Rear differential and Fel-Pro gasket

[Larryjb]

I used the Fel-Pro gasket for my rear differential. I appeared to seal well for a number of months, then started to drip. I retorqued the bolts as they had become slightly loose (maybe down to 25 ft-lbs, torqued back up to 30 ft-lbs). That seemed to stop the leak for a couple of weeks, and now it's leaking again. I had cleaned up both surfaces very well, removing the old gasket material. Fel-Pro advertises that it can seal over imperfections in the gasket surface.

Has anyone else had trouble with this Fel-Pro gasket? Should I just redo the whole thing and use RTV? Is there another gasket that is better?

 

[strutaeng]

What axle? A long time ago I bent an axle on my 99 Silverado 10 bolt hitting a curb when I drove on a patch of ice and spun out. My mechanic replaced it and used black RTV. That was maybe in 2013. I don't believe it's leaked.

The new axles come with factory gaskets, at least the 2014 "12 bolt" axle I tore down did.

 

[Trey Hardy]

I used the Fel-Pro gasket for my rear differential. I appeared to seal well for a number of months, then started to drip. I retorqued the bolts as they had become slightly loose (maybe down to 25 ft-lbs, torqued back up to 30 ft-lbs). That seemed to stop the leak for a couple of weeks, and now it's leaking again. I had cleaned up both surfaces very well, removing the old gasket material. Fel-Pro advertises that it can seal over imperfections in the gasket surface.

Has anyone else had trouble with this Fel-Pro gasket? Should I just redo the whole thing and use RTV? Is there another gasket that is better?

Some advice against it but I’ve always used RTV and I’ve NEVER had a leak. However when you go to do your next fluid change you’ll have to scrape all that shit off and re do it
Even my buddy’s who used the metal gaskets would use a thin layer of rtv on the gasket top and bottom for ***** and giggles

 

[Onlyone]

I always use the OEM gasket. It is the best. No cleaning old gasket or rtv.

 

[swathdiver]

We've been reusing our original gasket for years, 5 times now at least, put it back on again yesterday. Still have a new one on the shelf. The OE 8.6 gasket is rubber with impregnated metal and of course, reusable.

That blue Fel-Pro should have been used with RTV on both sides but I would ditch it for the OE if mine were yours.

 

[gooffeyguy]

Either the reusable OE one or a LubeLocker reusable gasket

 

[Doubeleive]

I used the Fel-Pro gasket for my rear differential. I appeared to seal well for a number of months, then started to drip. I retorqued the bolts as they had become slightly loose (maybe down to 25 ft-lbs, torqued back up to 30 ft-lbs). That seemed to stop the leak for a couple of weeks, and now it's leaking again. I had cleaned up both surfaces very well, removing the old gasket material. Fel-Pro advertises that it can seal over imperfections in the gasket surface.

Has anyone else had trouble with this Fel-Pro gasket? Should I just redo the whole thing and use RTV? Is there another gasket that is better?

if possible get the fel-pro metallized gasket, that is there premium line, I don't know about the gmt800's but on the gmt900's the oem gasket is metallized at least the one they sell now is. you should not need any "sealant" if everything else was good then I would suggest getting a new cover as they can warp around the bolt holes and leak. they are cheap to replace

 

[OR VietVet]

I have always used Fel Pro gaskets with never a problem. You said the bolts loosened. That is not the gasket fault. Once the leak started, there is a path for the fluid to wick out of. Retensioning will slow for a period of time but typically leaks after. I always use a very very very thin film of Permatex sealer on both sides of the gasket with completely clean and dry surfaces. I also let set up for an hour before refill fluid.

 

[Larryjb]

I have always used Fel Pro gaskets with never a problem. You said the bolts loosened. That is not the gasket fault. Once the leak started, there is a path for the fluid to wick out of. Retensioning will slow for a period of time but typically leaks after. I always use a very very very thin film of Permatex sealer on both sides of the gasket with completely clean and dry surfaces. I also let set up for an hour before refill fluid.

