pozzello

Hello everyone,

After months or lurking these forums and wanting a 911 since I was a kid (hahah I recently dug out my Porsche SC model car from my mother's basement) I finally bought a 1997 C2 Coupe. Wow what a car !

It's a low mileage car (27000) but I'm already having some transmission issues.

After two weeks of ownership I still can't get a smooth shift (especially from 1st to 2nd but also 2-3) and my shifting is clunky like I was just learning ! Strangely enough yesterday with the AC on my shifts were MUCH smoother - shouldn't it be the opposite ?

The gearbox also feels slightly notchy as if the clutch isn't fully engaged. This only happens up-shifting (1-2, most noticeable from 2-3, a little less 3-4, and very little from 4-5 and 5-6). I had the gearbox fluid replaced with Redline 75W90 NS (the old fluid was black) and while the throw action is much smoother the notchiness still remains. I don't mash my gears and no problems downshifting. With the engine off I noticed a slight creaking engaging the clutch pedal.

Any ideas ?


Paul

uberlawyer

My C4S was exhibiting similar issues: Rennsport Motor Mounts from Carnewal, Golden Rod and SSK from FD Motorsports solved the issue.

Since you have a C2, you should also investigate the transmission mounts.

PS Welcome and enjoy you p-car

mpruden

My gearbox felt similar when I got my car. Good news is that the fix was relatively easy, compared with cracking open the gearbox. This is just my experience after trail and error.

1) check to see if your engine mounts are worn out and sagging. Ditto for gearbox mount. If so, they can cause the shift linkage to go out of alignment a bit.

2) Swap out the Redline NS for Porsche factory fill from a dealership, either the Shell or Mobilube PTX. I've tried 3 different kinds of gear oil, including the Redline and the Mobilube is much better. There are a lot of opinions on gear oil, but from my experience this is the best. They can sell you the 4 liters out of their bulk supply if you bring in a container.

3) Flush your clutch system with fresh fluid.

4) If this doesn't get the car shifting better, replace the slave cylinder.

5) Shift very softly - especially 1-2 and 2-3.

6) Get those RPMs up before you shift. It really smooths things out in my car.

7) I doubt this is the problem, but might as well confirm that your shift linkage bushings are not wearing out. You can test the 4 black rubber ones by lifting up on the gearshift lever. It shouldn't move much.
The other 2 white bushings are a single point of failure and you might as well replace them as well. They are only a few bucks a piece if I remember correctly. I've replaced and lubricated all of these bushings on my car and it shifts very smoothly.

8) If it's still too notchy, you may have significant synchro wear. Uh oh.

phoneyman

Two potential issues I ran into when I bought my 993, which had a very notchy 1-2, and under heavy load to high RPM, sometimes when I depressed the clutch the shifter would shoot out of 1 to neutral.

Anyways, the two issues:
1) the motor mounts are old/saggy/shot/whatever and the engine is cantilevering off of the tranny, putting undue strain on the coupling bits. This is pretty common, usually higher mileage cars but I'm sure it can happen on garage queens.

2) The rubber bits in the shift linkage are old and need replacement. There is a rubber 'shim' in the shift linkage between the shifter and universal joint connecting to the gear selector shaft on the tranny. Lots of people replace this with a golden rod (RS-style) from FD Motorsports.

Also there are lots of posts here about who-likes-which tranny fluids, and I dont remember where people ranked Redline. From what I remember, the 'NS' designation is important depending on if you have the limited slip/ABD setup or not. Try searching around using different variations of search terms for tranny fluid.

Good luck.

pp000830

Seems like way too few miles to be synchros or a worn clutch under normal driving. Rule out other sources of the problem first. IF the clutch is not fully disengaging the engine from the tranny all sorts of odd shifting feel is possible. Shift linkage and master/slave clutch, clutch peddle cluster lever or clutch actuator parts in the bell housing.
A reasonably good technician should be able to sort this out ASAP.

Andy

BobbyT

Another possible cause of this problem is a little rust or corrosion on the transmission input shaft, which prevents the clutch disk from disengaging properly, so it drags a bit and makes the shifts feel notchy or clunky. Unfortunately, this requires separating the engine/transmission, cleaning off the corrosion, and applying the correct lubricant. After trying many other things on my 95 C2, this did the trick.

nine9six

Bobby, can you do this with a partial drop, or does the motor have to come out?
I know you're gonna say its much easier with the motor out...What motor/trans work wouldn't be!

pozzello

@uberlawyer : I was eventually going to update some of those parts but shouldn't it shift smoothly with the stock parts ? Thanks :-)

@mpruden : how do I check the engine and gearbox mounts ? I don't even know where they are Is flushing the clutch an easy DYI ? How about replacing the slave cylinder ? I tried pulling up on the gearshift lever and it only moves a few millimeters. I hope it's not the synchros, the car was very well maintained and a single owner car and the rest of the car is flawless so I doubt he abused it... but who really knows.

