Weird Safari auto problems

[Muzza]

I have a couple of weird auto problems with my 91 Safari 24v 4.2 Diesel RE4RO3A auto

1. It's reluctant to upshift into 2nd gear and needs a lot of revs to do so. When it does shift it does so very harshly ( not good ).
Problem still exists if manually shifting the T bar from 1st to 2nd but I can force it to upshift into 2nd sooner by flicking the power mode switch into "Hold". ( It would still be a harsh shift but because you know when it is going to change you can ease the throttle off to soften it ).
Putting the power mode switch into "power" position just makes the problem even worse.

2. The overrun engine braking clutch on Drive ( 3rd ) is not working but is perfect on 1st, 2nd and Overdrive.

I was suspecting a TPS or sensor problem but everything else works properly.
Is there a common solenoid or something else that would cause these two problems as they seemed to have appeared about the same time.
It's self diagnosis test is showing no errors but has 16 short flashes rather than the 10 that the manual says it should have.
Oils good, no obvious problems before this, 170 k's

Cheers

[churchill]

Make sure the kick down cable (if it's present) is not rusted or jammed.

[Crash bandicoot]

mine did eactly this when i changed from computer controlled pump to mechanical as the TPS was on the fly by wire throtle and engine speed sensor was on the computer controlled pump.

The trans ecu relied on these inputs from the engine ecu/sensors to operate properly.

So that narrows it down, the hard shifting is the line pressure solenoid but that is only the effect, the cause will be either the trans temp sender or engine speed sensor as depending on the speed of the engine depends on the pressure of fluid used to compress/engage the clutch packs in the trans. at the moment you have full line pressure by defualt.

you still have over drive which mean the torque converter lock up is working but not the over run clutch as that requires the speed sensor to be working....
which sorta tells me the ecu knows it's doing high speed to lock up automatically so it's getting a road speed reading (Over run clutch not engaging at high speed because TCU doesnt know engine speed is slowing.) 1st an 2nd over run clutch engages regardless not dependent on a speed reading.

there are two by the way, has engine speed and trans speed for matching gears. it will be one of the two.


only manual i have handy at the mo is for the 1A but should be the same


by those deuctions i'd say speed sensor.(not to be confused with RPM signal which is different)

[Muzza]

Thanks for your comments guys ...
What "Crash" says seems to make sense, but what was throwing me off the track was the fact of the overrun not working on "D" but OK on the other gears.
I assume the 2 sensors you are talking about are the ones on the left side of the auto just above the shift linkage, not the one on the right side of the transfer case just before the brake drum.
Is there any way to test them ( preferably in place ) and where's the best place to source them from.
Prior to these problems starting I had tried unplugging the line pressure solenoid resistor as discussed in "Jatco 50 cent trans mod " ( but have since reconnected the factory one ). Interestingly others have commented that they noticed problems with there overrun clutch since they tried disconnecting or substituting the factory resistor.
From what I have read, the trans temp sensor is to stop it shifting up to overdrive until it warms up and gets enough line pressure so shouldn't be the issue here ?. I was told that if the trans temp sender is bypassed it needs to have a resistor put in its place ??
Cheers

[Mattman]

Great post Bud

To test the speed sensor you really need a scope to graph its output

[Crash bandicoot]

Thanks for your comments guys ...
What "Crash" says seems to make sense, but what was throwing me off the track was the fact of the overrun not working on "D" but OK on the other gears.
I assume the 2 sensors you are talking about are the ones on the left side of the auto just above the shift linkage, not the one on the right side of the transfer case just before the brake drum.

will have to find the manual unless some one here is more familiar with the 3a safari trans but there will also be 4wd/2wd signal on transfer aswell etc

One will reading input from the engine the other will be reading out put speed or if you are over running (coasting)it will technically be input speed from the axles turning
Is there any way to test them ( preferably in place ) and where's the best place to source them from.

easiest way to do it is to find the brown 8 pin plug and on the trans side of the loom to the transmission and give a power feed to the grey wire, this is the over run clutch, and go for a drive if once you get into drive and take your foot off the gas it will either start to slow from the over run clutch engaging or will keep coasting, but once again, thses are effect's not a cause...as the solenoids are simply an on off actuator, it's the sensors that are the brains that tell them what to do.

