Anyone have problem with their posi chattering?
 

The posi unit in my 70 chatters bad when turning but only seems to do it when it gets some heat in it. All winter long I haven't had a signal problem, today I drove the truck about 40 hwy miles and when I got back to town and was going through parking lot I thought my rearend was going to lock up. It felt like the spiders were binding up and popping. Later after it cooled down I drove it about a mile and it was gone. But after a few miles it was back. It did it last summer also but as the cooler weather set in it went away. Today it got into the 70s and like clock work it came back. Anyone else have it porblem? I pulled the plug and it was full of fluid..

Re: Anyone have problem with their posi chattering?
 

Change the fluid out with a quality 75/90 gl5, then put some additional posi additive in

Re: Anyone have problem with their posi chattering?
 

One of my trucks was doing that when I purchased it... fine when cold, would chatter and bind up when hot. As kwmech suggested, a fluid change and adding the proper additive completely cured the problem. Good luck!

Re: Anyone have problem with their posi chattering?
 

GM posi additive, ebay or local GM dealer

Re: Anyone have problem with their posi chattering?
 

Agreed. Stopped my brothers chatter

Re: Anyone have problem with their posi chattering?
 

First drain old fluid and add new

Re: Anyone have problem with their posi chattering?
 

Change the fluid , and I have always used ford friction modifier , the stuff that stinks real bad , then find and open parking lot , and do 10 donuts one way , followed by 10 donuts the other way , you don't have to go fast , that should cure it . If they sit for awhile [especialy if dry] they tend to bind ,my camaro would do it just barley turning the wheel , until I did the donuts , now its cured

Re: Anyone have problem with their posi chattering?
 

Thanks guys!! I will try that this weekend. I changed the fluid last summer and used the additive from the parts store, I will run out to the dealer and get some gm stuff. What brand 75/90 do you guys like? I think I used castrol when I changed last summer. The truck set a lot for about 7-8 years before I bought it back, I now drive it everyday.

Re: Anyone have problem with their posi chattering?
 

the old oil brand debat will never end, technology is so far that I don't think anyone can screw up oil these days.

but ya gotta get the good GM/AC Delco additive, I use to buy cases of it and sell it on ebay. Id give ya one if I had any left. [easy sale and feedback boost.]

Re: Anyone have problem with their posi chattering?
 

I agree on the GM posi additive.

FWIW, when I don't want to hear chatter in my truck, I leave my wife at home. :) :lol:

Re: Anyone have problem with their posi chattering?
 

* GM Posi addiitive is whale oil. I'd change the fluid with the additive, as others said.

Re: Anyone have problem with their posi chattering?
 

i prefer to use royal purple as there is no need for a posi additive when using royal purple

Re: Anyone have problem with their posi chattering?
 

as a former service mgr from back when those trucks were fairly new...find you a large parking lot and turn the wheel hard left and make several turns with the wheel locked and then turn it to the right and do the same thing, it'll be fine. its just the plates sticking this will free them up. and it works!

Re: Anyone have problem with their posi chattering?
 

Not for a LONG time now, it is a synthetic blend. BUT I have been building custom differentials for years now and the FORD fluid additive wins hands down. I soak the clutches in the additive before I rebuild a power-loc.

Re: Anyone have problem with their posi chattering?
 

Thanks for the great info! I should have known they have changed it, I still have my old school bottles from my GM shop days.

Re: Anyone have problem with their posi chattering?
 

I agree with everybody the additive will fix it ! I had a 69 SS350 camaro and it did that and the additivie fixed it ,,,,, but the rear tires squeeled I never did get it to stop doing that LOL

Re: Anyone have problem with their posi chattering?
 

I agree that you need to drain and fill with new lube and friction modifier. To make it easy, there are 2 differential gear lubes I've used in the last year that come with the friction modifier already added. I used ACDelco Dexron 75W-90 LS Gear Oil in my 1999 Vette and Mobil 1 Synthetic Gear Lube LS 75W-90 in my 2001 Jeep Wrangler. Both solved the problems. It should be noted that Mobil 1 is not recommended for Vettes.

Re: Anyone have problem with their posi chattering?
 

Thanks guys!! I ran out to the local gm dealer and they were out of the additive and didn't think they would have any by the weekend so I ran over to the ford deal and they had it. So I picked it up and guess I'm going to use that. If I run royal purple and it says it doesn't need the additive do I put it in anyways? Or should i run regular 75/90 so I can run additive?

Re: Anyone have problem with their posi chattering?
 

the only thing royal purple is good for is ? wait royal purple is not good for anything ! I would not put that junk in a lawn mower ! get you some good 80w90w and go !

I used to work at a new motorcycle dealership and ANY bike that someone put royal purple in ate the lobes off the cam bottom rod bearings went out , you could put that mess in a perfect engine and in 300 miles it would be rattling and sounded like a sewing machine , take them apart oil looked like sludge full of metal PURE GARBAGE !

Re: Anyone have problem with their posi chattering?
 

Soooooo you dont like royal purple? lol thanks for the heads up.

Re: Anyone have problem with their posi chattering?
 

everytime i put synthetic in the rear end,, IT BROKE!

Re: Anyone have problem with their posi chattering?
 

exactly !

Re: Anyone have problem with their posi chattering?
 

i put synthetic in my rebuilt posi rearend and got rid of it still going strong at 100000 miles

ever since 1995 every new truck i ever got from GM came from the factery with synthetic rearend grease in the posis that i had

Re: Anyone have problem with their posi chattering?
 

I've never tried synthetic in the rear end before, I have always ran regular 80/90 and my el camino with the 496 in it runs mid 10s hanging the wheels a little bit off the line. The ring and pinion in it is 18 year old Richmond street gears in it. I do run Mobil one oil in all my stuff except my duramax and I just run regular rotella in it. I'm on my 3rd new dmax and always ran rotella with no problems..

Re: Anyone have problem with their posi chattering?
 

I just bought a 68 that the posi chattered. I figured the previous owner had old/bad diff fluid plus I wanted to see what ratio it had so I pulled the cover. I put in 80/90 along with GM's additive and went for a test drive. The rear end was very unpredictable, it would lock on turns and be open on a few straight line burnouts. I noticed a few posted to do 10 doughnuts left and right. Do you think that will solve my issues or is some mechanical work needed?
Thanks