RPM WS6

iTrader: (3)

That's unfortunate, considering that the original factory recommendation was actually for conventional. But this LSD has been out of production for 18 years now, so I guess they don't bother to service them at this dealer with the proper gear oil any longer. That's bad news for their customers.

For best operation and longest service life, I'd stick to the original recommendation.

GM does still offer the proper gear lube, part #89021669 (80w90 conventional). Original part was #12345977 but the new number is the same lube.

Looks like the part number for the LSD additive has changed, was previously #1052358 but now seems to be listed under #88900330 as mentioned by FirstYrLS1Z above.

FirstYrLS1Z

iTrader: (4)

to AnotherWs6-how was it with 4.56s' ?
Wonderful !!! A4 w 4.56,incredible 1st and 2nd gear. Response was immediate and strong. Back in the 60s' musclecar era,GM didn't have to be concerned with CAFE mpgs. Camaros and Chevelles were all optional to 4.88 gears.

Steve91T

Been doing some reading.

What do you guys think about running standard gear oil with no modifier. I know it'll be noisy, but it will also work better. Seems modifier is there to make the LSD quiet and not using modifier will not hurt it.

Thoughts?

RPM WS6

iTrader: (3)

Some people claim that the Torsen is quieter with the additive, but most agree that it's entirely optional with that rear.

With an Auburn, I would not skip the additive, nor do I see how it could work any better without it. Mine has always worked perfectly with the additive, I can't see any advantage to not using it.

FirstYrLS1Z

iTrader: (4)

NO,it will not make it work better. the additive is used to allow it to function as it was designed.

Steve91T

I've been searching the web for way too long now on whether to use friction modifier of not and what I have concluded is there is a lot of crap information out there's.


From what I gather, the best is to use 80w90 non synthetic.


And I'm not going to use the friction modifier. Some say it will wear the auburn quicker, some say it won't. But it definitely will make it have more lock up, which is what I want. I know it will be noisy.

Since eventually I'm going to put a better LSD in there anyway, I really don't care about longevity, so I figure I have nothing to loose.

I'll do this tomorrow and see what happens. I have another track day in 3 weeks, do I'll see how it performs.

RPM WS6

iTrader: (3)

My Auburn has worked perfectly for 18 years with the additive. I don't see how it could possibly have worked any better without it, I don't see what sort of advantage you think you'll be gaining by not using it.

Good luck to you.

dailydriver

The main reason for that is that there are NO Auburn diffs used in GM's current line up, and even NONE since they were used in the '93-very early '99 f bodies.

dailydriver

He's looking to launch harder off of the apexes/corner exits, as this car is used on a ROAD COURSE, not the street/strip ONLY, like most on here.

Now, whether or not the lack of the FM additive will help promote that type of off corner lockup or not with the Auburn's cone clutch set up, who knows??

Steve91T

Exactly. So I've got a bottle of FM in the garage. In 2 weeks I have another track day, I'll be able to see how it performs. I'll also get a couple of weeks of street miles. If it doesn't do well, I can add the FM. If I blow it up, I'll put the torsen style out of my 99 parts car, although I don't think that'll happen.

FirstYrLS1Z

iTrader: (4)

The additive is a 'friction modifier'. The EP additive in gear oil prevent the clutch from grabbing/locking. That's where the 'noise' comes from,the cone clutches lock and then unlock because of the 'straight' lube,the modifier allows them to stay locked up to their designed torque setting as designed.

Steve91T

You're saying the modifier allows them to stay locked longer? The LSD is more effective with the modifier?

I mean no disrespect but I think that's barckwards.

FirstYrLS1Z

iTrader: (4)

I guess we'll see as you're gonna start out without the additive as a tryout. Let us know which works better for you,no additive or additive.

Steve91T

Will do.

Steve91T

Update: I filled the diff with Lucas regular 80w90. I did mostly highway driving with a couple of parking lot maneuvers. I notice a little noise in tight turns but nothing bad. On the way home I made a hard right turn from a stop and got on the gas hard. The LSD locked up hard and sideways I went. The same LSD with the expensive grape flavored synthetic gear oil, I would have lit up the right tire.

I'll drive it more tomorrow, but so far the diff actually seems pretty happy with no friction modifier. Much happier than the synthetic stuff.

RPM WS6

iTrader: (3)

You aren't comparing apples to apples here though. You made two changes; a switch from synthetic to conventional, and no additive. You'd have to try the proper conventional with and without the additive to see which is better for your purpose. The issues before may well have been due to the synthetic - something the Auburns usually aren't happy with regardless of additive or not.

You might find that it will work even better, or at least work as well but be quieter, with the additive in addition to the proper conventional 80w90 that's now in place.

AnotherWs6

iTrader: (17)

^^^^Agreed, but if it's working it's working. I don't claim to really know why, but differentials often don't like synthetic. Which is fine with me....$

Steve91T

Yeah I agree that I'm not fully testing the theory with no addative, but I'm not going to waste the money to keep draining and filling the diff. It seems to be working really well, so I'm going to leave it alone. I'm going to drive around town more today so I'll get a better idea of how it's working.

I've got another track day coming up. I know the LSD with the synthetic stuff wasn't working well at all. This track has a lot of right hand turns and I kept lighting up the right tire on exit. Going back to the same track will be a good test.

Thanks for everyone's help and opinions.