G50 with LSD gear oil

[Techno Duck]

Replaced the gear oil in my '88 with G50 and factory LSD. Car shifted great before and had no LSD chatter or noise previously; not sure what was in there or how old it was so replaced it for a baseline.

I refilled using Redline 75w90 NS. Ive put about 60 miles on it so far and it still shifts great, however ive noticed i can really hear the LSD and feel it through the seat of my pants on tight low speed turns. I figure i need to add a bottle of the friction modifier; per Redline they recommend 4% concentration which works out to be 1-bottle (4 ounces).

I wanted to see if any others have experience in this area and if 1-bottle of the friction modifier really was all that was needed, or if i should use less... ive also read add 1 ounce at a time until desired results are achieved... personally i dont care to keep getting the car even on stands, opening the fill to siphon some fluid out and pumping friction modifier in! I dont want to overdue it either.

Also wondering what others that have a LSD equipped G50 have used as far as gear oils. I was deciding between the Redline 75w90 NS and Mobil 75w90 Delvac. The Redline i could get locally and i had good success in it with my 951 gear box. I wonder if the Delvac may be just as noisy as the Redline.

163k miles on the gearbox and i do not believe it has ever been opened so i am sure the clutch plates on the LSD are shot anyhow. Car is pretty much all street usage so it doesnt concern me too much.

[group911@aol.co]

Lsd must not be too shot if you feel it locking. I've had positive results with Delvac. Hopefully, Matt will chime in.

[safe]

I talked to a Castrol representative about this. Porsche recommends gear oil with no LSD friction modifiers for the G50.

[Techno Duck]

Bob, any excess noise / chatter from the LSD running Delvac? I am not opposed to changing the fluid again. I would jut like to reduce / eliminate the noise; to me it just doesn't sound right! I was thinking the Delvac would give the same results as the Redline as far as noise goes. Car is all street driven; might see one auto-x or DE in the future just to see how the car feels.

[group911@aol.co]

No. I actually started with another oil after a rebuild and had all sorts of issues and the Delvac took care of it.

[Matt Monson]

I've never been a big fan of Redline but that's largely biased by how it shifts on the track. If it were me I would try the LSD additive first. While I tell my customer not to use them that's because they make the LSD less effective. LSD additives are NVH items. How well the additive works will be influenced by how worn the LSD is. If it's freaky shagged the plates will be in there with essentially no preload, allowing them to rattle a bunch.

If you are happy with how the Redline shifts I wouldn't waste money on another oil. Try the additive. If that doesn't work budget an LSD rebuild in your future.

[Techno Duck]

Appreciate the input; I'll report back in a few weeks when I get a chance to add the friction modifier. Most of the old posts are either for the 915 or non LSD G50 so there wasn't too much to go off .

[shrtshck]

Experienced the same issue after changing the transmission oil in my 87 G50 with factory LSD. A small bottle of modifier was all it took to solve the problem.

Before changing the oil add the modifier and see if it addresses the noises you're hearing, my guess is it will.

[jamesrg]

Looking to do my baseline tranny fluid change on my G50 LSD. Is the recommended fluid Redline non slip or Delvac or Amsoil severe gear?

Thanks

[Techno Duck]

Originally Posted by jamesrg

Looking to do my baseline tranny fluid change on my G50 LSD. Is the recommended fluid Redline non slip or Delvac or Amsoil severe gear?

Thanks

I used Redline 75w90NS with about 1/2 bottle of the Redline friction modifier. It has been working great for me the past 4k miles.

[DanielDudley]

I was under the impression that NS was for boxes with Porsche syncros. It has been years since I used it, but I only used it after consulting with the Red Line factory hotline, and only because I had trouble shifting in low temperatures.

I wouldn't be happy driving unless I was sure I had the right stuff in my gearbox.

[jamesrg]

Not sure if I should go with Redline or Kendall, leaning towards Redline after further reading.

No idea what is in it now, but it is a bit tougher for reverse and first when cold.

[Matt Monson]

Redline NS works well in cold conditions for G50 owners who street drive their car year round.

[KTL]

Did the noise go away when the friction modifier additive was added? Reason I ask is because my initial reaction was, are you sure it's the LSD making noise and not just the transmission in general? The early G50 transmissions are pretty darn noisy. Some of them with a lot of miles on the clock make all sorts of clattering noise at idle with the trans in neutral and the clutch engaged. I believe the general noisy behavior is one of the reasons they originally used that big giant rubber damper in the clutch disc instead of a typical spring centered disc.

[jamesrg]

Originally Posted by Matt Monson

Redline NS works well in cold conditions for G50 owners who street drive their car year round.

Thanks!

Is it similar to oil with temps? Meaning it works better in cold environments when cold because it is thinner vs our Texas summer heat where protection will be compromised due to the heat?

I can handle the 10min of tougher shifting when cold but better protection during the summer months if that is the trade off.

[Techno Duck]

Originally Posted by KTL

Did the noise go away when the friction modifier additive was added? Reason I ask is because my initial reaction was, are you sure it's the LSD making noise and not just the transmission in general? The early G50 transmissions are pretty darn noisy. Some of them with a lot of miles on the clock make all sorts of clattering noise at idle with the trans in neutral and the clutch engaged. I believe the general noisy behavior is one of the reasons they originally used that big giant rubber damper in the clutch disc instead of a typical spring centered disc.

It quieted right down after adding in the friction modifier. I could both hear and feel the LSD in the drivers seat when making tight low speed turns around town. No longer a problem now. The noise from the trans stayed the same regardless... it is a really noisy box. I recently switched to a 930 spring centered disc with a KEP Lite pressure plate. Its actually not any louder than it was with the stock pressure plate and rubber disc... i do get quite a bit more chatter engaging 1st gear unless i slip the clutch a little more.

[KTL]

Thanks for the feedback. Good to hear it fixed it for the time being. Think about taking out the diff and getting it serviced. It's pretty easy to do

Agreed on the clutch stuff. I had a KEP clutch with the '75-'77 930 disc. A bit expensive but a nice way to improve throttle response. Also helps shifting since it's easier to match revs with the lighter clutch assembly