Rocks7ar

Hey gentlemen,
I decided that, after seeing the amount of oil that appears to have leaked out of my differential, to re-seal the cover with RTV sealant..
My question is, how can I tell what differential I have?!? It's a 12 bolt.. I know it has 3:73 gears.. And also, what kind of oil do I need to put in the differential?
Last question. Having no idea where to get the right gasket, can I just use RTV Sealant to seal the rear cover?

Thanks again.

Rocks7ar

Looking into Royal Purple's MAX GEAR oil. Is that going to cut it?
Also want to switch my transmission fluid to SYNCHROMAX. Comments, please.

AL SS590 M6

Easiest way to get a cover gasket is to take the cover to the parts house with you. I always use a gasket with a skim coat of silicone on each side.

The 3 12 bolts that I have dealt with all called for 90-140w gear oil and if it has an Eaton HD posi do NOT use synthetic lube.

rskrause

I use generic stuff from NAPA in the tranny and rear. Synth is just wasted $$ there as far as I am concerned. Engine oil is a different matter. Much higher temps and load and much more contamination. Also, a poump has to move it around. That's why tranny and diff fluids last virtually forever and engine oil needs frequent changes. As in the previous post 80, 85, or 90W-140 should work fine in just about anything.

Rich

Rocks7ar

How many quarts/liters are we looking at? 3 or 4?

AL SS590 M6

Get 4 but it won't take quite all of it.

rskrause

And don't forget friction modifier, depending what type of posi you have. If you don't know and can't tell once you get the cover off, add it anyway. It won't do any harm.

Rocks7ar

What would you guys recommend for Gear-oil/Lube?
I was set on MAX-GEAR.. Then I was hearing that AMSOIL is superior?

AdsoYo

Brent Franker has a page dedicated to instructing us on how to perform lube changes including the rear differential and it's step-by-step.

http://www.bfranker.badz28.com/fbody/lubeoil.htm

It looks like he recommends SAE 75W-90 Mobil 1 Synthetic Gear Lube. Cost - $14.82

He's aimed at the 10-bolt but it's more or less the same.

Injuneer

All 12-bolts have the same 12-bolt pattern on the cover, so they all use the same gasket.

Rocks7ar

Sweet! Thanks boss.

AL SS590 M6

If it has an Eaton clutch type posi in it and you use synthetic fluid you will ruin the $400+ posi. I've said this twice now so if you throw $400 away by being enamored with synth oils it's on you.

Rocks7ar

How can I figure out the typr of rear end it is? I REALLY want to know..