[rollout]

Any tips on using the RTV silicone gasket making goo? Am planning on removing rear Diff cover, cleaning magnet, and re-installing. Will use the RTV per club recommendations, but have no experience with it. Best guess: clean both surfaces really good. Apply bead to cover surface, bolt in place. Couldn't be easier?right?

What about drips and globs, and how tough is the stuff to work with? Is there a better brand? Should I wait till it skins over to mate the two surfaces?

Have read that I don't need to wait to add new fluids, but the other details are a bit fuzzy.

Appreciate the input.

 

[Anthony]

-Remove cover
-Clean Magnet
-Scrap sealant off of rear end and cover, really well
-Clean surface with paint thinner or brake cleaner as final step
-Put new sealant on cover
-Install cover on rear end
-I tend to wait about an hour before refilling, gives the RTV a chance to dry
-Refill fluid, don't forget the friction modifier if equipped with LSD
-Done
-Find an empty parking lot and do 8 figures to work the gear oil into the clutch packs, only on LSD rear end.

I have pics and more info, if you need on my site.

 

[Silver Ghost]

Make sure you get an "automotive" grade. Color doesn't matter, but red is typically for high temperature (under hood) applications. The automotive type RTV has special additives in it to protect against break-down in contact with oils, greases, and other lubes. Bathtub caulk (made with much the same ingredients) doesn't.
You don't need a lot of RTV but you need to make sure there are no open spaces in the bead to allow liquids to leak out.
Make sure the two mating surfaces are clean - don't leave any gear oil behind. Clean the surfaces with a good solvent - acetone, toluene, even gasoline will work. Make sure it's all dried before applying the RTV.
Apply the bead of RTV and wait about 1/2 hour for it to skin over. Then put the cover back on and bolt it down. You should be good to go. RTV typically requires 24+ hours to fully cure, but you won't be subjecting it to any unusual stress, so once it's started to skin over, you shouldn't have any problems.

Joe
38 years making RTV and stuff like it.

 

[greg]

Joe:

What happens when you want to take it off the next time? Is is hard to scrape the RTV off?

greg

 

[Silver Ghost]

Yeah - it's an adhesive/sealant and will pretty much stick to the surfaces. You'll need to scrape it off next time. The good news that it's probably stronger cohesively than it's adhesively and when you start to scrape you may be able to pull it all off as a strip.

Joe

 

[greg]

Gotcha, thanx Joe.

greg

 

[FSTDANGO3]

Greg you can buy a gasket removal bit for your drill it's mildly abrasive when you put it in a cordless drill after removing covers just go around both surfaces once or twice it comes right off and leaves it nice and clean
Steve
VP
DOC

 

[Volphin]

Mopar RTVs

I have always found a small sponge with a nylon scrubber works best on the small bits left over. Go in a slow circular motion. The high speed gasket scrapers just push it around. Peel off what you can. I like the Mopar Orange. (So does my air ratchet :lol: :lol: :lol: :lol: ) Use Mopar black for engine oil apps. Orange for diffs and Trans RTV when needed. They're different formulas for a reason. I found a Permatex that's the same as Mopar Gen 2 black. Same smell, color and properties. I bench tested it. If I find the PN I'll post it. This is important as the Mopar Gen 2 has a one year expiration on the tube. Permatex stock is going to be somewhat fresher. Maybe Joe can shed some light on why?

Bill

 

[Silver Ghost]

Re: Mopar RTVs

Use Mopar black for engine oil apps. Orange for diffs and Trans RTV when needed. They're different formulas for a reason. I found a Permatex that's the same as Mopar Gen 2 black. Same smell, color and properties. I bench tested it. If I find the PN I'll post it. This is important as the Mopar Gen 2 has a one year expiration on the tube. Permatex stock is going to be somewhat fresher. Maybe Joe can shed some light on why?

Bill

Almost all RTV uses the same chemistry to cure, and acetic acid (that vinegary smell) is a by-product of the cure mechanism. Some of the proprietary high-end RTV's (GE Silicone II for example) use a slightly different mechanism and the odor is different.

As to your choice of color for application, I'd use the Mopar Orange under the hood (and maybe the transmission) and the Black for the diffs - just the opposite of your preference, Bill.
The Orange RTV is more likely a temperature resistant grade. The color is probably the result of an additive designed to give high temperature performance. It's probably in the Black as well, but unless it's specified in the components listing, you wouldn't know it. For Automotive grades however, both the Black and the Orange will have an additive that helps resist degradation from contact with oils and lubes. Black Bathtub Caulk won't have this additive so you can't rely on color to tell the additive components.
So, to make a long story even longer, the Orange will give you both high temp AND oil resistance while the Black will most likely have Oil resistance but not necessarily high temp resistance. Regardless, make sure you use automotive grade not your normal household sealant.
As to expiration, that's up to the manufacturer (or packager.) Unopened you may be able to use a tube more than a few years down the road. Once you've opened a tube, it'll start to cure almost immediately and be useless a few month later.
Hope that helps.

Joe

 

[Volphin]

But?

Joe, any idea why Mopar changed to an orange on their diffs citing a "chemical conflict" with some of the axle lubes? Or was that just for the synthetic lube?? When I pulled them for the first time, they were adhered with orange. :? :? (Quite well I might add.) I know I read this somewhere. Don't have it handy though? Oh well, I guess the point is, as long as it's sealed against contamination the RTV is doing it's job. My rear diff has a MH cover with an O-ring. I'll never scrape that one again.

Bill

 

[Silver Ghost]

Just because they had to reformulate the sealant doesn't necessarily mean they had to change the color. The material specs should call out the color but doesn't have to. They may have changed manufacturers.
Most of my work was in heat-cured not RTV rubber, but many of the performance specs were similar. We made compounds in red (orange), black, blue-black, and gray for similar applications.
So as a general rule, read the label and make sure what you're using is for the right application. But, you can probably use any RTV for diff seal; I'd consider it a relatively low performance application (as opposed to under the hood.)

Joe