schwank

Except a dedicated Porsche transmission shop explicitly instructed me NOT to ever run Redline in our transaxles. Internet forums are all well and good, but I will trust a transmission shop with many years experience building Porsche racing gearboxes. I did run MT90 in my original NA box and it seemed OK, but after paying $$$ to have a box built with a new LSD unit, I'm gonna listen to the shop. I change the fluid annually regardless.

We have probably 10-12 local 944 Cup cars and they are all running Swepco 201. Have yet to see any sort of failure. Greg Fordahl uses it in every car he builds.

That said, I have yet to see any scientific studies regarding wear in a 944 transaxle. Given their age at this point... I doubt we will.

951mcomm

NE1 ever use the Lucas w LSD in their box

bgiere

MT-90 gives me the best syncro engagement by far.

Kburke

Ok I did this recently when it was cold in VA. I changed it to 75/90 mobile 1 synthetic. I noticed the results ASAP. Shifting in cold weather and in general has never been better.

6ocyclehum

I just did this today. Drove the car daily all winter, and it was quite a bear to shift first 5-10 minutes. Did some research today and have to agree, Amsoil, Swepco both seem to be good choices. I happened to have a bottle of Mobil 1 75w-90 LS on my garage shelf, and it fared pretty well in my research also. Picked up 2 more bottles at Autozone. Can't get Swepco or Amsoil on the fly here. This has to be one of the easiest things I've done yet on the 951, I didn't even have to jack the car up. Noticed a difference immediately, shifts very smooth from the get go. The stuff I drained out looked like a pink yogurt type stuff, and I searched and think it was Redline Shock Proof oil. Shifted fine when warm, but really lousy when cold. The Mobil shifted about the same warm as the Redline, just fine. If I notice anything weird in the next few months, I'll probably try the Amsoil or Swepco, but for now the M1 seems to be a very good improvement.

6ocyclehum

Oh yeah, forgot to say, I filled mine until it started to come out the fill hole. A bit difficult to get it 6mm below the lip! I guess you could jack it up a little with the fill plug out and spill out a little. Seemed that what I read up on it, everyone was filling it to the edge without any problems. I wouldn't even consider a non-synthetic for this. Synth is cheap here, dino can't match it's cold properties (which was my entire reason for changing it) and this stuff stays in a long time. I sealed a leak in my old Jag diff with Mobil 1 gear lube.

knfeparty

Amsoil has been good for me. I used LSD additive once I got the LSD. If I have to open it up again I'll probably try Swepco.

joonas

Can you aske them why they told you that?

JohnKoaWood

I have used Swepco without an issue for street use... Made me decide against a rebuild as it quieted everything down and made shifts flawless...

schwank

I asked about fluid for the LSD and said I was currently running MT90, which they immediately dismissed. I couldn't let it slide so you know I had to ask. I was told that it does not offer adequate protection and that based on their experience synchros would wear significantly faster. In some cases the new formulas can be too slippery and not protect adequately. Their specific fluid recommendations were the Porsche branded gear oil or Shell Helix 75-90. Unfortunately it is downright impossible to get the Shell in anything other than 55 gallon drums in the States.

I do believe that in many aspects this is like the oil debate, except with even less scientific data to base a decision on. Each person has their favorites. And as I mentioned earlier, you are not likely to find a comparison with actual scientific examination of wear specific to our units. Redline may be all well and good quite frankly. Many people swear by it and if gearboxes were exploding you would not hear that. However I don't know how many people have run Redline for an extended period and then actually reviewed the wear inside the box.

All I know is that a Guard LSD costs more than I paid for the car itself. Add in synchros and labor, and it is a job I don't want to pay for again soon. If you want more specific info, contact the guys at GBOX in Boulder, CO. Paul Guard personally endorsed GBOX as one of the best builders in the country when I spoke with him on the phone. So I have to trust that they know their stuff.

joonas

Seems that Shell oil is specifically designed for transaxles
http://www.shell.com/static/shellrac...nts/75W-90.pdf

Words like transaxle, hypoid, EP and LSD seem to be important but I cannot find information what kind of oil parameters we should be looking.

joonas

Shell Transaxle 75W-90
http://www.shell.com/static//au-en/d...fferential.pdf

Transaxle transmissions – Heavily loaded “transaxle” transmission where hypoid axle and gearbox are in the same housing and lubricated by the same product. Particularly in sport passenger car drive train systems. Automotive transmissions – Heavily loaded axle drives, synchronised and non-synchronised gearboxes.
Porsche Approved

Potomac-Greg

I just had a transmission failure and I have no idea what caused it. My gearbox fluid story is long and confused! This is (was) a 1988 944 n/a non-LSD box. One of my first services was to drain/refill the transaxle. The gunk that came out was nasty. I put in Mobil 1 75/90. It ran fine-- shifts were good, but had some gear (rattle) when starting out in 1st and 2nd gear, and only when warm. After a season, I swapped in Redline MTL. It made shifting super quick regardless of ambient temperature. But when warm, it also created gear rattle.

I ran about six 20-minute sessions at Summit Point about a week ago and by the end of 5 sessions, the gear rattle was intense, and there was a lot of drivetrain lash when I came on-and-off the gas in any gear. I still ran the last session. Shifting never deteriorated -- quick and smooth -- but the noise and lash seemed to get worse. That night I drained and refilled with Mobil 1 75/90 to see if it had any effect on the noise -- and it did not. Still noisy.

Now I'm buying a replacement box. The original gearbox only had 72,000 miles on it. The early failure could have been the MTL, or the Mobil 1 or the stuff that probably soaked in there for 20 years before I got the car. Any thoughts here? What sort of transmission failure leads to drivetrain lash, but does not affect shift quality at all?

schwank

Joonas... I would have used the Shell but after calling distributors it is only available in 55 gallon drums. Obviously that is not practical for those of us that need under 1 gallon per fill per year. And that's racers changing it annually.

joonas

I understood that. I am just thinking what gear oil properties makes gear oil best for our cars transaxle. "Specifically designed for transaxles" sounds weak.