Dion's WD21 Terrano

Some time last year (or maybe 2011?) I bought a WD21 Terrano, TD27T, automatic, off eBay. It sat in my yard for a while waiting for a roadworthy and some love; the previous owner had sold it in frustration at not being able to fix the auto gearbox, which has some really strange behaviour. With the TPS plugged in, it was completely clueless, flaring really badly between gears and never locking the TC in OD. With the TPS unplugged, it shifts at the low throttle point without flaring (very firm in fact) but it locks the TC at 60km/h, which is inconvenient without much power from the engine. Accelerating onto freeways is difficult. It almost seems like an issue with the line pressure solenoid, so thinking I was clever I swapped the box out for another, which is a shit job without a hoist.

It didn't change anything. I had some big $$$ problems with my D21 so I got the Terrano roadworthy and registered and towed a bunch of crap with it while I moved house, including my old D21:


Whilst towing one of the less heavy loads (go figure), it overheated randomly. That was a problem that would resurface later. I swapped the TCU and "ECU" (really just an EGR controller that also feeds RPM signal to the TCU) with other units, still no change to the behaviour.

I put some D22 wheels and tyres on, they rub the chassis on the front pretty bad at full lock. I've been living with it.


I figured out the water pump would leak when the system was at low pressure and sitting for a while (hence the random overheating; leave it for a while and it has no water), plus I had never heard the fan engage fully so I replaced the water pump/clutch assembly with a no name eBay special. None of the bolts were seized! The block looks alright:

When I pulled the radiator to replace the water pump, it crumbled in my hands, so I ordered a new radiator, the most expensive on eBay. It's made by KoyoRad (Japanese company, made in Indonesia), aluminium (painted) core, plastic tanks, but with really a nice plastic moulding finish, and well put together, so I guess the money goes somewhere:


Unfortunately I couldn't buy one for an automatic (the trans oil cooler runs through the radiator bottom tank), only the manual one, so I needed a trans oil cooler too. A separate cooler is high on the list of recommended mods for the auto W/D21s so I didn't mind too much. I bought a "large" oil cooler made in Canada by Long with 5/16" barbs from eBay and mounted it to the air con condensor on the driver's side, as there's not much space (it just clears the grille) and nowhere better to put it. Still space for a thermo-fan on the passenger side for when I decide the aircon doesn't work in summer traffic:


That's about all so far; still trying to fix the auto box (you can't get an english language FSM for this imported model) and much more to do, but keeping it on the road is work enough for me at the moment.

G'day dion.
Sounds frustrating with the trans prob.
When I bough mine the guy thought the trans was buggered but all it needed was about a litre and a half of trans fluid put and all was good again.
Re the d22 alloys I'm running a set on mine with 23/85/16 tyres it scrubbed quite a bit to start with but all I did was use a couple of 8mm spacers and a set of rear wheel studs(they're longer) and adjusted the lock stops.
Still has a good turning circle and doesn't touch at all even when on stupid angles out bush.
Cheers craig.

Sounds like the basic auto operation is fine,its just not getting the right signals at the right time
Could it be vacuum related ?
Some of those older autos use a vacuum diaphragm setup to determine when to shift
Just a thought

Thanks guys, keep the ideas coming, I'll try anything.

I've cycled the fluid up and down around the "full" point and it seems not to make any difference. Swapping the whole transmission ruled out all the solenoids and most of the sensors. Surprisingly these transmissions are fully electronically controlled. I've adjusted the TPS throughout it's range and swapped in another one, still no behaviour change.

I have a theory that the line pressure control, which includes an inline resistor, might be at fault. When I next have time I'll pull off the drivers kick panel and try to track it down.

When you changed oil did you drop the pan and change filter?
Have you done a full flush as a considerable amount of oil stays in torque converter
There used to be a product designed to clean oil sludge and free sticky valves b4 u do a complete flush
Goodluck,im sure you will solve it

I can only think about this from a D40 perspective, but it seems like the functions are similar.

If the box is locking the TC at too low a speed, then either the revolution sensor on the gearbox (which is how that car should be getting its speed reading) is wrong, or that signal is being misinterpreted by the gearbox. That's one problem - and it might be affecting the gear change issue as well.

No expert on those boxes, just throwing out an idea.

sparra04 said:

When you changed oil did you drop the pan and change filter?
Have you done a full flush as a considerable amount of oil stays in torque converter
There used to be a product designed to clean oil sludge and free sticky valves b4 u do a complete flush
Goodluck,im sure you will solve it

Click to expand...

Thanks Sparra. Changed the whole box over, but when I did that I didn't change the filter, no. I guess I should. When the box came out the TC got emptied.

Old.Tony said:

I can only think about this from a D40 perspective, but it seems like the functions are similar.

