hunterpeaks

Is there such a thing? I am thinking I need one.

I have re-built my G50 Transmission this winter, and it's still grinding gears from 2nd to 3rd, after about 30-45 minutes of hard driving on the track.
UGH.

Never happens when just driving around and won't happen in the first session of the day. But, always in the 2nd session of the day after about 30minutes of hard driving and lotsa gear changing. Then it's like the oil never cools after that and it will grind in the remaining sessions.

Can I buy one? Do I need to make one? Anybody help?

Thanks.
Hunter

J Smith

Unless you're running a big hp engine (350+), you really shouldn't need a cooler for a G50. It ceratinly doesn't hurt anything to have one, and most likely will help in the long run. I take it you've been on the track already this year, and I can't imagine it's been all that warm , so the possibility of overheating the trans fluid is slim.

I had the same problems as you with my G50 for the last 2 seasons (notchy grindy 2-3 upshift when hot), had it rebuilt this winter, and the problem is gone. This is with a basically stock 3.2, 225 rwhp. I ran a 40 minute race last weekend at VIR and it was silky smooth the whole time.

What kind of fluid are you using?

Geoffrey

You'll want to ensure you are using Mobil 75/90 Delvac and not a LS type gear oil. You'll have to add a cooler but it isn't that hard and you can use the fill and drain plugs so you won't have to machine the housing.

PedroNole

I would venture to say that it's the fluid you're using and not that you need a cooler. What fluid are you using?

hunterpeaks

hmmm. o.k., maybe it's the fluid then.
I am using Swepco 201.

http://www.pelicanparts.com/cgi-bin/...llon%2C%20Each

Should I change it out?
Hunter

Cory M

Henry at Supertec put together a trans cooler kit for our 1988 911. We had issues with it locking up on hot days when doing double stints. Since he installed the cooler we haven't had any problems.

http://www.supertecperformance.com/

Use the fluid Geoffrey recommends, the Swepco is for 915 transmissions which have a different style synchro than your G50. I don't remember all the details about why but you can probably find out with a search.

Geoffrey

It has to do with the amount of friction modifiers in the gear oil. Too much and the gear oil is too slippery and the syncro can't spin the gear up properly.

J Smith

yep, the G50 doesn't like swepco. I bet that's why you're having some problems.

Like Geoffrey said, Mobil Delvac is what you want

richard glickel

Geoffrey,

Just out of curiosity, would the Mobil Delvac work well with the 968 trans?

R.

PedroNole

Out of serious curiosity...what IS a friction modifier?

d15b7

hi!

this isn't a porsche specific answer (and as such, may be incorrect!) but i always thought that the 'friction modifier' that was required by some cars was typically for use in rear diffs with clutch-plate style limited slip diffs; they require gear oil with special additives to enable the clutch plates to do their work properly....

i owned a 1996 mustang cobra that required a special friction modifier be used when the diff fluid was changed out (came in a small bottle to be added after the fact). or, you could order specific gear oil with the additive already in the lube....

good luck with your tranny!

todd

Geoffrey

I'm not a chemist, so I don't specifically know. Fricition modifiers are used in plate type LSDs (like Porsche) to keep the plates lubricated so they move and don't stick. You'll notice it when you turn as the plates slip/grip/slip/grip rather than being smooth. Too much of the friction modifiers and the gear oil is too slippery and the metal syncro can't grab the metal gear to spin it up correctly.