Cobra4B

Summer of '06 I had my gearbox rebuilt under warranty for bad 3rd gear synchros. I first noticed it trying to quickly throw it in 3rd on the highway and accelerate. I felt a little drag on the shifter, that drag turned into a small grind at VIR, that small grind turned into a moderate grind that could not be avoided even w/ a very puposful push on the clutch pedal and an easy downsift into 3rd.

Mechanic said everything looked great inside except the 3rd gear synchros were worn out. They allowed me to order RPMs modified 1-2 fork, the steel 3-4 fork, billet keys and pads, and rebuilt it for me.

Well this past outing at VIR I was having no so smooth downsifts into 3rd most often at the front straight slowing for T1 at VIR full. I usually shift from 5th to 3rd and complete the downshift when I slow enough to make it. I started really focusing on my foot technique and it seemed to get better.

Since I'm going from 4th or 5th to 3rd on the 2 big straights at VIR a tradional double clutch wouldn't be hard to accomplish... this of course would remove any and all strain from the synchros.

Anyone double-clutch still?
Anyone have issues w/ 3rd gear synchros?

I've read that the rear mounted transmission accelerates synchro wear because when you're downshifting the synchros have to account for the mass/weight of the entire dirveshaft and have to speed that up too as it's rotating at input shaft speed. In a traditional front mounted trans setup the drivehshaft rotates at the necessary speed to maintain vehicle speed, when you downsift only the gears have to be sped up right?

I don't want to fark my trans up again and have to pull it next year? I like having confidence in my equipment and not be wondering gee, I wonder if it'll grind now.

0Randy@DRM

3rd gear is always the most beat up on the track. Aftermarket shifter not adjusted??? Shifter rod worn out??? Just trying to help

Randy .

Cobra4B

No clue on the shifter rod... it's an oem C6Z06 shifter and I made sure to fully adjust it w/ the pin when installing and followed oem torque values on the bolts/connections.

All other shifts are fine... all other upshifts/downshifts.

Cobra4B

ttt... anyone else?

John Shiels

tranny that's how mine went

Cobra4B

John how many transmissions have you gone throuh? Do you double clutch it now?

I'd ask how many "trannies" you go through, but that might be too perosnal

John Shiels

:o

I had a M6 50,000 track street no coolers, m12 3-4,000 M12 track only & coolers forgot the little piece that brokes nname. M12 200 or less miles went to VIR 14 hr one way and it went same piece broke . Now another M12 1000-2000 miles.

Went to VIR and dropped torque tube. VIR and me also sick at VIR never could finish a session one weekend. Four wheels off in 9 years twice at VIR on first lap cold and damp/wet at thee old tree going slow. Once at Pocono first lap cold and wet going real slow. N spins yes double clutch match revs.

racerwannabe

i have lost 2 in the black car with stock motor...3 in the red car,, first one at 70 miles......gm told me no speed shifts ,,no in a hurry shifts,, no no no ...so i got a transzilla from rockland ...and so far smooth and no problems.... every time the trans went out it has been 3rd gear syncro problem... i know of several others just like that also..one thing we have done is pin the shift rod..can't move like the stock one did...
Johnny

96CollectorSport

I talked with George at Rockland and he told me the new Tranzilla's have dog ring gears instead of the triple syncros. Pretty awesome stuff.



How are you going to grind that!!

0Randy@DRM

It doesn't grind it has a crunch to it, everytime in and out. They are cool but also wear out on the street.

Randy

Cobra4B

So what's the consensus... you guys learning how to truly double clutch?

fmrfast

Just remember Clutch in, neutral, clutch out, blip the throttle to match the next lower gear selected (while maintaining brake pedal pressure) clutch in, select gear & go. It sounds complicated, however it does not take very long & will save the trans synchros. When I started racing,,, the car I used was a non synchro gear box formula ford so double clutch downshifts are 2nd nature for me. Like anything else once you do it a couple of thousand times you will not have to think about it.
There are many discussions about how long this takes. It takes me around 1 second I guess, never timed it. The point I am trying to make is; I am always on the brakes longer then a second or 2 so the time it takes to complete this double clutch downshift is a non issue.
Have Fun!