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Originally Posted by stupenduzzman
I recently purchased a 2001 4.6iS. I bought it to tow my trailer and racecar around, however I've experienced some interesting things while towing. I always tow in manual mode. First, occasionally when cruising in 5th gear the engine revs will go up by 500 rpm as if it has shifted down but it still says it's in 5th gear and after a little while the RPMs drop again. The RPM change is not large enough for it to be a 4th gear change. What could this be?
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This is just your torque converter lock-up clutch engaging & disengaging and is perfectly normal
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Secondly, after cruising for a while and usually while going uphill or with headwind, the transmission will automatically shift into 4th in manual mode. It will not allow me to shift into 5th even if I'm going downhill afterwards. Occasionally it would even shift into 3rd, again without me doing anything. It will get stuck in the lower gear for a short while and after about 5 minutes or less give me control back to shift up.
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The transmission ECU will override you in manual mode if it feels you are doing something inappropriate. The controller is programmed with a number of driving modes including ‘Hill Mode’ which it automatically engages if it detects a combination of high engine torque, high throttle angle and low engine speed. Different shift maps are used depending upon its calculation of the severity of the gradient which will hold the transmission in low gears to varying degrees.
Phil