RacerJJ Posted March 16, 2009 Report Share Posted March 16, 2009 Yesterday, in the fourth round of my race, I stalled up the converter preparing to launch and when I launched, I felt the truck kind of slip forward then take off really slow. As I went down track, I noticed that the truck wasn't shifting so I lifted just before the 1000' foot cone and coasted the rest of the way. In doing that, I still crossed the finish line at 73 mph and 15.26 seconds (I normally run 14.0's). I drove back to my pit thinking I had broken something. No code was thrown. After letting it sit for a while, I went to put it on the trailer and I took a little drive and everything shifted just fine. I even stalled it up and did a full throttle launch and it shifted into second fine. In thinking about after the fact, the best way to describe what it felt like was a motorcycle leaving a stop in the wrong gear. I think I may have left the starting line in third gear rather than first somehow which explains my speed and ET despite not shifting. Some background...I recently re-wrote my PCM several times trying out different tunes and operatiing systems. During this race, I felt at times that truck was kind of re-learning itself. A similar shifting issue happened once before about three years ago but a code was thrown for shift solenoid B. I had the code cleared and the person that cleared it said nothing was wrong and that modified transmissins do this often. My trans currently has a PI 3200 stall converter, Transgo shift kit, and billet servos. Any help or ideas would be appreciated! TIA... Quote Link to comment Share on other sites More sharing options...
RacerJJ Posted March 16, 2009 Author Report Share Posted March 16, 2009 Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted March 16, 2009 Report Share Posted March 16, 2009 sounds like a possible TPS issue to me Quote Link to comment Share on other sites More sharing options...
RacerJJ Posted March 16, 2009 Author Report Share Posted March 16, 2009 Could that have to do with my truck still kind of learning after all of the "write entires" I've done with the PCM lately? It shouldn't be in the tune as I have reloaded my previous tune in and that's what I was running at the time. Quote Link to comment Share on other sites More sharing options...
detjoe Posted April 13, 2009 Report Share Posted April 13, 2009 bump this! was at the track and a very similar thing happened to me. did not shift, I think it made it into second but not into third. I have not messed with any flashing of the PCM. My short time was the same but I was done by the 1000' and let off. Checked the fluids, left the track while I could still drive home and it shifted fine, and manually held third, so I am guessing some kind of glitch?? oh well Quote Link to comment Share on other sites More sharing options...
black00chev Posted April 13, 2009 Report Share Posted April 13, 2009 Could it be something as simple as just needing a fluid change? Quote Link to comment Share on other sites More sharing options...
detjoe Posted April 14, 2009 Report Share Posted April 14, 2009 nope this fluid has under 500 miles on it, still pink! Quote Link to comment Share on other sites More sharing options...
sswake Posted April 14, 2009 Report Share Posted April 14, 2009 Check me off on this list also. Mine won't shift out of second at wot. I talked to a good friend of mine who is a GM tech and he told me they will do this when the clutches are burned up. I don't really know but I've started saving for a tranny rebuild. Sounds like the cam swap will have to wait. Quote Link to comment Share on other sites More sharing options...
detjoe Posted April 14, 2009 Report Share Posted April 14, 2009 this was second into third, and it shifts now?? I will get on it again and see if it does it at WOT but I think it did last time. Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted April 14, 2009 Report Share Posted April 14, 2009 If its hanging gear and winding out until it shifts, or doesn't shift at all, it sounds to me like burnt bands. I had an issue with my old trans winding out to over 6200 before clicking into 3rd gear, even when the commanded shift was at 6000....turns out hat I had a burnt 2-4 band that was causing some slippage. A new Kevlar 2-4 cured it for a while, but it wound up coming back anyway. Thank god that trans was put out of its misery........ Quote Link to comment Share on other sites More sharing options...
RacerJJ Posted April 16, 2009 Author Report Share Posted April 16, 2009 Mine is not an up-shift issue. Mine lainched off the converter (stalled to about 2800) in third gear. I think I figured it out though. This has happened to several other GTO owners that I race with and on the HP Tuners forum, there was a fix for this in the tune. It has to do with MAP at WOT in relation to TPS. I will find the link and post it. Mine has been fine since I did this. Quote Link to comment Share on other sites More sharing options...
zippy Posted April 17, 2009 Report Share Posted April 17, 2009 Mine is not an up-shift issue. Mine lainched off the converter (stalled to about 2800) in third gear. I think I figured it out though. This has happened to several other GTO owners that I race with and on the HP Tuners forum, there was a fix for this in the tune. It has to do with MAP at WOT in relation to TPS. I will find the link and post it. Mine has been fine since I did this. If this is the first time it's ever happened to your truck how would you know if that really fixed it? Sounds to me like the pcm somehow assumed there was no VSS and put the trans into default mode which will only give you 3rd gear. Why would you pre-load the trans that hard on launch if you have that much stall? It creates alot of heat and is hard on the trans. If the converter is flashing like it should you should be able to launch off idle or just above idle and get the same 60' time. Quote Link to comment Share on other sites More sharing options...
RacerJJ Posted April 17, 2009 Author Report Share Posted April 17, 2009 If this is the first time it's ever happened to your truck how would you know if that really fixed it? Sounds to me like the pcm somehow assumed there was no VSS and put the trans into default mode which will only give you 3rd gear. Why would you pre-load the trans that hard on launch if you have that much stall? It creates alot of heat and is hard on the trans. If the converter is flashing like it should you should be able to launch off idle or just above idle and get the same 60' time. You're right Zippy, I have no idea but it hasn't done it since so I like to think that I fixed it. I have been trying to launch at a lower RPM but I am just used to stalling it that much. I will keep trying. In the past, when I have launched at a lower RPM by mistake, i noticed that it didn't have the same 60' time but that could have been due to something else. BTW, what is VSS? Quote Link to comment Share on other sites More sharing options...
Krambo Posted April 17, 2009 Report Share Posted April 17, 2009 BTW, what is VSS? Vehicle Speed Sensor (IIRCC) Quote Link to comment Share on other sites More sharing options...
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