Prior to these problems starting I had tried unplugging the line pressure solenoid resistor as discussed in "Jatco 50 cent trans mod " ( but have since reconnected the factory one ). Interestingly others have commented that they noticed problems with there overrun clutch since they tried disconnecting or substituting the factory resistor.
From what I have read, the trans temp sensor is to stop it shifting up to overdrive until it warms up and gets enough line pressure so shouldn't be the issue here ?. I was told that if the trans temp sender is bypassed it needs to have a resistor put in its place ??
Cheers

as mentioned earlier, I have line pressure by defualt due to removing the computer etc simply unplugging it just makes shifts harsher but will allow you to get overdrive from cold.

if that is all you had done it may pay to hard reset everything by disconnecting the batteries and leaving the ignition in the ON position, place a brick on the brake pedal over night to drain any residual power from the trans ecu.

before reconnecting put everything back to factory and try again, see if you get the over run back. but i'm pretty sure it's to do with the speed sensor.

[Muzza]

Awesome !
Thanks for your help and comments "Crash"

I will try "hard resetting" as you described ( might as well do the easiest first ) but if that fails will need to identify the 2 speed sensors.
The two I saw above the trans shift lever sound like they might be for the "4wd/2wd signal on transfer" that you mentioned but the back RH one on the transfer case is obviously a output shaft sensor. I better have another good look underneath and see if I can see any others.

[ChurchurDan]

The transmission speed sensor is in the side of the main transmission housing. Normally when these fail the trans wont shift up from first.
The other speed sensor is a signal out of the instrument cluster.

RPM shift point is largely determined by the TPS and so is overrun clutch engagement. I would be checking this first, also it is the only sensor that suffers from mechanical wear. They are easy enough to test with a multimeter.

[ChurchurDan]

Some light reading
http://www.240edge.com/manuals/89-90_240sx/auto_tra.pdf

[Crash bandicoot]

Cheers for that dan, i dont know why jatco didnt just use the speedo output for both signals.

[Muzza]

Awesome ... thanks ChurchurDan

Ha ha ... I found that manual online about midnight last night ... haven't had a chance to work through it though.
Interesting that the other speed sensor comes from the instrument cluster as I had my rev counter repaired and thinking about it this problem occurred about that time .... Hhhmmmmm seems abit of a coincidence
Finally got the self diagnostics to work with a different sequence of instructions ( the ones in the manual were wrong ). Indicates 2 faults
Long flash on 3 - Throttle sensor shorted or disconnected
Long flash on 7 - Lockup solenoid shorted or disconnected

Thanks guys
Certainly narrowing the problem down now ..........

Bugger .. shouldn't have said that .......
famous last words

[Crash bandicoot]

I plugged the TCU and TPS back into the loom in my truck and went for a drive with manualized dpdt switches in "normal operation mode so to speak. didn't make an iota of difference, still had no lock up or over run untill i flicked them on manually,

if that;s any help to ya., i have no dropper resistor, or speed input from the engine to the tcu.

[Muzza]

Finally got a chance to do some testing.
TPS was still at factory settings ( yellow paint on adjuster ). Readings were a mile out but managed to get them in the ball park by rotating TPS fully. 0.43 -> 3.85 ( recommended 0.5 -> 4.5 ). Gears now shift when they should and lockup on OD also comes on and stays on when it should. ( I am still a bit suspicious of the TPS being abit flaky. )
But .....
Shifts still have full line pressure and overrun clutch still not working.
Tested Revolution sensor ... Tested OK
Tested Speed sensor ... Fail ..... Voltage was all over the place 4.36 - 1 +- ( should be 0 - 5 v )
From what "Crash" said the Speed sensor from the instrument cluster controls line pressure and overrun clutch and these 2 problems seem to have surfaced since I had the Rev counter repaired.
Will get instrument cluster checked out.

