Riff

One piece of info, the fact that transaxle was covered in oil doesn't mean that it is leaking. There is a breather hole on the top of the tranny and if over-filled will coat your tranny in oil, ask me how I know
Anyway, I switched my gearbox to Mobil-1 synth over 3 years ago and have had smooth shifting ever since.

HTH

IceShark

Yeah, I was going to mention that breather hole but figured they didn't tip the car on its side to overfill and cause kick out from gears churning. So how did you overfill? On a slope?

I'd clean off and see where it is coming from. Maybe oil cooler tube related?

I also used Mobil 1 gear lube once. Found a disturbing amount of metal shavings when inserting finger into bottom of case as I always do. A 2 year oil change. While it could be due to some self reinforcing gear wear, I think it was due to the Mobile 1.

Tabor

Adrial: You can use Redline MTL in the 944 transmissions. Our transmissions call for GL4 rated lube. The Redline website says not to use it in rear differentials because cars with rear differentials take GL5 rated oil 99.9% of the time. But if you use GL5 rated fluid in our cars, you will ruin your synchros.

Most rear wheel drive cars do not have a rear transaxle, only a rear differential. And rear differentials do not have synchros in them!

Skip

Hi guys, sorry to be so late on this... and not trying to stir up the opinions after the initial poster... so I'll just answer directly to it:

Regarding Synthetic vs. Dino:

While it seems that an already leaking tranny would be the wrong place to put synthetic, most who've done this have not complained of any higher leak/seep rates. I would assume this is due to the operating temperature and oil pressure differences between the motor and the transaxle. So, it's your choice... [probable] better long-lasting protection and smoother shifting or play-it-safe.

Regarding the GL4/5 issue:

Oil weight:

In high-performance applications where the temperatures may get higher than street use, it is common practice to use a bit higher weight oil (75W90 vs. 70W80), and higher still if the tranny/diff is not externally cooled (80W140).

What about GL-5 vs. GL-4:

The main complaint against GL-5 use in syncro'd trannies is because the chemicals used to provide the extreme pressure protection can be corrosive to synchronizers, which are commonly made of brass or bronze. Here's what the 944 factory manual has this to say: "Filling capacity Approx. 2.0 liters hypoid transmission oil SAE 75W90 to API Class GL5 or MIL-L-2105B, or SAE 80 to API Class GL4 or MIL -L-2105."

Which one is right?:

In the end, it is up to the owner. Though statements of GL-5 use in a syncro'd tranny are somewhat against... history and sales of GL-5 lubricants (like Redline 75W90) continue to be favorable. This is a heavily debated topic, even within the industry. The only things we can assume for sure is: 1. Don't use FM in non-LSD transaxles 2. Don't add FM to make the clutches lock up sooner in LSD equipped cars.

Check here for a Tech-Session article on how to change the tranny fluid:
944 Transaxle Fluid Change

For more info about FM and such, check here:
944 Transaxle Fluid

Capacities are: 2 liters for non-oil-cooler equipped, and 2.6 for oil-cooler equipped (depending on how well you drain it)

Also, the one liter/quart gear oil containers with the nipple fit nicely up there... redline bottles require a sort of funnel. I use aluminum foil shaped over the end like a funnel... works great

I've personally been through Mobil One, Amsoil, and Redline (75W90NS) and have to say that Redline is by far the best! Better cold shifting and way less box-o-rox noises on deceleration. Syncros feel fine. YMMV

Good Luck!

adrial

OK, My ruling:
1) Clean up the tranny, try and find out where it's leaking from...how badly..etc
2)If not leaking, lean towards redline MTL.
If leaking, lean towards shell 80W90 dino oil.

I'm gonna stay away from GL-5 rated oils though...I don't feel there's any reason to push my luck with GL-5 when GL-4 is readily available.

adrial

OK, I haven't cleaned the tranny yet, but I just had a look at it. It definetely appears to be have wet oil on it. Currently it's nothing to worry about. However, I don't know if the PO was running synthetic or not. Is there any way to tell by testing the fluid? (without sending it out to be tested..). If the tranny has synthetic in it right now...I'll stick with synthetic. The reason I am considering synthetic again is that the Shell dino oil is GL-5 rated. I am having some problems finding a GL-4 rated gear oil. Redline's fluid on the other hand is right there in front of my face. The only problem is that it might cause me to need a tranny rebuild/check the tranny fluid very often.

Also, I just found that the tranny fluid was replaced in March of 2000 only 6,000 miles ago. I would have to assume that dino oil was used because it reads "3.5 pints trans oil - N/C." The trans fluid change was done along with a belt roller, adjuster, shaft roller and aux belt tension. Total bill was $488 + tax.

So basically...even with all this help I'm still at a loss. Can anybody recommend a GL-4 non-synthetic tranny fluid?? Or should I push my luck and go for synthetic?

If I do decide to go with Redline...Should it be Redline MTL or Redline MT-90? The only difference is oil weight... MTL is 70W-80 and MT-90 is 75W-90. I would expect 70W-80 as that is closer to what is recommend in the owners manual. "Filling capacity Approx. 2.0 liters hypoid transmission oil SAE 75W90 to API Class GL5 or MIL-L-2105B, or SAE 80 to API Class GL4 or MIL -L-2105."

Craig944

If you find a leak, after you fix it, I suggest you go with Moly Base Gear Oil for your transmission.

Tabor

Most manual transmission cars take GL4 rated fuild, it should not be hard to find. I know that "Sta-Lube" makes one. I have 3 quarts of it in my garage. I purchased it before decideing on using the Redline Fluid. You can call Sta-Lube at 1-800-272-8963, they will probably know where you can find some. I think I got mine at Discount Import Parts in Portland, OR, but I may have picked it up at Baxter Auto Parts.

BentOn944

The shifting problem you describe may be a synchro gear problem. I put Redline MTL in my 944 transmission and immediately noticed smoother shifts, especially when the transmission is cold. I believe this is because the synthetic is thinner (lower viscosity). Where a synthetic will hold up better with temperature and shear properties, a non-synthetic has to be thicker to compensate for reduced viscosity when warm. When I did the oil change, I used a cheap $2 - $3 Kerosene siphon pump.