I went to ford today to pick up rear diff fluid, im changing out my rear diff cover for an aluminum one and fluids have 83000 on them. So he says when you put the rtv sealing on, you let it skin over then bolt it on and let it dry for 24 hours before putting fluid in it because the synthetic oil will eat through the rtv if you add it to soon. Thoughts? I read most guys were only doing a couple hours and then putting fluid in. This was one of their mechanics that I was talking to..And when adding the fm to the fluid should I start with a full bottle?4oz. And add more if needed..Thats what he recommended.

 

what i do is: tonight i would drain and clean the surfaces real good and then put the rtv on the cover and let sit for 15 minutes. then bolt the plate up to the rear diff and be done for the night. go out in the morning and fill her up. when i add the fm i just dump the whole tube in and then fill with diff fluid but i get the tube from autozone so i dont know how much is in the ford fm tube. i have had trouble in the past getting my f350 diff to seal up but when i waited to put in the fluid until atleast 12 or so hours later its been all good.....

 

I agree with Bill.

I wished I would have waited atleast 12 hours to refill. instead of 1 hour, because now I see oil seeping along the bottom edge.

 

Sounds like this is what ill do too.. Ford friction mod is a 4oz bottle

 

First, make sure the fluid you have doesn't have the FM in it already. Mine did. If it doesn't, add 2oz. and test drive by making sharp left & right turns. If you hear chattering, add the last 2oz. You can add it through the VSS sensor on the top of the diff if you don't have enough room to add it through the regular fill hole.

 

I dont think the motorcraft 70/140 has fm in it but now that you mention it ill doublecheck. Ill take your advice and add 2 first and test drive. You can always add more but to much and your s.ol.. Lol... So i just looked at the bottle and it says for limited slip rear axle. Also says the addition of friction modifier may be needed, consult your vehicle book or something like that. Should I take from that statement that there is or isnt fm i the bottle already?

 

hey guys i dont have a limited slip diff, so if i were to change my fluid and the fluid i got has friction modifier in it will it hurt anything? i am thinking not. what do you all say?

 

Nope -- it won't hurt a thing. The FM is for clutches in an LS diff. Since you don't have any, it doesn't matter (just like using it in the front diff).

 

I only waited about 30 mins before filling my diff. no problems with leaks. Use Royal Purple 75-140, it has fm already in it

 

How long has it been since you change your oil Jay?

I didn't start to see signs of seeping for a couple of months later.

 

two weeks ago. SSSHhhhhhhhhhhh!!!!!!!! knock on wood.

 

I hope you don't have any issue with leaking Jay. please let us know if you do.

Myself, I will be doing it over again and won't be refilling for at least 12 hours.

 

To be on the safe side ill to the removing of the plate and fluids and resealing the evening before and refilling the next day just because I would hate to have to replace 80 bucks in fluids again. I dont use my truck when im sleeping so drying overnight is no big deal. Lol. Well sometimes when I dream I do!! Lol

 

I did mine months ago, and I didn't wait but an hour or two. No issues so far. Which type of RTV did you use? I used Gray Permatex. I also used RP 75w-140 w/FM.

 

This is what i used Joe -