Any automatic transmission guru's in here?

Olivedrabcj7 · Jul 24, 2015

99 Jeep WJ with the 42RE. Took it out for a shakedown run after the axle swap. First time I have driven the jeep for more than 10 minutes since I have owned it.

We are on the first trail of the day and about 15 minutes into it, i go from park to 1st gear on the shifter and try to accelerate and the jeep bogs and dies. I put it back in park and try again. Same thing over and over. It wont move. It will idle in gear just fine, but once you press the gas pedal it will try to move and then stalls the engine. It does not have these symptoms in reverse. It will sling rocks in reverse. Put it back in any forward gear and floor it and it stalls.

Towed it off the trail. It runs ok on flat ground but lacks power. If you try to accelerate hard it falls on its face. Try to powerbrake and it stalls. Put it in park or neutral and you can floor it and the engine will rev to the moon and back without hesitation.

Replaced fuel pump
Replaced fuel filter
Cleaned throttle body
Scanned for codes (none present)

It only does this when its warmed up. When cold or after sitting overnight it has no symptoms, shifts perfectly and has power in all gears.

Is this a solenoid problem? Stuck in a high gear? Pump? Clogged filter? Something else? I dont feel like it is engine related because it has 100% power in reverse. This is only when it is in a forward gear does it fall on its face.

Any guru's want to take a stab at diagnosing this over the interweb?

LightBnDr · Jul 24, 2015

Dang I personally hate diagnosing on the phone or Internet but here it goes.

I run the same Trans and have built more than 50 of them.

Sounds like you have a multiple gear tie up combined with the TCC engaged. Typically the gov pressure solenoid and transducers give all the trouble in any of the RE designs.

Though they only cause 2nd and 3rd gear starts which just feels like super sluggish but doesn't cause any stalling.

A stalling condition only when in gear is usually a TCC engagement at idle.

That can be as simple as TCC stuck on which is rare especially if you only wheel this rig because unless you run in second gear at high speed or faster, the TCC never engages so the solenoid doesn't really get hot/worked.

Plus the solenoid is normally open so if it fails its designed not to engage TCC at all.

So the best idea I can give is the converters in Chryslers have pretty junky for a long time and if it's ever been rebuilt, no telling who reconditioned the converter. I would be more inclined to say a TCC issue but honestly I didn't see that issue in anything but a 48RE behind a diesel.

Like I say much smarter to diagnose in person to actually feel what's going on.

Best test right now is warm it up. Duplicate the stalling. Unplug the Trans. See what it does.

With it unplugged it operates 100% hydraulic default. Should start in 2nd/3rd gear and feel sluggish but should not stall. If it does, I'm still looking at more than just the Trans.

I posted this and then re read your original.

If it idles like a champ in gear, it can't be TCC engaged in the converter. It will die immediately if TCC is engaged. So rather than delete anything I said above, maybe it will help with another prob in the future.

I'm lookin somewhere else for the problem at this point

Olivedrabcj7 · Jul 24, 2015

Thanks for taking the time to help with this and hammer out the lengthy reply.

Scenario: when its acting up, if I get on flat ground and hold the brakes, put it in gear (any forward gear) and then press the gas while holding pressure on the brake pedal, the engine rpms will come up from idle to 1100-1200 ish and then drop to almost stall, and then back up and down over and over and over as long as I am holding the gas down. Put it in reverse while holding the brakes and press the gas, it will powerbrake and spin the tires on asphalt, no hesitation.

Like you, I thought about the TC lockup as a possible problem. But after thinking about it, if the TC were locking up it would stall as soon as its put in gear.

This is almost acting like the engine is defueling under load. Sort of acting like a rev limiter or something.

LightBnDr · Jul 24, 2015

I absolutely hate being wrong. Ask joho

There is a laundry list of things I'd be going after but since I can't put hands on it, I don't really wanna lay it all out. Lol

First thing that comes to mind though is when in forward range the engine torques one direction so I'd look at the harness leading to the crank sensor for chafing and rubbing the firewall. I just wouldn't expect temperature to effect that though.

Other than that man good luck to you. Post up what you find

Olivedrabcj7 · Jul 24, 2015

Replaced gov pressure solenoid and sensor. No change.

Replaced throttle position sensor. No change.

patooyee · Jul 24, 2015

LightBnDr said:
Dang I personally hate diagnosing on the phone or Internet but here it goes.

I run the same Trans and have built more than 50 of them.

Sounds like you have a multiple gear tie up combined with the TCC engaged. Typically the gov pressure solenoid and transducers give all the trouble in any of the RE designs.

Though they only cause 2nd and 3rd gear starts which just feels like super sluggish but doesn't cause any stalling.

