We've had our 2006 C6 since new. It has headers/intake/exhaust, typical stage one stuff ...and a custom shift linkage. The linkage was designed by a mechanical engineering PHD student at Georgia Tech, who I believe designed other linkages for Hurst. But this one was his own. It was one of his first and he installed it in our own garage. It always had faster throws than stock and was less notchy, but over the years it's gotten pretty bad on downshifts from third to second and second to first ...at least for me (to the point where I have to double clutch it ...OFTEN). My wife drives it daily and claims no problem so I figure she's gentler and my problems are probably due to the linkage going a bit too far when I nail third and throw everything off a bit.

So two questions: Recommendations for 1) Someone on the northside of Atlanta who might be able to play with it, replace bushings, etc or 2) The latest hot setup for a silky smooth C6 linkage. The car has only 55,000 miles and being a 6 speed I'm thinking we'll put it up and keep it even if we get a new one, so I'm willing to invest. My oldest granddaughter just turned 16. The rule of my family is "You don't get your license until you can drive a stickshift", and I'm embarrassed to have her learn on the C6 as it is (all kids & families have gone to the darkside on all their cars so it's the C6 or nothing).

BTW if anyone out there knows that PHD student I'd love to contact him (not looking for any freebies BTW but would have him do whatever he thinks). HELP! Thanks, Dan Casey Canton GA

 

IMHO you're not going to have much success finding someone to repair a custom built shifter, unless as you noted, you're able to locate the original fabricator. Much simpler solution would be to replace with a good after-market unit like the MGW shifter.... https://www.mgwshifters.com/shifters/corvettes/88

 

My shifter was very notchy. A ton of experimentation and mine shifts awesome at times to a just a bit of "notch" when cold.

Doing the easiest things first I recommend the Venom Mod, AMSOil Dextron III, fluid clean fluid, and if you have the original "linkage" - I'm talking about the rod from the shifter box going into the transmission - there's a double U joint under a rubber boot at the transmission end that might need to be lubed.

The 3 to 2 downshift is notchy for me also. I nearly always double clutch rev match for that shift. I love the sound and the shift is nearly effortless with the double clutch. Good luck.

 

I did the anti venom mod on my 07 Z06 with 2 washers and I kept hitting the internal gate in the trans and locking myself out of the next gear.
I decided the notchy feel was not so bad and removed both washers.
Amsoil torque drive ATF also seemed to help .

 

MGW Shifter (latest model)
Amsoil Torque Drive Fluid
Venom Mod (1 Crush Washer)

That's my current setup and the shifting is butter and super precise. Have been running it like this for over 15k miles.

 

I was on a track (CVR) years ago, and all off a sudden my shifter was still as Hell. Stick wouldn't move, unless I REALLY pushed/pulled. Turns out my torque tube had "shifted" causing an alignment issue. I was stuck in 3rd gear. I had to yank it to get into N.
Turns out all the gears were effected identically.
Pushed it into 1st, hard. Decided to put it on the trailer.
So, all gears worked perfectly, including reverse. It's just that there was a "sideways torque" that needed overcoming. Again, it was the "torque tube" mounts that had shifted. Once shifted back, the trans shidter was like buttah again.
Strange thing, is I rarely hit alligator feet, so I don't know the cause of the torque tube miving, but it did. Only moved 20 thousanths or so, but that's enough...

 

I put Pennzoil synchromesh in the T56 in my 2000 Firebird, also equipped with an MGW shifter.
It was much more notchy than my Z06. Now smooth as butter.

 

TMOD customs you need a new lower shift box, you won't believe the wear when you take it apart,

 

[QUOTE=Dutch08
Doing the easiest things first I recommend the Venom Mod, AMSOil Dextron III, fluid clean fluid, and if you have the original "linkage" - I'm talking about the rod from the shifter box going into the transmission - there's a double U joint under a rubber boot at the transmission end that might need to be lubed.
.[/QUOTE]

Excuse my ignorance and I know this is an old post but the double u joint and rubber boot that you referenced, how can I access those? What is involved in accessing that area??

 

The back end of the linkage passes through a large hole on top of the torque tube's rear bell housing. Inside the housing there is a single U-joint attached to the gearbox's shift rod with a roll pin. None of it is accessible without separating the torque tube from the gearbox by at least a few inches. In other words, you'd have to partially drop the gearbox (and therefore the exhaust, tunnel plate, and rear suspension).

You should be able to evaluate the back of the linkage by disconnecting the front from the shifter and moving the linkage around. If it moves freely I doubt anything is frozen in back.

 

Could you explain in detail the "double clutch" technique ?

 

Another vote for TMODCUSTOMS. I got the entire 20% reduction shifter assembly unit (lower box and shifter ensemble). I'll never use anything other than a TMODCUSTOMS.
i also had my TR6060 upgraded/reconditioned by a top Tremec distributor and he strongly recommended Havoline or Castrol MERCON V which is what i had my mechanic put in my transmission. No transmission issues yet, rock steady.

 

Clutch pedal down, shift to neutral, clutch pedal up, blip throttle to rev match, clutch pedal down, shift to second, clutch pedal up. "Double clutch" meaning the clutch pedal got pressed twice.

That is the only way to rev match gearbox internals using the throttle. Single-clutching like the C7 does automagically just matches the speed of the flywheel and clutch disc, which isn't interesting.

Everyone will tell you this is unnecessary with a modern synchromesh. It is kind of true, except that "modern" synchromeshes have barely changed in 50 years, and most manual cars with miles on them have synchros that are worn out. Case in point, this thread, and thousands like it.

 

UPSHIFT .... 1. clutch pedal down, 2. Shift 3. clutchpedal up **
DOWNSHIFT ... 1. clutch pedal down, 2. Shift to neutral 3. clutchpedal up 4. RevMatch with throttle blip 5. Shift down 6. Clutchpedal up.

You can use down shift method for upshifts but the engine is losing revs anyway to so you don't need the "blip". It is more of timing issue.

 

Thank you so much for explaining!!