gearbox slipping under load

[Fozza]

got the bad news that i might be in for a rebuild of my auto on my NS DiD (200,000+ kms on the clock).

when i started towing my van i wasn't aware that i should be towing in 4th and was towing in D. going up a slight incline the paj went into limp mode and N started flashing. turned the car off and then back on to finish the trip. i cleared the codes and couldn't really get a straight answer as to what the issue was.... fast forward a few months, been towing the van in 4th on the highway and then when i come into town (60kph) i just switch into D. but going down a hill and then back up the paj changed to 5th and then went to limp mode again.

i've been to see quite a few mechanics and spoken to a few auto trans guys and all signs are pointing to an overhaul of the gear box which is not going to be a cheap exercise... will be going to see a recommended auto trans specialist as soon as they're back in on Monday... will get his opinion but am fairly confident it'll be the same. the codes coming up are the incorrect ratio for gear 5 and the last time it came up with incorrect ratio for gear 4 as well. I think the codes were P0735 and P0734. I had the tran fluid flushed as part of a full service just before the last incident as well so confident it's not bad fluid.

i'm taking off on a 6 month trip with the young family in a couple of months so need to have the car in top notch as can't risk getting into trouble in the outback. thinking about just going all out and spending the extra money on the heavy duty valve upgrade from wholesale automatics...

anyone had any similar issues and any recommendations of what to do before going for a full rebuild? thanks in advance

[4wd26]

are you keeping an eye on the auto temps whilst towing?
if so what temps are you generally sitting at

[Fozza]

are you keeping an eye on the auto temps whilst towing?
if so what temps are you generally sitting at

No. I don'thave a temp gauge installed and my obd app doesn't seem to have that functiom either. I'm using the torque app

[KrAsh]

Look at a trans cooler, inline or ditch the factory one in the rad altogether.

How was the oil when changed, was it discoloured, smelt burnt? Generally autos die from kickdowns and labouring, but there are usually telltales to what's happened. Towing in 4th isn't gospel, just be wary of the terrain you are in.

The limp mode definite gearbox related, not a VGT issue? I'd find a second hand box first before going the rebuild, they aren't known to be a weak box. We towed a tandem trailer full of karts and race gear no issues in D.

[old Jack]

but going down a hill and then back up the paj changed to 5th and then went to limp mode again.

The Auto is electronically controlled so sensors send signals to the AT ECU and the ECU controls the solenoids that operate the hydraulic valves. How do you know that it wasn't an electrical fault that caused the limp mode rather than a actual condition within the transmission. I cannot see why the trans would go into limp mode when going downhill as the load is removed from the trans.

OJ.

[DaveE66]

Had a similar issue with my ns when I had the first version of the Tc lock up switch. Mine would go into limp mode as soon as it dropped into 5th gear.
Turned out to be the 5th gear solenoid died.
Mechanic replaced with a new one and I have not had an issue since that was over 50000 kms ago.
The tc lock up switch caused the issue with mine.
I would get that checked first.
Can be replaced without removing transmission. Mechanic removed the pan and was able to access from there.

Dave

[Fozza]

The Auto is electronically controlled so sensors send signals to the AT ECU and the ECU controls the solenoids that operate the hydraulic valves. How do you know that it wasn't an electrical fault that caused the limp mode rather than a actual condition within the transmission. I cannot see why the trans would go into limp mode when going downhill as the load is removed from the trans.

OJ.

It only does it on incline. Has done it a few times and always on incline under load. Can see how my post could be misread. Meant to say I was towing in D because was in 60k zone it changed to 5th going down a hill and then slipped and went into limp mode going up a hill just after coming down

[Fozza]

Had a similar issue with my ns when I had the first version of the Tc lock up switch. Mine would go into limp mode as soon as it dropped into 5th gear.
Turned out to be the 5th gear solenoid died.
Mechanic replaced with a new one and I have not had an issue since that was over 50000 kms ago.
The tc lock up switch caused the issue with mine.
I would get that checked first.
Can be replaced without removing transmission. Mechanic removed the pan and was able to access from there.