A stalling condition only when in gear is usually a TCC engagement at idle.

That can be as simple as TCC stuck on which is rare especially if you only wheel this rig because unless you run in second gear at high speed or faster, the TCC never engages so the solenoid doesn't really get hot/worked.

Plus the solenoid is normally open so if it fails its designed not to engage TCC at all.

So the best idea I can give is the converters in Chryslers have pretty junky for a long time and if it's ever been rebuilt, no telling who reconditioned the converter. I would be more inclined to say a TCC issue but honestly I didn't see that issue in anything but a 48RE behind a diesel.

Like I say much smarter to diagnose in person to actually feel what's going on.

Best test right now is warm it up. Duplicate the stalling. Unplug the Trans. See what it does.

With it unplugged it operates 100% hydraulic default. Should start in 2nd/3rd gear and feel sluggish but should not stall. If it does, I'm still looking at more than just the Trans.

I posted this and then re read your original.

If it idles like a champ in gear, it can't be TCC engaged in the converter. It will die immediately if TCC is engaged. So rather than delete anything I said above, maybe it will help with another prob in the future.

I'm lookin somewhere else for the problem at this point

I don't have trans issues, nor the trans in question, nor ever plan to work on transmissions for a living. But I WOULD give several cases of beer for an opportunity to come build a few transmissions with someone like you who can explain it all in depth to me as we go.

joho75287 · Jul 24, 2015

LightBnDr said:
I absolutely hate being wrong. Ask Joho

True story....but he hates a noob having to go back and redo work he did already even more! :****:

Olivedrabcj7 · Jul 24, 2015

Video of what its doing. This is holding the brake pedal and half throttle
https://youtu.be/jUXvFy5U68U

Olivedrabcj7 · Jul 24, 2015

Further diagnosis:

When powerbraking I noticed the engine raising up on the drivers side by an inch or more. I put a ratchet strap from the drivers side motor mount down to the axle to prevent the engine from torquing. Voila, i can spin tires (yee yee). This issue is completely related to physical engine movement while under load. Prevent the engine from torquing over and its 100%. Something is happening when the engine moves that is killing power, as the engine falls from the removed load it gets power again. Sounds like a wire shorting somewhere to me. Any ideas?

LightBnDr · Jul 24, 2015

I thought I covered this above?

Number rule of fight club......... Never replace electrical parts unless you know they have failed

Did you look at the crank sensor harness?

Olivedrabcj7 · Jul 24, 2015

Cant see the CPS harness itself but there is nothing else back there that could be causing this problem. The rest of the engine wire harness is on the passenger side which is getting slack as the engine torques over. I looked for wires on the drivers side that could be being pulled as the engine rotates over but there is nothing to see. Has to be the CPS rubbing the firewall or bellhousing

LightBnDr · Jul 24, 2015

Hey this is part of the first rule of fight club. You better put hands on that thing and see an issue before you replace it.

I say that because now when your on the trail your gonna have some kind of issue and a guys gonna say, man that sounds like a TPS and your gonna say no way it can't be I just replaced it 4 months ago.

Then next week your Trans is gonna start in 3rd gear and your gonna say no way I just replaced the gov solenoid and transducer.

Is your name Tyler Durden ?

Lol, middle finger joho

In all seriousness, find the problem and fix it once. Like measure twice cut once

grcthird · Jul 25, 2015

Look at your motor mounts, if they are torn and allowing more movement than normal, this will cause wires to be pulled out of place like you are experiencing.

Olivedrabcj7 · Jul 25, 2015

Thanks for the help. Still not sure what wires could possibly be pulled the way the motor torques toward the pass side. There are no wires on the drivers side of the motor to pull. I havent had a chance to get to the crank sensor yet. Im at a kids birthday party this afternoon. I may try to mess with it tonight when I have some time and it cools down outside. Im betting big on the crank sensor hitting something when the engine torques over. There arent many other sensors on the 4.0 that will cut power like this.

biggin · Jul 25, 2015

My yj would start sputtering and die when I would bounce up on something when hitting stuff pretty hard. Pissed me off to no end! Figured out that I had my Trans tucked up to the body so much that when the force of the jeep coming down hard, the body would hit the cps and deflect it off of the fly wheel. I cut a hole in the floorboard/firewall area and it stopped. I bet your engine and transmission is torquing up and hitting the body on the drivers side due to a bad motor mount.

Olivedrabcj7 · Jul 26, 2015

Problem solved.

Main engine harness had a short where it passes behind the valve cover. Bolt had rubbed through the bottom of the wire loom and was shorting a wire to ground. Taped it up and zip tied the harness up out of the way. She runs like new.