Rear Diff Fluid LSD additive

[nmaier2201]

To all you beloved forum members who opened this thread going “son of a #*$ didn’t bother searching the forums or FAQ. I’m going to paste a link and tell him to shove off”

I have read a bunch of threads and looked over stealth V’s instructions on changing the fluid…. It’s all very easy. I’m not here to debate whether RP or amsoil are better either… any “quality” 75W-90 fluid will do just fine.

My question is: It seems like ½ of the people on the forum are running with the LSD additive and the other ½ are not (according to past threads). What “should” I do? Do I use it, or don't I?

Some say it helps with the noise, others say it makes no difference at all…. I’m not looking for people to say “I used that additive and my rear blew out.” Or “I didn’t use that stuff and my rear grenaded” I’m sure both things have happened to at least one person….

According to the letter of the law…. Should I use Limited Slip additive # 1052358 with amsoil SEVERE GEAR 75W-90 Synthetic… or not? My guess is “yes” … but I’d like to check with the experts…..as always

[PISNUOFF]

Call AMSOIL's tech support. 1-715-399-TECH(8324) 8-5 CST

[urbanski]

rp doesnt need it

[nmaier2201]

Roger that. I did call those guys. The tech guy I talked to sounded pretty confident that the limited slip lube wasn't needed and that the SEVERE GEAR Synthetic Extreme Pressure Lubricant 75W-90 already had the "viscosity" needed in the rear end, similar to the GM gear oil and additive.... I already read the same for RP... I think lollygagger stated it didn't need it either.

Similar? aww come on tech dude! So I didn't want to skew the results by posting that... but if I didn't reply I didn't think anyone else would vote on my sweet poll LOL

Originally Posted by PISNUOFF

Call AMSOIL's tech support. 1-715-399-TECH(8324) 8-5 CST

[MauiV]

My pinion seal was replaced today and I left a bottle of Royal Purple for them to replace with. I havent picked the car up yet but hopefully my clunk is gone with the RP, new pinion seal and new diff bushing. They also replaced end links and clips on the rocker panels. May be more that I dont know about yet too.

[C66 Racing]

I use the AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 (stock code SVGQT) and don't use extra additive.

I think the answer to your question is a little subtle. Many fluids include the limited slip additive in them. The above linked AMSOIL Severe Gear that I use has limited slip modifier in it. I use this fluid without extra additive in both my CTS-V and my 02 Corvette Z06. Neither diff chatters. So to say that I don't have additive is a little inaccurate. I don't have extra additive.

My recommendation (if you go with the AMSOIL). Add it without extra additive, do a bunch of figure 8s to work the fluid into your diff and drive it and see if your diff chatters. If it doesn't - you're good. If it does, add a bottle of AMSOIL Slip-Lock Differential Additive (or GM equivalent).

The downside to too much limited slip additive is that your diff clutch plates will have more slip than intended and thus your limited slip diff will be less limited slip. Maybe not a problem for a daily driver, but you will lose some performance due to more wheel slip from the unweighted rear tire under hard acceleration (such as the inside rear coming out of a tight slow speed corner).

[nmaier2201]

Now THAT'S what I was looking for! an explanation... and it was a good one too. Now I got what too much or too little will do to you, and how to remediate and make sure I have the right amount. Thanks you guys for schooling me in limited slip additives. Now I can set it up right, the educated way.

[C66 Racing]

Originally Posted by nmaier2201

Thanks you guys for schooling me in limited slip additives.

My pleasure.