Rick Lee

Yesterday, I was driving over 100 mph for much of the way to Vegas in 6th gear, way out in the desert. When it came time to downshift, I couldn't find 5th at all. I had to coast in neutral, blip the throttle and got it into 4th, which felt rough. Shifting back up into 5th and 6th was like butter. I drove around in Vegas traffic for a while and all was fine at slower speeds and I never got up to 5th gear. Driving home today, same thing happened. I discovered that very quick double clutching would get into the next lower gear, but it never felt quite right and once or twice I heard that terrible grinding noise, while trying to push it into gear. WTF is this? How is it so sudden? All was fine last time I drove it.

I last changed my tranny fluid a year and 6k miles ago, Mobil 1 75/90. I have the factory short shift kit. How can it be bad synchros if upshifting is always fine, but downshifting is always bad? I removed the rubber shift coupler plate about two years ago and replaced it with a chunk of poly from a cutting board. Seems to me, if that had gone bad or melted, I'd have had bigger, more consistent problems. Anyone ever have this happen?

AOW162435

Rick,
How are your engine mounts?


Andreas

Rick Lee

They're the billet aluminum solid kind, have about five years and 30k miles on them. I am suspecting them now too, as the car feels like I'm driving in very high winds when at speed. I will take a closer look with a jack and ramps today. Too bad Wevos are out of stock. I hear the Boxster tranny mounts will fit 993 motors. Is that true?

NP993

You should check your engine crossmember. They're known to crack or break with solid mounts...

Rick Lee

Yes, I looked at that. Just put her on ramps and used a floor jack at the case seam to raise it some more. I didn't see any flexing or obvious movement around the mounts or the carrier. I may pull all that stuff off just to inspect it more closely anyway. Looks like a bit of a headache to get it all out and I surely don't want to reinstall it before I get the Rennline reinforcement kit or new motor mounts. Rennline is saying mid-November, which is probably when I'm moving. It'd be a huge problem to make my car immobile and then not have the parts arrive in time to move it to the new place. Luckily, I have a lot of garage space now.

Rick Lee

Got the driver's side motor mount out and it looks new. Hardware could use replacing, but the mount is in fine shape. I can't see any damage to the carrier either. I poked around the shift linkage underneath the car and it's a tad loose, but I can't imagine it causing all these problems.

trophy

How old is your clutch, could it be your clutch not disengaging completly?

Rick Lee

Clutch is RS/LFW and about four years old. Slave is same age and I flush it completely once a year. I'm pretty sure that's not it, or else I'd be having problems in other gears too and at lower speeds, no?

Hawk2109

As your gearbox gets to really humming, 100 MPH etc, the gears are forced to slow from a greater speed when you downshift. Your issue is in the gearbox in all probability, and most likely just needs to be rebuilt.

I would be happy to talk to you about this in more detail if you would like.

Warmest Regards, and happy to help,

Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell

Hawk2109

As your gearbox gets to really humming, 100 MPH etc, the gears are forced to slow from a greater speed when you downshift. Your issue is in the gearbox in all probability, and most likely just needs to be rebuilt.

I would be happy to talk to you about this in more detail if you would like.

Warmest Regards, and happy to help,

Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell

Hawk2109

not sure why it posted twice, sorry about that.

Rick Lee

I don't downshift at high speed. I downshift when my revs get below 3k and I need some more power. Sorry, but I'm pretty far from being ready to call this a necessary rebuild. There were never any problems before Sat. No funny noises, no hard shifting. I'm gonna do some more investigating. If it really needs a rebuild, I'll do it after Xmas when I've moved into my new house and gotten my garage all set up.