Ak3249

I have a stick 993 Carrera with 12k miles, the tranny fluid has never been changed and the diff fluid was changed once on break in around 1997.

I would like to change both fluids but am afraid that as they’ve been in the car so long it may do more harm than good. At the moment the car has no problems, the synchros and diff are quiet and smooth.

Any advice or help would be appreciated.

AOW162435

The tranny & diff are one unit with respect to the oil. There's only one drain plug and one fill plug.



Andreas

pp000830

If you are not experiencing shifting issues, as you shouldn't on a low miles unit such as yours, even with missed gear oil changes at recommended intervals changing the gear oil is good-to-go. and you are done!
Unlike in your unit I have read endless circular discussions on Rennlist concerning shifting feel on 80K miles + units and the use of various brands and viscosities of gear lubricant. My view is as the synchronizer friction rings become worn their ability to grip and synchronize the gears is diminished very gradually over many miles of use. At some point, their ability to grip is so tenuous that very small changes in lube viscosity or temperature can result in significant differences in shifting acceptability. At this point, I feel looking for a gear lubricant one likes better may not be the answer. The transmission may simply need to be serviced and have its worn synchros replaced. On the upside, unlike earlier 911s the 993 does not require the engine to be removed to service the transmission.
Andy

chsu74

Don't forget to bleed the clutch pedal if you refresh the gearbox oil.

IainM

+1 on clutch while yer in there
nothing wrong with changing 20yr old oil
just take the fill plug out before the drain plug
🙂

LimeyBoy

It will do good rather than harm. Not much you can do wrong - I think it is 'easier' than engine oil change. As mentioned above, clutch bleed at same time is smart and takes not much more time once you figure out the bleed nipple access. Transmission oil changes are cheap and worth it if you can envisage what goes on in there at road speeds.

Ak3249

Thank you everyone for all the advice and help, much appreciated.

evilfij

On an automatic, the clutch material in the fluid can be all that is holding the transmission from slipping so changing could cause issues. On a manual, there is no such concern. Same with the differential which is part of the transmission. Change away.

pp000830

+1

911F1

If you go OE Porsche brand. Best price I found was here with free shipping. Keep us posted

part#99991754600. You'll need 4 liters and get yourself a pump.
https://www.porscheoftampaparts.com/...754600&Submit=


https://rennlist.com/how-tos/a/porsc...n-fluid-387420

pp000830

Doesn't list the size. Is it enough to fill the tranny?

The DIY instructs to remove the drain plug first. Common knowledge is to remove the fill plug first just in case the fill plug is stuck so one hasn't gone ahead and emptied the gear lubricant just to find one can't refill it.

AOW162435

Replacing the transmission fluid is brutally easy. Drain the fluid (less than a gallon), run a ~4’ length of tubing from the driver’s side wheel well, through the suspension, into the fill port. Attach a funnel and slowly pour in one gallon. Remove the hose and let the excess drain from the fill port into your drain pan. Install fill plug, done.



Andreas

IainM

This was too slow for me so I epoxied two tubes into oil can top, one to bottom of can other just thru lid
used my compressor to "power bleed" the oil into the tranny
start low and work up pressure
i was done in less than 5 mins

JasonAndreas

The $8USD Harbor Freight gear oil hand pump/changer makes short work of it too.

911F1

Its sold by the liter