Engine/Transmission (1998.5 - 2002) Mobil 1 and Limited slip

[Texas Diesel]

I was told that Mobil 1 75W-90 has the LSD additive in it already. The bottle seems to indicate the same. Anyone have any direct experience here? I dont want to fry my clutch pack.



I've heard that Amsoil users have successfully run with out the modifier too.



TIA

 

[emjay]

I don't have any experience with that particular lube, but (and someone please correct me if I am wrong) the modifier keeps the friction discs from grabbing, sometimes making a snapping sound on tight corners. The conclusion that I have drawn is that if it says it's good for limited slip diffs and it doesn't make noise, you're probably OK.

 

[LSMITH]

I run the Mobil 1 75-90 and I need modifier in large quantities. My LSD is a freakin spool without modifier regardless of lube, so you may not need it. I would put the oil in and drive it a little, Add MOPAR modifier in 2 oz increments until the chatter stops, and use only MOPAR modifier. I have tired several modifiers and Mopar is the only one that will get rid of the chatter in my LSD. I have had up to 21 oz of the parts house modifier in with no improvement, last time 8 oz of the Mopar did the trick.

 

[Texas Diesel]

It keeps the tires from scrubbing in corners too.



Unless I can determine that I dont need it positively, then 8 oz is going in. I'm not gonna take a chance. I have 55,000 warranty left on the axle and dont want to damage it myself. However, too much modifier will keep the plates from holding

 

[drag racer]

I can only share my direct experience, so FWIW, I have a Mag-Hytec cover and have run 8 qt of Mobil 1 75W-90 with no modifier and it has worked just fine.

 

[Neal Cassady]

I am running Mobil 1 75W-90 without any modifier. Haven't noticed any grabbing or binding yet. Did seem to pick up close to 1 MPG when I switched from the factory fill to synthetic.

 

[fox]

The responses are all over the chart!!

I have Mobil 1 in mine and tried it with-out but they chattered. Then I added 1/2 a bottle for a few days and it almost cleared up, added the rest and it is fine.

 

[jwilliams3]

I use Trans X limited slip modifier every time I change Diff fluid, usually about half a tube in my Dana 70.

No chattering and no "scrubbing in corners", I wouldnt take the chance of not adding, add a little modifier, I dont think it will hurt anything.



--Justin

 

[Texas Diesel]

UPdate:



7 Quarts of Mobil 1 75W-90 went in. No friction modifier yet, no scuffing in corners or turning on dirt. The LSD locks GOOD, real GOOD, enough to cause wheel spin if punched with one tire in the dirt and one on pavement, both tires spin equally. I am nervous about not adding the Mopar stuff, I bought two bottles just in case.



What do all you rear end experts think? Add 4-8 oz or leave it alone?

 

[Bob Cochran]

No rearend expert by no means. I think the experts will say no 2 rearends are built exactly the same some don't require friction modifier some will. So do the figure 8's and add just enough to stop them from scrubbing in the turns. To much and the clutchs slip and LSD don't work. Sort of like baking a cake; which I coudl never do!!!!:--)

 

[DEZLPWR]

Mobil 75w-90 synthetic front & rear here and no chatter w/ no additive... .

 

[Vaughn MacKenzie]

I ran the Mobil 75W90 syn gear lube and did not like it. Lots o' chatter, added friction modifier, and lost a lot of my LSD effectiveness.



Switching to Amsoil 75W90 cured the above problems, only had to add a little modifier after 20k miles and LSD effectiveness improved noticeably.



Up front I did the opposite. . . went from Amsoil to Mobil Delvac 1 in the motor :rolleyes



Vaughn

 

[Pit Bull]

I did the Mobil 1 75w90 the other day and I added 8 oz's of Mopar lsd modifier, service manual called for 12 oz's. No chatter, hell maybe to much modifier. I might of turned my lsd into an open diff. Oh well it's cheaper then new clutch packs

 

[Texas Diesel]

Originally posted by Vaughn MacKenzie

I ran the Mobil 75W90 syn gear lube and did not like it. Lots o' chatter, added friction modifier, and lost a lot of my LSD effectiveness.



Switching to Amsoil 75W90 cured the above problems, only had to add a little modifier after 20k miles and LSD effectiveness improved noticeably.



Up front I did the opposite. . . went from Amsoil to Mobil Delvac 1 in the motor :rolleyes



Vaughn

You're exactly right, lots of chatter but locked up perfectly, added 8 ounces, now the LSD doesnt lock up right. Perhaps I should have stopped at 6 ounces



Interesting note, I had synthetic in before since new, so I put standard 90W gear oil and rear end temp was 20-30* higher, did this for several days consistantly. Then I put in the Mobil 1 again, and now 23-30*F cooler on the same run repeated several times.

 

[LSMITH]

Originally posted by Texas Diesel

You're exactly right, lots of chatter but locked up perfectly, added 8 ounces, now the LSD doesnt lock up right. Perhaps I should have stopped at 6 ounces

Hence my suggestion to add 2 oz at a time. You are faced now with the choice of running it the way it is, basically a pegleg, or dumping the diff for a refill and adding a little at a time to get it right.

 

[Texas Diesel]

Lsmith, I did add two ounces at a time as you suggested, here is what I did wrong.



I put Mobil 1 in and no modifier and drove it around, seemed fine, then, later on, it started chattering badly, so I added 2 ounces, no improvement, added 2 more, (4) drove it around a dirt field and no improvement, added 2 more, (6) drove it around a dirt field and no improvement, added 2 more (8) drove it around a dirt field and still had minor chatter that want away in the next day or two.



My conclusion, after running with no modifier it took a couple of days to get the stuff worked back in. I should have added perhaps 4 ounces when I added the Mobil 1 and then allowed more time between subsequent 2 ounces.



Your idea was right, my procedure was flawed.

 

[LSMITH]

TD, drive figure 8's as tight as you can on a hard surface like a parking lot. Do 8-10 of them and then drive it for a day or two before adding more modifier. Dirt will allow the inside wheel to slip easier, and will not force the plates in the LSD to slip. Slipping the plates is what gets the modifier altered oil into the plates.



FWIW, mine is not as grabby when the diff and oil is cold as it is when it is at operating temp.

 

[Gary - K7GLD]

Like one fella up above sez - replies are all over the map on modifier vs no modifier due to wide variations on individual LS clutch packs and pressures - it's quite common on all LSD's both in cars and trucks. I've been involved in exactly the same discussions on several Camaro SS boards - with the same results we are seeing here...



Regardless of the brand or type of lube used, ya hafta do the individual test bit to properly tailor LSD action to the lube you select - some of us will need plenty of modifier - others will need none - it's not particularly any indication one brand/type lube is better or worse than another - merely LSD differences...