I have 75k on my truck and I should probably do the diffs... Has anyone used a fel-pro gasket instead of the RTV sealant on their diffs (front and rear). I'm just worried that the expensive oil will leak out since I have the LSD.

Also do you just crack the diffs drain and seal it back up or do you need to spray something to get all the oil cleaned out?

Thanks in advance!

 

From what I know RTV seals as good or better then alot of gaskets. But ive never used it, Since I have not replaced any Gaskets myself yet.
I wouldnt worry to much on cleaning the old stuff out completely, If you do id say clean it out with new oil so you dont get any contamination. I plan todo my Rear Differential this summer.

 

Fel-pro all the way here. EXCEPT the transmission pan. I noticed it had been rtvd from the factory so I just did it again instead of waiting for the gasket.

 

Interesting... the factory book says to use RTV sealant so I assumed that's how it came from the factory. Reason I'm asking is because the RTV has to cure and you only have so much time to work with it. I figured the gasket might be easier (no rushing to get it on and once torqued I can put oil in), but if it doesn't seal properly there's no point. Rebel you changed the diff and put a felpro in? No leaks so far? Any issues with it?

Reject what fluid are you thinking of using (assuming you're putting synthetic 75W-140 if you have the LSD)? I'd like to get Redline (if I can find it) or Royal Purple since it has the friction modifier already in it. I think Valvoline also has one with it. Or are you going to get the synthetic and add the friction modifier yourself?

 

I've always used gaskets when they're available and I've never had problems.

It's true that RTV seals very well, BUT you have to make sure everything is perfectly clean when you put it together, or it will leak. And RTV is a PITA to clean off when you're changing the oil.

Don't worry about flushing out the old oil. I usually leave mine to drain for a couple of hours with the cover off, but even that isn't necessary.

 

I did change my rear end fluid for Royal Purple. I used the fel-pro gasket. No leaks at all.

 

Also on the front diff cover there's two numbers to torque it. The table shows 30ft. lb. (page 3-48), but in the text where it tells you to install it in a criss-cross pattern it says 16.5ft. lb (page 3-52). Know which one is correct?

 

So here's what I did. I bought the Fel-Pro gasket for the rear along with Permatex Gear Oil RTV gasket maker. I cleaned both the cover and diff from the old RTV. I applied dabs of the RTV around the cover... then applied the Fel-Pro gasket to the cover... then applied dabs of RTV around the gasket and a bit extra around the imprinted numbers. I put the cover back on and torqued to 30ft lbs. I waited an hour then filled with oil and so far no leaks.

When I took a look at the front diff I saw it was going to be impossible for me to get my torque wrench in there to properly torque the bolts for it down. So I pumped as much gear oil as I could and put in new oil.

 

i just did a LSD swap. used the gasket along with some gasket sealer(not RTV). the RTV is fine too use, just if you take it off you will hate your self for putting it on...

 

If you clean off all the residue of the old gasket, and then use a solvent such as carb cleaner to clean the cover and mating diff surface, RTV will give you a better bond/seal than the paper gasket & you won't loose any oil. When you put the cover on, pull the bolts just snug - not tight, until the RTV sets somewhat and then go back and pull the bolts tight to the recommended torque.

I usually just loosen all the bolts holding the cover, then remove the ones on the bottom, crack the cover open and let the old oil drain completely.

Unless you see reason to really flush out all the old oil, don't do it. The seals and clutch packs aren't designed to be impervious to everything. If you do see any large particulate matter in the oil, then you might do a light spray with carb cleaner and then let it drip dry. Fine metal particles are common - I'm not sure if the plug on these is rubber or steel with a magnet. If it's a magnet, you'll see the metal filings attached, this is normal wear.

If you need to fill through the inspection hole, you might find it a bit difficult. I tend to use a piece of vinyl tubing that fits over the plastic oil bottle spout, then I tape that onto the spout with a bit of duct tape, then I stick that tube into the inspection hole and squeeze the bottle until all the oil goes in (I re-use the same spout with tube on all the other plastic bottles). As you're squeezing the oil in, have something underneath to catch any drips.