I'm planning on replacing the rear diff cover next week and I have the dreaded question about gaskets. From reading past posts, it seems a lot of people are against the pre-made gaskets and prefer the RTV type.

Perhaps this is my lack of experience, but the pre-made one seems so much easier. Here's one I was considering so you can see the gasket that comes with it.

http://www.autozone.com/autozone/cat...076&questions=[com.autozone.diy.valueobject.NavigationItem%40f0c3 3a%2C+com.autozone.diy.valueobject.NavigationItem% 40a124b4]

Basically, my question is why are these gaskets so bad? I've never used RTV and I guess I'm worried I'll somehow leave a small hole/gap when applying it and have to do it again. Am I overthinking the RTV or is it honestly a pain?

Last...anyone know the correct torque of the bolts for the cover? Or, is it no big deal and just crank'em down?

thanks,
pf

 

I'm old school. I use a gasket. My ram didn't come that way, just a big globbed mess of factory applied silicone that squeezed out into the inside of the differential. I usually use a thin layer of sealer to glue the gasket to the cover, let it setup fo a few minutes while I finish scraping the housing clean and gettting the old fluid out. then I put a thin bead on the gasket before affixing it and the plate to the housing. I use good 'ol permetex one. It does make for a bit more scraping should you decide to R&R the cover again.
If you "crank 'em down" you 'll have a bunch of broken bolts to curse out. They snap real easy. I found 15ft lbs in my Chiltons for 1/4 inch bolts. Snug 'em then torque 'em easy.

 

Dry gaskets are fine for brand new assemblies, but on an older vehicle that has been serviced several times, RTV is the way to go. It will fill in any surface imperfections left behind from scraping old gasket material off and unlike paper/cork/composite gaskets it can deal with some warpage and expansion/contraction of parts from temperature. It really isn't that difficult to get a good seal with RTV. Basically, all you do is squeeze out a uniform bead of material, usually about 1/8", let it set up for about 15 minutes and then reassemble the parts. Make sure the mating surfaces are clean and dry. Some people like to use RTV with gaskets, but there really is no need for this. Make sure you get the right RTV for the job. There are high heat formulas, some that resist oil better than others, some for high pressure or immersion applications and some for use with fuel or other corrosive substances. The general stuff for use around the house is usually not recommended for automotive use.

As for botl torque, you really should follow the manual on this. Unless you've been doing this awhile and have the right feel, mistorquing fasteners can lead to cracked/warped parts, stripped threads, damaged fasteners, parts separation and lost fasteners. I know you're new at this, but now is the time to learn to do things right. Spend a little money on a good torque wrench and learn how to use it. It will come in handy for many other chores should you decide to get more involved with maintaining your vehicles.

 

+1 on torquing correctly. as far as gaskets are concerned, it's honestly all based on the type of job you're doing and personal preference. some people do things differently than others. as far as a gasket for the rear differential, i would just get a really good gasket like a felpro...i dont see a need for rtv unless the mating surfaces are really scarred up.

 

i use black rtv and about 10-15 pounds of torque on those LITTLE bitty bolts. i also put a little rtv on the threads to keep them from backing out.

 

Miami...quick question. From the books I've seen about RTV, they suggest squeezing the RTV out on the tube, then spreading it evenly your finger. That's the part where it seems it would be possible to spread a little too thin or something. Do you do this?

 

It depends on the part. For a diff cover I just leave the bead alone and assemble. For small parts I will usually spread it evenly with my finger or a popsicle stick. The thing is that once you screw down the part much of the RTV will squeeze out anyway. What remains is a thin, uniform layer in between that does the sealing. The stuff that squeezes out is insignificant. It is what remains that you don't see that does the work. As long as you don't leave any bare spots or gaps the squish should do the trick. About the only place I wouldn't use RTV is on valve covers. And for something like an intake manifold you have to use some amount of RTV at the block ends. Things like diff covers, water pumps, t-stat housings, sensors...I use the goo.

 

just don't put too much on so it doesnt squeeze out all over in the inside of your differential. lol

 

Are torque wrenches that important for rear ends in particular or are you (and the others) just suggesting them in general? I have been working on cars since I was around 10 (helping my dad) and have never used a torque wrench. I usually just snug everything up and have never stripped or broken a nut or faster. I don't go hog wild and crank things down to the point of breakage. If you are suggesting that rear ends are more fragile than other parts, then I will have to keep that in mind since I haven't done a rear end yet.

 

I suggest a torque wrench for anyone new to working on their car, regardless of the part. I rarely use a torque wrench except on things like heads, pinion nuts or other critical parts subjected to heat/cool cycles that depend on proper torque. But I have years of experience in working on vehicles and have pretty good feel for when a fastener is properly tightened. Someone new to this probably doesn't and that inexperience can lead to everything I listed earlier. In the case of a diff cover, they are so thick that they're pretty hard to warp from over-tightening, but you have to consider that a leak from even a small warpage will likely go unnoticed and could cause all the fluid to eventually leak out over time. And undertightening can lead to fastener loss, also easy to go undetected under the vehicle.

When I had my Harley shop I regularly saw the damage that can be done by some DIYer who thought damn tight was the right torque spec.