this in my 4x2. Anyone using Redline or another syn lube in a high mileage 4x4 pickup? Any other good alternatives or recommendations?

Redline works fine for my in my '85:
- http://www.4crawler.com/4x4/index.shtml#SyntheticGearOil

Another vote for Redline MT-90.

Yes they sponsored our race car and NO that's not why I recommend it. Good stuff

Thanks to everyone for for the responses. The truck wouldn't pass emissions the other day and it looks like it has a burnt valve. Compression in #3 is about 50 PSI. Looks like I'm going to have to tear it down. Bummer.