Any of you guy's running more than 1 bottle of additive in your 12 bolt?? I have always had this terrible clunk coming form my rear end when I turn left under power.. What do you think about using an extra 1/2 bottle in effort to stop the clunk??

I have gone through just about everything else & the posi just seems super tight..

TIA
Scott

I'm running 2 bottles in my 8.5 & using regular oil too not syn.
Mine will still chatter a bit accel. on a corner.

I just had an eaton posi installed. The rear end guy told me not to use synthetic oil because the posi does not respond well to it. I put one bottle of addative in seems ok. What brand of addative are you using?

Do you need the additive if the bottle says safe for limited slip rears? I just filled our 12 bolt with Valvoline and the bottle said safe for limited slips and non-posi.

SOME fluids have the stuff already in there... I use Royal Purple and do not use additive.

I just had an eaton posi installed. The rear end guy told me not to use synthetic oil because the posi does not respond well to it. I put one bottle of addative in seems ok. What brand of addative are you using?

I'm using GM posi additive..

Scott

That is good stuff.. What type of posi is it? What type of oil are you using?

I am running a ford 9", but the guys at Currie that built it specificly said to use non-synthetic oil and 1 bottle of ford friction additive.

I use Lucas 85-140 non-syn gear oil with a True Trac locker.

I have absolutely Zero noise...

I know it's not a 12 bolt but I am sure the guys at Currie know what they are talking about when it comes to the oil reccomendation.

Steve

That is good stuff.. What type of posi is it? What type of oil are you using?

I am using regular 80w90 gear lube, & its a stock posi unit..

Scott

Don't use synthetic gear oil!

I just had my one year old Eaton unit rebuilt because I used Redline in it since new. Too much slippage burned up the carbon fiber clutch pack. Common 80W-90 will work fine. Add the GM posi additive if needed...which I didn't.

When I put an eaton posi and gears in last year all the info supplied with the posi unit said was to not use synthetic and also add the additive.

Scott it sounds like you covered all of your bases. You might try dumping the oil and refilling, but it sounds like you just did? You said it was a stock posi is it a 30 plus year old unit? if so I do not see how adding some more addative could hurt. Are you sure the niose is coming from the diff.? Just a thought.

No synthetic in the new carbon fiber Eatons, huh?

Guess that might explain the odd noises coming from mine during tight turns in parking lots (running AMSoil.)

Wish Eaton would have had a disclaimer in there about it.

Ironically, my posi has about 10K miles on it and it just started recently making noise. First 500 miles had dino juice, then the next 6K or so with the AMSoil. No noise at all. Then earlier this year I smoked a pinion bearing and trashed the ring and pinion. I changed bearings, ring, and pinion, but didn't touch the posi. I put dino juce in it for breakin of the new gearset and that's when the noises started. After 500 miles on the new gears I went back to AMSoil and the noise subsided a bit, but it's nowhere near as quiet as it was before the gear change.

When did Eaton start saying no synthetic lube with the CF clutch units? I probably bought mine 4 years ago or so and there was no such disclaimer.

I did not get my info from eaton. The guy that installed it is an eaton dealer I asked him what type of oil to use he said "80/90w with an addative and not to use synthetic eaton units do not like it".

Scott it sounds like you covered all of your bases. You might try dumping the oil and refilling, but it sounds like you just did? You said it was a stock posi is it a 30 plus year old unit? if so I do not see how adding some more addative could hurt. Are you sure the niose is coming from the diff.? Just a thought.

Well I ended up putting 2 full bottles of GM lube in & low and behold, ALOT of the noise went away :hurray: .. Now if I could just figure out why there was metal shavings in there when I drained the lube :eek: .. R&P gears & all bearings are new, with less than 100 miles on them :angry: ..

Scott

Scott, how did the gears look??? I'll talk to Dave.

They didn't look too bad.. The mating surfaces have been worn it (dull finish worn off)..

PS, hows it going?? Give me a call sometime..

Scott

I build differentials for a DCX dealer and all my diffs get 2 bottles of modifier and 80-140W synthetic. Zero problems. They are friction style limited slips so the principle is same as a GM corporate axle. In fact they are almost identical internally. I don't how anybody could claim the synthetic would cause slip unless they build it too loose to begin with. The friction modifier should be taking care of any "slippage" issues.

I don't how anybody could claim the synthetic would cause slip unless they build it too loose to begin with.

Actually, it looks like Eaton does. :(

Copied and quoted directly from the Eaton brochure...

"The Eaton Posi Limited Slip Differential was first introduced in 1961 on a 1/2 ton GM Pickup Truck. It gained notoriety during the 60's/70's muscle car era. Today, we offer the Eaton Posi Limited Slip Differential for older/newer automobiles and light trucks in the aftermarket.

Eaton Posi Limited Slip Differential are set apart from every other positraction units by:

Its strength, durability and toughness gives you traction when you need it, to get out of the worst situations and it's repairable.

Performance limited slp positraction units for Street Performance, Hot Rodders, Off-roaders, and Drag Racers. Eaton Posi Performance Differentials feature a patented carbon friction material designed to endure the hostile extremes of Formula One racing brakes and clutches. Made from high-temperature carbon fiber wrapped with a carbon anti-wear coating, these virtually indestructible discs thrive on repeated harsh engagements and thermal abuse, without performance loss. The patented carbon-carbon fabric maintains its lubricity to provide smooth, quiet operation over the life of the vehicle.

When the traction disappears, your Eaton locker automatically kicks in, locking the rear wheels together and sending power to both. The result? You and your truck keep moving when everyone else is standing still.

*IMPORTANT APPLICATION NOTE*

It is strongly recommended the Eaton Posi LSD to be installed using a Mineral Based 80W90 Gear Oil and a 4oz. bottle of Limited Slip Additive. The Eaton Posi LSD in NOT recommended to be used with synthetic gear oils. "

Strange that GM, Ford, and DCX all REQUIRE synthetic in their H/D posi axles.

Strange that GM, Ford, and DCX all REQUIRE synthetic in their H/D posi axles.

Very true. Plus the new over the counter GM synth stuff now has a Grape scent to it. :p

Rebuilt my posi last year and had the same problem (it only makes noise when turning left). It already has one bottle of additive in it but I think I'm going to add another and see what happens!

I'm with Bill on this.

I just installed a Eaton Posi along with a set of Motive gears and the paperwork with the Eaton said - It is strongly recommended the Eaton Posi to be installed using a Mineral Based 80W90 Gear Oil and a 4oz. bottle of Limited Slip Additive. The Eaton Posi LSD in NOT recommended to be used with synthetic gear oils

Right or wrong for the ~$400 posi, it's got the petroleum based gear lube and the GM additive in it ;) Each to his own........ :) :) :)

my dad is doing a dodge truck right now, had to get a new carrier unit because someone had the rear open for some reason and apparently used reg. oil and possibly no additive. their rears require synthetic lube and an additive (sent with the carrier direct from dealer)

cost the guy $650 in parts alone