Not specifically Isuzu related, but does deal with cars and i figured one of my much more knowledge isuzu buddies might be able to offer some advice....

I've been driving my friends '90 Jeep Cherokee to save a little gas/tire wear on the Rodeo the past two weeks. Anyway, yesterday the auto tranny starts screwing with me and i know absolutely nothing about auto trannys.

first off, its a 3-speed automatic. What happens, it waits til about 500rpms below redline to shift into 2nd (4500rpms). shifts smooths and grabs fine though. and secondly, if you let off the gas, the rpms drop and then when you repress the accelerator the rpms have to climb back up before you get any power. haven't been fast enough to see if it shifts into 3rd or not. And it does this same deal in D, 2, or 1. And this behavor happened instaneous. I drove it normal one moment, parked, and then this. It cooled overnight and still have the problem this morning.

Now, about all i know to check on these things is fluid level... which seems to be fine. Also fluid appears to be in fairly decent shape, no burnt smell or bad discoloration. I hunted for vaccumm leaks but didn't see any obvious ones.

any of you guys with more automatic tranny experience help me out here and hazard a guess as to what might be going on and what I can look for? this sounds more like a problem than a failing auto tranny, right? i'd definitely appriciate it any help.

-Rob

Is it electronically controled or does it go off of throttle position by wire? If it is electronically controlled, I'd check for a 'power' button that might be depressed, that delays shifting to get 'more' power out of the gear. If it is controlled by wire, I would check the wire to see if it is getting caught up on something and not allowing it to go back fully and allow the transmission to shift.

Richard

Rob:

This is the only thing I know of that you didn't already mention, so take it for what it's worth (which ain't much <img border="0" title="" alt="[Wink]" src="images/icons/wink.gif" /> )

I had an '89 Cruiser with the same symtoms you describe (fluid was full and not obviously roasted, goofy shifting, etc.). Sterling McCall Toyota in Houston (I knew the Service Advisor so I doubt it was a hose-job) found the problem to be a snapped "detent cable". Now I couldn't even guess whether the Jeep tranny has one, but the cable runs from the throttle to the whatchamagizmo-thingy inside the tranny that actually controls shifting. Apparently, this cable (along with the vacuum inputs) tell the tranny to shift or not. Both vacuum and the cable were required to function normally, but either one would provide a "limp-home" mode should the other be damaged (like mine was).

Again, I know squat about Jeep slush-boxes, so your mileage may vary, other terms and conditions may apply, not valid without coupon, see store for details.

Good luck, (hope this helps)
Kevin V

Hey ROB, I just recently sold my wifes 90 cherokee and it had the same symtoms as you discribe. It wound up fixing itsself though. One thing I did find out though is that it has somethin to do with the throttle position sensor (TPS) on the pedal itself. Mine started acting up after I changed the crank sensor and then just fixed its self one day. There is nothin wrong with the tranny its self, just a sensor. I think the TPS runs about 150 bucks for a new one. I would maby suggest resetting the computer to see if it will fix it. hope this helps.

RB <img border="0" title="" alt="[Big Grin]" src="images/icons/grin.gif" />

Thanks for the input guys. I'll do some more inspecting and try resetting the computer like you mentioned Richard. I'll report back if any of that works.

I gotta get this thing working today to avoid having to call my buddy and tell him i broke his XJ <img border="0" alt="[Satan]" title="" src="graemlins/satan.gif" />

-Rob

After what KevinV mentioned about, I remember now that my friend's mustang was doing the same thing. I wouldn't shift normally. You would have to reach red line before it would shift. He took it to the ford dealer and they fixed. What they said was wrong was that a spring inside the transmission and come loose. After they replaced the spring it worked fine. I don't recall what spring they said it was, but I just remember that it was some spring inside the transmission. Hope that helps some.

Richard

I garrantee you its not internal. Its just a sensor, just gotta find whitch one. Should be the TPS on the go pedal. Its the lockup tq converter thats kickin in and out incorrectly and the TPS is what controls the tq shift.

