has anyone changed their gear oil out with Mobil1?

i changed mine when i put on the new diff cover plate, and i'm getting a bad "whine" from the gears now..

i put the ford diff fluid additive in there, but it didn't go away.

is it because it is a different weight oil? help!

 

I changed my gear oil back in mid 2001 when I installed the mag hytec rear diff cover. I used Mobil 1 75-90 synthetic and added one tube of friction modifier. I have no rear diff noise and have driven the truck a hard 20K miles since this was done...

 

same here. Put in 3.73's Mobil 75-90 No problems.


Might be your clutch packs going??

I'm no gear head though.

 

Ditto. Mobil 1, 8 oz. Torco friction modifier, quiet as a churchmouse.

 

i guess i'm going to have to change it back to the stock stuff.. it's getting worse..

 

If you don't have a stock set I have mine still.

 

Really? i work at a lube shop and put 75W90 mobol 1 in fords all the time, along with the friction modifier. Try changing it again.

 

QKSILVR: i still have the stock gears.. all i did was change the diff cover & fluid.
i'll keep you in mind if my gears are bad.. thanks!


BlueL: everything was fine till the trip back from word ford challenge.. i started to hear a whine on the way back.. the whine has now become a roar that people driving beside me can hear!

i tried backing up fast to see if it whined then, but it doesn't.
hard left & right turns are okay. no popping or "chittering" of the tires. roar doesn't go away..