Help needed diagnosing intermittent overdrive '99 Gen 2.5

[nckwltn]

Update 4

After 3 months and several thousand miles, the problem is back. I suspect an overdrive solenoid, and posted a picture earlier in the thread, however, that is not the transmission that I have.

On closer inspection, I have a 30-43LE trans. It appears to be common in a lot of vehicles.

I removed what I thought was the overdrive solenoid, only to find that it wouldn't come out all of the way, and the part that was in the trans was connected to a spring. I didn't want to yank the spring out. I found a picture of another 30-43LE and circled the piece that I tried to remove.

Anyone know that the circled thing is?






Link to list of other vehicles with same transmission: http://msport97.proboards.com/thread/9944/

 

[Toasty]

How are you checking your fluid level?

 

[nckwltn]

How are you checking your fluid level?

Vehicle running, after having driven several miles (the last couple of times was after I got home after my 18 mile 60+ mph commute) on a fairly level surface, but does have a slight slope where the rear of the vehicle is lower. I'll stop in a dead flat parking lot and check again today.

What's strange is that after doing the fluid flush in October, it has been working great up until last week.


I did notice that on my drive home yesterday, as soon as I let off the gas after having the intermittent problem during that drive, even when OD engaged my RPM would immediately drop 500 or so... today, on my drive to work, before I started having the problem the RPM didn't drop at all when letting off the gas. Indicating that yesterday my torque converter wasn't fully locking up yesterday... right?


The problem usually only happens after everything is well warmed up.... which kind of has me thinking temp sensor at this point.

 

[Toasty]

Running and in Neutral? I believe Park does not engage the pump which could give you a false full reading. Or so I can remember.

 

[nckwltn]

Running and in Neutral? I believe Park does not engage the pump which could give you a false full reading. Or so I can remember.

In park for sure.... will test in neutral, Thanks for the good suggestion!

 

[nckwltn]

Running and in Neutral? I believe Park does not engage the pump which could give you a false full reading. Or so I can remember.

Did the check with car in neutral after a 40 min drive home at about 50 mph.... fluid came up right in the middle of the marks on the dip stick. I had an extra 1/4 quart and dropped that in this AM just for fun.... From what I'm reading the 30-43LE trans is pretty solid, so I'm leaning toward something electrical telling the transmission not to stay in OD or lock the converter.... will probably go with figuring out how to measure the temp reading in real time while I'm driving.

 

[KyleT]

Maybe a throttle position sensor issue? I believe there is a check to confirm or recalibrate it.


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[nckwltn]

Maybe a throttle position sensor issue? I believe there is a check to confirm or recalibrate it.


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Not sure, but happy to give it a go and report back!

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[nckwltn]

***update

Drove around in the SoCal rain over the weekend, totally lost overdrive for a couple of days.

After a 40 minute drive home I crawled underneath, tapped on the trans temp sensor a little, and noticed that on the connector on the other side of the transmission looked like it had some electrical tape wrapped around the wires.

I moved the wires around a little and then drove 40 minutes with no transmission issues.


Will investigate further this weekend, but this all seems to be pointing to the temp sensor.

 

[nckwltn]

Still no luck figuring this out. I tapped into the wiring harness that goes between the TCM and the transmission. There is a connection below the radio. When the trans slips out of 4th, the TCM is sending voltage to the solenoid that engages 3rd.... all of that to say, the trans isn't going into 4th because the computer isn't allowing it...

This rules out the shifting solenoids in the transmission. I've also checked the TPS and it seems to be working according to the voltages and resistance. Right now I'm monitoring the trans temp sensor to see if it is flaking out.

But I'm almost thinking the might be a TCM issue. The one thing that leads me away from this being an electronic issue is that when I started having the issue bank in October I changed the trans fluid (with mitsu diamond) and the trans shifted great for the next 3 months....




Anyone have a spare TCM for a gen 2.5?

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[howirolla]

This ever get solved? Mine just started doing the same damn thing.

 

[nckwltn]

This ever get solved? Mine just started doing the same damn thing.

Not sure.... I swapped out the TCM and haven't had the problem since... however, the problem seemed to crop up when in colder and humid/moist conditions..... going to have to wait to verify if fixed.

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[yatin_ash]

I've the exact same thing going on with my OD...
Were you guys able to solve this?

 

[nckwltn]

I've the exact same thing going on with my OD...
Were you guys able to solve this?

can't say for sure if it's solved or not. Have a new daily driver so doing very few miles on the Montero. But after the TCU swap, it's been working great. The TCU swap even included an off-road trip covering 500+ miles of trail and pavement.

If I had to guess, I'd say find a TCU from a gen 2.5 and swap it out. Takes about 10 minutes.

 

[yatin_ash]

I've been through fluids, sensors, solenoids. Now I'm checking the torque convertor cause I'm getting P0741. I scanned on a professional scantool & it says torque convertor does lock. My guess is cause of overdrive the torque convertor is slipping. TCU will be next.

Mine is a Gen 3 but I've seen soo many posts for the same problem of almost every montero variant.

Thanks for your advice.