So in my other thread I'm trying to tighten up my tailshifter slop and have drained the tranny to check the roll pin on the shift shaft.

I'm gonna have to fill it back up but want to know what's best to use in the tranny.
I would like to also know if any addatives are recommented to help out with seals/ syncros/ you know friction modifier that kind of thing.

Thanks in Advance!

Do a search or you run the risk of starting a shooting match. Lot of opinions and suggestions.

I've already searched and the general thing is Synthetic tends to eat up the syncros fast. Which is something I want to stay away from since my syncro's alreay have issues but really wanted an idea of weight 75-90 or straight 90 and if I could add something to prolong the syncro life or improve the shift quality.

Swepco is the hot gear oil for 901 trannys.

a lot of people will say swepco, I'll just say any new, fresh decent brand will work fine, and save you some cash

QUOTE (Jaiden @ Oct 7 2005, 04:33 AM)

I've already searched

My bad....

I have always just used plain jane 80w90. Never tried Swepco. Some swear by it.

good luck

I guess that's what I'll look for Swepco... If I can't find it I will go with a 80-90w or staright 90. I will not be driving the car in the winter so The thicker viscosity will probably work best.

Thanks Again!

Whatever you use, and I have used 80-90-140 for years, be sure you get straight GL 5! GL4, or anything that says on the label that it's compatible with anything else but GL 5, is gonna do bad things to your tranny. You also don't want any friction modifiers, because your synchros depend on synchros!
I've been repairing Porsche trannies for 35 years, and I've seen what the wrong gear oil can do. The Cap'n

QUOTE (Cap'n Krusty @ Oct 7 2005, 09:51 AM)

Whatever you use, and I have used 80-90-140 for years, be sure you get straight GL 5! GL4, or anything that says on the label that it's compatible with anything else but GL 5, is gonna do bad things to your tranny. You also don't want any friction modifiers, because your synchros depend on synchros! I've been repairing Porsche trannies for 35 years, and I've seen what the wrong gear oil can do. The Cap'n

I have some coastal 80/90 that says GL5,GL4,GL3

is that bad stuff?

someone here told me the coastal stuff works.

QUOTE (Cap'n Krusty @ Oct 7 2005, 06:51 AM)

Whatever you use, and I have used 80-90-140 for years, be sure you get straight GL 5! GL4, or anything that says on the label that it's compatible with anything else but GL 5, is gonna do bad things to your tranny. You also don't want any friction modifiers, because your synchros depend on synchros! I've been repairing Porsche trannies for 35 years, and I've seen what the wrong gear oil can do. The Cap'n

I know on modern trannys that use yellow metals, most GL-5s can do bad things because of the additives. What is it about GL-4 that would be bad for the 901? Not enough EP additives?


Andrew

what is the consensus on the redline gearoil?

QUOTE (phantom914 @ Oct 7 2005, 07:03 AM)

QUOTE (Cap'n Krusty @ Oct 7 2005, 06:51 AM) Whatever you use, and I have used 80-90-140 for years, be sure you get straight GL 5!  GL4, or anything that says on the label that it's compatible with anything else but GL 5, is gonna do bad things to your tranny.  You also don't want any friction modifiers, because your synchros depend on synchros! I've been repairing Porsche trannies for 35 years, and I've seen what the wrong gear oil can do.  The Cap'n I know on modern trannys that use yellow metals, most GL-5s can do bad things because of the additives. What is it about GL-4 that would be bad for the 901? Not enough EP additives? Andrew

Tranny oils are NOT numbered sequentially because the higher numbers are better, or newer, it's because the specs are different. Like your house number, which indicates its location. Not better, nor worse, than the house next door, just different. The designers of your tranny had some specifications in mind, and GL5 meets that set of specs. GL4 doesn't. Aspirin is spec'd as a pain reliever, Neosporin is an antiseptic ointment. You take aspirin for pain, and you rub neosporin on a cut. You use the product meant for the specified use. Run GL5 in a GL4 designed tranny, and you'll experience greatly degraded shifting synchronization and, they say, brass deterioration (although there's brass in a 901 tranny and it doesn't seem to hurt it).
GL5 isn't meant to function optimally in a tranny designed for GL4 (like the G50), so why use it? If you can't find it in your FLAPS, order it! You have NO business in your FLAPS anyway. They have little, if anything, specifically for your car, and the counterpersons are apt to tell you anything you want to hear in order to get you out the door with a lightened wallet. .

