had this looked at 2.5 years ago. They changed the transmission oil and serviced it then. It's playing up again, slow to change gears unless it's going downhill, overrevving when changing gears uphill or flat. Problem started 3 weeks ago, seems to be getting worse. The local mechanic did the service on the transmission, it was an ok job and though the car ran better I didn't feel it was perfect, not sure if I'll take it back there but it is due for a tune up. It's a magna TH, any ideas where I can look to diagnose the problem although I do understand that transmissions are complicated I'd like to be able to rule out the simple stuff first.

With light foot how many revs does it do on the flat before it upshifts from 1st to second? and what speed is it doing? it may be the TPS (throttle position sensor) it could need to be reset or may not be working properly.

Hi Deano,

It does somewhere b/w 1800 and 2000 revs to change from 1st to 2nd on flat and speed is approx 35 km per hour. I haven't noticed much change in behaviour for flat and downhill but any sort of incline and it takes forever to change gear.

Those numbers sound correct, that's what my 4 speeders do anyway on light throttle. Revving much higher on inclines before changing gears is normal too.

Over revving when changing gears is not normal, I did a full throttle takeoff at traffic lights yesterday - don't ask why - and the 1 to 2 change bit hard enough to chirp the tyres.

How many km on the gearbox? Could be low fluid pressure, worn clutches.

Around the 150000 kms. Are there any tests you can do to rule out some of the possible causes?

Around the 150000 kms. Are there any tests you can do to rule out some of the possible causes?

If you have tiptronic shift you could try shifting manually and see if that improves things.
A dealer could do a line pressure check, but beyond that not much you can do.
I'm assuming the battery hasn't been disconnected recently and the gearbox is relearning shift patterns, and that no CEL is evident.

You could note down all the problems you have observed and contact a gearbox specialist, it is not impossible for a 150,000 km old gearbox to be failing unfortunately. An experienced autobox repairer would be able to guess fairly accurately from the behaviour of your gearbox what the internal problem may be.

Thanks MadMax, not sure about the tiptronic and not sure how to check if I have it. No battery disconnection.

Tippy = having a + and - next to your gearstick so you can change gears when you want to.

Being a TH probably not, but you can still use the different positions 1,2,3,D to change manually.
Try lifting the right foot when you nudge the stick from say 2 to 3, and 3 to D and see if that reduces the flare in rpm.

No Tiptronic on my car, played with the gears but not conclusive. In the end took it to mechanic because needed brake work done and mechanic adjusted the computer which seems to have fixed the problem. Not sure of the veracity of the mechanic but says that he had to play with the computer for an hour to get it to work right. I asked why the computer had changed its setting he said he sees that a lot with magnas, the computer settings change for no reason. Not sure whether one of those electronic scanners would have picked something up but am seriously contemplating getting one if they can help.

.... mechanic adjusted the computer which seems to have fixed the problem....... Not sure whether one of those electronic scanners would have picked something up but am seriously contemplating getting one if they can help.

Yeah right -don't think your average mechanic is going to be able to adjust anything in a TH computer - more likely he removed the battery to the computer and then did a relearn road test - something you can do yourself.

No a new fangled scanner won't work with a TH - they don't support OBD

Yeah right -don't think your average mechanic is going to be able to adjust anything in a TH computer - more likely he removed the battery to the computer and then did a relearn road test - something you can do yourself.

No a new fangled scanner won't work with a TH - they don't support OBD
That easy, yep even I could have done that, thanks for that I'll remember for next time.

It is quite possibly what Deano TS said - an adjustment of the throttle position sensor - and a relearn.

About 8 years ago I saw what an experienced transmission mechanic could do to with a friend's TS Magna.

It was behaving similar to your car, and D S Jones at Seven Hills spent about 15 minutes adjusting the TPS
and road testing and achieved a very worthwhile improvement and did not charge him anything.

No fluid change was carried out.

I have been using him ever since whenever myself or family needed trans. work - but also using the TPS adjustment
to improve the shift quality on my R31 Skylines.

The final version Series 3's 1988-1990 with the JATCO re4r01a 'box are notorious for flaring and misbehaving when they get older.

When I first got my 1990 model 9 years ago it was really poor, until I spent some time copying what I saw the
trans. mechanic do.

Now with 300,000km and it's as smooth as silk.

