kcsoa22

Ok, quick question. What weight fluid does an 89 8.8 take? I would like to use a synthetic like mobil 1, I think they are suppose to have the friction modifier already in it.

Is that true, or should I add the modifier anyway, and I can not find which weight to use for the diff fluid.

What do you use?

dillon1340

i used royal purple that had the friction modifier already in it. i put friction modifier in with it though (i didnt read the royal purple bottle until i was done). didnt cause any problems but when i replaced my axles i just put straight royal purple in it.

tmajikman

I used 80w 90 weight, synthetic with a seperate friction modifier that I got at advance auto.

ZachW04Stang

I always add frition modifier even it the gear oil aready has it. You don't know how much is in the gear oil and you need 4 ounces total for your rear end.I run royal purple 75-90 gear oil and motorcraft friction modifier.

kcsoa22

Thanks guys, I guess I will just add the modifier to be on the safe side.

mjr46

these guys are right I do the same!!!! never any probs!! better to be safe then sorry!!!

dillon1340

what does friction modifier do anyway?

scrubadubb

i think it stops the fluid from foaming up. not sure though. but yes i put it in too.[sm=lol.gif]

ALMOST STOCK

It makes the surfaces more slippery.