Car bucking ...
 

LS1 car, auto, 3500 PT yank..

Car is bucking on light/ no throttle(~40-50MPH...), soon as on the brakes.. bucking goes away.. trans/converter issue?

Any changes made recently that might have set it off?

Sounds like it could be the converter not unlocking soon enough....if you stay off the gas and let the car slow down, does the bucking continue, or does it stop? If it stops, when does it stop?

I assume that you are tuned based on the mod list....might wanna ask the tuner about the lockup settings.

- Justin

That was my guess... converter locking at too low of a MPH.

I did have the car on the dyno recently looking for new #'s... and had an issue that I couldnt manually get the yank to lock.. but the dynojet only had 2400lbs of force.


On these cars, is the TCC solinoid in the converter or external?

No way man, mine does the same thing along with KirkEvils car too. If you ever figure it out lemme know, it bugs me to not be able to go 40.

I mean, like how bad...?

Its really annoying, have you tried to drive it in D and not [D]? Seems to tone it down with mine but its still there.

annoying yes.. lol... can someone else in the car feel it too or no?

mine does it to but when im on the gas around 40 then at a coast it stalls. at first it just did the bucking

I am not sure if this is true, but when I first asked about this, people said it could be the engine lugging due to the fact I am running 3.23s and a big stall. But I am not sure about that.

What kind of tune are you running?

Same Damn Problem!!!!! 3600 TCI stall in mine 98z, my dads stock 01 vette does the same thing at low mph in 4th, that was my guess the pcm locking the converter at to low of a mph in the rpm range.

ive never had a problem till recently nothing changed

are all of our trans' about to take a ****?

yeah, mines been recently too...

I have a TTP tune in the car right now.

I also run 3.73 gears, so shouldnt be an issue there.

I figured I was the only one with the problem. Weird.

anyone else think of a soultion? i'm pretty sure its the tcc locking up.

That would be my guess too, cause if you put it down into D its not as bad, I think [D] has a problem around 40 ish searching for where to lock up the converter.

i feel a little bucking(almost like a light pulsing of brakes) when i let off the gas once in a while. never really noticed if it was a specific speed, i just always thought i was crazy because no one else notices it.

yeah... mine is pretty bad.. as soon as i tap the brakes, gonzo..

i dunno if mines that bad.........it just stalls now when i coast

i dont have mine stall...

maybe i'll take a look at the tune...

Im sure that someone with a scanner can make sure that the TC is locking up.
Check fluid levels. All your TC's could be taking a **** on you as well.
I know there was a big defect on the new Tundra's TC's saying that owners were describing a vibration above 40mph coming from the trans. They found that the TC were bad, and they were all replaced under warranty.

We all I would bet have different converters....

Whats the stall on each of your converters?. I have a theory but it could be wrong.

3600 ish for me. Stock 3.23s.

OK, so it looks like everyone is around 3600 (give or take a hundred). I think the problem is the design of the TCC/program in relation to a stock converter, then adding in a converter that isn't as tight. I think if you guys need a minium of 1600RPMS or slightly higher in RPM's for this problem not to happen. Since you all have different gears and I believe the program asks for MPH ( I am not positive about this though, I would have to look again.) some calculation might have to happen but what it sounds like is happening is that while the purpose of a TCC circiut is to stop slipping and the whole point of a performance converter is to slip and that the engine and tranny aren't spinning at the same speed when engagement is suppose to take place, so like a manual car getting the clutch jerked too quickly the car bucks/stumbles a little.

So we just gotta live with it?