Posi Fluid

[PaulZ]

Last time I changed the rear fluid Naps said the fluid they gave me was fine for the limited slip. Now I remember there is a special additive Ford sells. What does it do? 99 Ranger.

 

[alwaysFlOoReD]

I believe it allows the clutchs to slip. If not added then when turning corners you will get weird sounds as the clutches grab and let loose continuously.

 

[SenorNoob]

^ He's right.

From what I've heard most synthetics either have it included (cause it doesn't really matter in an open diff) or a slippery enough on there own to not need it. Verify with whatever brand you used..

 

[PaulZ]

Thanks guys. I’ll never find the Napa receipt but sure he said I didn’t need it. Think I’ll get some anyway. Ford parts counter?

 

[SenorNoob]

Should be available from your regular parts store.

https://www.oreillyauto.com/detail/c/motorcraft/motorcraft-friction-modifier/mot0/xl3?srsltid=AU7gw4UBRv3dmCpq1qYn1wwumJfeMJZnmkA-LxuQ1J9sTOvX04nfCGSZ

 

[PaulZ]

Called them. They dont have the Motorcraft bottle but they do sell a friction modifier. Hmm, right nearby…

 

[19Walt93]

I use the Ford Performance friction modifier because it's the old formula and works better than the new environmentally friendlier stuff.
By the way, your rear end is a Traction Lok. A posi was the weak kneed GM that kept breaking until the high performance guys swapped in a Ford rear end. You wouldn't call your truck a Tacoma, would you?

 

[pjtoledo]

@PaulZ what NAPA fluid did you use? still have the bottle?

 

[lil_Blue_Ford]

So, the assumption based on this is that you do have a limited slip, but have you verified this? The axle code on the door sticker will have a number and a letter, the axle tag will say something like 3L73, and if you jack up the rear axle (both wheels off the ground and in neutral), spinning one tire by hand will spin the other side the same direction.

Limited slip additive in an open rear doesn’t make a difference.

Most synthetic gear oils and some non-synthetic include friction modifier. There’s arguments over if what is in the oils is enough or not. No modifier at all in the clutch type limited slip can cause noise, binding, tire scub and damage to the clutch material. Too much modifier and the clutches can’t grab.