Hi. have a 99 high mileage odyssey in which the transmission was recently rebuilt. Originally this car had orginal honda built in cooler in the rad and also an external cooler to tow up to 3500 lbs.

After many years of good service the OBD flipped a code PO740 and I got the tranny rebuilt. In doing so the shop disconnected the built in cooler and replaced the external cooler with a new one. as far as I can tell it is no more than a 1/2 inch line with a 3/4 x 5" x 12" core. They said this would provide more than enough cooling for towing 3500 lbs.

I got about 6000 miles on it no problem while NOT towing. Last week I towed about 2500 lbs for about 200 miles and had the tranny kick out P0740 again. the MIL light came on during an hour long stretch of hilly highway. so i took it back to the boys... tranny fluid was brown and smelled very bad.

They say they cannot find anything really wrong with it except the burned fluid after taking it out and rebuilding it again under their shop warranty. They said it may have been the torque converter overheating.

Does anyone know how much cooling or cooler volume is needed to keep the temperature in line with the design intentions while towing 3500 lbs on a gentle uphill grade for 4 hours at highway speeds? (moving from sea level to inland) For that matter is this a likely cause of the problem?

 

It may be related to this...
http://www.sonnax.com/system/pdfs/35...pdf?1320330979

Ask them are they aware if any issues with the 98-02 transmissions and see if they can reply before showing them the above. Did they rebuild your original trans(it will still have the VIN tag on it) or did they replace it with a rebuilt unit(missing VIN tag/different VIN)?