How much can I lean on shift time and line pressure ?

[LittleSlow1]

I have a 1998 Trans Am, 3600 stall. The trans is bone stock about 50,000 miles on it.

My question is hard hard can I lean on the line pressue and shift times? And not have to worry about over doing it and hurting the trans.

Shift times:
Right now it looks like my shift times are about .4 to .6.
If I go too low will I have to worry about it hanging between 2 gears ?

Line Pressure:
When I log line pressure it doesn't get higher than 50% (remembering off the top of my head).

The car is a street strip car. I run the NMCA Late Model EFI class. And currently the car will run 12.70s consistantly on a 80 degree day. I am running a 13.0 index which mean I gotta slow the car down. I'd like to not have to slow the car down as much. Is there any trans tuning I can do to pick up 2 tenths ? I feel as if the trans could shift harder and faster.

Also I have my WOT shift points set for 6000 rpms and the correct WOT mph, but the car shift out of 1st @ just under 6200 and out of 2nd @ just under 6300. I feel as if I raise the line pressure and lower the shift time it should help the trans shift a little closer to the set point. I'd like it to be plus minus 100 rpm if thats possible.

If needed I can post up my tune and some track logs later.

Please help.

[EC_Tune]

Remember that it takes time to make the shift so move the RPM & MPH down accordingly.
You can lower the shift times a bit. .4 is plenty slow at WOT. I would try .25 and see if it shifts better. You have to monitor delivered torque or you won't know where you are on the tables.

[LittleSlow1]

I have a 3.23 rear end. And from what I can remember the car shifts out of 2nd at about 6300. I have WOT shift rpm set to 6,000 and WOT shift MPH set to 75 mph, and the normal driving charts are set to 75mph at 90% to 100% throttle. At 6300 when it shifts I think the computer said I was going 83mph. These are the only numbers that stick out in my head right now, that I can remember, with out checkin the log on my laptop at home.

I understand it takes time to shift; In the past I've tried lowering my WOT shift rpm down to 5800 but I saw no change. I guess mabey I'll just have to try it again.

I am logging Delivered trans and engine torque, line pressure %, shift time 1-2, shift time 2-3, latest shift time and Force current.

I tried lowering the shift time. It seemed better going by feel but when I log shift time it still shows .6. Also, at WOT it still feels the same, but it would shift faster at 3/4 throttle or less. I also set the shift modifyer cell 220 - 320 torque to 0 up to a trans temp of 233, just to make sure that wasn't changing anything on me.

I tried raising line pressure. I really felt a difference then, but not at WOT. I'm a little confused with logging line pressure %. Does 100% equal max line pressure as in 96 ? The highest line pressure % I see is about 30%. Or should I not use the pressure % and only go by Force motor current ?

I'd really like to get the car to shift faster and harder at WOT to mabey get a tenth or so of my ET, but I don't wanna risk hurting the trans. If I hurt the trans I'll be done for the year.

Saturday I was at the track and did a base line run of my current tune and then some runs with 1 tune I only lowered the shift times to .25 and the other tune I tried giving it more line pressure using the delivered torque/line pressure table, plus the.25 shift times from the above tune. I saw no improvement, so I put my base tune back in the car. (when I say base tune I mean the tune I had in the car before I started messin with the trans shift times and pressure)

I do have logs from this weekend and tunes I can PM or email you when I get home if you'd like to look at them.

Unless I'm missing something or don't understand how to add more line pressure (most likely the reason) mabey the trans is just too tired to get more line pressure ? Its got just under 50,000 miles on it.


Although I'd really like to keep the computer controlled 4l60 in my car for obvious reasons and the car I'm sure is more consistant letting the computer shift it, I'm almost to the point of saying the hell with it and puttin a TH400 in the car.

Thanks for your help EC !

[EC_Tune]

As to the logged line pressure: I'm not 100% sure what that equates to off the top of my head.

Basically you want to see where you are on the torque, translate the base line pressure table (200-300 ft. lbs = xx.x line pressure) take the line pressure value and trans temp to find out where you are on the Force motor table. Then you can move the line pressure table around to fit once you know where you are at on the force motor table.

[LittleSlow1]

ok, I'll give that a try.
Thanks !!