Yesterday I was driving around and I decided to have some fun. WOT'ed out a few gears on the highway and around town. Nothing I would consider overly aggressive. However, After WOTing out third, I went to shift to 6th (on the highway) and I was greated by a nice gear grind. WTH? I then gingerly slipped it into 6th... Upon approaching a car, I punched the clutch, blipped the throttle, and downshifted to third. Only to be greated by the same grind. Ahhhh, crap. Gingerly slipped it into fourth and tried it again. Same result. Tried 6th. Same result. Anytime I skipped a gear on an upshift, it ground. Anytime I downshifted, it ground. I was EXTREMELY careful and made a point to be sure I put the clutch ALL THE WAY on the floor.
However, if I gave it a few seconds between disengaging one gear and engaging another, it would slide nicely into gear. So I cruised in 6th trying to figure out what to do.
This is where it gets weird. After about ten minutes, I tried it again. No problem. I could downshift from 6th to 3rd, no problem. Punch the clutch, blip the throttle, drop it into third, mash the gas. Just like normal. WTH? :confused: :confused:
Later in the day after WOTing out 3rd passing some cars (silly two lane roads), I got the same geat grind going from 3rd to 6th. Rest of the afternoon, no problem.
So my question: what the heck is going on? I've heard of people having clutch dis/engagement issues on the track, but I thought it resulted in a clutch pedal that failed to return fom the floor. My pedal acted just fine.... I had no problems getting OUT of any gear. The clutch doesn't seem to slip (though it would be hard to tell because I had to granny shift to keep from grinding) Anybody? Help? Nothing more embarrasing than looking like you have no idea how to drive a 6 speed. :smash:

 

I have the same problem with my M6. :( I've experienced similar problems with other manual transmissions in the past. I believe it is caused by the fact that 6th to 3rd, 4th to 6th, shifts that change shafts need to be made a little slower so the syncronizers have a chance to catch up. If you "ease" it into 4th while setting up to pass, you'll probably find that you can move out into the on coming lane and really slam it into 3rd for that rush we all enjoy. :D

 

I always run through all of the gears for synchro reasons. No probs.

 

Umrswimr,

It sounds to me like the clutch disk is not releasing from the flywheel....normally referred to as a "dragging" clutch.

I don't know if it will help, but you may have moisture in the hydraulic fluid...it is hygroscopic. If so, possibly the moisture is absorbing enough heat form the headers to vaporize. While the fluid is compressable the vapor is not and as a result the throwout bearing is not traveling as far as normal.

Upon cooling, vapor condenses back to water and you get back the travel. Same thing when you get moisture in a brake system and get it hot enough to boil.

I'd try changing the clutch fluid and bleed the system and hope that it fixes the problem.

Good luck.
Mark

 

Thanks MDT... I'll give that a try. Any specific fluid you recommend?

Hey- will you look at that: Somebody has a Techtip with my EXACT symptoms. :smash: Man I love this forum.
https://www.corvetteforum.com/techti...=141&TopicID=1

 

Umrswimr,

I'm using DOT 4 brake fluid. I just use a turkey baster and pump out the reservoir every couple of weeks. Got rid of all that black gunk that way.

I would think that if this routine is carried out on a regular basis, replacing the fluid in the reservoir at each oil change....easy to remember that way....that hopefully moisture wouldn't build up in the system...if in fact that is the problem.

If renewing fluid and bleeding doesn't pull you out of it, then I think in most cases they replace the actuator(pushes on the T/O bearing.).

Mark

 

Thanks... I opened the clutch reservior to find the fluid nearly black. I removed as much as I could with the baster, but it didn't help much: the fluid is still pretty dark and I still grind on down/upshifts if I don't run through all the gears. Again- only really happens when the car is warm...

It's really strange: any time I skip a gear going into 6th (3-6, 4-6) or down into 4 (6-4) it grinds. No other gears do it (6-3 works just fine) and it doesn't do it if I run through all the gears without skipping one.
It would seem to me that if I had boiled the fluid it would affect all the gears equally... Why doesn't it do it on sequential shifts? Only skipped shifts involving 4th and 6th... Can't be the synchro because BOTH of them started doing it at the same time. Can't be the tranny fluid because I changed to Redline AFTER this started and it didn't fix it... ARGH!
:confused: :confused: :confused:

 

Blipping the throttle is to match the gearbox rpm's with the engine rpm's. If I am reading your post correctly, you are blipping the throttle with the clutch in. How could you be matching revs if the tranny is not even connected to the engine when you rev? Needs to be done in nutral. Clutch in, tranny to neutral, clutch out, blip, clutch in, downshift. Scuze me if I read your post wrong.

Oh yea, lots of racers don't skip gears, they run through them in order even when they need to change more than one gear. That may be related to a previous comment about syncro speeds lagging.


[Modified by olephart, 5:19 PM 9/30/2002]