The bolts probably didn't actually loosen. Probably the gasket compressed slightly, thus requiring to be re-torqued. The second time I checked the torque they were right up to 30 ft-lbs.

I might consider a new cover then, and try an OEM gasket. That fluid is expensive.

 

[treehan77]

Lube locker works great

 

[EddieC]

The rebuild shop used rtv and it leaked in 2 months. Trying to snug it a bit made it worse.
I installed an oem (dry) that only cost about $11 bucks and no problems since.
So far on our truck, the factory generally got it right.

 

[ScottyBoy]

I have used OEM gaskets, Fel-Pro, and "Victor Reinz" gaskets, and ALL of them have leaked on me within a year. After suggestions from members here and other forums, I bought the reusable Lube-Locker gasket. I've had it for over 3 years now with ZERO leaks. I've changed the rear diff oil at least once since buying this gasket, and it sealed right back up just fine. No leaks, re-usable, installs completely dry with no RTV or gasket dressing or anything. That all adds up to a WIN in my book. It also pays for itself after you re-use it a few times.

 

[SnowDrifter]

I use lubelocker on mine

Buffed the surfaces down flat/smooth, lube with a little differential fluid, good to go

 

[ScottyBoy]

Also, use a paint marker to mark your fasteners after you torque them all down. That way you can have a quick visual aid to show you that all the bolts are still tight when you inspect the brakes and undercarriage. I started doing that when I found some of the bolts got loose over time. I got tired of constantly grabbing a ratchet just to see if they were all still tight. The paint marker makes it a LOT Faster and easier.

 

[oldchev]

I used Lube Locker " LLR-G850 "on my 2004 GMC Yukon Denali. That was excess of 5 years ago. Still completly dry.

 

[Rocket Man]

I second LubeLocker. That’s all they make is reusable diff and trans pan gaskets. Best made imo.

 

[03yukXL]

I used the Fel-Pro gasket for my rear differential. I appeared to seal well for a number of months, then started to drip. I retorqued the bolts as they had become slightly loose (maybe down to 25 ft-lbs, torqued back up to 30 ft-lbs). That seemed to stop the leak for a couple of weeks, and now it's leaking again. I had cleaned up both surfaces very well, removing the old gasket material. Fel-Pro advertises that it can seal over imperfections in the gasket surface.

Has anyone else had trouble with this Fel-Pro gasket? Should I just redo the whole thing and use RTV? Is there another gasket that is better?

I always have used a bit of rtv on mind even with the gasket. Never had one leak

 

[EddieC]

I am wondering if some of the leak experiences might be related to reusing the old cover that might have some deformation with a new thin gasket. I can imagine that the cover might get out of wack if attempts are made to retighten bolts.

 

[OR VietVet]

I am wondering if some of the leak experiences might be related to reusing the old cover that might have some deformation with a new thin gasket. I can imagine that the cover might get out of wack if attempts are made to retighten bolts.

Just like the old tin valve covers, you are supposed to inspect and flatten the bolt holes flat before reinstalling with a new gasket. When you tighten the bolts, the tin would pull in against the diff housing and create a very small divot/cone shape in the tin. If reinstall, without flattening that tin, you do not have a flat gasket surface.

 

[Larryjb]

Just like the old tin valve covers, you are supposed to inspect and flatten the bolt holes flat before reinstalling with a new gasket. When you tighten the bolts, the tin would pull in against the diff housing and create a very small divot/cone shape in the tin. If reinstall, without flattening that tin, you do not have a flat gasket surface.

I wonder!

Is it possible some one overtorqued the cover bolts? If this is truely the case, I might be best off either getting a new cover, or just using a bead of RTV only. This seems to be the most reliable solution, if done properly.

I'm now leaning more towards just using RTV. I understand I should be using RTV for gear oil.