@phoneyman : I'll really have to check those motor mounts !

@pp000830 / BobbyT : I took it to an indie mechanic in town late this afternoon and after a quick drive he thought the output shaft might be corroded... not what I was hoping to hear. But he also said to just drive it.

uberlawyer

You'll effectively need to take them off and inspect them for damage. Engine mounts are easily visible - the two round things on the left and right of the engine bag towards the rear bumper. But most likely you won't be able to tell anything about their condition just by looking at them. For the transmission mounts you'll need to lift the car.

An yes, it SHOULD shift ok with the stock parts. But even for a low mileage car, it's 20 years of aging rubber that you're relying on. I understand that the nylon cups can even fail altogether, at which point you can be left stranded. In addition, Porsche's design for the shift rod does not necessarily help precision when shifting.

pozzello

Late this afternoon I took the car to an indie mechanic in town. He took it for a quick ride and thought the car shifted great, but that the creaking in the clutch was indicative of a corroded input shaft and could account for the notchiness in the gearbox.

A few more things I noticed :

- when I pull away from first gear, when the clutch grabs I hear a slight knock like something is sliding back - could that indicate worn engine mounts ? And
- standing at idle, when the rpms dip a little low, sometimes I can feel something underneath the car knocking around, like the transmission or engine is loose - I'll try to record the sound tomorrow.

As for the clunky shifting (yet smooth with the air conditioning on) he thought it might be a stuck idle control valve... So when I got home I took out the ISV and cleaned it out with bicycle degreaser.. and sure enough I have a much easier time getting smooth shifts in all gears ! Not quite sure I understand the correlation...

mpruden

Engine mounts - If you have no record of them being replaced, go ahead and change them out. If they are extremely worn, you can see the engine exhaust tips sagging and can actually feel the bottom of the mount. It should be tight, not sagging an inch or more. https://rennlist.com/forums/993-foru...ne-mounts.html. The engine mounts are the round metal things about the size of a small saucer. They are visible near the very back of the car when you open the engine compartment. (hint, search images.google.com for "993 engine mount" for about 10000 pictures of these)

Slave cylinder - this can be a frustrating job because it has to be done by feel. I found it was pretty easy, but think I just got lucky. https://rennlist.com/forums/993-foru...-bleeding.html

Flushing clutch - http://pcarworkshop.com/index.php/99...Cylinder_Flush. It is an easy job, but you ideally need to buy a power bleeder. It's a good thing to have if you are going to do work on your car anyway.

Gearshift movement of a few millimeters. Wow, that's a lot more than mine, but may be normal for other cars of this age. I don't have enough experience to know for sure. Regardless, I doubt it is the cause of your problems, but if you want the car to shift "factory fresh" you should keep this on your long term todo list. I would get the consumable parts to a known good state first. (specifically engine mounts and clutch fluid)

All of these jobs are DIY, even for a novice. Just do your research up front and ensure you have the right tools for the job. Ask questions here for help.

BobbyT

nine9six,

On my 1995 C2, the transmission can be dropped with the engine left in place. I don't know for sure about other model/years, some may require dropping both.

911F1

I had very similar issues that the OP is experiencing when I first purchased my car. I replaced and serviced a few things on this same list.

-New RS motor mounts. Stock mounts were shot.
-Motul Motylgear 75w 90 fluid
-Bled the clutch slave with Motul RBF 600 brake fluid. Power Bleeder is a must
-Short shift kit from FD motorsports.

Next on the list is FDmotorsports golden rod.

I can now say my 1st to 2nd and 2nd to 3rd shifts feel really good. Much improved! All of these items should be on your list to service at some point.
Might as well do them and see if it helps. Another thing to think about is getting the fluid in your trans warmed up. Go on a nice drive and see how it feels. Good luck!

earossi

All posters have given good advice. My vote is for new motor mounts which will make a huge difference in shifting. I installed the RS mounts which are less than half the cost of the OEM mounts. Stiffer than OEM, some minimal transmission of engine noise; but a huge difference in shifting. The age of your car, not the mileage is the key. All rubber is suspect.

uberlawyer

I went for Motul Gear 300 LS instead. It's just brilliant!

My only concern is the LS denomination - it is specially formulated for LSDs and I selected it for this reason, but since anyway I want to make another transmission fluid change soon (just to check how things go because the post-purchase fluid change showed the fluid as BLACK-BLACK), I may opt for the plain vanilla Gear 300.