If the box is locking the TC at too low a speed, then either the revolution sensor on the gearbox (which is how that car should be getting its speed reading) is wrong, or that signal is being misinterpreted by the gearbox. That's one problem - and it might be affecting the gear change issue as well.

No expert on those boxes, just throwing out an idea.

Click to expand...

Hey Tony. The TC is locking at a low speed because it has no TPS signal because it's unplugged; the default position seems to be "idle throttle". With the TPS plugged in it only locks the TC above 70% throttle (this doesn't change when you adjust the TPS); this is bad because in order to get the TC to lock at highway speeds, you have to plant it, and that just makes you drive everywhere at 130km/h and 20lphk. :S

What about a switch in the TPS so that when on, the TPS is connected and the TC doesn't engage unless you plant it (normal operation) but if you want it engaged at 80km/h, throw the switch and off it goes?

Yeah that's an option, or easier still I can just put a switch on the TC itself and control it manually... but something is still wrong and the flaring between gears makes it undriveable with the TPS plugged in. I'd like to find the root cause. It's just proven to be a difficult nut to crack.

The TPS is just a variable resistor, right? Could it be worn, providing an erratic return signal?

Yeah it's just a potentiometer and two switches (full throttle & no throttle from memory). I've measured the resistance throughout the range on both the TPSs I have, one has a dead spot, the other is all good, no matter which one I put in the car the behaviour is the same.

Then it's the interpretation of the signal from the TPS, can't be anything else - if the TPS is good, and the electrical connections to the TPS are good, then it's the transmission controller. I assume that's external, which is how you control the TC (and we can't in the D40, because the TCM is internal) - did you change that when changing the gearboxes?

The TCM is external to the gearbox, it's in the rear right quarter panel (as far as possible from the gearbox; Nissan cut that crap when the copper price went up) and the "ECU" (EGR controller) is in the rear left quarter panel. I've replaced both, at separate times and separate to swapping the gearbox (one variable changed at a time). No change to behaviour. Unplugging the ECU makes the TCM dumb to the engine RPM, but it still has input shaft speed to be able to make decisions so it doesn't change the behaviour. Unplugging the TCM puts it into limp mode (permanently 3rd gear, TC unlocked).

I think it's in the wiring. I'll measure the dropping resistor on the line pressure control tomorrow, and see if it matches whatever random RE4R01A manual from a similar era I can find, since there isn't an english manual for my car available.

So the dropping resistor is on the RHS guard under the bonnet, it's a big ceramic JECS unit. Mine has a resistance of 12ohms; the service manual I found for a skyline or something (same trans) had an allowable range of 11.5 to 12.5 ohms, so I guess it's fine. But, when I drive the car with the TPS plugged in, and the dropping resistor unplugged, the boosted line pressure almost gets rid of the flaring problem. It's still detectable, because acceleration isn't smooth, but now I can use 4th gear TC unlocked and freeways aren't such a struggle.

So still a mystery but getting closer. Can anybody with an auto Terrano tell me when their torque converter locks? Mine doesn't lock on the freeway unless I absolutely plant it... Come off the throttle and it unlocks.

Haven't touched this thread in a while.

End of 2013 the engine seized and I haven't looked to see what went wrong.

Started rebuilding and turboing the QD32 to drop into it.

Stripped and cleaned:


Honed:


Fresh welchies:


The head had the typical cracked pre-combustion chambers... When I sent the head off to get hot tanked, valves re seated etc I got them replaced, not sure if it helps as they'll crack again pretty quick but it feels wrong putting the head back on with them all messed up.

Photo from part way through assembly, just before head went on:


Welded in a 1/8" NPT bung to the TD27T log manifold for the pre-turbo EGT:


Made up a stainless blanking plate for the EGR crap that the JDM E24 van my turbo gear came out of had:


Had to find a gasket through the parts microfiche... The TD42TI patrol exhaust manifold to EGR tube gasket is a match.

Dion said:

Mine doesn't lock on the freeway unless I absolutely plant it... Come off the throttle and it unlocks.

Click to expand...

For future googlers, the problem is that the indexing of the spigot which actuates the throttle position sensor can be assembled on any angle, but must be indexed correctly; when my pump was rebuilt the shaft was incorrectly indexed. I used a lab power supply to get a steady 5V and a USB oscilloscope and set the shaft indexing for the target sensor output voltages from the TD27 (non-chassis specific) engine manual. I will post the values up when I have the manual nearby.

Years ago I picked up a Long Ranger TR-25 140L Pathfinder fuel tank second hand unused, for not very much money... they don't seem to make them any more.

You lose the factory bash guard when you go to this tank, luckily the sheetmetal thickness is fairly hefty; the unit weighs about 30kg. Some Motospray stone guard applied with a brush since I didn't want to splash out on a schultz gun to apply it:

Nice work Dion, fuel tank upgrade is a good idea especially with how fuel prices go up and down, for a steal you say too, you lucky bugga. How was motospray stone paint to work with?