Hey guys im going to be changing some of the fluids in my truck today and i was just wondering where i could find out what kind of fluids to use?. The owners manual didnt really give and information and the local auto parts wasnt much help.

Im going to be changing the front and rear diff...tranny and t case.

I was told to use 75w140 in the front and rear diffs. So i think im going to buy some synthetic fluid for those. But i was wondering if i needed to run any additives?

As far as the tranny and t case go i was told to use synthetic ATF fluid for both but somebody told me to get sythetic mercon for the tranny. and not to run any additives in the tranny or t case?

Also does it matter what brand of fluid i use?. Ive heard really good things about penzoil and royal purple?...But i was just wondering what you guys are running in your trucks?

 

I run Amsoil Synthetics in my rigs but that is my preference and have had nothing but great experiences with all of the products I have used. How much towing are you doing? 75W140 is really for severe heavy towing or heavy towing on a constant basis. I am sold on synthetics and there are some on the forum who say that switching to synthetics will start or find leak points on your engine or transmission. I have two daily drivers Summer ride right now has 188,000 and the winter ride has 183,000 and both were used when I got them. Switched exclusively to synthetic front to back and zero problems.

 

I pretty much never tow...im not saying that im never going to tow...but right now i dont tow anything. But i do haul pretty heavy loads in the truck often. Should i still run 75w140 or should i switch to something else?. Im also going to run full synthetics. But if i run synthetics in the diffs do i need a additive?. And if im running synthetics in the t case and tranny do i need any additives?. Thanks

 

I am running 75W90 Synthetic from AMSOIL and added the the limited slip additive in both rear axles on both trucks. I also use the same oil in the front axle on my 4X4 now that being said here is what I found. I am in Upstate NY where it gets cold not as cold as some but -15 or -20 is not out of the question. After switching to synthetic the 4X4 still spins over on the coldest days like it was 50 or warmer out. The transmission shifts like it should and the truck moves like it should instead of like the brakes are on. The reason I am not pushing thick honey around until it warms up. The summers here also can be hot not as hot as others but 95 to 100 is not out of the question either. Synthetics are much more stable in this heat range and don't breakdown as quickly or at all when Dino-oil would have failed.

Here is what I am using.

93 F-250 7.3L 4x2
Engine 5W30 Series 3000 Amsoil w/synthetic oil filter from Amsoil
Trans (E4OD) Amsoil Synthetic Automatic Transmission fluid
Axle Severe Duty 75W90 Synthetic w/additive

88 F-350 7.3L 4X4
Engine 15W40 Synthetic w/By-Pass filtration gives me 13qt capacity.
Trans (C6) Amsoil Synthetic Automatic Transmission fluid
Front Axle Severe Duty 75W90 Synthetic Rear Axle same w/additive

I use the 5W30 in the F-250 because thats the summer ride and the rig I mainly drive to work during that time. It performs great for it's application and I don't use this truck as heavy as the other one.

I use Amsoil but again my preference and won't say one is better than the other and won't entertain any discussion of who is or is not. But I do support synthetics all the way.

 

i run royal purple synthtic in everything but the motor. i run it because its good stuff and i get a good deal on it from work. i run 75 90 in both diffs on my truck i dont have limited slip so i dont use an additive. synthtic mercron in the trans and transfercase i dont use any additives in them either i see no need to.

 

As far as the additive, you only need to run a friction modifier if you have a limited slip differential.

If you jack up one rear tire with the transmission in neutral, does the tire turn easily?
If it does you probably have an open differential or the clutch pack in the differential is shot.
In that case the additive is not needed.

However if you can barely turn the tire that is off the ground, you have a limited slip differential and you need the additive since the clutch pack is still in good shape.