02 TB TCC unlocks/locks at hwy speed

Printable View

03-04-2012
waynehartwig

02 TB TCC unlocks/locks at hwy speed

2002 Trailblazer 4x4 4.2L I6 4L60E

When cruise control is on, it switches often between lock and unlock. Hold speed steady with gas pedal, and it stays locked in. Obviously getting better MPG with pedal and not cruise.

Because of the complaint, I 'moved' the TCC lockup point down (less TPS) and unlock point up (more TPS), but that did not help. Based on feedback, it didn't even help. User says it did this with stock tune as well.

Am I missing something in the tune where I can change the cruise TCC lock/unlock?

Thanks for the help!
03-04-2012
nhanson

What is the duty cycle at?

Also fluid level is good? Could be a bad solenoid if it keeps switching on its own.
03-04-2012
gn2beatu

The TB will not stay locked unless you have your foot on it, its in the TCM.

You can buy a modified TCM to keep it locked from Alvin @ PCM4LESS.

Find him at tbssowners.com - I think they are $179ish and will even let you lock at WOT, and will also let you lock it in 2nd gear which the stock TCM wont.
03-05-2012
waynehartwig

Quote:

Originally Posted by nhanson

What is the duty cycle at?

Also fluid level is good? Could be a bad solenoid if it keeps switching on its own.

Duty cycle is at 100% max and whatever stock is at min.

Fluid was changed and still does it.

Can't be a solenoid, because if he drives via foot it stays locked. It's only when cruise is on. Same speed, same road.

Quote:

Originally Posted by gn2beatu

The TB will not stay locked unless you have your foot on it, its in the TCM.

You can buy a modified TCM to keep it locked from Alvin @ PCM4LESS.

Find him at tbssowners.com - I think they are $179ish and will even let you lock at WOT, and will also let you lock it in 2nd gear which the stock TCM wont.

In 02 they didn't have a TCM.
03-05-2012
Dr. Nopps

Quote:

Originally Posted by waynehartwig

In 02 they didn't have a TCM.

I've got an '01 and it does the same thing, whether on our (earlier) cars/trucks that function is controlled by the BCM or PCM I wouldn't know, but his general knowledge of the situation is still accurate. Not something we can just fix with a quick read/edit/flash. Contact the guy he mentioned anyway at least for more info if anything. Mabey he will do BCM's as well or provide other options/ideas. (segment swaps, switches) You should put back your stock TCC settings, you most likely did after not getting the desired result. For me it was WAY easier to just allow the TCC for at least final gear to apply about 3-6 MPH earlier- just to be safe don't go nuts, and raised the areas in the Maximum Duty Cycle table that already contained the highest values there by about again just to be safe 3%. (Three percent) or in other words .03 Sorry, just that I'm almost positive someone had misread me in the past on this and we don't want you cooking any tranny's. This would allow me to turn lower RPM's and actually with the slight addition in load, I can hover the gas pedal around half a percent to about 2 percent and with at least no drastic decelleration or hill decents it usually stays locked in. If the only thing you tow around is a small boat or jetski you should be alright with the extra load, but if you tow anything even a little tough you may want to leave Duty Cycle alone and/or stay on the small side of those adjustments.

P.S. Does anyone know or at least have an idea as to why GM started doing this with their transmissions? The earlier ones weren't like this.