Giovanni

Anyone has a good write-up? How many quarts? Fluid type?

Also, what is the best fluid type/brand for a open differential? How many quarts?

Thanks,

Jim M.

Drain both the trans and the diff. You need a 17mm hex "L" wrench or socket wrench. When drained completly, reinstall plugs and fill until it comes out the fill port, which is the correct level when the car is on a level surface. IIRC you need a gallon of the prefered fluid.

RyanPerrella

try a search I am pretty sure this has been covered.

Pretty straightforward. The only issue is that it takes awhile to pump in 4 liters of fluid into the case. Other then that its no different from an oil change. Oh and dont f-up the drain plug and torque it correctly. (torque specs are the same for the automatic plugs as well, you may find those specs before you see them for a manual due to rarity with manuals.)

Tampa 928s

Make sure you remove the fill hole open first "top one"or you will be sorry you didn't.

Giovanni

lol, I remember someone else also posting that.

Should I go with redline, purple, mobil1 or just the conventiional oil?

Rob Edwards

4.5 quarts of Redline 75W90 in my '90 will fill it just to the bottom of the upper drain hole, and starts overflowing. Dunno when the drain plugs changed from 17mm hex to 10 mm hex, but mine are 10 mm. IIRC torque on the drain plugs is 16 ft lbs, same as all the rear cover bolts.

FlyingDog

Find a synchro safe GL-5 oil. Redline, Royal Purple, and Mobil 1 are popular choices. Heinrich didn't like the new M1 formulation last time he changed it. I am happy using Redline now, but I think I'll try RP next time since I bought a few gallons of 75W90 for my Jeep.

928ntslow

To answer the fluid type question, I have tried all 3 and can tell you that the only decent stuff for our tranny's is the Redline. The Mobil One is not so good for the tranny synchros and makes it too tough to shift...even after warm up. The Royal Purple is OK once the tranny has heated up...until then, good luck shiffting into any gear and not grinding gears in the process. Redline is nirvana. from the get go, it has the correct properties to allow for smooth shifting as it has some nice funk in there to coat the synchros. After the tranny warms it's like a hot knife through butter. Redline allows the quickest shifts from what I have found.

Mike Frye

+1 on the Redline, when I first got my car this was one of the first things I did and I did a bit of research on here. I picked the Redline and it's good stuff.

My first shift into 2nd gear on really cold mornings is a little tough but all other gears and all other times are smooth as butter. I have no doubt that my tranny is original and never rebuilt and it's still smooth after over 210k miles.

Some people put a hose up through a hole by the battery and fill it from the rear hatch with a funnel, but there's room above the tranny for a quart of stuff if you have a filler with a shut off. Also, if your garage is cold, warm up the oil bottles first or it will take FOREVER!!!

cdbtx

Try the Redline 75W90NS.

byrdman454

Some info on the net says that the 75W90NS is good for manual transmissions, but not approved for limited slip applications unless it is spinning too much under racing conditions. The 75W90 is approved for limied slip apps, but might allow gear clash if used with manual transmissions. Which version is best for the Porsche 5-speed with limited slip?

Vilhuer

For 928 manual transmission 1/3 of one Redline stuff and 2/3 of another. I can't never remember if its 1/3 or 2/3 NS version. There should be correct mixture mentioned in archives.

Giovanni

So you should use a combination of 75W90 and 75W90NS in a limited slip transmission??? I thought all transmission were the same and the differential is what makes the difference.

Is it safe to say all manual transmission should use 75W90 and use a combination of 75W90 and 75W90NS in the differential if its an LSD?

Vilhuer

Since gearbox and diff side share same fluid its always compromise and neither can use stuff which would be best possible fluid to use. Using one or another will both result less than perfect results. All NS is too much for other part while not having any at all is bad for another. I can't ever remember if it syncros or LSD which needs NS and which one of them doesn't like it if there is too much of it. Its all in archives.

Lizard928

from my research the NS is what the syncros like, but it can cause LSD clutch chatter (not good)

I plan on trying the NS stuff with some GM LSD additive as I have found it works wonders for stopping LSD clutch chatter.

Back in the 70s though they used whale sperm in LSD diffs to prevent LSD clutch chatter. How many of you knew that?