The "correct" way to make adjustments is as per the workshop manual, disconnecting the TPS, loosening
the TPS securing nuts (7mm??) and making adjustments using a multimeter to measure resistance
between the TPS terminals.

This would work well when the car and sensor is new but when it's older, careful very gradual adjustment and road test,
rinse and repeat as needed, until it's just right can work just as well.

I've experienced it myself and at no cost.

So far, my TL AWD doesn't misbehave in any way, so I can't give any specific guidance as far as Magna's go, but if it
starts to hang on to gears under light throttle I have reasonable certainty as to what I will need to do.

Obviously, if a 'box has significant wear this may not work, but fortunately I did not have a wear and tear problem
with my Skyline, only an adjustment problem - as did my friend with his TS Magna.

Good info there Leadfoot, remembered something else the mechanic said and charged me for and that was that he added some conditioner to the transmission, whether that helped who knows?

TS Magna TPS adjustment . . . yep, touchy thing.

When new, the transmission stayed in second gear as you slowed down to a stop with throttle off, to reduce creep at traffic lights. It would only step down to first when you put your foot down again. Totally not noticeable to the driver.
As the TPS drifted off tune through wear, you would either get a horrible clunk into first slowing down for traffic lights, or a clunk when you put your foot down from a stop as it shifted from 2 to 1.
A tweak to the TPS by trial and error fixed both problems.

MadMax Does this apply to the 2.6l TP as well?


Used to have a horrible clunk about 10 metres or so before stopping or cornering.
Fiddling with the TPS position seems to have resolved that (well almost!), as I rarely notice these thumps.

MadMax Does this apply to the 2.6l TP as well?


Used to have a horrible clunk about 10 metres or so before stopping or cornering.
Fiddling with the TPS position seems to have resolved that (well almost!), as I rarely notice these thumps.

Sure does apply to the TP.
The manual method of using a multimeter to set the TPS doesn't seem to work well once the TPS gets old, trial and error adjustment until the gearbox behaves itself is the only way.

Two problems that can be tuned out that way:
(a) As you describe, a clunk from 2 to 1 at low speed as you slow down throttle off.
(b) A hesitation on takeoff while the gearbox changes from 2 to 1.

AFAIK the gearbox is in 2nd at idle and stopped to reduce creep, ie it shouldn't change to 1st when you slow to a stop, and it should pick up 1st as soon as you put your foot down again without that being noticeable to the driver.

If those problems can't be tuned out by slight TPS adjustments, I'm guessing it is time for a new TPS.

I
Sure does apply to the TP.
The manual method of using a multimeter to set the TPS doesn't seem to work well once the TPS gets old, trial and error adjustment until the gearbox behaves itself is the only way.

Two problems that can be tuned out that way:
(a) As you describe, a clunk from 2 to 1 at low speed as you slow down throttle off.
(b) A hesitation on takeoff while the gearbox changes from 2 to 1.

AFAIK the gearbox is in 2nd at idle and stopped to reduce creep, ie it shouldn't change to 1st when you slow to a stop, and it should pick up 1st as soon as you put your foot down again without that being noticeable to the driver.

If those problems can't be tuned out by slight TPS adjustments, I'm guessing it is time for a new TPS.
This is interesting. I would have thought that if the TPS is worn then its operation would be erratic, but not very predictable. Does this fix apply to all models?

I've never replaced the TPS in the KH, now at 245k's and 15 years old with no shift clunks as described above.

Also, does the TPS adjustment ever need to be reset just as a maintenance task?

MadMax,
Interesting you mentioned hesitation on takeoff.
It sure does that as well, would actually feel like it was going to die momentarily.

Never tied the 2 symptoms together (clunk or hesitation as it fancied).

But, in my case that hesitation issue was compounded by a break in the accelerator cable sleeve.
It would provide extra instability in throttle position on takeoff, especially with the car warmed up (presumably warm cable lubricant works better).

With the accelerator cable fixed there is only a slight hesitation now (I can live with that!).

...
AFAIK the gearbox is in 2nd at idle and stopped to reduce creep, ie it shouldn't change to 1st when you slow to a stop, and it should pick up 1st as soon as you put your foot down again without that being noticeable to the driver..
Which model are you speaking of here? I notice my KL drops to 1st when coming to a stop.