KZJ78 Transmission problems

A month or 2 back my 94 Landcruiser, KZJ78 started dropping down a gear as I was cruising on the seal, usually on an ever so gentle down slope. It wasnt overdrive, it was the normal gears. Might not happen for 50km's, might happen in 5km's. Very sporadic, and sometimes I might get 100 km's or more then it would do it several times. I turn the overdrive off for a minute or 2 travelling at about 3000rpm/100kph, then switch it back in to overdrive and it seems to go away until next time, or it could do this every 5 minutes for ages. Bloody frustrating.
Has been to mechanic 3 times, first time had the oil all drained, flushed, filters cleaned and new oil put in. Worked for about 100km. Second time the mechanic fitted a large as accessory oil cooler cos he said the original oil had been heated. I had towed a trailer a couple of times where the AT Temp light came on, so knocked it down a gear or 2 until it cooled down. Third time was last week and he replaced 3 wires in the loom that may have been shorting, possibly the sensor sender wires, who knows.
Went for a big arsed drive today and bugger me it still does it. totally random, no rhyme or reason when it will do it. Drove 50km, dropped down, did the old Overdrive off for a minute or 2 and it fixed it. Drove over another 100km and then it started at ti again.
Any one have any idea of where I start looking to find the fault?

Throttle position senso if it has one perhaps

Quite possibly the ECU, common on the KZN130 surfs to loose overdrive etc, there’s a guy in Nelson who was on to it fixing the ECUs use to just post them to him, can’t remember what he’s was called, might find him on google or trademe

Have changed ECU, no changes to trans, same, same. Its dropping down from top gear with the overdrive on, seems like its top gear, not overdrive.

Yes, would think along Mimms2 line and is it really worth ploughing too much money into, when a refurbished auto unit would go 3-5K??

They're a bugger when they do that stuff, and an expert will pull it down and tell you "oh it was a solenoid wire that had lost its insulation. $30 part.

My Safari started doing something very similar 6 years ago so I picked up a manual box for 5 hundy and a clutch plate at 8 hundy and machining the flywheel at $150 and two days under the beast and its a manual now. Very happy :)

No, couldn't be arsed. Don't say I notice any difference. Will gps both the Y61's at 2 grand and see if there's a difference. The shorty was a manual from the get go and the LWB was an auto. Will get back to ya.

Very little fucking around actually. All mounting points are identical. Front drive shaft identical. Crossmembers identical. Clutch footbox just has a plate bolted across it on the auto. Brake pedal just needs a parting off wheel through it to reduce its size to manual version. Was two days work. And that's counting heaving the gearbox off the wife when she got stuck under the transfer case as the fuckin trolley jack had a slow leak in it:o

our bog std terrano did something similar years back....scratching head I believe it was the switch on console that changes the way the auto decides to change...we used to call it american or european...one revs way higher before changing eg holds gear for longer ,the other changes at much lower revs.....
disconnected offending switch and havent had issue since...

Quote:

---

Originally Posted by mimms2

Upgrade to a nissan :P

Got me. Prime reason I don't deal with "automatic" and computer controlled shit. I like levers.

Rattling a brain cell or two, torque sensor? Crank angle sensor? wheel speed sensor? Some computer fucking sensor?
Can you have fault codes read? (OBD)

Solenoids all tested good? Valve body clean?
I've heard that flushes on higher mileage wagons can stir up crap, which then leads to failure.
How many kms? might not be worth mucking about.

---

My Nissan Safari used to do it. Had it into auto trans specialist, no joy. Read online that it was a common problem. Connection for the trans juice temperature sensor was sloppy, registered too low a temperature and it would lock out the long cogs. Pulled it apart, cleaned and tweaked the contacts. Never had the problem again.

Quote:

---

Originally Posted by mimms2

Was just curious as I looked at buying/converting, as many people gave up on their auto boxes at 2-300km. Thought it might be cheaper but by the time you have to fuck around the entire driveline, didn't seem economical.
Check your chassis number for what diffs it came with.
Also depends what you want out of it as well. Taller obvious better for highway, lower for mud fucking.
Think some of the SD33 MQs came out with 3.9 diffs, which could be put behind the TD42 to plow 37" tyres all day long. Probably top out at 60 on the road, but they'll peel the skin well off your pudding.

---

You have the gearing mixed up, you want the 4.6 heads for 37” tyres.
All td42 GQs likely have 4.1 (both auto and manual) the TB42 y60s I have seen have the 3.9
The RD28 gqs have the 4.6 (hard to find) everyone wants them...

That’s a diesel right?

My ‘96 series 80 developed symptoms like yours.

Similar numerous diagnostic interpretations

We ultimately traced it back to a failed injector pump.

Goes like a rocket now!!!!!!

Thanks guys, I've been taking all these ideas and passing them on to my mechanic. He's trying all the "simple" ones first cost he's reluctant to spend my money on anything major, in case it turns out it was a simple fix - I like that thinking. He is concerned with the state of the oil he took out of the sump, but tells me it was only burnt oil, no sludge or bits of "stuff" etc. And is now leaning towards it being more than a simple fix. The trans model is A343F.

Simple as mud! Are the 3 wires all in to the same plug thats on the side of the trans? This is sounding like I could actually do that.

Quote:

---

Originally Posted by small_caliber

Yes they are, the connector will be on the passenger side toward the rear of the case and you should be able to back probe the plug there.

The solenoids are supplied 12v+ through the wire and earth through the case.

Use leds (which have a + & -) for the lights NOT a bulb

---

Excellent, when I can find some spare time I will give it a crack. We're in the middle of the harvest right now so not much spare time. Thanks small_calibre, much appreciated.