at 70km/h uphill only in Overdrive, Transmission hesitates

[snoozin]

1996 Trans sport with 360K KM on it. FWD, It has Overdrive and Drive position on the shift lever.

The slipping happens while driving up a hill at approaching speeds of 70km/h to 100km/h. (43mph to 63mph) in Overdriver Only.

Only occurs while the transmission is in Over Drive. If I put in Regular Drive there is no problem.

It feels like the van makes a loud jolt/clunk noise from the transmission when it hesitates/slips at those speeds uphill (mostly) or downhills.
If I'm doing 120KM/h (74MPh) and then go up the hill, The transmission doesn't slip.
It happens on the smallest inclines, barely a hill.

I read up about this issue. So far I'm guessing I need to check the Torque converter clutch fuse under the hood.

How would I know if the torque converter clutch was the cause?
Thanks in advance. This is a Nice forum.

[LMP]

OD shifter position ALLOWS 4th gear...but 4th gear actually engages only at 80 kmh normally...but well, it is possible . TCC, on the other hand, does apply in 3rd gear, the top gear in D, this based on my '93 with the 3.8 YOu can detect this by noticing a small jolt and slight lowering of rpm while car is driven in D at constant speed of very moderate acceleration over 40mph/70kmh .
What you describe seems to be caused by lack of hydraulic presssure.....and over 70 mph in 4th, the engine runs the transmission pump fast enough to generate adequate pressure, which you get at a lower speed in 3rd gear since engine runs faster.

You have the vacuum transmission modulator in '96...it controls the pressure in the transmission.
www.avigex.ca/xport/modulator97.jpg
www.avigex.ca/xport/modulator.jpg
If you unplug the vacuum hose to the modulator, this mimics full throttle and transmission will operate at maximum pressure. Try this for a test and report results...MAybe the modulator irself is faulty too....that would be an easy fix.

[snoozin]

Where can I find the modulator?

[LMP]

OK the picture with a read arrow is not very clear..

www.avigex.ca/xport/modulator.jpg
picture from '93 3.8 with same 4T60E transmission

..it is located on front of transmission torque converter bellhousing , clearly and readily visible on mine. You might have to remove some intake air ducts to see more clealy. There is a vacuum hose going to it...With engine running in park, vacuum is maximum and disconnecting the vacuum tube drops vacuum and is like going full throttle from a transmission point of view and this increases hydraulic pressure in tarnsmision which normally sounds as a slight increase of transmission whine...but that can be covered by ambient noise.

BTW, yesterday I tested the minimum speed at which 4th gear engages on mine, and it is around 77kmh. Tcc had applied in 3rd gear around 65kmh.

[LMP]

..found that out
http://www.automotiveforums.com/vbul...d.php?t=889024