Auto box 5th gear selection

[Mick W]

My auto box Collie has always driven perfect but has a strange anomaly. 5th gear will not select until the water temperature has risen to 'normal' on the gauge. Knowing the cooling system is shared with the auto box I've had the cooling system flushed and the auto box oil and filter changed as a precaution anyway. Always starts, runs, drives, revs, kick-down works, no overrun, no smoke, overdrive works, Power start works, 2nd start works.

The handbook makes no mention of it for standard driving, I always know when 5th will kick in on the temperature gauge and once temperature is normal auto selects all gears when driving.

I've also noticed that the system cools down really quickly so after a 10 mins stop it has to get up to 'normal' temp again before 5th will engage.

I get no codes showing so 'assuming' the sensor is ok and is the trigger for the ECU to allow 5th gear engagement.

 

[Shayne]

I'd put that down to a character trait and if it bothered me probably try fully synthetic oil because i believe it has a greater tolerance to heat thus changing little in viscosity hot or cold .

 

[Mick W]

@Shayne that's what I'm thinking as its normal and has driven this way consistently for years not just started. Just reading some of the threads and you get paranoid about everything!

 

[Shayne]

Aye it does start making you look for things to fix i think we all fall foul of it

 

[chadr]

I'm assuming your 1999 Collie's (as per you sig) autobox is standard. If so, then it should be a A343F gearbox, which is 3 speed with overdrive. So you might loosely call it a "4 speed". The 5 speed box wasn't introduced until the 120 was a year* or so into production, so around 2004 or so.
* need to confirm exactly


Never noticed the delayed lockup symptom on mine, probably because of where I live; to get to a road where I can do 50mph+, I usually need to drive a few mins, which brings the temp to "normal" before I can get to use lockup .

 

[Beastrider]

It’s the same behaviour on mine but I believe it’s deliberate programming for most autoboxes - (not just Toyota) - they keep the engine revs a bit higher until the transmission oil has warmed up.

 

[karl2000]

So how does it ever get to 5th on a 4 speed box?

 

[Shayne]

I'm still incredulously digesting that an auto might have character

 

[karl2000]

They get even more character when the ATF is low

 

[chadr]

So how does it ever get to 5th on a 4 speed box?

Jam it in Reverse? Drive it off a cliff? I have no idea.....

 

[Mick W]

So how does it ever get to 5th on a 4 speed box?

Another one of those behavioural characteristics...

 

[Geoff 28]

I don’t know if your Collie has the same set up Mick but a few years ago my Amazon stopped selecting 5th completely and with no warning.
The “experts” told me it needed a new ecu (over £1100 at the time) but after some digging I found that the wiring loom in the box has two integral temp sensors as well as the solenoid plugs, 1 for the trans temp warning light and the other one to prevent it selecting 5th until the fluid warms up. A new loom sorted the problem (great result as it only cost £60)
If the temp is around 6 or 7 degrees it needs nearly 2 miles before selecting 5th and it’s so consistent it will change up at exactly the same spot every time.

 

[Mick W]

@Geoff 28 makes sense that. Working as spec