[two_stangs]

Both of my cars are slightly modified. Not too much. And street driven in Southern California.

It's time to change the gear oil in the rear end and I wondering which would be the best. I was using Valvoline but want to go with something sythetic.

Like Royal Purple?

Let me know.

 

[Carl]

I use Royal Purple 75w90 gear oil and have nothing but good things to say. I have been told that Red Line is also good stuff but have never used it. Give Royal Purple a shot you wont be disapointed.

 

[black87gtconv]

I think all the synthetics are pretty good and dont really know which is the best for gear oil. I use Red Line and love it so that is what I would tell U to do!!

 

[dupont4sure]

how can you tell what weight of oil to use

 

[need4spd90]

ford issued a TSB a few years back that was calling for 75w-140 synthetic gear oil in all 8.8 trac-lok rears

heres the section from it:

AXLE FLUID REQUIREMENTS HAVE BEEN
CHANGED. ALL VEHICLES BEING REPAIRED BY
THIS TSB MUST HAVE REAR AXLE LUBE
XY-75W140-QL INSTALLED, IN PLACE OF
75W90-QFEHP. AS PART OF THIS REPAIR,
CHECK AND REPLACE IF NECESSARY THE
CURRENT XY-75W90-Q“FEHP” METAL TAG, WITH
A NEW 75W140 TAG (F3TZ-4121-AA).
ADDITIONALLY, REMOVE THE MULTI-COLORED
LABEL WHICH IS LOCATED ON THE RIGHT SIDE
AXLE TUBE, OR BLOCK OUT ANY/ALL “FEHP”
OR “75W90” REFERENCES ON THE LABEL.

i run royal purple 75-140 in mine

 

[Brutal Metal]

Amsoil:bigthumbsup

 

[THOR74]

I tried running synthetic in my 8.8 Traction-Lok and it kept slowly leaking out of the pinion seal, due to the fact that its molecules are smaller than regular fluid.

So I went back to Valvoline 75-90 conventional (as per owner's manual) (with friction modifier additive) and have had no problems since.

Some seals that were not meant for synthetic can leak if synthetic is used. Thankfully, I've used synthetic in engine, tranny (T5), brakes and have had no issues.