Want Smoother Shifts? Try This!

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ROADSTR6

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(Also Posted in Driveline)

I had done some research in the past about a mod that can be done to the T56 to make shifts much easier and smoother. The Z06 guys swear by it (They call it the Anti Venom mod...hehe). The mod is easier to do on a 'Vette than on a Cobra due to clearance issues between the trans and the tunnel on our Cobras. Maybe one of you guys can figure out a way to do the mod with the tranny in but I couldn't. Anyway, I just had the trans out of my car to replace the clutch so I decided to give it a try...and I'll be damned...IT WORKS! I HIGHLY RECOMMEND THIS MOD! By all means, if you're doing a clutch and you've got the trans out, try it.

Here's the trick:

Remove the big bolt that is high up on the passenger side of the T56. The bolt will take a 15/16" or 24mm socket to get it off. No fluid will come out. No springs will fly out. Nothing catastrophic will happen. This bolt has a ball and spring setup behind it that applies pressure to a detent in the trans.

What you want to do is to shim out this big ol' bolt with a washer (or washers) by about 1/16" to alleviate some of the pressure on the spring. Go either to NAPA and get part #704-1357 or Pep Boys or Autozone will have the same washers as a Dorman Oiltite part #65277. These are 13/16" or M20 copper oil drain plug washers and the pack of two costs $1.79. Yup. That's all! Put two of these washers under the bolt I described and tighten it back up. YOU WON"T BELIEVE THE DIFFERENCE IN YOUR SHIFTS!!! IT'S AMAZING!!!


My car has always been hard to shift...really notchy going in and out of gears. It always felt to me like hitting a wall in between shifts. I got the MGW and it helped a little. I've done the RP tranny fluid and I even did the friction modifier fix but neither one did much to help mine. THIS DID THE TRICK!!! Now it shifts smooth as silk. Try it. Bet you'll love it! :rockon:
 

rotor_powerd

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Hmm, sounds interesting. What does this detent actually do, though?
 

03slobra2

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Does this make it feel sloppy then???

Also how did this change the 2-3 shift... that's the mother F'er for me....
 

SVT GI

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Dang, I just put a clutch in too...wish I would've known, sounds interesting.
 

Wayne64SS

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OH SHIT!!! This is a great post, I'm going to do this when I have my trans out (real soon) to get my clutch done. Would +rep you if I could.
 

CobraBob

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I would ask the same question asked above. What is the purpose of the detent and for the amount of spring pressure dialed in at the factory. With that in mind, I wouldn't just do a mod like this without knowing what potential adverse side effects you might experience at some point.
 

ROADSTR6

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I can't say for sure what the intended purpose of the detent is. Maybe somebody more technically familiar with the T56 will chime in. I did run all of this by a guy I know who has rebuilt many, many T5's and a few T56's and he said that he didn't think the mod would cause any problems. FWIW, the 'vette guys have been doing this for a long time. The actual ANTI VENOM Mod that is so highly regarded among those guys is nothing more than a billet replacement bolt for the original bolt that I am proposing to just shim out with washers. From what I've gathered, the ANTI VENOM bolt (which the ANTI VENOM guy is selling for $60 by the way) totally eliminates all spring tension on the detent. I could see how shimming this out too much could possibly cause shifts to be sloppy. About 1/16th (or the thickness of two washers) is all I can recommend because that's what I did but you could probably do more. Shifts are still very crisp and the 2-3 shift is glass now, especially with the MGW.
 

rotor_powerd

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Quoted from a post in the links provided above:

"The detente bolt is spring loaded and connects the shifter to the transmission via the shifting rod. Inserting washers lessens the spring pressure resulting in less force needed to shift gears."

Sounds like the only negative would be reducing the tension too much and making the shifter sloppy. I'll keep this mod in the back of my mind for whenever I get bored or my tranny is out.
 

03slobra2

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Seems like the corvette guys love this.... interesting.

I am going to do it this weekend... I will try to take pics along the way and document it...
 

SlowSVT

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The detent probably holds the shift cam in place holding the tranny in gear. Not sure what the effect of reducing the spring pressure on the cam will have on the transmission.
 
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