Thanks guys for all your help ...... Hopefully got to the bottom of it.
P.S where's best place to source another TPS if I need one.

[ChurchurDan]

The speed signal comes out of the speedo, there are only 4 screws, ignition, earth, signal in, and signal out labeled as either 2p or 4p. It is easy to check at the cluster and they are really prone to failing.

[Muzza]

Thanks for that.
Not quite sure how I check that with the mulitmeter.
Interestingly when I checked the fault codes on it today I was only getting fault 3 - ( faulty throttle position sensor ).
Fault 7 - ( speed sensor error ) seemed to be OK. Might have been a poor connection but ........
I am thinking it may still be in the TPS so will put in a new one and if the problem persists will get my sparky to check the speed sensor circuit.
I certainly now have a better understanding of how these box's work which is really good. Obviously my TPS has never been set properly and/or faulty since I have had it without me realising it. Drives better now than it ever has but just need to fix the overrun clutch and full line pressure issues which have only recently occurred.
At some time I need to drop the auto out to replace the engine main seal ..... Is it worth upgrading it by putting in a Jatco shift kit or similar. I realise the auto doesn't have to come out to do this but assume it is easier than springs dropping everywhere.

Cheers

[ChurchurDan]

It is a positive switched output so on a multimeter you should see a pulse that gets faster with increased speed. Im guessing it will be a 5v pulse and your meter will be too slow to measure it but it will fluctuate and show if you have an output. Ideally you want to scope it.

[Muzza]

Cool !
Thanks

[Muzza]

Decided that it was most likely still a TPS problem and looking at them there appears to be more than 1 relay in it which could be giving trouble.
My auto sparky said there are no after market ones made and will need to get a genuine one from Nissan. Rang Nissan and they said the TPS is not seperate and I would need to buy a whole injector pump ...... WHF ..... what Bullsh!t ...
So is it right that there are no alternatives( can't imagine that there arn't ) and I need to get a 2nd hand one, prefer not to as that could be worn too.
Any ideas ??
Thanks

[Crash bandicoot]

TPS from similar year safari terrano, vanette etc that was an auto should have the same one, I still have the one bolted to my injector pump for the "one day" ill get around to wiring it up but never needed it.

[darinz]

Have had similar problems. Chased it all around to the TPS, bought a brand new one from Nissan (they do do them you just need to give them the part number) and it didn't solve the problem!
My problem tuned out to be wiring not the sensors themselves. To fix it I ended up bypassing a whole lot of factory wiring.

[Muzza]

Thanks Darin.
What was the price Nissan gave you as the only new ones I have been able to track down are on EBay and are $350 AU.
It might be best if I grab someone else's TPS and try it first in case it is a faulty speed sensor or wiring . Was reluctant to buy 2nd hand in case that unit was also worn and a bit "Flakey"
I have got the TPS fully advanced and it is definitely shifting better and holding lockup ( only just ) and seems to not have as much line pressure on the shifts like it did but still more than original ...
But .. it still doesn't have overrun on Drive.

Cheers

[Muzza]

I think that I have had 2 issues simultaneously
TPS was miles out of adjustment and voltage still not fully within specs ... but this has fixed the gear shift points and OD lockup clutch problem,
but I still have full line pressure and no overrun clutch on Drive
tested
"Revolution sensor" OK
"TPS" OK
"Speed sensor" OK
'Engine revolution signal" ... NOT OK as showing only getting 0.5 v instead of 9.5-12v per specs

Questions
1. Can I assume that the over run solenoid is OK as over run is working on 1st 2nd and overdrive
2. Would a faulty "engine revolution sensor" cause full line pressure and no over run clutch on Drive
3. Is that the sensor at front left side of engine just under the water pump ( 2 bolts holding it on )

Cheers