Permatex in place of a gasket on a F-20

F-Dean

Well-known Member
I am trying to seal the joint where the transmission bolts to the rear-end case on a F-20. I cannot find gaskets so am going to use permatex or some type of gasket sealer.

What type should I use?
 
Permatex makes a product called "The Right Stuff". It is pricey (24.00 tube), but I used it on my JD 40 and on my JD H with great results. I know that some local shops originally started using it on differential covers and solved the problems with the leaks as well. I have a 1939 F-20 that needs some attention and I will use this product for sure. Hope this helps, EB
 
I agree, that is the only product I use now, and it is fantastic stuff, but expensive. Make dang sure the surfaces have no trace of oil on them prior to applicating the sealer, I use brake cleaner to insure this.
 
I'd not recommend the traditional #2 (sticky black) Permatex.

However I've had excellent luck with both Permatex "Ultra Black" and "Ultra Blue" RTV gasket makers on applications like yours. Just be sure to follow the directions regarding surface prep, application thickness and assembly time.
 
When I was working on my jeep transfer case a friend suggested some sealer that is made for transmission oil. I believe it is made by permatex and is a little more expensive, but not that much than ultra black or others. I got it at NAPA. I think it worked better than regular silicone. It is grey
 
I'm not very familiar with the F-20, but if someone has a gasket it is easy to get new ones made for very little cost. I have had various gaskets made for cars, trucks and tractors. The paper ones usually cost me between $1 and $5 each and the place I have used has no minimum run on paper gaskets.
SadFarmall
 
Ultra black rtv or the gray rtv are the best, I have used them for that very purpose, that is what manufacturers use for engine oil pans, rear diff covers, etc, it works very well, and after it dries you can trim the excess so the purists won't scold you.
 
My experience with rtv has always been successful. I sealed my F-20 and F-30 trans, bull gears, etc. with the grey and have no leaks. There is a reason that Meritor and Rockwell recommend the Grey for there rear ends. Each of them have specific uses. By far the best for your trans is the grey RTV. The black "Great Stuff" seems to be okay also. Please don't use the Blue or High Temp Copper sealant where you have contact with petroleum products. They break down after a while and eventually start to deplete. Good luck with your restoration.
 

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