This is a bit late....but have you checked the vacuum line and vacuum modulator on the transmission? Slipping out of gear and then catching again can be a symptom of a bad vacuum modulator. I don't recall if vacuum would be affected by temperature but it would make sense if it did. If you pull the vacuum line on the trans side and see trans fluid, that's a sure side your modulator needs to be replaced. If a mechanic hasn't checked this because they didn't experience problems, it's certainly worth a look before you go rebuilding! Changing the transmission fluid AND filter is a great practice, so keep that up even after you get this problem solved.
Also, are you sure you have enough fluid? I know that may be a stupid question but I know a few people that actually have to over-fill their transmissions a bit in order to eliminate slipping problems.
If you do have to replace the transmission, see if you can find a C6. By far one of the best automatic transmissions Ford has ever made. It's a heavy duty trans and is well-suited for towing.
One other thing I just thought of - are you sure all of the cooling lines are unobstructed? I would definitely install the largest auxiliary cooler that will fit. It never hurts to have it oversized.
Last edited by E-Rock; 10-23-2007 at 06:24 AM.
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