I'm not positive if he adjusted the misfire tables. I'll have to e-mail him and inquire. EDIT he did not adjust them, he's going to check in the morning if the previous shop did.
I had no issues like this with my 99. I'm guessing because it did not have as much electronics involved.

The tuner at the second shop actually contradicted himself by saying "if its not severe enough, it will not throw a code" and another day said "its bad enough to start replacing parts" But, still no codes. That was really all the identifying that was spoken about.

I'm not quite sure how to go about this, I'm having a hard time trusting anyone for an honest opinion. I know a miss has to do with air, fuel and spark. But where to start is the question. I replaced my plugs and wires the first week after getting it back from the original shop.

I don't know man, I'm just taking it day by day and hoping whatever I do next will resolve this headache.

Thanks for your time, I appreciate it.

 

I had a TCI converter once that vibrated like crazy at idle. Long story short, the converter was out of balance or the mounting pads weren't centered. They gave me another one and the vibe went away.

The reason the misfire tables need to be adjust is BECAUSE of the misfire codes... see once the computer gets a misfire DTC, it disables TCC lockup... then after it doesn't register a misfire in a given length of time, it reinstates lockup. Some cams (from what I understand) and converters require you to alter the tables to where they don't register a code, that way TCC is none the wiser; however, since OP doesn't register any misfire codes, this wouldn't be an issue.

OP... let me guess... converter locks up at low speed, you get into the gas a little bit more (not enough to unlock or downshift, but enough to put a load on the engine/drivetrain) and then you experience the bumping/shudder?

If this is the case, there are a couple of different things you can do.
A) bump up the speed that light throttle TCC lockup happens (from 43 up to 50 or 55mph)
possibly
B) bump up the line pressure in the tune where low speed lockup occurs.

With a higher stall, it's been my experience that when lockup happens at stock lockup mph, the change in rpm is substantial and it lugs the hell out of the engine. I have a 5.3 w/ 3.42 gears, so lockup in 4th gear @ 43mph put me about 1100 rpm, and my cammed little 5.3 did NOT like that. @ 55mph, I'm ~1500 rpm.

I recently went through the Tc shudder deal. Dr. Tranny's shudder fix helped a good bit, but only masked the problem. I *believe* the problem is the transmission pump has a problem supplying the needed line pressure to keep the TCC locked under load at such slow engine speeds. Upping the lockup to 55 does 2 things... it gets the engine speed higher thereby increasing line pressure, as well as reducing lugging/low rpm load on the engine.

I say 'possibly' about the line pressure because you can force the regulated line pressure (what gets sent to the converter) higher... problem is if the pump is doing all it can do at such a slow speed, and the regulated line pressure = pump line pressure, it still may not be enough.

Now, if my theory is correct (I didn't have the opportunity to test this on my old transmission) you could force the line pressure up AND lock the TCC manually in HpTuners at your regular lockup mph (or lower) and the shudder would still be there because your input speed of the pump hasn't changed.

 

So, without having a code. Do you NOT think it is from a miss?
Do you think its the pump?
Even though I have no codes, HP Tuners did pick up misses when we went for a road test.
Sounds like the pump could be part of the problem.

 

If I understand the information that I've read correctly, the misfire code HAS to register in the PCM before it unlocks the TC. It's not terribly uncommon to see some random misfires, but it has to be frequent enough to register before the computer takes action. There is a threshold that must be met (frequency during a set time) before a code is registered.

Correct, you would not want to max out line pressure across the board and leave it. That would cause very abrupt/violent shifts and probably screw something up over time. What I am suggesting by bumping up the line pressure is really 2 parts. 1 is for diagnostics only. You can run the Force motor amps down to 60-40 or hell 0 mA just to see if it will lock solidly. If it does, then the tune can be written so that the computer commands higher line pressure only at lockup for a long term fix. This will leave all other shifting parameters alone, but give the clutch enough pressure to stay engaged.

I'm not sure what would cause a 20mph shudder... I doubt if the converter was unlocked that you would feel a random, sporadic misfire. it sounds like the guys that have been monkeying around with the tune didn't know what in the hell they were doing.

