Shift Time and Pressure Correlation

[WillRyan]

To start off, this is has to do with my experience with the 4l60e that has 180,000 miles in my 1500 4x4 Z71.

With the way I previously used to tune the trans for a faster, firmer shift, I would set the shift time to my desired speed, like (.250 sec) and then would adjust the shift pressure just by comfort feel. Or whatever felt like it worked with that shift time. Everything was fine, even when pulling a light load. But then one day I had to hook up to an all steel 18ft Car Trailer and loaded our rolling chassis hot rod project on it to take to the chassis shop. My worst nightmare had occurred. I experienced shift flare, and or, shift slipping with this amount of weight behind the truck. My first thought was its going out...

After some thinking and driving it easy, I thought to myself, GM sets the Shift time and Pressure to work in conjunction with each other. How about I go back stock, lower the Shift time by say 40% and then increase the pressure by 40%. With that adjustment, I did get the chance pull the same heavy load again, and have experience a pleasant shifting trans ever since.

So my reason for this post, am I right to go about that way of tuning from now on? I mean it works, but I thought my other way of tuning worked as well.

How do you guys adjust shift time and pressure?

[Russ K]

On the 4 speed GM auto trans, I leave the shift times stock. But the 4L60-70 trans need the Corvette 2-4 servo. For the base shift pressure table, I first change the 0 ft lb column of the 1-2, 2-3 & 3-4 shift table to 0. Then change the 640 ft lb column of the 1-2, 2-3 & 3-4 shift table to 40. Now highlight the whole table & click on the "Interpolate Between Horizontal Bounds"
button.

Now the shift table will be 0 at the 0 ft lb column & 40 at the 640 ft lb column. Now copy this table & click the "Undo All Changes" button. Then right click on the table, go to Paste Special > Add. This will add 0 psi at the 0 ft lb column of the shift pressure table & 40 psi at the 640 ft lb column. You can set the shift pressures different for each gear if desired.

The editor should clamp the max pressure to 96 psi. Also change the Max Pressure to 96, as it usually is 90 stock. If you what firmer shifts, increase the value at the 640 ft lb column or lower the value for softer shifts.

Also zero the 96 psi column of the Force Motor table.

Russ Kemp

[WillRyan]

Thank you Russ, I have actually used your method I believe to adjust pressure before.

Will have to try it again with factory shift times.

[brandong007]

I had a random 2-3 slip where it wouldn't hold 3 or 4th gear just cruising at 60. I didn't think much about at as I have had 4-5 trucks and never had a tranny issue. I don't mean to doom and gloom, but I was eating my buddy's Titan in my 5.3 swapped GMC Canyon Crew Cab 4x4 doing some Interstate pulls from 2nd on a stock Tranny with 170k. It took my TQ mgmt removal and heavy foot pretty well for 70k mi. after the swap, but at 170k mi during one of these pulls at 6,400 rpm (I was mildly cammed) I didn't make it to 3rd and it would only hold second gear with medium throttle...any more and it would flare...bye bye tranny....I won the drag lol, but he beat me home cause I had to ride 2nd gear @ 50mph. My trans guy said 3rd and 4th clutches are weakest point in the 4L60, so he rebuilt and beefed up with stronger clutch pack, sunshell, and a few others and modified the valve body, and it kicks but now....a little too much at times. At 50% throttle, any shift at 4k or above will chirp my 32" x 11.50" tires.

Any way, I hope yours truly was in the tune, and at this point don't be trying to fix with a trans flush b/c that will also flush what little friction material you have left with those miles. Just curious...if you pull your trans dipstick and touch a white tissue paper, what color is it? Mine was a little on the burnt side... a mix between pink and light brown. It should be pink unless you have a bunch of clutch material in the fluid. Good Luck with the tranny issue.

[WillRyan]

Good info! Will check fluid when weather clears up.

So far there have been no problems since the tune adjustment. I can only hope it keeps chugging along!

[Maxspeed96ct]

On my built 4l70e , shift times are .250
Shift pressures are increased by only 1% across the board since I have a shift kit and built trans . All tq mgt is 0

If you don't have a shift kit , 10% increase across the board is a good number to start with . And make your max about 96 or 98

Adjusting the force motor also helps, but that is a topic to indepth for me to explain. There's some good threads kicked around on it .

[WillRyan]

Will check it out.

So far I've been running around with the shift speed reduced 40%, and the shift pressure increased by 40% along with a 0 to 20 Interpolation using Russ K's method! It is doing well!

[tnbubba]

as a HP tuners newbie.. A BIG THANK YOU from a crusty old 2 wheeled go fast fart..

esp the idler tune files and help and other stuff you posted..
learning this stuff quickly is not for faint of heart!

workign on stuff..and trying to figure out shift tables for a performabuilt 4L 60 E in my truck

I noticed In one of your posts when you chagne line pressure to 96 psi you change the force motor current to 0?
what about 100?? Frank at performa recommends stock settings as most of the internal stuff take scare of pressure issues
I was wondering the rational for the changes..
I know i'll have to experiment with torqe reduction and shift times for daily driver mode..

again thanks for all the info youhave posted