Dave

Cheers. Will definitely get that looked at first

[Dicko1]

I would fit an Ultragauge to get an accurate auto temp readout,. It could be the auto temp putting you into limp mode.. I,ve seen my auto get to 110 when going up a hill in D. i4th in sports mode greatly reduces temps. Great unit for monitoring your temps whilst towing. Most people who think they are going along sweetly in an auto towing in D done have an auto temp display and would be very surprised at the high temps of the transmission.

[Fozza]

Look at a trans cooler, inline or ditch the factory one in the rad altogether.

How was the oil when changed, was it discoloured, smelt burnt? Generally autos die from kickdowns and labouring, but there are usually telltales to what's happened. Towing in 4th isn't gospel, just be wary of the terrain you are in.

The limp mode definite gearbox related, not a VGT issue? I'd find a second hand box first before going the rebuild, they aren't known to be a weak box. We towed a tandem trailer full of karts and race gear no issues in D.

Mechanic said oil was ok. gettinga 2nd hand one was my first thought as well but the thought of picking one up that had some issues scares me a bit. Probably worth looking into again. Cheers

[craka]

Like the other said, get a scanner and see what your auto temps are. From memory if too hot the auto shutsdown by design and the 'N' will start flashing.

Just read further and saw you have the torque app. It can read auto temp, but you have to configure a custom PID. I know I have my configured that way, I'll see if I can find the information, pretty sure it is on these forums somewhere.

How long since auto was serviced? What auto oil is being used? As from all reading here the auto in these beasties are quite particular on what they can use.

Found the link on how to configure torque pro with auto temp guage https://www2.pajeroclub.com.au/forum...ad.php?t=47197

[old Jack]

Does the NS have the Jatco or Aisin trans fitted?

OJ.

[craka]

Does the NS have the Jatco or Aisin trans fitted?

OJ.

Jatco I think. Why?

[KrAsh]

gearbox slipping under load

May or not be a related symptom to cause the issue but anyway.

Our NS when comes out of lockup does a big flare before taking up again, this will happen when going uphill at a cruise speed or even a kickdown for a lane change or speed up. I recall this being a similar thing in the two Pajero my old girl had early 2000s. Maybe just a trait of the 5spd I'm not sure as only been in three cars that do it. Does it everytime, has also thrown the ASC off light a couple of times. Silly logic in the parameters as it always unlocks too late , even a slight tap of the pedal doesn't unlock it where in most autos I've driven you can do this to preempt the additional acceleration.

Got me stuffed

[old Jack]

Jatco I think. Why?

The PB/PC Challenger has the same 5 speed Jatco auto fitted but it has a higher stall ratio torque convertor, TC lockup only 4th and 5th and a very poor ECU program. When the trans was fitted to the Pajero it had TC lock up in 3rd, 4th and 5th and a lower stall ratio TC and better ECU programming so it is less inclined to go into limp mode when working hard.

Common myth is the "limp modes" are generated by excessive ATF temperatures but the "AT Temp" warning light does not illuminate. My belief is the trans is going into "limp mode" because of excessive TC slip at a given vehicle speed and throttle position over a certain period of time. When you get the "limp mode", power is cut and the "N" display flashes, remove foot from the accelerator, place trans selector into "N" and then back into "D" and gently apply the accelerator, this will reset the limp mode whilst the car is in motion. Sure the excessive TC slip causes elevated ATF temps but adding an extra ATF cooler does not prevent the "limp modes", monitoring ATF temps, using 4th and keeping an eye on the rpm vs speed can almost eliminate "limp modes" but it is not exactly a relaxed way to go travelling.

Plenty of reading in these links;

https://www2.pajeroclub.com.au/forum/showthread.php?t=26645

https://www2.pajeroclub.com.au/forum/showthread.php?t=51723

https://www2.pajeroclub.com.au/forum/showthread.php?t=53736

https://www2.pajeroclub.com.au/forum/showthread.php?t=36892

I have also seen the Jatco box go into "limp mode" caused by a faulty engine coolant temperature sensor/wiring, it was over reading and this cause the Engine ECU to signal the AT ECU to put the trans into "limp mode" even though the engine coolant was not too hot. There are multiple sensors that feed information to the ECU's and if this information is incorrect due to faulty sensors and/or wiring then false l"imp modes" can be triggered.

For the OP who's auto has done 200,000kms, yes it may or may not need an overhaul but I would be eliminating the electrical side of the system first and start monitoring ATF temps first.

OJ.