Ok, first I am no expert when it comes to our trucks and what is best to use as far as manual transmission fluid and gear oil.

Truck specs:
2001 Sport, 4.2, manual, 3.55LS
Not sure but I believe I have either the 8.8 or 9.75 rearend and not the 10.25. Not sure how to tell.

I have heard alot of great things about the "Redline" products and have been trying to search for websites with more information.

Now I come to you pro's out there with the experence. I have the instructions that pfellow wrote, I would add excellent job. However he suggest using Redline 75w90 which has the friction modifier in it.

After reading my owners manual it recommends 75w-140 GL-5. I read that the Redline 75w90 is a GL-4. I plan on changing the gear oil at approx. 30,000 intervals.

First question, should I use the Redline 75w90? Or does anyone know of a fluid that Redline makes that will meet the GL-5 spec.?

Next question is on manual transmission fluid. Mercon is what is recommend for my manual. Redline has two that will meet it both are the same price. One is synthetic high temp ATF, and the other is ATF-D4 which states it is designed to meet the requirements of the new Dexron IV specs and the shear stability requirement of the new Mercon specs. Which one should I be using?

Finally, if you could add with your comments any recommendations on where to buy, either stores or online or both would be great.

Thanks for you help.