Is LSD additive needed? 75w90 recommendations?

[lowpassat]

Hello all,

I am wanting to change the manual trans/diff oil in my 83s.

It has the optional LSD but with it only being 40% lock up is the additive needed?

I think I'd rather stick with conventional oil, Valvoline seems to make the only conventional 75w90. What are you guys using?

Thanks!

[Danglerb]

The additive is to increase the slipperiness to avoid chatter, iirc, usage depends likely on clutch wear in the LSD.

I think I used Red Line, some like Mobil 1, or Royal Purple. Dino is likely fine in 75W90. Factory fill sure has a nice stink when you open up a transmission, full of sulfur.

[Crumpler]

The additive is to increase the slipperiness to avoid chatter, iirc, usage depends likely on clutch wear in the LSD.



I think I used Red Line, some like Mobil 1, or Royal Purple. Dino is likely fine in 75W90. Factory fill sure has a nice stink when you open up a transmission, full of sulfur.

Totally. I remember opening mine and the smell was god awful. Lol.

[Pete R]

If you live in a cold climate, synthetic will really help cold shifting.

[S4hounddog]

Make certain the oil has a GL-5 API rating, no LSD additive is required. I use 75W-90 Redline in my LSD 928S4.

[Yellowb1rd]

Funny this thread was created, as I pondered this as well recently. I just replaced the transaxle fluid in the 5-speed only yesterday. I had heard lots of good things about the RedlineNS, but I didn't want to use synthetic. Also, the transaxle is non-LSD, so I was looking for something sans (without) friction modifiers, but it was virtually impossible to find a conventional off the shelf brand in the store without friction modifiers. Friction modifiers do the trick for LSD, but tend to work against the syncros in a non-LSD trans. Also, most local parts stores seem more focused on synthetics, which again, I wanted to avoid, not having LSD. So.....

Although there isn't a lot of input (specific to Porsche) about Valvoline VV820 75-90, I just used that, as I've typically had great experience with Valvoline products in the past. Although it doesn't state per se that it has friction modifiers, the product info mentions that it's OK to use in both LSD and non-LSD setups (GL4 and GL5) alike. Time will tell if it was the right choice, and if not, I'll swap it out, as it's not a difficult job. The bugger is extracting ALL the oil out of those bloody bottles, even with the manual pump.

[AirtekHVAC]

I used the GM stuff, recommended somewhere.....I don't have a pic of the bottle handy, was not bad expensive, and seems ok, of course it has all been liftbar run, not on the road....I'm going to change it again after I road test her, if I can ever get it ready..still need to install drivers side CV, and rebuild the FD.

OMG the old fluid stank!!! I thought it to be the original from 1978...

[lowpassat]

Thanks guys!

I think, like Yellowb1rd I am leaning toward just filling with Valvoline conventional 75w90.