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Transmission "Power" button.

These control/alter the shift points on the AW4 4 spd auto trans. In 'comfort' the tranny will upshift sooner & softer(?) than in 'power'. In my 89 I really can't telll much of a difference between the two settings, but in the 88 (with fresh rebuild) I can. I leave the 88 in the 'power' mode.

I'm pretty sure they are an 87-90 (non-HO) thing and IIRC went away with the intro of the HO 4.0 in 91, but I am not clear on that. The earlier 4.0/AW4 XJs had a seperate tranny computer, and in the newer ones this function becamer integrated with the engine computer. I have heard that the new default setting is close to the old 'power' setting.
 
My 91 HO has the power comfort switch. The manuals say it was only available from 87 to 90, but the switch is really there and it does work. I’ve messed with it a little bit and it doesn’t seem to make a whole of a difference. Then again, it has 95k miles and nothing has ever been rebuilt. Hesco has a Torque converter relay package available (http://www.hescosc.com/HES8790TCR.html). I don’t know of any body that has used it.

Coyote
 
I have it on my 91 also. And I can really tell the difference when I put it in power mode(I normally do it when towing).
 
woody said:
The earlier 4.0/AW4 XJs had a seperate tranny computer, and in the newer ones this function becamer integrated with the engine computer.
Click to expand...
I've read that in several post here and I'm confused because I've seen the tranny computer from '98 and '99 XJ's. It is not part of the engine computer. I also checked car-part.com and they list a seperate computer for every year from '01 back to '91. I didn't bother checking any further back than '91.
 
As I recall you are supposed to use the "power" function when towing. I leave mine in comfort because it shifts to OD much quicker and the engine doesn't spool up so much driving around town. While towing I do use it and it really works better especially with a heavy load.
 
Randall Edge said:
I've read that in several post here and I'm confused because I've seen the tranny computer from '98 and '99 XJ's. It is not part of the engine computer. I also checked car-part.com and they list a seperate computer for every year from '01 back to '91. I didn't bother checking any further back than '91.
Click to expand...

The tranny computer in post-91 models is still separate, but receives input from the engine computer, where in the pre-91 Renix models it used a separate section of the throttle position sensor independent of the engine control. This might lead some to believe that the ECU is now controlling the transmission.
 
i leave mine in power and havent really played with it... as stated it adjusts shift points a little higher.. i've been told that the bigger the tire you're turning the more noticable it will be..
mike
 
The only time i have noticed any difference is towing and/or when going up a long steep hill. no driving difference notice when driving distance.
 
"The tranny computer in post-91 models is still separate, but receives input from the engine computer, where in the pre-91 Renix models it used a separate section of the throttle position sensor independent of the engine control. This might lead some to believe that the ECU is now controlling the transmission."


Ah I see :) My bit of learning for the day. Thanks Matthew!
I've only been in a couple of them newfangled XJs, and all 5 of mine are '87-'90.
 
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