AW4 screwing up only when in "Power" mode

So some of you probably remember a while back I posted that I had some VERY intermittent trouble with my AW4. It happened to me like 3 times where I'd be driving along and all of a sudden it would either slip on me or it wouldn't shift out of a gear. Well I was driving it in power mode then so I thought maybe switching it to comfort would make some difference. I've been driving it in comfort for like 3 weeks now and it hasn't messed up once. Is this within the TCU, wiring, or is it hard to tell without diagnosing it a ton? It was rebuilt about a year and a half ago and still shifts (when it's not acting up) like a brand new tranny. What the hell is going on? Anyone know?
Thanks in advance,
Collin

Mabey a sticking solenoid.

My understanding of the power switch is that it is just that - a 12v switch. So that really points all fingers towards the TCU.

An inspection of the wiring connections and the harness would be in order!

If it shifts fine in "comfort" and has issues in "power", just leave the switch on the comfort setting. Problem solved.

BigBlackHeep said:

So some of you probably remember a while back I posted that I had some VERY intermittent trouble with my AW4. It happened to me like 3 times where I'd be driving along and all of a sudden it would either slip on me or it wouldn't shift out of a gear. Well I was driving it in power mode then so I thought maybe switching it to comfort would make some difference. I've been driving it in comfort for like 3 weeks now and it hasn't messed up once. Is this within the TCU, wiring, or is it hard to tell without diagnosing it a ton? It was rebuilt about a year and a half ago and still shifts (when it's not acting up) like a brand new tranny. What the hell is going on? Anyone know?
Thanks in advance,
Collin

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To me that would seem like a dirty/bad TBS or a bad speed sensor. I think I would change the speed sensor first. It can work ok at lower speed (Comfort range) but crap out at higher speeds (Power range)

anony91xj said:

If it shifts fine in "comfort" and has issues in "power", just leave the switch on the comfort setting. Problem solved.

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Comfort mode sucks though, it's not near as responsive.

langer1 said:

To me that would seem like a dirty/bad TBS or a bad speed sensor. I think I would change the speed sensor first. It can work ok at lower speed (Comfort range) but crap out at higher speeds (Power range)

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TPS was just replaced and adjusted. I've never screwed with the speed sensor though. What's its function besides to umm...sense the speed?

Could be a problem with the Transmission Control Unit if its equiped with one. My 90 XJ has one. I accidently bumped the connection loose when I had the kick panel down and it wouldn't shift properly at all for me.

The speed sensor will tell the AW4 "hey... we're at 45mph here", in conjunction with the TPS saying "and on light throttle" so the TCU will deduce that you should be in 3rd+lockup (or somewhere around there, in power mode).

A bad speed sensor may lead the TCU to think "5-10mph" (really, "0mph" is more likely) when you're actually at 45mph. Thus the TCU would try to put you in 1st gear (you'd never make it to 45mph).

You can test the speed sensor easily. It cycles on/off once per rotation of the output shaft. Slap a volt-ohm meter on that guy and verify that it does that.

Intermittent problems are the worst, and they will make your diagnosis painfuly difficult. The best you can do, short of replacing parts proactively, is keep a log of "what and when". I.E., "accelerated from 35mph to 55mph in 3rd gear/power mode and would not upshift."

good luck