Problem with VR auto 4L60E trans not going into 4th

[alpha_au]

Anyways, I've got this problem with my VR berlina 94 (4hdd trans, original 213xxxkms)

It just won't go into fourth gear (overdrive). I have tried absolutely everything and still can't find what is wrong with it. It started about 8 months ago with it (after 5 or so minutes of driving, once it was warm I guess) slipping a few times whilst in fourth on the highway and eventually popping out of fourth and back into 3rd. It did this for at least a couple of weeks every time I drove it far enough. After this period of a few weeks it just ceased going into over drive all together.

I have had a complete service done about 3 months ago on the trans, it did nothing but perhaps make the shift slightly smoother. I have had a complete electronic diagnosis done using the proper diagnostic tool, that showed no errors whatsoever. Today I took it to a transmission 'specialist' who looked over the car for a good while and couldn't find one problem with the transmission and said "I've never encountered this issue before"

I have checked and had professionals check all the obvious things that it could be (tps, accelerator cable, etc) but all seems fine... The workshop I took it to today said that normally the bands/clutches go on the 2/4 ship thingy (sorry don't know too much about trans' ) and sometimes the 3/4 shift band/clutch goes but he said they're both fine and that he's a bit stumped and would have the remove the trans from the vehicle to inspect the inners. I obviously would like to avoid this due to the hefty price of removal and re-installing it (300+)

If anyone has ANY help or knows any workshops around the northern suburbs (of Adelaide) who has dealt with this issue or something like this and might know a solution please reply as I'm getting pretty desperate.

Also, the trans shifts great, isn't rough, there is no lag between changes, works in 1,2,3,D,R and P, power button works, there are no noises from the box and it has been serviced recently.

[delcowizzid]

there is a temperature switch in there that will stop it going into 4th if the ecu thinks its too hot

[alpha_au]

Thanks for you input/help, where abouts is the switch located in the trans and is it a matter of swapping it over for another one? Is there a way to test if its working?

[hako]

Here is a link that has your problem and the fix as delcowizzid suggests....you'll need to read the whole article.
4L80E Transmission [Archive] - SixFiveTurboDiesel.com