Good afternoon, I am looking to change the gear oil in my '86 f150. I have the borg-warner t-18 4 speed trans. I would also like to change the fluid in the transfer case, dont know which it is offhand, and the differentials. I believe I heard not to use gear oil with additives in the trans because it will ruin the yellow metal (synchros) but it is ok to use in the differentials? I was looking for some good synthetic fluid for all three and would like input on products that have worked well for the community. Also, which weight would work the best. Thanks in advance.

 

Here is what my list says.
Transmission 75w90 gear oil.
Front axle 80w90 gear oil.
Rear axle 80w90 gear oil.
Transfer case Automatic transmission Fluid.
If the rear axle has a limited slip diff you will need the LSD additive.

 

Thank you Lazy K. This is my first standard transmission, and first truck so im still learning : ) How can I tell if the truck has limited slip differential. It is four wheel drive. The book also talked about the manual steering gear with a sector shaft cover and a filler plug tower, I would like to change the fluid in it as well. I am unsure of what it is and what it does, the chilton manual doesnt have any diagrams or pictures of it. I havent had much luck finding pictures of it online either. Also, if the rear axle does have a limited slip diff and I have to add the additive, should I add it to the front as well?

 

Oops, I just noticed a typo in the thread name. It is a **1986** F150, four wheel drive, with the t18 trans.

 

Ford Axle Code Chart .: Articles Match the axle code on your door sticker to thei chart to see if you have a LSD or not. Your front axle will not be LSD so does not need the additive.
As for the steering box, do you have power steering or manual steering?
And the info is for a 1986, as stated in your post.

 

Thanks, ill check that out. I have power steering.

 

Power steering, then ignore the part about the filler plug on the gearbox. That uses the PS fluid to lube the box.

 

I just looked at the door, I believe I saw A16, the number was a bit faded but it looked right.

 

Did some research and this is what I found. Axle code "16" is a Ford 9" rear with 3.50:1 gears, no limited slip option. Can anyone confirm that this is correct? Thanks : )

 

What RW says about the steering gear. You can, if you wish, flush the steering fluid and replace with new fluid.
As for the axle I don`t know what code 16 is for. Maybe look for a tag on the axle itself around the differential housing for a number?
However if all you need to know is if the axle is LSD or not then do this. With engine off and parking brake off shift the trans into any gear, chock a front wheel and lift both rear wheels off the ground. Now rotate one rear wheel by hand, if the other wheel rotates in the opposite direction then you have a LS differential.

 

16 is a 3.50 open diff 9" axle. However, that doesn't mean that a previous owner hasn't swapped in a LS unit.