2nd Gen Non-Engine/Transmission Limited Slip + Synthetic = ?

[JJW_ND]

Add additive on an as need basis

Gary:



I know you read this board as much as I do. From what I have read and experienced the older 94 - 97 had much tighter LSD which require LSD additive to keep from making noise then the later 98 and newer LSD even though they are all the same basic Dana 80 (manual trucks). They were very tight. This is how my 96 is. I have to add two bottles of Mopar LSD additive to keep it quite. It does not make noise then yet on a gravel surface or wet surface the inside wheel always leaves a noticeable trail. Ice and snow it is as though the rear gear is welded solid (love it this way). I have sampled ever 40 - 50K changing about the same interval. I have had very low metals but got moderate to higher TAN with longer change intervals (heat was taking its toll). The first 5 years I hotshotted pulling illegal long and illegal heavy loads for 700+ miles at a trip. All bearings still stock. Left wheel seal still factory (right changed at 15K prior to sythetics). Factory cover. Went through lots of tires but rear gears and drive train is bullet proof!



Even with all the hard miles and very tight characteristics... . it is still tight as the day it was new (even when adding two Mopar additive bottles to Amsoil S2K 75W50!



My work ride is a 2001 set exactly the same. At 20K I changed it over to 75W90 Full synthetic just like I have had such good luck in my 96. Added only one bottlees of additive. Guess what... . LSD slips some. When it is changed at 60K I will start with no LSD additive.



I am going to speculate that if a Dana LSD slips with straight synthetic and NO LSD adiditive... . Something is not set up correctly. It is not the oil!



jjw

ND

 

[jsimpson]

I couldn't get rid of the chattering in my Vette's limited slip no matter how many bottles of additive I used. Then I switcheed from Amsoil gear oil to Amsoil 3000 racing gear oil. No additives, no chattering, no problems.

 

[redram]

Don't be to hasty to apply a "bad" label to "all synthetics' just because one guy (or several) had a potential problem.



It could be the particular "brand" that was used.

It could be that the incorrect viscosity grade was installed.

It could be that the "synthetic' was installed in a worn out clutch pack that wasn't functioning due to abuse, lack of maintenance, or age.



Kinda of like labelling ALL radial tires bad just because they are "Firestone 500" radial technology and are round and black. Oo.

 

[Gary - K7GLD]

"Don't be to hasty to apply a "bad" label to "all synthetics' just because one guy (or several) had a potential problem. "



*I* don't see any of the above as a "bad" thing, or in ANY way a mark against synthetics use in LS differentials - merely something to be aware of - and IF proper LS operation IS of importance to you, you should be as careful to check for proper LOCKUP, as you are for chatter!



On the other hand, if plain and pure lubrication is your only concern, then no need to concern yerself as to whether the LS lockup is still functionl or not...

 

[Loren]

I had no idea I'd open such a can of worms when I posted that my limited slip (LS) differential no longer is.



I cannot be certain that the change to synthetic oil is what caused the loss of LS function because I did not do a before-and-after check. I changed the differential fluid quite some time back, and was curious to know whether or not the synthetic would affect the LS. I had read posts stating that some members lost the LS function with synthetics. It is certainly possible, although unlikely, that my differential clutches have worn out in the 55,000 miles I have driven my 2000 truck.



I tested the truck by jacking one rear wheel and attempting to drive off the jack with the other wheel on pavement. The truck didn't move, although the wheel that was in the air turned.



As far as following the instructions for changing differential fluid is concerned, I performed the steps exactly as described in TDR #32, pages 88 and following. I wrote that article and would appreciate any feedback if the procedures are not correct.



Loren

 

[Sled Puller]

I didn't see anyhting about figure 8's in the article, and I would add 1/2 bottle if it chatters at a time, instead of a full bottle.



On the sidebar note(from the editor?)



It says,:" The Amsoil synthetic is almost too slippery. It takes a lot of slippage before the non spinning tire gets power"



That, is incorrect.





