So I've been reading thread after thread about the rear differential replacement/sealing/fluid/etc etc etc.. and I've decided that mine needs to come off and resealed and filled, etc...

First off, thanks to pretty much everyone who has contributed to a thread regarding the differential.

I've decided to go with Black RTV and I the recommended 75W140 Synthetic Gear Lube... at $10/liter (and I need 3 ofcourse..)

My questions are..

1.) Do I NEED the synthetic? I do a lot of highway traveling and I never really off road (or plan to..) and really only use 4 wheel drive during the winter, truth be told. I will be towing a small boat (13 footer..) but thats about it.. I was hoping to save a few bucks on the gear lube. Im not cheap, but money is money!

and..

2.) Does anyone recommend the Blue RTV over the Black, or vice versa, and why? What about the red?

Thanks!

 

75W140 Synthetic is what your truck requires. You will also need the Friction Modifier from Ford. The Motorcraft 75W140 is about $27 a qaurt from your dealer, and the Modifier around $10. I love the black RTV when sealing anything from water pumps to diff covers.

Just remember to clean the surfaces with a razor blade than wipe the mating sufaces with brake cleaner to ensure a good seal.

 

I dont need the Fric Modifier because I dont have limited slip... or at least thats what im reading...

 

i used orange rtv on the 9" under the 77 F150 4x4 between the carrier housing and the axle housing when i swapped another carrier housing on last fall

has been fine

i hear the 4x4 guys use ordinary white caulk on rear ends to seal them

and you could always get the gasket from napa or dealer btw



good luck

 

*cough* Walmart *cough* has 1QT Bottles of SuperTech (Their own brand..) 75W140, says Synthetic... for $10 a bottle.. I saw it as too good to be true.. it doesnt say blend or anything, just synthetic.. thats why I was kinda hopin to use that instead.. but I figured I would ask. If it works fine I'll use it!

 

You do have to use a 75w140 in synthetic. I have used the red rtv on 3 of my rear ends now works good. If its an open diff you do not have to have the friction modifier. I'm sure the wallyworld **** works or they couldn't sell it but I wouldn't trust it in my truck.

 

I recommend NAPA RightStuff sealant. Clean & degrease both surfaces, put a thick bead on, bolt it on ONLY tight enough to make it stick ALL the way around, then let it sit for 15 min - 1 hr before torquing the bolts properly.