Eaton Posi Chatter?

[T-TopFlyer]

I have a fairly new Eaton Posi installed in my TR, so that is the only place I can think this issue might be coming from. I also have 16x8 wheels with 245/50/16 tires as well. Starting off slow with the wheel turned even the slightest bit I feel a chatter/vibration. Going faster while turning, or at any speed in a straight line there are no issues. It hooks up very well and makes no other noises. Is this normal or something to be concerned about?

[Electrajim]

Some posi's will chatter a little. Depending on how new it is or how it was treated, it might need a rebuild but I doubt it. Try changing the fluid with synthethic lube, and mabey some posi additive.
Just one or both ought to take care of it.

ElectraJim

[PaCemkr86]

drive it some more, and do some burnouts.. break it in.. but for the most part that normal for nice and tight working posi track

[T-TopFlyer]

Originally Posted by PaCemkr86

drive it some more, and do some burnouts.. break it in.. but for the most part that normal for nice and tight working posi track

"Burnouts"......Heck yea, by all means! Thanks for the permission and peace of mind.

[monzaz]

Eatons will do this. The preload clutch springs are right on the edge of being too tight for the street. BUT this is a good thing. Chatter usually means TIGHTNESS. That means posi is good and working...It is trying hard NOT to break loose. Try more posi additive


NO SYNTHETIC!!!! Eaton will not warrenty your unit if you use synthetic fluid. Period.

If this really bothers you you can switch outthew heavy 400# preload springs to 300 (corvette stock or stock 200 from the 70's a-body cars.) Hope this helps. If your car is any kind of muscle car then just deal with the little chatter. It will not ruin anything. It is ok. Jim J D Race

Oh if that is not enough chatter for you they also make 800# springs, OUCH!

[Electrajim]

Originally Posted by monzaz

NO SYNTHETIC!!!! Eaton will not warrenty your unit if you use synthetic fluid. Period.

Anybody know why the manufacturers are "dissing" the synthetic gear lube?
I've read this too in Auburn manuals.
http://www.auburngear.com/aftermarke...structions.pdf

..OH, and frequent doughnuts, or drifting will loosen up the posi too.

ElectraJim

[T-TopFlyer]

Good to hear that this is normal from a tight posi. I'm used to the factory units which usually don't do this. I can usually make those brake loose at least to do a little wheel hop going around a corner. This one is almost impossible to do that with.

As far as gear oil and additives, what is recommended as far as brands and quantity of each the oil and additive since synthetics are probably out of the question?

[monzaz]

Brand- well we really try not to pin anyone to one brand. Just silly. We are not supported or sponsored by any oil companies so that money sway is not there for us...LOL Any Gear lube that is fairly brand name and any weight will do in our book. penzoil, valvoline, etc. is all good we even had Walmart brand in a pinch work...lol. Just as long as it is MINERAL BASE OIL. The additive is critical for the clutches and cones to control chatter.

Synthetic- NO ONE is dissing the synthetic gear lube. It is great stuff when used in the right application. You do not use synthetic in new motors becuase it is SO good at what it does...it prevents wear -the rings would never seat proper in the cylinders to produce the power and compression. You need some abrasion to seat and seal the ring to the cylinder wall. It is like lapping a valve in its seat...same principal <spelling?

The reason not to use it in the friction type (performance type clutch/cone) is that the fluid is so darn slippery the cones and clutch do not grip like they should and the fluid will cause a inconsistancy in all driving terrain. The synthetic is used to STOP friction...the performance posi unit rely on the friction to keep the clutches and cones LOCKED along with preload springs. Only in turns do you want release. That is caused by the weight of the car turning the axles at different relation speed in a right or left turn. (inside tire covers less distance then the outer in a turn.) Straight away a posi does not wear. SO... if you always went straight forever...your posi essentially would never wear out. REALLY. Hope all this info helps you out understanding how fluid and LSDs work togehter for the performance you want.

Jim

J D Race.com

[novaderrik]

i guess that Amsoil synthetic gear oil that i ran in the rear end of my Nova with a rebuilt Eaton posi for 5 years was bad for it. the tightness of the posi was surely a symptom of impending failure.. same with the thousands of other people that have run syntetic gear lube in cars with Eaton posi units in them were hurting the performance of their rear differential.
and GM, Ford, and Chrysler- along with pretty much every other car maker in the world- must never get a good ring seal in any of their brand new engines that get synthetic in the oil pans right from the first time they are fired up.

[monzaz]

Right... But if you want your warrenty I would be safe. I have opened up tons and tons of 100,00 mile + rear diffs with nothing more than mineral gear fluid ...probably from the 60's...lol... never changed . These gears are perfectly fine. There was NO synthentic back then...??? Right?
Any race car will be broken in and dynoed before even hitting a chassis... The engines are broken in already and I assure you it is NOT synthetic fluid. As for Productions cars I have not a clue.... But I can almost guarentee the first run is not synthetic unless there is a additive that is added upon the first oil run. It is not like synthetic fluid will harm the engine nor make it stop running. You merely want to do everything you can in a imperfect world to try to get the most you can from your build...right? So quick ring seat on a motor will produce maximum power right away and you able to get using that compression and power now. Jim

I do however know the GM diffs. I am sure they can and will run with synthetic. Again synthetic does not ruin the posi... just makes it less efficient and in turns you can notice the chatter the gentleman was talking about. Back in the day when they used daisy wheel clutches chatter was a bad thing for the clutches...they would shatter from violent chatter because of the flawed design of the clutches. What kind of clutches did you use (composite, carbon fiber, steel, etc.)? what was the preload spring pressure you used( 200, 300, 400, 800)? These factors will make a difference. But again NOT all synthetics are the same either, some are better than others and have different additives. So If you want to be safe and have zero issues with warrenties and operation of the posi... go with the manufactures recommendations(until they change it again!). This is still The land of the free for a while...you may use what ever you feel is correct. Just have FUN.... lol

I am not hear to start anything...just trying to help the guy get his posi working and to tell him important manufacture info that is listed in the packaging of the Eaton posi unit. I will check into the gm ford and chrysler engine break in procedure for you too.