Royal Purple and LSD Chatter

[Cooker]

I recently installed Royal Purple 75w90 into a 1998 Dana 70 with 80k miles. After install I went out an ran several figure 8's in a large parking lot. The rear end was quite and smooth for about 600 miles but now it is chattering on turns.



Has anyone had to add any friction modifier to the RP gear oil? I'm thinking I will try 2 ounces to smooth it out and quite it down again.



Thanks.

 

[RustyJC]

Every one of these LSD's seem to behave a little differently based on their setup. I'm running RP 85W-140 (we tow heavy) in my truck's Dana 80 LSD and have no chatter whatsoever with no supplemental friction modifier. If I did have to add the friction modifier, though, I'd add only a little (as you state), do the figure 8's to see if the chatter disappears and repeat the process until the chatter is gone. As you know, with too much friction modifier, the LSD function is compromised. The LSD will ultimately tell you what it wants.



Rusty

 

[BV]

Royal Purple

I ran RP 85/140 for 10k without having to add the skunk oil.

 

[paccool]

I ran RP 85-140 for several years. The LS was just rebuilt when I put it in. Without the additive it chattered. I put in 4 oz of the Dodge additive and it worked well. About 15,000 miles later, all of a sudded it started chattering again. I drained it and refilled with conventional oil with a bottle of LS additive and it was fine. Have about 6,000 miles on that fluid, all is well. Most of the 6K was towing miles and had it on the Dyno up at piers for about 10 runs.



Because of the problems with the rear end oil, I drained the RP engine oil out and went with Amsoil. I have a bypass setup and the RP engine oil had about 15,000 miles on it with a test at 8K that was fine. Ran a sample on the RP as I pulled it, test came back OK to use. . Up to this point I was sold on the RP oils. Not bashing RP, just sorta lost some confidence in RP so will stay with the Amsoil.



Edited- was a 4 oz bottle of LS additive, not 8oz.

 

[mikel]

I've got the RP 85-140 in mine and I don't get a chatter. It's been in there over 20,000 so I guess if it were going to chatter it would have done it by now.



Maybe my LSD is just a little more wore out than yours...



Add a little additive at a time and do the figure 8's like you said in your post. I's imagine that will take care of the chatter.



Mike

 

[Texas Diesel]

I have to add OEM modifier to my rear axle at intervals, seems the additive wears out or some how becomes compromised, I have Mobil 1 75W-90 synthetic in it. I had a F**D replace-a-matic transmission that needed a bottle of modifier every 6 k miles.



Sounds normal to me what you observe.



Add it slowly and give it some time before increasing the additive. It is easy to add too much modifier and starting with a litttle chatter and adding modifier till it goes away is the best way to determine how much your LSD needs.



One more thing, the Dodge Modifer is best IMO.

 

[Matt42]

I Did, and It Didn't

I changed over to Royal Purple 85W-140 last year, and added the 2 ounces of Daimler-Chrysler anti-chatter armadillo oil at the same time. No chatter. Might not have chattered without it, but I wanted to minimize trips under the truck.

 

[frijole]

Royal Purple

Cooker, I have heard of incidents like this before. General concensus was that putting a synthetic gear oil in a differential or transmission that had a lot of miles on it was the problem. Seems the increased clearances caused things to not work as hoped. I put Valvoline syn gear oil in my Grand Cherokee, with no modifier, and 30K miles later I got chatter like crazy. When I opened it up I got some metal out along with the oil. I then switched to 70-140 Royal Purple, and the chatter went away. No comment on additional metal in the lube as I haven't been back in there. Maybe the modifier has a life span? I darned sure would call RP and tell my story and see what they have to say. Good Luck and keep us posted. Ron

 

[RJOL]

Put RP 75 X 90 in my Dana 80 LSD, several thousand miles ago, without adding any friction modifier. It never chattered and I never had to do any figure 8's. Had about 35K on the truck when I changed it.

 

[Extreme1]

When I installed my LSD with Amsoil I had chatter after a few hundred miles. I added 1 oz of the Dodge modifier (it is the best) and it's been fine ever since. Add 1 oz at a time like mentioned above.



This LSD is enough for what I need, big posi burn outs!

 

[Cooker]

I just wanted to post an undate.



I added 2oz. of the Dodge friction modifier and that help a little but not much. I added 2 additional ounces and it is quite and chatter free again. It does not appear that the additional friction modifier has affected the performance of the LSD at all.



Thanks for the info.

 

[Texas Diesel]

You're right, best to fine tune the modifer to each diff. I suspect that there is a lot of difference in preload on the clutch packs, that is why some add no modifier and others have to add 4 ounces of oil to their modifer kinda of like have a alcohol blood level of . 08.

 

[Dane]

When I opened it up I got some metal out along with the oil.

Don't let em chatter for too long or the clutches will be gone :{