I got a quick question, I have a 98 f150 with orp and was wondering what weight to run in the transfer case? Someone told me I should run Mercon ATF trans fluid. Doesnt seem right to me??? Also, If I run the redline in the rear axle..do i still have to add the stuff for the limited slip?


thanks
Justin

 

I was wondering the same thing and no one seems to have replied to this post yet. The Chilton's catalog for my 98 says the same thing. Should I use the ATF? Do I need to replace this fluid every 25k miles like the rear diff fluid?

Thanks.

 

I'm pretty sure that the transfer case takes 80-90 fluid. I'm not positive, but I don't think I would put ATF in there.

If you have the limited-slip, then yes, you still need to add the friction modifier. Be prepared for heart failure when they tell you how much it will cost for the diff fluid.

 

I just rebuilt the rear diff. Truck has ~80k on it. I used the 80-90 with friction modifier on the rear and figure I should change the fluid on the front as well, but I haven't found anything yet, other than the Chilton calling out to use the ATF.

I figure the 80-90 would have been what I should be using, which is why I question the Chiltons. Anyone done this yet?

 

The T-CASE on the 97+ F-150s takes ATF.

The rear diff takes 75W140 Synthetic and the front takes 75W90.

I have Amsoil ATF in T-Case. It was drained recently for a clutch job and they put dino oil in it. I have afriend that sells Castrol synthetic ATF and I will try that.

Regards

Jean Marc Chartier

 

JMC is right, I got confused between the TXF case and the front diff.

Hee hee

 

ATF in the transfer case NOT 80w90!

I just did my rear diff fluid change/cleanup and used Redline 75w90 synthetic. Ford recommends 70w140 but some factory techs have said they get a lot of trucks in with rust and corrosion in the rear axle because the OE synthetic doesn't absorb water.

Anyhow, more than a few sources have told me that you don't need a friction modifier when using Redline diff oil. My rear diff functions as before, no chatter or hop or anything. Friction modifier is usually a fine powdered material that makes the oil more slippery so the clutches in your LS diff don't grab. I got mine at www.mopacauto.com for around $13 a quart and you need just under 3 quarts in the 8.8inch diff. The redline oil is a nice clear golden light brown colour. Stinks like the other gear lubes... I call them "yummy lube" for that reason.

 

I forgot to mention that I did not use friction modifier with the Amsoil 75W140 in my rear diff. So far no problems with chatter or rust??????

Regards

Jean Marc Chartier