I'm switching out a rear chunk in an 8 3/4, its a 3.91 with a cone type sure grip, do I need to add the sure grip additive? Also whats a good fluid for the rear, its out of the car so its completely empty, I'd like to go synthetic, do I need the additive with synthetic?

Also The bearings have an o-ring around them where they slide into the houseing( Green bearings maybe?) do I need to replace them, they look like there in good shape. I bought a complete narrowed rear so I dont know what it had done to it.

Thanks

thats a good question since a cone style diff is metal on metal , no fiber type discs in there. but i always used the additive in mine when i had one. i use sythetic oils and coming from the amsoil dealers mouth , he said you dont have to use the additive with their gear oil.
as far as your axle bearings go, check and see if there is a lot of play or slop by spinning the bearing moving it side to side. it sounds like you have the green bearings.

yes and no..depends on the oil you use,some have it already...the ferd additive is what I use

yes those ar green bearings,check for side play and up and down on the axle

if they "feel" good then clean the end of housing

you can run them with or with out the axle end seals that are in the housong tube end

you can look and see if it has them or not while you have the axles out

I ran my greens 9 yrs with the inner axle seals,swaped them in Feb,and run with out the axle seals as of now,no leaks yet?? the o-ring seal it fine

some say eventuly the gear lube will work its way into the seald bearing and wash it out and cause them to leak

up to you what you want to run..

its just double insureance to run the end seals along with the o-ring on the greens

same with the gasket for the ham,some do some dont use it,rtv works fine as does the gasket

when I use a gasket I soak it in WD40 a little before install,it will keep the gasket from sticking with the next R&R of the ham

Thanks for all the info, the o-ring looks fine, but what do the inner axle seals look like, I have the axles out now, waiting for the new pig, and I only remember seeing the o- ring and a gasket under the flange were the axle bolts up. I didnt notice any play in the axles, so the bearings must be in good shape.

Also anyone know what other syntetics dont need the additive, royal purple,mobil one, ect...

Butch

I don't recommend synthetic lube for a used cone sure-grip.

Use conventional, 85 W 140, GL-5 grade gear lube, plus 1 bottle friction modifier additive.

Dr. Diff,
Thanks, I trust your recomendation, I'll go that route. Why, would synthetic cause it to wear faster or might it cause a used unit to slip too much? Just curious.

Butch

Synthetics may result in leakage and lazy sure-grip operation.

Auburn does not recommend synthetics for new units either.

Thanks alot for the info, good to know.

Butch

I used 80-90 and a bottle of friction modifier, no issues yet.

What about the inner seals, yeah or nay? Looks like they are not in there right now and it wasnt leaking, shoud I put them in anyway and can it be done at home?

I'd put the seals in, they aren't expensive or hard to install.

I wasted $12 with my seals,thats why I dont have them now



use a seal driver and not so big a hammer,beer when your done

Doctor diff is the rear axle doc,he will have all you need for it,good guy to talk with

I got a new set of greens and seals shiped for a good price

I will be getting the seals again,when I change the pinion seal soon,I will after its done this time

got to get another set of greens and seals for the 3.91 sg I just got,he wil be the one I call