OK, it's a 2001 4X4 with 3.55 LS leaking rear diff.

I Searched and found that FORD Calls for 70-140 Synth gear lube, but many say to use 75-90 Synth. Is there a reason to go with the 75-90 or has ford changed the recomendation?

I plan on changing the rear diff cover and to use blue RTV sealant (cause I have some already and I like it)

I have an AMSOIL dealer practically next door to me and planned to use that. I think I already have a bottle of 75-90 if that's the prefered.

I'll pick-up a bottle or 2 of FORD Friction Modifier.

It leaks very very little, not enough to drip, just enough to discolour the bottom left corner of the cover. I suppose just trying to re-torque the diff cover bolts wont stop the leak right...........?

Thanks in advance
Dpostman

 

I used Amsoil 75w140 on my rebuild. I broke in the gears with some cheap 80w90 oil, and no friction modifier. After running it for a little over 500 miles, I drained the axle and cleaned out the old oil as best I could with a brush and some clean solvent, then I blew it all clean with the air gun. Then I resealed it and put in the Amsoil.
I wouldn't use that friction modifier if I were you, all it does is make the clutches slip more easily. I'll take a little noise while taking a turn over a loss of traction any day.

 

Thanks for the reply.

I should've been more precise: I don't plan on swaping any gears. These are well broken in at 102 000Km (60K miles) I Just plan on doing the lube job. And about the Friction modifier, I mentally can't handle those kind of noises very well, and "a little loss in traction" can easily be compensated with a little turn of a ****

OK so 1 vote for 75-140

Anyone else?

Dpostman

 

Its not just a little extra noise you'll be getting, but a lot less milage on your clutchs by leaving out the modifier. The extra noise is from the clutches building up heat, which is destroying them. If you want more traction, do it right and put in a locker. What are you breaking in. If the diff is set up right there is no break in. Does Ford use break in oil from the factory?

 

Use the 75W140. That is what Ford recommends. It should be the same price as the other stuff. FWIW I use the 75W140 synthetic without the friction modifier. It is in the oil that I buy.

JMC

 

Thanks JMC,

Looks like it's gonna be 75-140.

dpostman