Need help-Can't reduce shift times!

[Mach2]

I am new to this forum and just started working with EFILIVE this weekend. I am trying to tune my 2004 GMC Envoy XL (5.3L 4x4) for better towing. My goal is to reduce shift times and firm the shifts up a little. I am most concerned about the 1-2 shift.

I started by following Joecar's tutorital. I increased line pressures by 10%, reduced torque reduction 10%, and changed desired shift times to 0.3 seconds. This gave very little improvement in shift quality and WOT 1-2 shift times of 0.5 seconds.

I tried several other things to improve the shifts to no avail. On my latest attemp I removed all torque reduction (set table to all zeros), removed abuse management, set desired shift times to 0.2 seconds, and bumped line pressures by 30%. I logged spark reduction due to torque management, engine and delivered torque to ensure I removed all torque management. I then logged line pressure, rpm, and speed. At WOT the 1-2 shift took 1.0 seconds and was not firm. 2-3 shifts were improved. Line pressure during the shift was 90 psi (I have the log but do not know how to post it).

I know I want to leave torque management in, but I want the shift times around 0.3 to 0.5 seconds. What else can I try to get the desired results?

Any suggestions would be greatly appreciated.

[ScarabEpic22]

OK man, since you have a TrailVoy (TrailBlazer/Envoy) I can help you out.

These trucks are a little different, what you want to do is take the shift times to .1, bump line pressures to ~20% over stock, and remove all the TM from the 1-2 and 2-3 tables in the trans section. I know for the LL8 (4.2L I6 engine in the TV platform) that there is also an engine TM section under Engine->Spark->Torque Management that Ive 0ed as well and now it shifts like a beast (also have a vette 1-2 servo so my LPs are stock)!!! And no, with the engine you have and the engine I have, it is safe to run 0 TM as long as you arent towing all the time, and when you tow I would suggest maybe 10-20% of all TM be left in, just to make sure the trans doesnt work overtime.

If you email me your tune I can do all this in like 5-10min, Ive done it for a couple other people now. To post stuff I think you have to have like 10 posts...

[joecar]

Mach2, welcome to the forum...

Erik will get you sorted out.

Some vehicles are the exception, or have something different going on.

[Mach2]

Thanks guys, I will give it a try tonight, but I must admit I am a little skeptical. I verified on my last tune that I hadall TM removed by watching both torque values (never deviated) and spark reduction due to TM (zero all the time). I had the desired shift times at 0.2 across the board, and at WOT the 1-2 shift still took 1 second (at 70% TPS the 1-2 shift occured at 5000 rpm and took 0.5 seconds).

I trust the Corvette servo really helped. Is this something I can replace by dropping the pan, or is it in the side of the case?

[cmitchell17]

Im about to figure out where I can get somone to put in a vette servo for me.

Ive got a 2000 Chevy truck with a stock 4L60 and I can not get it to shift faster than about.7 or.6 seconds at WOT.

Ive heard you need a vette servo. That is probably exactly what you need becuase the vette servo is like 30% bigger or something.

There is a cover on the side of the trans that you pop off replace some seals and pins and put in the servo. No dropping pan. I can't trust myself to do it myself so im going to get a trans shop to do mine. It is supposed to only take 20-30 min but there is a o ring you have to get in right or the transmission case cracks or explodes.

[Chevy366]

Yeah , transmission shift kits are the way to go , whatever brand you use .
Everyone I have ever talked to says shift kit for better shifts .
Best hundred bucks I ever spent , TransGo kit , I put it in myself , worked for a trans shop at one time .

[ScarabEpic22]

I have to say ney to the Transgo kit, I had the HD-2 one for my TB and it basically f-ked my trans up for a year. I installed it myself and followed all the instructions to a "t", but I think there must have been some installer error. Ohh, well, I wouldnt have spent the $$$ had I known that I would have been getting EFILive less than a month later and could change the shift stuff that way... I waas able to pay my trans guy $500 to R&R my valve body plus replace my variable force motor and now it shifts awesome with just the stock internals + vette 1-2 + tune (with stock line pressures).

Vette servo can be done, you do have to drop the trans crossmember to get access to it on the TB/Voy platform. I would have a trans guy do it and have them change the filter at the same time.

If you want to send me your tune file I can check it out and see whats up.

[Mach2]

Thanks for the advice.

I stopped by a trans shop I trust tonight. He installed a Corvette servo for $50. He did not have to drop the trans member, but he did need to remove the trans mount to allow the trans to drop enough to get the servo out.

Bottom line, this helped a lot! The only modifications I had in the PCM at the time were all shift times were set at 0.275 seconds, line pressures were up 10% from stock, and TM was reduced 10%. 1-2 shifts WOT now are fairly firm and 2-3 shifts are quick and fairly firm. I figure a little more tweaking of shift times (0.2 seconds) and a little more line pressure down low and it will be exactly where I want it.

Here is a warning to those who are removing all TM. When I had 90% TM, the 1-2 WOT shift took 0.5 seconds. With all TM removed, the shift time increased to 1.0 seconds. If you do not have enough pressure on the servo, all the extra torque causes the band to slip more, and delays the shift (and burns up the band).

[Chevy366]

Thanks for the advice.

I stopped by a trans shop I trust tonight. He installed a Corvette servo for $50. He did not have to drop the trans member, but he did need to remove the trans mount to allow the trans to drop enough to get the servo out.

Bottom line, this helped a lot! The only modifications I had in the PCM at the time were all shift times were set at 0.275 seconds, line pressures were up 10% from stock, and TM was reduced 10%. 1-2 shifts WOT now are fairly firm and 2-3 shifts are quick and fairly firm. I figure a little more tweaking of shift times (0.2 seconds) and a little more line pressure down low and it will be exactly where I want it.

Here is a warning to those who are removing all TM. When I had 90% TM, the 1-2 WOT shift took 0.5 seconds. With all TM removed, the shift time increased to 1.0 seconds. If you do not have enough pressure on the servo, all the extra torque causes the band to slip more, and delays the shift (and burns up the band).

Thanks for the info , nice to know .
Was reading some of joecar's comments and views on shift times and pressure settings , http://forum.efilive.com/showthread.php?t=1723&page=3 post #23 was interesting .

[joecar]

On F and Y cars (which have the 'Vette 2/4 servo) you can get the 1-2 shift firmed up alot (easily break traction at 45mph on the factory tires) without a shiftkit... and 3-2 shifts were just plain outrageous fun...

On sticky tires, though, this can be very harsh on the driveline (that 10 bolt axle is weak, and the trans. may not live too long).

I don't know what GM has done on other models (have they simply installed the smaller servo, or have they done other things...?).

(The GM trans. calibration is usually pretty mooshy and vague, quite so on the F car, and maybe except on the Y car, but seemed to respond well to tuning).