Car bucking ...

[NJ Torque]

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?

[Tru2Chevy]

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

[NJ Torque]

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?

[LTb1ow]

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.

[NJ Torque]

I mean, like how bad...?

[LTb1ow]

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.

[NJ Torque]

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

[69BirdX]

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

[LTb1ow]

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?

[camaro2you]

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.

[69BirdX]

ive never had a problem till recently nothing changed

[NJ Torque]

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

ive never had a problem till recently nothing changed

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.

[LTb1ow]

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

[NJ Torque]

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

[LTb1ow]

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.

[creeper]

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.

[NJ Torque]

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

[69BirdX]

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

[NJ Torque]

i dont have mine stall...

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

[BigAls87Z28]

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.

[LTb1ow]

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

[Formulalt1]

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

[LTb1ow]

3600 ish for me. Stock 3.23s.

[Formulalt1]

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.

[LTb1ow]

So we just gotta live with it?

[Formulalt1]

So we just gotta live with it?
No, the PCM can engage lock up whenever it wants. You just need to recalculate to make sure you are at the correct MPH in relation to your RPM based on your gearing for this to happen. Another words a stock converter can stall as high as 1300 under wot but the tranny and engine at 1K under light throttle are pretty much in sync, this is not the case for a 3600 stall. 1600 RPM's - 1800 RPMS should do the trick though.

[69BirdX]

well mine just started and have had the verter for awhile..........i think mine is casue my egr valve is bad. My car just started throwing codes for that so we shall see

[Formulalt1]

Like I said I could be wrong but since your car is doing something different or slightly different from the rest I would say its a different problem and especially since you are getting codes unrelated to the transmission or TCC circiut specifically.

[LTb1ow]

Would a free scanner work?


I have TTS and a cable, I could throw up a scan of mine if you know what you are looking for.

[Formulalt1]

Would a free scanner work?


I have TTS and a cable, I could throw up a scan of mine if you know what you are looking for.
I just looked at the tuner cat table for setting the TCC and it is in MPH's. So I would have to mess around with the numbers but I am sure I can give you a number that should work. The disengagement should stay the same as it shouldn't have any negative effects on that end but give me a day, I also want to mention this to a friend of mine who tunes these cars and make sure I am giving out correct info here. I usually handle minor changes here and there but don't want to give out any bogus info, so I would rather touch base with a pro.

Edit- You have 3.23's, right?

[sweetbmxrider]

yeah he has 3.23's

[69BirdX]

Like I said I could be wrong but since your car is doing something different or slightly different from the rest I would say its a different problem and especially since you are getting codes unrelated to the transmission or TCC circiut specifically.

i agree

[Formulalt1]

yeah he has 3.23'sOK based on the numbers I put together you want to engage lock up at or around 55MPH (give or take a few), still waiting to get in touch with my buddy to make sure this number works though.

[Whiplash Performance]

If anybody that has this problem and is local to me (North Plainfield/ Central NJ) I will be willing to do a log of it and try to diagnose the problem and possibly fix it, at just the cost of HP tuner credits.