. From someone who was obessed with limited slip performance, and constantly watching both tires, the key was the figure 8s. No figure 8's, one wheel spin. Do the figure 8s, both wheels spin.

No modifier, no chatter.



It really is, that simple.

 

[dezeldog]

I see everybody's going the Amsoil route. Thats what I have now but was wonering what the difference is with Valvaline Syn. 75w90 is. It's time to change and the Valvaline is readly avaiableTIA





Jim

 

[Israelson]

Hmmm...

ALL,



I just used the Valvoline synthetic blend 75W-140W and have added 2 bottles of Mopar friction modifier and have seemed to reach a perfect medium. I get just a tad of chatter around sharp turns.



Some Thoughts:



I wonder if the synthetic blends may give us the best of both worlds since it seems the Limited Slips were designed with dinosaur oil in mind.



It also seems the amount of wear on the L. S. has a lot to do with acheaving the proper mix of oils and the performance of the L. S.



Will the friction modifier seperate from the gear oil after setting for a period of time making it neccessary to blend the oils (by driving) for proper performance? My instances of wheel slip have been after the vehicle has sat for a least several hours or days, then taking off from a stand-still. I understand it could just be the need of circulating the oil (blended or not) period but that could be a factor in some of these cases.



Is it possible for a TDR magazine special with the engineer or designers of these limited slips, whomever they are?



Erik Israelson

 

[dflack]

confused

Either its too late or I'm too tired here, but I've read many many posts on the LSD in the past couple of weeks, especially since "its time" for me to do a routine lube/modifier change on my truck. Please don't bully me because I'm new here - I just want to know what the method and procedure is for assuring a successful outcome. I don't have the article mentioned from issue 32, I don't want to drive my truck off jackstands, and although I've seen "certified technicians" at the dealer prying off differential covers with a chisel and a hammer, I've never seen them perform any "figure 8's" or use fancy torque sensing tools after refilling the differential (in one shot) with who knows what. If different years have different requirements (or different models dana 60-70-80) I'm not seeing a consensus on that either. Heck, I'm even ready to open my checkbood and get the Mag-hytec cover for future ease of changes... . at least we agree on that?

If there is a "right answer" am I just not seeing it? Pray tell, how would I know it was "right" if I had it done by the pimple faced "certified technican" at the stealer, other than tearing up my (neighbors) wet lawn?

No need to gang up on me here guys, I am just saying that I am anxious to use the TDR as a better resource, but frankly I'm lost on this one.

 

[Chipstien]

I am one of those that put in Amsoil and all is well. I can do burn-outs on pavement, grass,dirt and gravel... ..... it does not matter.

 

[Sled Puller]

Take cover off and drain old lube.



Clean cover, reinstall.



Add lube of choice.



Depending on lube of choice, add correct amount of friction modifier, as mentioned above.



Do several figure 8s, to relube the clutches, all is well.



If it chatters, add a touch more friction modifier, or not, as the chattering is not hurting anything, it is just annoying.

 

[pcarlson]

I was pricing some MOPAR oil and Mobil oil at the dealer the other day as I have a diff fluid change coming up and they told me the MOPAR stuff is not true synthetic but rather a "Synthetic Blend".



Anyone know any different please chime in. The bottle says synthetic but according the the parts guys here its a blend just like the Valvoline Synthetic Blend which is who they said made the MOPAR gear oil.

 

[cap-n-cray]

Red Line Synthetic Oils?

I just change my rear differential cover to a Mag-Hytec. I am using Red Line 80W140 Gear Oil, on the advice of a friend. It said it does not require a friction modifier. Anyone have any experience with Red Line?



Cary

 

[jsimpson]

No, not with Redline. But with Amsoil synthetic gear oil in my Corvette, the LS would chatter after high speed runs, no matter how many tubes of additive I used. I switched to Amsoil racing synthetic gear oil, and I have no more chatter even with NO additives at all.