Shane

Lets' revisit this. 1986.5 5sp manual tranny, with open diff. What has proven to be the best choice for gear oil with this set up? Redline? Mobil 1? Other?

Give me your thoughts , please!

Mike Simard

Mobil 1 SHC 75-90. The trick is that it can't be the common stuff at the store but must be the SHC which will probably need to be ordered.

hacker-pschorr

Royal Purple smoothed things out in my 81 - same old story though, I have no idea how old the stuff was in the trans. So any new gear lube is better than the sludge in there now.

Shane

I followed a link John V. sent me for some redline by the case.

This is what the website said about Redline:



So Hacker you might want to flush out the Royal Purple and put in some of this Hacker Safe stuff...

Shane

Anyone here take Dougs' recommendation and put it to the test??

Flott Leben

I use a blend of Redline 75W90 Non-slip synthetic and ShockProof Heavy for a little extra protection and am very happy. It is a little thick when cold which makes shifts a bit notchy but when warm it is very smooth. You can also call them and they will provide you with some good info: (707) 745-6100 or (800) 624-7958.

MarkRobinson

Flott has it down: i have 2 bottles MTL (90w) + 3 (2.5 really) Shockproof in my gearbox: not that it needed it, but it's extended so/so syncro wear on other 928's I've owned. Need to short-shift (2200rpm or so) for first 2-3 minutes, but then it's great.

Andre Hedrick

What is your cocktail for the tranny?

Flott Leben

I have a 5 speed so it is all one box for me. Mark's proportions are pretty much what I used as well. I am not sure there is much difference between the Redline MT90 and the 75W90NS. [edit: I just checked Redline's website and MT 90 is a GL-4 while the 75W90NS is a GL-5 lubricant]

Louie928

Redline 75W-90NS.

Shane

How does that do for the cold morning shifts Louie?

sublimate

If you have an LSD, should you use something different?

I have a 5spd (with marginal syncros) and an LSD. Any reccomendations?

a4sfed928

I've seen this topic discussed before with only opinions to back up the claims, has anyone done back to back comparisons of different oils in the same manual trans?

Fabio421

I use a synthetic made by Schaeffer{s specialty lubricants and it has molly added. Great stuff

Louie928

Hi Shane,
Cold morning shifts with the NS seems to depend on your synchro condition same as with any other transaxle lube. On my '90GT, Gerry's '85 & '89 cold shifts were no problem. On my '87 with really bad synchros, I have to be careful for a few miles. I usually double clutch, or skip second, for a while. It's fine after that. I'm talking about temps below about 40F. Before I changed to Redline, the '87 was almost undrivable when cold. I believe it had Swepco in it. The Redline being synthetic is dramatically better than non-synthetic when cold, and better than a straight synthetic due to the NS (non-slippery) component. Regular synthetic is too slippery for the synchro clutches to grip as they should. I use it 100% in my '90 with PSD and '87 with LSD and have no unusual differential behavior. I talked to Redline tech about their Shockproof and they said it wouldn't be recommended for something like our transaxle where the same lubricant is used for the differential and tranny gears. It is primarily for differentials only for drag strip use. My question to them was for their lubricant recommendation for my GT tranny which I do not want to shred the gears under high torque load. Evidently, whatever is in Shockproof would have the tendency to force the gears apart in the tranny more so than if it wasn't in there. The "cushion" it provides for the differential gears isn't what you want in the transmission. As the gears mesh, excess oil has to squeeze out or it forces the gears apart as a hydraulic lock situation. The case stretches a bit, the shafts bend a bit, and the torque load is put on the teeth closer to the tips.

Edit: I don't mean to imply that Redline NS is the only tranny oil to use. I've had good experience with it to minimize the effect of worn synchros. Other types may work as well, or better.