GM Syn. Rear End Fluid=No need for LSD Additive?

[Striker]

I was about to replace the fluid on my 99 WS6 that came with a LSD from the factory so I went to GM for some new fluid.

The parts guy mentioned that if I opted for the Synthetic, it eliminates the need to throw in the GM LSD additive that is typically added along with the conventional fluid.

Before I dump the synthetic in the rear end housing, is this true or will I be buying myself a new LSD?

 

[EricF]

that's true. However it wouldn't hurt to add it.

even some conventionals say it has the lsd additive in as well, I always put it in anyway.

 

[Trav]

I've seen it go both ways, some chatter some don't.
The answer to your question is yes the synthetic fluid is does have the additive in it but i have not idea how much.

Try it and if there is no chattering then its fine, if it does then just add the additive no need to drain and refill.
I had a new ZO6 that used synthetic OEM and it chattered slightly in left turns, the additive cured it pronto.

 

[Striker]

Originally Posted By: Trav
I've seen it go both ways, some chatter some don't.
The answer to your question is yes the synthetic fluid is does have the additive in it but i have not idea how much.

Try it and if there is no chattering then its fine, if it does then just add the additive no need to drain and refill.
I had a new ZO6 that used synthetic OEM and it chattered slightly in left turns, the additive cured it pronto.


Thanks Trav,
Go with the GM additive or otherwise?

 

[Trav]

Its been my experience that you cant go wrong using OEM when it comes to speciality fluids. Go with the GM.

 

[Bob Woods]

I use the Mobil 1 gear lube in mine it already has the additive in it.

 

[bdcardinal]

What type of limited slip do you have? If you have a Torsen which i think those had, there is no need for an additive as there are no clutches for the additive to work with.

 

[MrHorspwer]

Originally Posted By: bdcardinal
What type of limited slip do you have? If you have a Torsen which i think those had, there is no need for an additive as there are no clutches for the additive to work with.


Correct answer. A 1999 should have a Torsen diff. No clutches means no additive.

 

[Whitewolf]

Correct.

 

[Striker]

Yes, it is a 99 and yes, I'm 99% sure it's a Torsen.

 

[dailydriver]

Originally Posted By: MrHorspwer
Originally Posted By: bdcardinal
What type of limited slip do you have? If you have a Torsen which i think those had, there is no need for an additive as there are no clutches for the additive to work with.


Correct answer. A 1999 should have a Torsen diff. No clutches means no additive.


Are we sure on that?

I've always heard/thought that the Torsen T-2s started with my model year (2000), and the '93s to '99s had the Auburns, but I could be (VERY) wrong.

Also, was it just the SLP 'built' SSes which got the Auburn Pro diffs, or did the WS6es also get them with the option package??

 

[Striker]

Any way I can know for sure, Dailydriver?

 

[bdcardinal]

Originally Posted By: Striker
Any way I can know for sure, Dailydriver?


When you pull your cover off and see gears with no clutches, you know.

 

[dailydriver]

Originally Posted By: Striker
Any way I can know for sure, Dailydriver?


I will call SLP today, or tomorrow (they would know for sure).

Then I will get back on here with their answer.

 

[Striker]

Originally Posted By: dailydriver
Originally Posted By: Striker
Any way I can know for sure, Dailydriver?


I will call SLP today, or tomorrow (they would know for sure).

Then I will get back on here with their answer.


Thanks Daily!

 

[dailydriver]

Originally Posted By: Striker
Originally Posted By: dailydriver
Originally Posted By: Striker
Any way I can know for sure, Dailydriver?


I will call SLP today, or tomorrow (they would know for sure).

Then I will get back on here with their answer.


Thanks Daily!


I spoke to Joe at SLP and he said the changeover to Torsen T-2s (from Auburns) happened LATE in the '99 model year (unlike most who state it was very early in, or the whole 1999 model year).

So sadly enough, the only way to know for sure is to take the cover off of the pumpkin, which you would have to do anyway in order to change the gear oil, unless you have an aftermarket performance, alloy diff cover (like a Mac, TA, LPW, Summit, etc.) with a drain plug at the bottom.

I suggest getting one of these if you plan on keeping the 10 bolt axle in your f body (and are NOT changing over to a; 12 bolt, S60, or Ford 9" like many do), as it makes life A LOT easier for gear oil changes, better heat dissapation, main bolt reinforcement, and a little more oil capacity.

Regretably, MAG HYTEC does not make a cover for our cars which will not interfere with the rear swaybar, and upper panhard bar.

 

[Striker]

Thank You Daily!

The car was built on June 18th, 1999. I guess I'll have to get whoever is doing it to look for the clutches.

As for changing the rear end cover, I agree that there are far better options. However, the car will most likely remain original for as long as I have it.