Trans upshift at WOT way too early ?

I have been having an intermittent problem at WOT at the track lately. The car will fall right on its face 'sometimes' at WOT.

http://j.cz28.com/wotupshift.jpg

Graph here. If you look at it, it seems the cpu is commanding the shift for some reason..... The previous 6 runs that day had no problems. I did change the tune before the 3rd run, otherwise it stayed the same for 4th to the 7th run. Log shows rpm, tps and mph (which is the parameters the cpu looks for i believe) Running in SD mode if that makes any difference. Trans is converted to vacuum mod. Of course this problem occured in the Final round :oops:

Is there more than 1 place the computer 'sees' vehicle speed ? The only thing I can think of is another intermittent problem : In the burnout box 'sometimes' the mph gauge will be lazy for 1-1.5 sec then jump up real fast.... It is not tied to the upshift problem 100%, (IE when this problem occurs, it does not indicate the other problem will on that particular run) but thought something might be connected there ?

I have the .tun file if anybody wants to take a look.

Thanks for any input here.
'J

Sometimes, Too much line pressure or a hot transmission will make it shift early. It thinks it needs to save the transmission from too high of pressure so it performs the shift early.

Or, When the transmission is past a set threshold, it will also use the hot perameters in the pcm.

Can you log TFT in degrees F...?

Quote:

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Originally Posted by wait4me

Sometimes, Too much line pressure or a hot transmission will make it shift early. It thinks it needs to save the transmission from too high of pressure so it performs the shift early.

Or, When the transmission is past a set threshold, it will also use the hot perameters in the pcm.

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So there is parameters in the pcm for the "to much pressure/hot shift early" ? I do not believe it was too hot, as it was ~50deg out, and I have a big tranny cooler. How to I get rid of that parameter ? It only started happening this fall. I have made many passes when it was much hotter out this summer.

All of my shift mph, and shift rpm tables match. (normal/hot/cruise) I did that to try to prevent this kind of thing from happening.

Thanks for the reply.
'J

Your problem sound like one I've been living with. See this old LS1Tech thread:

HELP! Short-Shifting out the hole - any ideas?
http://www.ls1tech.com/forums/showth...ht=shift+early

I posted details complete with some EFILogs. 8)

I was hoping to find something different happens when I program with EFILive and swap another PCM in there. We'll see.

Also, my Speed Sensor is off... using the same values I've always used for that size tire and rearend.

Thanks for the reply. :)

But, LIVING WITH ? :cry: :x

Hopefully there is an answer to this.

What other PCM do you plan to use ? just another 98 ?

When you say your speed sensor is off, how do you mean ?

This has happend 5-6 times now this fall. Happens to coinside with a motor swap, (~50-75 more hp) and efilive being released for the 98's. But you had it happen before, with LS1 edit. Are you running a MAF ? Were you when the problem has happened ? Maybe it's a 98 thing ?

I am getting a MAF code (SD mode), and an a/c pressure code, NO tps code.

'J

Yea, another '98... I was hoping LS1-Edit corrupted it or something.
When I get my tranny back, I'm going to see what it does with the EFILive flash. If it's still there, I'll swap a '98 PCM in that I bought.

Speed sensor? I mean the speedometer says I'm like 70 when I am really traveling about 66 or some ish like that. I have to check my logs and see what ratio I had to dial in to make my speedo read the correct MPH. But, it is off from what it should be.

I forget what code I get intermittently... I may have stated it in that post. Someone just suggested my torque is overpowering the transmission... no sh!t, Sherlock! :lol: But, it still doesn't make any sense.