As far as 55mph lockup is concerned, I switched from a stock stall and slightly more aggressive transmission tune to a 3000 rpm stall with a 55 mph lockup and only lost about 1-2 mpg around town. I believe a bigger part of that is my inability to keep my foot out of it to chirp 2nd gear. highway miles will not change since the converter is locked at speed anyway. Really though, if it works, what is more expensive... a 1-2 mpg loss or buying a new transmission?
As far as how it effects every day driving... It's been great. I don't have to drive in 3rd around town and now it doesn't lockup at 40mph which lugged the hell out of the engine.

I can't diagnose your issues for you. There are some things that we just can't see online. I'm just letting you know what I've experienced and what's worked for me.
I'm still going to put a pressure gauge on mine to see what my pressures are doing, but for what it's worth, it sounds like you are where I was last month.

I wouldn't get to excited right now about a pump being bad. It IS possible, but I think you have a bit further to go before drawing that conclusion. See if you can find a reputable tuner in your area... not a transmission shop, not the dealer, but someone that does in person tuning that is familiar with these setups. I think that will put you ahead of the game.

 

This is what's getting me. I'm aware of the misfires, I feel them. But, without codes its obviously not as bad as people say. So, why should I start replacing parts? Its frustrating.

So, would this only be for diagnostics purposes or will this be "tuned" in? I guess, will this be a temp fix until something gives or is this to resolve the problem?

Dude, monkeys could have done a better tune than the fools who did the original work.

What concerns me about lockup so high is most, if not all of my driving is around town and 2 lane country roads. I reach those speeds in the morning and my afternoon drive is around 45/50 maybe. Mine has been tuned to lock up in 3rd as well. Compared to stock, my tune seems to be more aggressive.

Did this happen after you installed your stall?

It shifts fine, both up and down. It only happens at lock up. I really don't think it is the pump.
I felt pretty comfortable with the last shop, he was very cool about me standing next to him the entire time, almost 2 hours, hah. He was explaining to me what he was doing while he was doing it. I will bring this up to him this week and see if we can make some time for him to go through it.

Thanks for your time spent21, I appreciate your help.

 

If you have mechanical issues, such as physically being able to feel a misfire this could cause the converter to shutter under lock up conditions.

If you have a shudder at 20 MPH and it's not locked up or in DOD mode, I would have to believe there is something mechanically wrong with the trans or the converter. Of course without us being able to see your tune or having the vehicle in front of us it's difficult to say.

FWIW, my lock up is somewhere above 50 MPH to make it driveable. I don't lock up in 3rd either. I can't stand that lug feeling. Even on a stock truck I modify the lock up speed. If it affects the MPG, it might be 1 MPG. I personally don't track it close enough as I know my DD needs some TLC to get the best MPG possible.

 

No troubles. I couldn't find much info specifically about this issue when I was trying to figure it out. I'm just giving back.

 

1FastBrick,
I feel a little hiccup in the idle, a chop. Its not violent or doesn't bounce me around.

That 20mph crap was from the first shop. Whatever they did with the tune made it act real funny and do some stupid sh*t.

Is there any way you can copy and paste that part of your tune?
Mine locks up at around 40 in 3rd and 45mph in 4th. I'm going to talk with the tuner and request a change in my tune.


spent21,
I'm sorry, excuse my ignorance, I did not know what Force Motor amps down meant. This tuning stuff is very confusing to me. Any knowledgeable tuner should know what this is. I am going to bring this up to the tuner, he should know about it if not I may have to find another tuner.

Douche is an understatement.

With my small tires, its like I have 4:10s.

Mine to. It seems to have become more pronounced after my stall.

Thanks again fellas.

 

I have not messed with the GMT 900's

Looking at my tune I guess it does have TCC lock up in 3rd

On my 2000 the TTC apply speeds:

3rd starts at 35 MPH and ramps up depending on TPS input.

4th starts at 54 MPH and ramps up depending on TPS input.

 

Mine is very close. Usually the rpm/mph matches so close that I never notice the 3rd lockup or it's there for so short a time that I don't notice it.

If I shift down to direct to keep it from going to 4th, it's noticeable.