Hey guys , was wondering what posi rear end fluid you guys had the best luck with. I know! posi's aren't traditional but one car has it and the other is a no brainer , so any help would be appreciated .I'm about to put a car on the road that i have been picking away at for 8 years . YES , 8 years ! Hey what can i say , Braces are expensive and all three of my little guys got em . LOL. Oh well , thanx again for any help. swaZZie. P.S. it is a borg warner unit for a mopar 8 and 3/4 .
i feel your pain .just got my daughter bracies last month, i like the GM additive you can get it at the deal.about $5 for a 4oz bottle .its all i use.
As long as you use some type of friction modifier in your posi unit - Chrysler called them 'sure-grip' you should be fine. It helps keep the cluthces lubricated and keeps them from grabbing and chattering. If you want to keep it all Mopar it's called "Mopar sure grip axle additive" and it's part number 4318060 You can get several aftermarket friction modifiers that will work fine, like Redline, Royal Purple, etc. You can most likely pick up some brand at your local parts store. Our local advance carries some but I forget the brand. Mix the required amount (about 4 ounces, usually) with the first quart of gear oil you put in, then top it off.
lots of the shops I sell to buy the full synthetic stuff from Royal Purple and Redline by the case. I've had good luck with the Redline in my own car.
the only stuff that works in every posi is the GM additive you get at the dealer. I've used it in 12 bolts, 9" fords and Dana 60's. It has never let me down, where everything else I tried did. Period.
The friction modifier/posi additive actually allows some slippage between your clutches - that's how it quiets & smooths the action. Road racers (who still use clutch-type limited-slip rears) don't use it & go to great pains to remove any residue when rebuilding. It will actually shorten the life of your posi/sure-grip/trak-lok...insignificantly on the street, but if you're a corner carver be forewarned.
I like the kendall stuff. however,don't get it on you...it's one of those "stinks that keep on stinkin'"
Hey ! Thanx fellas , the car wont get alot of miles considering it runs 11.5:1 compression and 4:10 gears . No corner carving here! Point A to B and quick! LOL . thanx again for the help guys . swaZZie
I am curious now about Flat Ernies comments about friction modifiers ! If this is an un-healthy route for posi rear end clutches , then what would be the alternative for making certain that no damage is done or that the life of my clutches isn't shortened prematurely. Posis are expensive and an *** pain to rebuild .Maybe we should all know the answer to this question or at least those of us that don't know. lol . Thanx again guys. swaZZie
In the situation of road racing where you change parts faster than socks it makes little difference on wear, they want grip and are trying to limit the slip further. The grip with no slip around a corner makes the clutches chatter and you will feel it unload when you’re on a slow corner and then stop. It feels like you got taped on the back end. The clutch pack is not a permanent no wear part. It is a service part that needs inspection and sometimes replacement. The additive makes it last longer and the ride better so you don’t feel it unload on corners. Hence that name limited slip. In an Eaton they reccomend either GM OR Ford additive. They don't mention MoPaR but it may work just as well. Eaton doesn't reccomend synthetic lube oils in their posi's because the different blenders don't always use the modifiers necessary to work with the clutch packs. The better racing blenders do like redline and royal blue. If you don't want to spend for a good racing lube oil you need to use mineral base oils (dino) it has the zincs and sulphurs for the limited slips.
Change the oil frequently. Expensive yes, *** pain maybe. Even though the BW unit is "not rebuildable" according to MoPar service manuals, it still can be dis***embled, inspected, and sometimes repaired. Just so you know, the 8-3/4 came with two designs of sure-grip units: The early version was used through '68 and was sourced from Dana. A miniature version of what is in some Dana 60 and Dana 70 axles. It is called a Power-lok and utilizes two clutch packs made up of steel plates. When the steel plates are galled or worn out, they are simply replaced. It has four differential pinions. The later version was used on '69 till '74 and is the Borg Warner Spin Resistant. It uses only two differential pinions and cast iron cones that are spring loaded against conical bores in the differential case. After many miles, the cones and housing wear. Eventually the cones "bottom" out axially in the case, making the sure grip unit ineffective. Similar to two stacked plastic drinking cups - they will spin if they contact on the bottom before the sides. The next thing that will happen is the differential pinions will gall on the pinion shaft, and the shaft will become loose in the differential case. It may then work its way out out of the case... most likely causing catastrophic failure of the ge****t as well. Seen it happen many times My recommendations for street use or drag racing either type of sure-grip: 1.) Use standard gear lube unless it chatters going around the corners. 2.) Change the gear lube often to remove the metallic wear particles that reduce the life of the gear set, bearings, and cone clutches.
Bottom line. The posi additives alter the effect of the positraction. Sure you don't get the chatter around a corner but the only reason is the clutches are SLIPPPING. When the clutches slip your giving away posi action thus defeating the reason for having the posi in the first place. An old trick for GM posi units was to drain the fluid and replace it with regular gear oil. It was reported to increase E.T.'s by a couple of hundredths. We used to rebuild the posi with oversize clutches (thickness), use regular gear oil and end up with a rearend that acted quite similar to a spool. A non-chattering posi is for girls, not REAL MEN. Frank
Lol , thanx Frank and everyone else for your helpful info .This has been a very good insight for me . swaZZie
If you do not want the chatter noise and all after you fill it and add the friction modifier, you need to do some figure 8's to the left and right to get it into the clutches. If you like the clunk and all just do what they say it will sound like it is broken. Useless
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