Transmission Power/Comfort problems

[Ecomike]

If the light doesn't go on, it's either the switch or the trans fuse. It feeds power through the black-yellow wire to B on the switch. In power, it feed voltage to the TCU on C over the tan wire. Sticking a voltmeter on the back of the switch and looking for +12v would tell you pretty quick if it's the switch, fuse or wiring. A bad TCU should not affect whether the light goes on.

Wow, Use a volt meter, what a novel idea! Took them thar words right out me mouth, LOL. :thumbup: :roflmao: :laugh2:

Once I got everything fixed and working correctly I noticed a huge difference between the shift point from 3rd to 4th gear. Comfort shifts at about 37 mph and power shifts at 45 mph on mine. 235R75 15s, 3.54 rear end, AW4 auto, stock 4x4. Nothing subtle about it.

 

[cygnus58]

For me, I notice shift point change more with throttle position/mph ratio.(TCU input being derived from 1/2 dual TPS and input from Trans speed output sensor)) than just with actual mph. I will pay closer attention but it seems mine shifts close to the same MPH on level ground in either position with reasonable throttle position.It's more about how far your foot is in it, and what your actual speed is at that instant. It CAN be very subtle flat terrain driving, If I am climbing a grade in comfort, and when I think (starting to lug a bit) that it should shift down, I flip the switch to power, it often INSTANTLY does downshift.
Will check my 3rd to 4th EcoMike, never noticed that...
And 3x on the Voltmeter.

 

[Muad'Dib]

Put my 2 cents here also... definetly sounds like a switch.
There is a HUGE difference in the power and comfort modes.... at least for me. When in power mode, it stays in gear longer. Also, when i floor it going say 55, ill accelerate fast, but if i flip that switch while doing so its like a whole new Jeep!! It even sometimes downshifts and takes off... This is of course from my experience... the difference should be very noticeable.

 

[Ecomike]

For me, I notice shift point change more with throttle position/mph ratio.(TCU input being derived from 1/2 dual TPS and input from Trans speed output sensor)) than just with actual mph. I will pay closer attention but it seems mine shifts close to the same MPH on level ground in either position with reasonable throttle position.It's more about how far your foot is in it, and what your actual speed is at that instant. It CAN be very subtle flat terrain driving, If I am climbing a grade in comfort, and when I think (starting to lug a bit) that it should shift down, I flip the switch to power, it often INSTANTLY does downshift.
Will check my 3rd to 4th EcoMike, never noticed that...
And 3x on the Voltmeter.

I deliberately ran tests on mine to see how I could get into 4th gear the soonest at about 35 mph to save gas, as I do a lot of city, 35 mph max driving. At 40 mph (apx) on flat terrain in power mode mine immediately shifts into 4th gear if I switch back to comfort mode. Power mode keeps it in 4th gear at constant speed or mild acceleration for about 7 mph more than comfort mode, so if it shifts at 38 mph to 4th in comfort mode, then it shifts to 4th in power mode at 38 +7= 45 mph, at the low acceleration end. At high acceleration I think it makes less diference.

 

[sadupont]

I went to the local NAPA store and found a switch. Miraculously, it fit the existing hole in the dash, wired it up, and the "power" mode is back. Works no problem. Noticable difference in when the torque converter locks up in third (later), and it won't shift to 4th quite as soon as in "comfort" mode. Biggest difference, though, in my opinion, is it's willingness to downshift. Get into it around 50 in "comfort" and it is really unwilling to come out of overdrive. In "power", it jumps right out of OD no problem and 75 comes up pretty quickly--feels like a different truck. It will be tempting to leave it in "power" mode all the time. Just drives much better, and more ably exploits the nice power from the 4.0L. If you drive it reasonably, I can't imagine much harm done to the fuel economy, but the jury's still out on that one.

 

[ehall]

Replace your TPS and it will probably even out a little bit.