trouble holding top gear in auto...

[gympiebrowns Senior Member Find all posts View Profile Close gympiebrowns]

gday guys am currently doing a trip up north when i noticed it very hard for the auto to hold top gear on the open road, we are loaded with CT and canoe on roof (<800kg combined would think) to hold top gear with out any hassle we would be doing 80kph and as soon as you hit a slight incline down she shifts, is this normal for a load on the back, i appologise for the silly type question but am concerned as we want to upgrade to a caravan which will be much heavier, any advise appreciated...

[wooley Avid PP Poster! Find all posts View Profile Close wooley]

With a caravan you should be towing in 4th anyway.

I find the same things happens with mine if it makes you feel any better.

[gympiebrowns Senior Member Find all posts View Profile Close gympiebrowns]

sure does Wooley....

[stevep84 Find all posts View Profile Close stevep84]

As Wooley said, when towing you should be using 4th in sports mode. The transmission will love you for it.

[Foxo Junior Member Find all posts View Profile Close Foxo]

Your gearbox is doing what it is programmed to do so that it doesn't overtorque your box and overload your engine.
Tow in 4th and your engine and gearbox will last longer and cruise control will work with more latitude.

Cheers,
Foxo

[Chriso57 Senior Member Find all posts View Profile Close Chriso57]

With the CT behind mine it will hold top gear at 100kph no probs. Any sort of incline yeah it will downshift thats what its designed to do. When Im in cruise mode I normally flick the shifter across to sports (4th) when approaching a hill just to save the car slowing down then downshifting.
Chriso

[sweetpea Senior Member Find all posts View Profile Close sweetpea]

gday guys am currently doing a trip up north when i noticed it very hard for the auto to hold top gear on the open road, we are loaded with CT and canoe on roof (<800kg combined would think) to hold top gear with out any hassle we would be doing 80kph and as soon as you hit a slight incline down she shifts, is this normal for a load on the back, i appologise for the silly type question but am concerned as we want to upgrade to a caravan which will be much heavier, any advise appreciated...

I also have a light camper trailer and my Prado (150 SX) now does the same thing.

I have just this week returned from another trip to the Red Centre and have found the same thing only worse.

In the last service the Toyota dealer did me the favour of upgrading the computer which had the effect of significantly changing the auto shift points. It now drops at least one but usually two gears at the slightest hint of an increase load.

I did a similar trip two years ago and this trip the fuel consumption increased about 12%.

The cruise control is now useless on anything except dead strait flat road. At the first sign of even the most gentle hills the speed drops two or three kph and the gearbox drops one or usually two gears and we do a near full throttle accelerate until about three or 4 kph above the set speed at which time it drops the throttle to zero and the gearbox changes back up and we slow back down to cruise speed.

The same thing happens when you enter a gentle bend in the road. Instead of slightly increasing the throttle to maintain speed the gear box drops back a gear or two and the car accelerates somewhat faster than you expect.

In the rolling hills around the Flinders Ranges there are sections of road with three or four very small hills in a row. If cruise control is engaged you can get an oscillation in the speed that is outright scary. Dring without cruise control it still drops one gear far too readily but it is not a problem.

None of this happened before the computer was upgraded and apparently there is no way to put it back the way it was.

Not quite sure why you would want to cruise in 4th when only towing a light little camper trailer.

S.

[vk2ss55 Senior Member Find all posts View Profile Close vk2ss55]

Mine was reflashed and yes it does change down more readily but I don't think it's any issue . That was not towing the c/t just highway running , I'll take notice next time I'm towing the c/t .
Cheers Ross

[fido666 Banned Find all posts View Profile Close fido666]

In the last service the Toyota dealer did me the favour of upgrading the computer which had the effect of significantly changing the auto shift points. It now drops at least one but usually two gears at the slightest hint of an increase load.

What other changes can be made by re-flashing the computer? I was told there weren't any firmware upgrades for the 150 but had remembered reading about it on PP, just can't find the right thread(s) now despite searching.

[Trevally Banned Find all posts View Profile Close Trevally]

The programming was to tackle the differential fluid temp warning issue of coming on too easily n too often. To stop this from happening toyota changed the temp. Alarm setting to a higher temperature. Then they realised this was not good for the transmission. So, to reduce the temp on the transmission, hence the fluids, they had to reduce the loads in the transmission n gearbox. To do this, the easiest way is to drop gears down quicker. This reduces transmission load n temperatures. High fluid temps reduce their ability to lubricate n ur transmission wears quicker. So the sacrifice is fuel n comfort. Toyota, I think it's about time u got a new gearbox out. This is starting to show its age. An extra cog or two will reduce a lot of this crap.

[sweetpea Senior Member Find all posts View Profile Close sweetpea]

To do this, the easiest way is to drop gears down quicker.

They should re-issue the yellow sticker for the window reflecting the increase in fuel consumption.