2nd Gen Non-Engine/Transmission Which RTV is the proper to use?

[JGheen]

Recently I changed out my differential oil and had a question about which RTV to use to seal the diff cover. I have always used Red RTV on my diffs since I owned my own vehicle and never had any problems. But I heard recently that Red gives off an acidic vapor after it cures that could contaminate the gear oil. Is there any truth to this? Would I be better off using balck or blue in a case like this? What is the difference between black, blue and red? I always thought they were all the same high temp RTV, with just a color preference for those who want a different color.

Thanks for the info.



Joe

 

[Gary - K7GLD]

I'm sure there are several very good choices - but if you want the absolute BEST RTV available, go to a Suzuki shop and get a tube of their1216 silicone - that stuff WILL NOT leak! But it IS pricey at about $25 a tube, which will do at least 4 differential-cover sized jobs. That stuff will actually provide a seal THRU residual oil, according to shop mechanics - I've used it on a couple of differentials, and to reseal a couple of lawnmower engines I've worked on - not a single leak in any of them!



Do yourself a favor, and drill and tap your differential cover for a 1/2 pipe drain plug, and you won't have to remove it again, unless you are concerned about debris on the magnet...

 

[JGheen]

Well, thanks for the info and advice there, Gary, but it didn't really answer my questions. I am not having any leaking issues, the RTV holds up fine and it really is not that big of a hassle to remove the cover to replace the oil as well as the RTV seal. I was just asking the difference between the different color RTVs. Is one better than the other? Are there any disadvantages to running the blue over the red, for example. Refer to my original questions, thanks.



Joe

 

[Gary - K7GLD]

I can't answer your question as to the difference in characteristics of different colors of RTV - and I couldn't when *I* had to make that choice myself - that's why I went for the stuff I pointed to above - good luck with whatever you choose...

 

[Bob4x4]

Axle RTV part# is05013477aa. It is orange and works great. The diferent colors are formulated to resist breakdown of the specific fluids they are recommened to be used with.





Bob

 

[JGheen]

Well, I used the red RTV because I never had any issues with it in the past and it seems the black stuff broke down and caused the leak, so we'll see how the red holds up.

 

[Gary - K7GLD]

"I am not having any leaking issues, the RTV holds up fine"





"it seems the black stuff broke down and caused the leak"



I don't wanna seem like a nit-picker, but somehow those 2 statements don't agree!

 

[JGheen]

Ok, this is getting way to out of hand. All I want to know is what is the difference between the different color RTVs, that's all. Gary, those statements are from 2 different comments. I'm just asking certain questions and no one has answered them. Are you trying to make me look stupid or something by comparing two different comments? If you don't know the answer to my questions then don't butt in with your nit-picking of my opinions.

 

[Gary - K7GLD]

Just teasing guy - don't get too hot under the collar, you're among friends...

 

[Jff24Gordn]

Go to NAPA and get "The Right Stuff" in a pressurized can. i use it on everything. My boss used it to patch a semi tire. It also comes in tubes, but the can is so much nicer.

 

[cumminspwr01]

Well, as far as I can tell by looking at the boxes of rtv in front of me the blue is listed as being "sensor safe" but lists nothing about resisting temp. The red is listed as high temp up to 650*F intermittently. The stuff we use to seal eaton and rockwell rears is also from permatex and is called ultragrey. It is listed as being heat resistant up to 625*F, oil resistant, and is non-corrosive. As far as the black stuff goes I cant help ya I dont have any here right now. HTH

 

[Gary - K7GLD]

I dunno if the "color code" bit is universally observed - but the Suzuki stuff I mentioned up above is also grey in color...

 

[cumminspwr01]

The mechanics around here treat that stuff like gold but we sell ours for five bucks

 

[Gary - K7GLD]

Is the stuff commonly available? I've never seen it displayed around here, and wouldn't mind having more like the Suzuki stuff on hand...

 

[swaite]

The Permatex web site suggests Permatex Blue for non-corrosive applications on machined mating surfaces. The Red seems to be tailored specifically for high temperature applications.

 

[cumminspwr01]

As far as I know you should be able to get it at napa or any other car parts store. thats where we get ours when we run out

 

[wcjp]

I've always used Blue for thermostat housings and Black for diffs. The most important thing with RTV is allowing at least an hour to cure. I always remove cover, remove old RTV, clean surfaces and reinstall with fresh Black RTV. This gives me an hour to perform other preventive maintenance.

 

[Paul Somers]

Ultra grey

A couple of years ago when i replaced my fluid it was suggested on this site to use Ultra Grey. Sure enough when I removed my diff cover the sealant was grey. Two years later and no leaks.

 

[WestTN]

Some RTV's release acetic acid when they cure. This is why they smell like old aspirin. These fumes are not good for oxygen sensors, so they should not be used on the intake systems of engines so equipped. Acetic acid fumes are not a problem with oils, etc. They also will not break down RTV.

 

[JGheen]

Originally posted by WestTN

Some RTV's release acetic acid when they cure. This is why they smell like old aspirin. These fumes are not good for oxygen sensors, so they should not be used on the intake systems of engines so equipped. Acetic acid fumes are not a problem with oils, etc. They also will not break down RTV.

Thanks, that was an answer I was looking for. I figured that the fumes shouldn't hurt the performance of the oils where it is used.