QUOTE (synthesisdv @ Oct 7 2005, 06:59 AM)

QUOTE (Cap'n Krusty @ Oct 7 2005, 09:51 AM) Whatever you use, and I have used 80-90-140 for years, be sure you get straight GL 5!  GL4, or anything that says on the label that it's compatible with anything else but GL 5, is gonna do bad things to your tranny.  You also don't want any friction modifiers, because your synchros depend on synchros! I've been repairing Porsche trannies for 35 years, and I've seen what the wrong gear oil can do.  The Cap'n I have some coastal 80/90 that says GL5,GL4,GL3 is that bad stuff? someone here told me the coastal stuff works.

Is it bad stuff? Yes. The Cap'n

I guess I have an oddball transaxle. I've been running Mobil 1 synthetic GL5 for about 2 years now in my yellow V8 and it shifts great. No leaks and shifts are easy and smooth, cold or hot. As far as the corrosion of yellow metals concern, I just go by the manufacturer's data sheet.
"Excellent rust, staining and corrosion protection of copper and its alloys"

You're SUPPOSED to run GL5 .................... The Cap'n

oops not redline, I meant royal purple

just picked up a couple quarts of Penzoil 80-140
it states meets or exceeds the specifications of GL5

I hope this will work.

I'll be swapping out the tranny in the future but hopefully not that near future!

QUOTE (Jaiden @ Oct 7 2005, 09:38 AM)

just picked up a couple quarts of Penzoil 80-140 it states meets or exceeds the specifications of GL5 I hope this will work. I'll be swapping out the tranny in the future but hopefully not that near future!

Should be fine. However, it takes nearly 3 quarts. The Cap'n

QUOTE (Jaiden @ Oct 7 2005, 10:38 AM)

just picked up a couple quarts of Penzoil 80-140

btw. we got SWEPCO in the club store (insert shameless plug here) ...

just in case you will need a refill again one of these days ...
Andy

I just checked my collection of Porsche manuals. All say to use a SAE 90 Hypoid gear oil in the transmission. No mention of GL rating. I'm not even sure when the GL-5 standard was issued - tried to look it up on the SAE official site but got frustrated and quit looking.
Next I did a web search and found lots of references to early GL-5 oils being harmful to transmissions that contain "yellow" metals. Our 901 boxes have bronze bearing cages so they qualify. More research indicates that modern high quality GL-5 oils all have corrosion inhibitors and say they are safe for transmissions containing yellow metals.
I have used Swepco, Red Line (GL-4), Royal Purple, and Mobil One GL-5 gear oils in my transmission for years. I have had three transmission failures in six years of racing my 914 - first with a 3.0 liter and then with a 3.4 liter. One failure was the ring and pinon, one was fourth gear and one was failure of the bronze bearing cage but think that the cage failure was due to excessive torque and not corrosion. All of the aformentioned gear oils performed well - good shifting and good wear protection. I think as a general rule we can and should use GL-5 rated oil as long as it is a quality brand.

Of course I bought 3 quarts

When my trans was rebuilt by Carters in bigbear Ca I was told to run GL5. The tranny siezed and I was promptly told that I should have run GL4. I was told that GL5 is for limited slip and I do not have that. My trans was re-rebuilt and has run GL4 for 30K or so. What am I missing.

No, GL-5 does not designate limited slip use. Many high quality gear oil manufacturers make two versions of GL-5 (and GL-4 for that matter), one for non limited slip and one for limited slip. The difference is that one has friction modifiers added. See Capn Crusty's explanation - GL-5 is a higher pressure rating. That's pressure between gear mating surfaces. GL-5 should give your gearbox greater protection as long as its friction qualities allow proper synchro engagement.

QUOTE (Jaiden @ Oct 7 2005, 04:07 AM)

I'm gonna have to fill it back up but want to know what's best to use in the tranny.

[QUOTE]

I'm wondering...
What do you do with old stuff?