Any way to defeat the overdrive?

[5-90]

That's just it, though - I'm not towing anything. The only rust on my truck is on the factory trailer hitch(the reason I made the concession and bought an automatic in the first place), and it's so bad that I don't trust it enough to tow with it. Regardless, this was occurring with myself and one passenger, and the rest of the truck full(to window level) with camping and hunting gear.

It doesn't drop back out of lockup until it downshifts all the way to third. If it would drop out of "4L" as you call it, and into "4", I would be thrilled, because that's exactly what I want it to do. Instead it bypasses "4", "3L", and jumps all the way down to "3". And at lower cruising speeds, it does "hunt", as it's constantly locking and unlocking. If I drive the truck in "D" for even a short period of time at 25-30 mph, it hesitates horribly and often times backfires if I give it any more than 1/2 throttle. Not so if I drive it in "3" or keep my RPMs up by speeding(which I try to avoid as best I can).

Yeah, but 75mph in 3rd gear doesn't make a whole lot of sense.

And herein lies the problem. I feel that "soft shift" when it shouldn't be shifting at all(hell, it shouldn't even be anywhere near overdrive at 25-35mph), and it won't give me that "soft shift" when it should(1/4-1/2 throttle at highway speeds).

I am a very attentive driver(this comes from years of driving manual transmission vehicles, including some requiring me to hold a CDL), and I have never in all my years of driving experienced this type of thing with ANY other automatic vehicle I have driven.

Hm - I've not had that sort of trouble either (and much of my driving background is similar to yours. I also had a private pilot's license for a few years, which also tends to make one attentive to the vehicle...)

You should "shift down" into 3L - it's always a "shift up" to go into it. The TCU has to read a steady-state cruise before lockup can be enabled. So, the pattern would properly be "4L/4/3/3L", if it's going to go from fourth lockup to third lockup. Sounds funky - but it's actually better that way. The lockup circuit should lock out automatic shifts until it is disabled.

I'm honestly having difficulty trying to figure out what's causing the trouble you're describing - not from your communication (which is solid,) but because I feel that I'm still missing some small datum that will make all the rest of it make sense. Could I talk you into doing something? Open up a Notepad doc (or whatever plaintext editor you prefer,) and just give with everything you can think of that might relate to the problem at hand. Include parts replacements, tests - and make sure you remind me it's RENIX.

Think "stream of consciouness" here - the primary objective is just to get everything down.

After you've worked on it on and off for an hour or so (don't devote your attention to it - you will miss something that way. Work on something else, and shift to it when you get that "Oh, yea!" idea that hits you.) clean it up a bit and get it to make sense to someone else. Then either post it here (preferred) or email it to me (you can, but I'd rather have this out in the open - that way, it's more than just me working on it...) and we'll see what can be done.

I just feel like I'm missing something small and vital - and that's the trouble I have with "diagnosis by remote control." What the owner would think is insignificant turns out to be the case-breaker.

 

[89xj]

would 30" tires be part of the problem?

stock is 27" or 28"

is the TV cable adjusted properly?

 

[CantonXJ]

would 30" tires be part of the problem?

stock is 27" or 28"

is the TV cable adjusted properly?

The size of the tire, IMHO, should not effect when or if the transmission downshifts relative to engine speed. The down shift is determined by the TPS and (I think) a speed sensor on the trans output shaft.

The TV cable only effects shift firmness, not shift points. It controls hydraulic pressure in the trans.

Dave

 

[89xj]

The size of the tire, IMHO, should not effect when or if the transmission downshifts relative to engine speed. The down shift is determined by the TPS and (I think) a speed sensor on the trans output shaft.

The TV cable only effects shift firmness, not shift points. It controls hydraulic pressure in the trans.

Dave

IMHO, larger tires affect shift points.

 

[CantonXJ]

Okay, granted, with larger tires you are likely deeper into the throttle to achieve the same acceleration. So by virtue of that, that TPS will trigger the TCU to upshift later and downshift sooner. Having said that, however, given the same throttle input larger tires would not effect shift points relative to engine speed. The shift points at actual ground speed (not indicated if uncorrected) would obviously be different.

Dave

 

[techno1154]

Larger tires affect shift points especially if the speedo drive gears have not been changed to indicate the true speed of the XJ. I too would have liked to flip a switch to take the overdrive off on hills instead of having the AW4 hunt for the correct gear of manually shifting it into 3rd and reving 3,000+ RPM. However, the AW4 do shift into overdrive with the shift lever in 3rd but only after a period of holding the pedal steady resulting in a steady speed.

What I am trying to say is, wether you use the pedal or the shift lever, the AW4 always shift from 4L to third then back to 3L if the preset conditions are met; steady speed and steady pedal. And by the way, it appears not to shift into 3L when speeds are above 70 MPH scaling hills. This does wonders for the old fuel economy. Ask me how I know :shhh:

I took the more expensive route after a year driving those rooling hills in Iowa carring about 250 lbs of gear. I regear to 4.10:1. I think this is necessary when using tires above 29".

 

[heyhar]

I too live in the mountains (Northeast PA), and have three XJ's with AW4s. What i will do is, if starting to lug on a hill, is just tap the brake pedal ever so slightly, so as not to accuate the brakes. This will unlock the TC without the tranny downshifting. It feels like 'passing gear', giving a slight edge to maintain speed. When you back off the throttle, the TC locks up again, and off you go. This seems to work on most auto trannys, but not in our Outback. That car is hellbent on quick up-shifts, so you need to work the shifter to hold a gear. In the XJs I try never to let it kick down with just the throttle, as it is an abrupt downshift, going from locked 4th to open 3rd. I will tap the brake to unlock the TC, then manually shift to third. What I've noticed is that with moderate, steady throttle, the TC will lock at about 35-38 MPH in third, and about 42 in 4th. Also, I have coolers on the two that I drive, and I feel that it makes for more consistent shift feel, and the fluid is like new at the 30k changes. Hope this helps a little.

 

[98stocker]

4.10 gears would probably be the most help. Mine does the same thing, and I am still irritated by it. I have 3.55's and 31's.

 

[CantonXJ]

... What i will do is, if starting to lug on a hill, is just tap the brake pedal ever so slightly, so as not to accuate the brakes. This will unlock the TC without the tranny downshifting. It feels like 'passing gear', giving a slight edge to maintain speed.

If there were some way to rig a switch to do this, it would do exactly as I'd like. Plus, I can't imagine that it would throw a CEL on later models like BrettM's TC lockup control.

Dave