Thai D40 ST Having Trans Problems

[martian-13]

Hello,
I have owned my 2011 Thai D40 St for about 6 months now, and I noticed a little while ago, that when accelerating hard, It seems to get stuck in-between gears almost.
Specifically 4th gear seems to be the problem child. For example, when im accelerating more that 75%-ish, as i cross the 60 km/h mark and the trans tries to shift from 3rd to 4th, it begins to rapidly shift back and forth between the two gears, similarly it does the same when accelerating hard at 100km/h when the trans tries to downshift into 4th for the extra pickup.
I have simply been avoiding this problem by being gentle on the throttle, however, steep hills at a decent speed also causes the same issues.
My question is, has anyone else experienced this? and is it something as simple as being low on trans fluid, or something like the trans ecu needing a recalibration, or is it something more serious?
Thanks in Advance.

 

[Old.Tony]

I tend not to push my car that hard but I do tow and I do go up hills so sometimes she does work a little harder - but I'm always in a lower gear when it happens.

If you're mechanically minded you could use a transmission flush then empty + refill and see if the problem's gone - it might just be some muck in the valving.

Failing that, there might be an issue with the mechanism that changes the gear into 4th (as that seems to be your "problem child" in this box) but that would need an automatic transmission expert and they are never cheap.

Try the flush first, it might fix the problem. Here's an example:

https://www.supercheapauto.com.au/p...ring-flush-300ml/642271.html?cgid=SCA01070703

 

[joe2006]

Hello,
I have owned my 2011 Thai D40 St for about 6 months now, and I noticed a little while ago, that when accelerating hard, It seems to get stuck in-between gears almost.
Specifically 4th gear seems to be the problem child. For example, when im accelerating more that 75%-ish, as i cross the 60 km/h mark and the trans tries to shift from 3rd to 4th, it begins to rapidly shift back and forth between the two gears, similarly it does the same when accelerating hard at 100km/h when the trans tries to downshift into 4th for the extra pickup.
I have simply been avoiding this problem by being gentle on the throttle, however, steep hills at a decent speed also causes the same issues.
My question is, has anyone else experienced this? and is it something as simple as being low on trans fluid, or something like the trans ecu needing a recalibration, or is it something more serious?
Thanks in Advance.

I have the same vehicle and apart from what "I consider" a design flaw with there being no torque converter lock up in 4th, the transmission has always functioned well, with no issue similar to yours.
I believe that the transmission holds about 12 litres of fluid and unless you do a full flush by taking off the lines and allowing it to be pumped through the system, you will only get 4 litres out by draining the pan.
Once I gave up on the disheartening service I was receiving and started doing my own servicing, I found that the transmission fluid was quiet dark. At each 10,000k service I would drain 4 litres until I had replaced 12 litres and I will now go back to the normal transmission drain interval of 40,000ks. Doing what I have done however, means that the transmission never had 100% new fluid. Still the fluid became progressively brighter at each 10,00k change.
I'm not saying that will help in your situation but have you checked the fluid or the level? I am assuming that unlike the later models, you still have a dipstick, albeit hard to find and with a small bolt, to discourage anyone from touching?