KZJ78: Wont Shift Above 3rd (1 Viewer)

[deepcrates]

Hi All,

Had my kzj78 sitting for a few weeks as I was traveling for work. Came back and took it for a spin and it wouldn’t shift past 3rd.

Also my gauge cluster lights kept resetting after I turn the car on each time. So I decided to get battery tested thinking it could be a battery issue. Turns out both batteries are faulty so I just popped two brand new red tops.

Took it out for a drive again and this time it would shift out of 3rd but it would do it very late. I’d be sitting at 3K rpm for a while before it decides to shift. Sometimes even maxing out the gear before it decides to shift.

Last time it was doing something fishy like this it was an ECU that had leaky caps. But I replaced my ECU last year. I also just opened the new ECU up to verify and its clean as a whistle.

Any ideas what else to check? Could it be a shift solenoid? Could be simply low ATF fluid. I added an ATF cooler months ago and the fluid level was good then. Could it be that since it’s getting colder the ATF cooler is keeping the trans to get up to temp. Didn't see any leaks when I just checked now.

Any other things I should check? Shift solenoid? Transmission flush?

 

[Tigris]

Hi All,

Had my kzj78 sitting for a few weeks as I was traveling for work. Came back and took it for a spin and it wouldn’t shift past 3rd.

Also my gauge cluster lights kept resetting after I turn the car on each time. So I decided to get battery tested thinking it could be a battery issue. Turns out both batteries are faulty so I just popped two brand new red tops.

Took it out for a drive again and this time it would shift out of 3rd but it would do it very late. I’d be sitting at 3K rpm for a while before it decides to shift. Sometimes even maxing out the gear before it decides to shift.

Last time it was doing something fishy like this it was an ECU that had leaky caps. But I replaced my ECU last year. I also just opened the new ECU up to verify and its clean as a whistle.

Any ideas what else to check? Could it be a shift solenoid? Could be simply low ATF fluid. I added an ATF cooler months ago and the fluid level was good then. Could it be that since it’s getting colder the ATF cooler is keeping the trans to get up to temp. Didn't see any leaks when I just checked now.

Any other things I should check? Shift solenoid? Transmission flush?

@deepcrates

Honestly I think it is still the ECUs fault. What I have learned when mine had the same symptoms was that the capacitors may look uncompromised and yet faulty. Electrolytic caps can leak "electrically" i.e. pass some DC voltage like a resistor of sorts without leaking any fluid.


The two shift solenoids are also suspect. I also replaced mine when I was troubleshooting my lack of shift to 4th.

If you haven't already, look up my write-ups on the ECU repair, shift solinoids, and ATF powered flush using the (Tigris) keyword.

Best of luck!

 

[Tigris]

Also, this may sound stupid but have you varied that your ETC button is not depressed? The ETC changes the shifting regime to taller intervals and no overdrive in order to make things easier when towing heavy. Just a thought.

 

[Gasha]

My money is on the cooler temps in the gearbox. Mine is the same on first drives in cold weather.
Regards

 

[AirheadNut]

Your symptoms sound a lot like the transmission issues I had with my first Prado, it wouldn’t stay in lockup when hot. Turned out to be the shift solenoids in the transmission. They were pretty easy to replace and fairly cheap. Doesn’t hurt to refresh the fluid and filter screen when you’re in there either.

 

[deepcrates]

Also, this may sound stupid but have you varied that your ETC button is not depressed? The ETC changes the shifting regime to taller intervals and no overdrive in order to make things easier when towing heavy. Just a thought.

Thanks Tigris! I did have the button pressed down. However, even after doing that still had the same issues.

I’ll replace the ECU with my old one (traces were messed up due to the leaky caps but soldered in jumpers and seemed to have worked). I’ll see if that changes anything.

I’m wondering if adding my auxiliary transmission cooler makes it more difficult to warm the fluid up enough for the transmission to shift in this colder weather (just below freezing lately). I tried warming it up for 5 minutes and driving leisurely around before trying to speed up into 4th.

I ordered shift solenoids but after searching your post I wasn’t sure which gaskets to buy. Lots of A343F for newer cars but not for my specific year.

Thanks all for your replies!!! I’ll keep you all posted on what happens next.

 

[deepcrates]

My money is on the cooler temps in the gearbox. Mine is the same on first drives in cold weather.
Regards

How long do you warm up the truck before you notice it goes back to normal? I’m wondering if my auxiliary transmission cooler is making it more difficult to warm up. I’m gonna put some cardboard in front of it to see if it helps warm things up.

 

[deepcrates]

Your symptoms sound a lot like the transmission issues I had with my first Prado, it wouldn’t stay in lockup when hot. Turned out to be the shift solenoids in the transmission. They were pretty easy to replace and fairly cheap. Doesn’t hurt to refresh the fluid and filter screen when you’re in there either.

I bought some shift solenoids. Was there any filters you bought or do you clean and reuse the filters.

 

[AirheadNut]

I bought some shift solenoids. Was there any filters you bought or do you clean and reuse the filters.

Here's a link to the info and photos I posted at the time: Builds - 1990 LJ78 in Montana - https://forum.ih8mud.com/threads/1990-lj78-in-montana.914546/post-10295666
The filter is just a metal screen, it can be cleaned out with solvent and compressed air and reused. I believe that any A343f pan gasket should work, they should all be the same. New solenoids are smaller and slightly different than the originals, but they fit fine.

 

[Jae Jae]

Hi, was the car sorted? If so what was the issue may I ask..