BlackHawk T/A

iTrader: (3)

What would cause the 2-3 shift to be "harsh", or sort of clunky, to the point where you feel it "hit" and you can hear it through the console? It shifts great over half throttle and at WOT still. This is a built transmission with the HD-2 kit, vacuum modulated.

jimmyblue

iTrader: (11)

Gear multiplication allowing the engine to roll
and bang the Y-pipe into the floorboard?

The same apply that will hard couple 200 lb-ft
and abruptly shock the drivetrain may let 300
slide against one loaded-up with gear multiplied
back-momentum.

performabuilt

iTrader: (25)

lockup could be applied in the 2-3 shift under light throttle , with a performance built tranny this could cause quite a shock

BlackHawk T/A

iTrader: (3)

It is not exhaust banging (I don't even have a Y-Pipe) and it is not the TCC locking up either, as it does not lockup 3rd gear in "D". It will only lock in 3rd in the "3" selection and I am well aware of that (it does make a good jolt).

This is different. This is the shift from 2nd into 3rd during normal driving. You can feel it hit, and the car will stop accelerating for the split second during the shock. You can feel and hear it through the console too if you hold your shifter while you drive, which I do sometimes. And it is only during normal driving. WOT shifts great as it always has with this transmission.

I was wondering if any of the more knowledgeable builders on here knew what could cause this. The car is sitting for the next 5 months so it won't see any attention, unfortunately.

performabuilt

iTrader: (25)

Does a rev bump sound like a good description ?

BlackHawk T/A

iTrader: (3)

Not sure what you mean? The revs do wait until the shock is done and the car will accelerate again. I say it like this in slow motion though, but it all really happens in about a quarter of a second.

performabuilt

iTrader: (25)

When I say rev bump what i mean is it would be like a momentary neutral
like go-quick rev up , then bump into third ,
What this would actually be is the 2-4 band releases , it is released by the 3-4 clutch oil if this happens before the 3-4 clutch comes on you will get what amounts to
1-2-1!-3 you would not feel a drag down like a down shift it wouild feel like the car went into neutral for a split second and the rpms would rise suddenly then when the shift actually happend 3-4 clutch apply you would get a bump not very different from how a neutral drop works ,

performabuilt

iTrader: (25)

well does it feel the oposite like the brake momentarly applies or a brief bind ?

BlackHawk T/A

iTrader: (3)

RPM's don't rise, doesn't feel like neutral at all. Thanks for the thoughts so far.

BlackHawk T/A

iTrader: (3)

Now that you mention it, it doesn't feel much different than a downshift to 1st, the sorta "hit" you feel when bringing the shifter down to 1 when already moving at a low speed. Except this is going into 3rd.

performabuilt

iTrader: (25)

in that case what servo are you using?
sounds like and overlap issue band and 3-4 clutch

BlackHawk T/A

iTrader: (3)

Sonnax servo for 2nd, Corvette or billet for 4th I believe.

Have you ever seen a transmission do this before?

It always feels like something is coming on too early, or too late, and things just aren't lining up timing wise on the 2-3 shift, except at more than 1/2 throttle where its great.

performabuilt

iTrader: (25)

yes actually I have , there are several situations that can cause this ,
1-3rd accum passage in plate blocked or to small after shift kit
2- not sure about the sonax but I do know if the release helper spring is left out of the fairbanks servo it will not release and you will get the bind up , Alot of people leave this spring out with the stock servos including the corvette which is fine generally , but in the case of these super servos its a must have in fact even the stock spring is not enough thats why they come with a stiffer spring (I would look into this first )
Since its likley and easy to check

SPRAYED 01

iTrader: (22)

Mine does the exact same thing. If it was locked into 3rd would this be okay for the trans or should i get it tuned out.

jm93camaro

iTrader: (2)

Mine does the samething. 1-2 is fine, 2-3 is way harsh and 3-4 is fine. It only does the harsh shift when slowly accelerating. But, than again, my trans is howling now and needs to either be rebuilt or replaced. Just thought I'd throw this in here.

RevGTO

iTrader: (12)

Mine has done the same thing ever since the Transgo was installed. Light throttle only 2-3 clunk into gear. I can feel the shock transmitted through the driveshaft to the rear end.

BlackHawk T/A

iTrader: (3)

Yup I had another thread about this and it looks like i'm not the only one. Only this time I wanted some insight from a builder and performabuilt has given his ideas.

For what its worth, the stock transmission doesn't do this (if its healthy) but it seems the Trans-Go kit is the culprit. Whether it is bad for it or not I have no idea, but it certainly isn't comfortable.

performabuilt

iTrader: (25)

some of the kits restrict the 3rd accum feed , This particularly with the larger servos corvette to some extent and the superservos more so may cause band/3-4 clutch overlap this will cause a split second almost braking effect during the 2-3 shift , Creating a driveline back lash and a clunk , We dont restrict the 3rd accum feed which is actually oil feeding the release side of servo fo that reason ,It also may result in premature 3-4 clutch failure.
In all servo cases the 3rd clutch oil is required to release the 2-4 band on the 3rd shift
if theres not enough you will get this bind up clunk effect

BlackHawk T/A

iTrader: (3)

That is exactly what I wanted to know. I am pretty sure they drilled out the feed holes though...

performabuilt

iTrader: (25)

Some of the kits have you use a small aluminum plug to block one feed , This is the one Im speaking of ,