Which RTV to use for rear differential cover?

[jwhjr]

I'm going to change the differential fluid on my 04 Silverado 1/2 ton in the near future, and I'm planning on using RTV instead of the paper gasket when I put the cover back on. I've changed the fluid twice already, but used a pump to get the old fluid out. This time I'm pulling the cover to see how things look and to clean off the magnet etc. There's a couple of the Permatex RTV products that look like they may fit the bill as far as using for gasket material. It looks like either the Ultra Black or Ultra Blue would work. Has anyone used either of these and had any issues with leaking? I'll be putting synthetic in if that makes any difference.

[crappiebuster]

The blue is suffecient.

[deadeye]

Pretty much any of them will work fine. I prefer the ultra gray, but they all work.

[Jeremy airjer W]

I prefer the grey myself. The nice thing about that is you can use it for many applications. The blue (and especially orange) is a sure sign of backyardigans under the hood. Not necessarily bad but not necessarily good either!

The black stuff will work fine also.

We have started using the "right stuff" black and grey with great results also.

The best I have used is the grey RTV from Volkswagen. Its expensive but I haven't run into anything that performs as well as it does!!

[jwhjr]

Thanks to all for the responses. I think I'll go with the grey. airjer - how long should I wait after putting the cover back on to fill it? It looks like it begins curing immediately, but I didn't know if there is a "best practice" on how long to wait before filling the differential up.

[Jeremy airjer W]

Clean up both surfaces. I like to sprak a little brake clean on a rag and wipe down the rear end (LOL there isn't another forum on FM that you can get away with that! ) mating surface. Apply a bead on the cover and install on the rear end. Tighten the bolts until you just start to see the RTV squeeze out. Let it sit for 20 to 30 minutes. Finish tightening all the bolts. Fill with fluid and enjoy.

Some old school info. Drive the truck in tight circles both left and right to get the new fluid out to the axle bearings. I don't know if there is any relevance to this but its what was done at the shop when I first started in the business and its been habit ever since.

[jwhjr]

Thanks for the info airjer! I'll be doing this in the next few weeks. If I feel ambitious at the same time, I'll try getting some pics of the process and post back.

[theoilman]

Airjer - if it is a limited slip or a locker the figure 8s are needed to reseat and circulate the fluid all the way. Many of these will chatter badly if you don't do a 'run-in' of several slow lazy figure 8s. If it chatters after the figure 8s add another 4-oz bottle of the limited slip friction modifier. With a standard unit you will never drain the fluid totally from the wheel bearings (with those that use the rear diff oil to lube them, some use sealed bearings, but then you already know that - for the benefit of others who will read this).

My preference on the silicone sealant is to use the black, either the regular or the super. GM uses the regular black from the factory on most.

Excellent comment on the brakeclean - spray it on a rag and wipe the housing surface. Never spray the chunk or the inside of the housing. Some of it will get into the casting and not evaporate totally - enough that it may be harmful to the new lube.

[chasineyes]

Any recommendations on what kind of diff fluid to use on a Ford Expedition????

[fishing tech]

75w140

[jr. borch]

instead of doing the figure 8 to get the oil around granted im sure it would work to get the bearings lubricated. what i would do is fill up the diff. then lift one side of the vehicle up so some goes into the bearing on that side and then check fluid again then lift the other side up and check and fill fluid if needed. that way your not likely to run your bearings dry at all. which i prefer to know my bearings are lubricated b4 they start moving.

granted this is what we do to semi's to make sure they have enough oil in the diff and the bearings. so it could be a waste of time but idk i havent done much with cars or regular trucks yet

[Jeremy airjer W]

I have done that in the past. It certainly can't hurt and once again you get to submerge the bearings in some fresh lube.