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.:help2:

[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. :D To post stuff I think you have to have like 10 posts...

[joecar]

Mach2, welcome to the forum... :cheers:

Erik will get you sorted out. :cheers:

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.:notacrook:

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.:notacrook:

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).

[ScarabEpic22]

Glad to hear it, and I didnt mean you had to drop it just loosen it so you can pull the trans down enough to get access.

And now you know what my shifts are like, 0 TM, new force motor (has Superior springs for more force I think), .1 shift times, and man I have no traction in my 4500lbs SUV from 1-2. Did a WOT 1-2 today in 2WD in the rain, started going sideways at 50mph...lol

[Mach2]

New issue came up last night. When it shifts 1-2 at 5000 rpm or above, I now hear a short screach coming from the trans. The shift is firm, but it sounds like bad. Initially I hada max of 25% TM. I took a TM curve from a 03 Corvette that has 35% TM and it comes in faster, but I still get the screach from the trans. Also slowed down shift times to .275 (from .2), still screaches. Going back to trans shop today to let them listen. After 53000 miles (15000 towing 3500+ lbs) I suspect the 1-2 band may be worn. Sigh.....

[ScarabEpic22]

Interesting, it must have really been slipping as I have the 4.2L I6 and tow my boats in the summer (~4100lbs) to my cabin 330+mi each way a couple times plus around Seattle. No problems thus far except for the Transgo kit which I brought upon myself...

[Chevy366]

New issue came up last night. When it shifts 1-2 at 5000 rpm or above, I now hear a short screach coming from the trans. The shift is firm, but it sounds like bad. Initially I hada max of 25% TM. I took a TM curve from a 03 Corvette that has 35% TM and it comes in faster, but I still get the screach from the trans. Also slowed down shift times to .275 (from .2), still screaches. Going back to trans shop today to let them listen. After 53000 miles (15000 towing 3500+ lbs) I suspect the 1-2 band may be worn. Sigh.....
That suxs , from what I was able to make out from the post joecar made is that you need to be careful with Shift Times , Tran Pressure and TM , sounds like one works with the other and if one is off it can have adverse effects on the Trans .
Lets us know what happens .

[ScarabEpic22]

That suxs , from what I was able to make out from the post joecar made is that you need to be careful with Shift Times , Tran Pressure and TM , sounds like one works with the other and if one is off it can have adverse effects on the Trans .
Lets us know what happens .

Good call man, and thats why a bunch of tuners are VERY reluctant to touch LPs as sometimes it can cause weird things like this to happen.

I would revert back to the stock LPs and then work on TM and shift timing from there. Maybe load the stock trans part into a test tune (i do this from time to time to test things) and see if it makes a difference?

[Mach2]

Leave it to the trans shop to make me fell like an idoit. The screach is coming from the serpentine belt. When the engine shifts quickly at 5800 rpm the abrupt change is causing the belt to slip. They took me out in a Silverado SS (6.0L with a shift kit - nice ride) and it does the same thing.

Hence I am good to go, and not a moment to soon. Leaving for a 700 mile trip this week-end towing a 3500 lb brick wall (i.e. deck boat).

Thanks again to all for your input.

[Aint Skeered]

ON my avalanch I have tow haul. it is set in performance (d1108) to .300 and normal at .650 to start out and then works its way down ( as tq rises) to .375 at 360 ft lbs of tq.
I dont want to loose the normal ride qaulity fo the truck but in tow haul mode i dont mind.
What would be the best way to do this, is the performance mode for tow haul only?

[Mach2]

Nothing I did made much of a difference until I had the Corvette servo installed.

I used 0.3 seconds across the board for shift times. I reduced TM by 10% and bumped line pressures 10%. Shifts are postive even at WOT with jerking the truck. I just towed a 3500 lb wall (read deck boat) 300 miles and the changes really helped while towing.

[Chevy366]

I use 0.00 in all shift times no TM or TR , tow haul I left alone don't use it much , but as I said mine is a $L80E slightly different .
I still believe a shift kit is a good thing it replaces some of the parts that may other wise fail with stronger parts , of course you tune for a shift kit different than without one .

[Aint Skeered]

where do you find the difference in tow haul and normal? is that the difference in the performance and normal?

[Chevy366]

where do you find the difference in tow haul and normal? is that the difference in the performance and normal?
Yep .

[Aint Skeered]

Thanks, I will leave normal alone so I can have the ride comfort and modify performance then.

[Aint Skeered]

ONe more quesion though, why would performance have more tq reduction then Normal? WOuld it tow better with equal tq reduction as NOrmal or would that be to hard on the trans?

for instance , at 240 ft lbs Normal is 11.00 and performance is set at 20.

[Chevy366]

ONe more quesion though, why would performance have more tq reduction then Normal? WOuld it tow better with equal tq reduction as NOrmal or would that be to hard on the trans?

for instance , at 240 ft lbs Normal is 11.00 and performance is set at 20.
I think if you look the PCM ups line pressure in Performance Mode , could be why .

[Aint Skeered]

would it hurt then to reduce the amount in tow mode of tq reduction?

[joecar]

When towing, the drivetrain is dealing with increased combined vehicle mass which means vehicle inertia is increased...

with less inertia a hard shift just jerks the vehicle...

with greater inertia a hard shift can't jerk the vehicle as much, so the drivetrain has to "soak" up the stress...

that's why TR is increased in tow mode.

[Aint Skeered]

i should just leave it alone. thanks.