RB

Damn I love my 5speed <img border="0" title="" alt="[Big Grin]" src="images/icons/grin.gif" /> I've had so many auto tranny troubles over the years I just gave up and wont buy one anymore. Sorry to hear about your troubles Rob. One more problem to add to the "HEEP". Get it? oh man I need help...

UPDATE: well, I'm still baffled as to what's causing this. Since i last posted, i've reset the computer, adjusted/reset the TV Link, and dropped the pan. The fluid was burnt (smell), but no containments, nor did i see any signs of metal in the pan. The filter also showed no signs of metal. But i went ahead and replaced the filter and fluid anyway. This makes me thing that perhaps i didn't burn out a clutch pack or cause any other internal damage, but i still can't find an explanation.

question, what would cause rapid RPM drop when you let off the accelerater (at any speed) such as i described earlier? I'm talking if i'm going 45mph let of the gas, engine RPMS drop to >1k. press the gas again and the RPMS have to climb to 2-3k before i get any power. is that a torque converter thing?

I *think* i did manage to get it to hit all 3 gears while driving today... though its really hard to get it to shift into 3rd. I think all the gears are there, just shifting is really mess up.

I was told the only things that could effect shifting in an auto tranny are the TV link (sometimes occpanied with a vaccum line that does upshifting and the TV just does downshifting, but not in my case) *OR* internel problem with the clutch packs as in i burnt one up. Make sense? or could there be more possible causes?

Any more thoughts? I'm fastly becoming a strong opponient of the automatic transmission.
I appriciate you guys advice <img border="0" title="" alt="[Big Grin]" src="images/icons/grin.gif" />

-Rob

Okay, guys. Stop. Rewind. Re-Play.

This is SO similar to problems I'm (AGAIN)having with my 91 Trooper. It is a cold start related problem. Up to operating temp., and the shifts are back to normal. Let me recap, based on the problems outlined above.

It'll stubbornly resist shifts up, and the high RPM gets scary. You have to push it hard to 3200RPM in first to MAKE it shift to second. If conditions require you to slow down soon after that, and it downshifts, you are back to zero. You have to push it hard again to make it shift.

After 20-30 minutes of this (we are close to 0 degrees this time of year, and its going to get worse), the gauges show the engine is warm beyond a certain point, the problem goes away. Once it's gone its gone. Until the next cold start, that is. So, for instance, every morning (or each night late, for the quick sprint down the road to the store) the problem is there. 20-30 minutes, give or take, depending on your mood, and whether you want to thrash the engine to warm it up a little faster.

Interestingly, I remembered something else. Just before I mention it, remember normal shifts would usually occur around 1400-1500RPM. First to second. This is in NORMAL mode. In POWER mode, what would be the shift point?? I don't have the exact RPM difference in shift points between NORMAL and POWER modes, but experimenting, using POWER mode during all this crap with the engine cold, pushes the shift point that exact difference above 3200RPM, not the original 1500RPM or so. I was experimenting with it. The POWER button will send the shift out even further. This has to have meaning. It is regular.

I was thinking a governor valve. Stuck. Up to operating temp., the surrounding aluminum body warms up, expands, and releases the stuck valve. I had convinced myself of this. But, thinking about this odd behaviour with the POWER mode button. When hot (normal operating temp) shift from first to second is about 1400-1500RPM. When cold (and playing up) the shift point is out to about 3200RPM. I haven't bothered to measure it exactly, but it is the same point everytime. In POWER mode, the shift point goes from 3200RPM, up to whatever...but it is the exact distance above the normal mode shift point at 3200RPM. Why? Assuming 3200RPM is a malfunction-related shift point, why is the POWER mode holding on (for later shifts) from 3200RPM. This tells me the POWER mode knows the shift point has moved out to 3200RPM.

Or I'm crazy.

Either way, I need serious help.

--Bighorn--