I have a 2001 Supercrew, 5.4L, 4x4, 3.55LS, w/ 4R70W, and 7000 miles. Question is, when running 55 or above , on expressway, I let up on the downhills and the truck runs away. Then when I accelerate at the bottom of the hill, the engine revs like the torque convertor is not locked up. After 1/2 second or so, the convertor locks and the revs come back down. I can sometimes see 400 rpm jump on the tach. Is this normal? I can see the torque convertor unlocking letting the truck coast to increase mileage, but how many rpm should it run past to lock again? Any body else notice this?

TIA,
randymechanic just not on transmissions.

 

randymechanic,
Well, I don't have the run-away issue downhill, but I do have the 400 rpm "unlock" after coasting and then applying throttle. Mine is a '97, 4.6L. I have 60K on now, has done it since I bought it with 29K on it...normal? I don't know, but mine isn't getting worse if that helps.
I have noticed now that I am driving it in a cold climate (20-30F) that the tranny won't go into lock-up for around 3 miles or so of 55 mph. It shifts into 4th, but runs ~1900 rpm at 55mph, when it "warms up" it will drop to 1600 rpm (normal) at 55mph. Do you see this or don't get it cold enough?

 

The shift sequence you are describing, (TC un-locking upon decel returning to closed throttle), is normal. When applying throttle again it will re-engage.

 

Remember that the shifting sequence is as follows: 1st, 2nd, 3rd, torque converter lockup, 4th. Try running with the "OD" off, you'll notice 1,2,3,lockup. The "OD" is to allow for 4th gear. The torque converter will lock up no matter what at the given speed in which it should. (unless of coarse you have the small pedal nailed to the floor!).. .
Rick..

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"99" F-150 4x2,SC, med red / silver, 4.2L, auto, 3.55's, 265x16's premium snd w/cd, 4 wheel antilocks, leer "too heavy" matching cap, Mobil 1.
"Gutless thing!!"

 

Thanks for the post. My Expy (4r100) does the same thing. It's a little annoying but I can't help but keep thinking it's the most efficient. It'd be noce to be able to control it......

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2000 EDDIE BAUER EXPEDITION 4x2

• Estate Green
• 5.4 ltr
• 3:55 LS rear
• Superchip!
• Airaid FIPK
• Gibson S/S Swept Side Cat Back Exhaust
• Hellwig Rear Anti-Sway Bar
• Edelbrock Performer IAS Shocks
• Xenon Super White Head and Driving Lights
• Clear Corners (installed then removed and reinstalled OEM's)
• Tow Package
• Rear Load Leveling
• Moonroof
• Century Child Seat!
• Front Polyurethane Anti-Sway Bar Bushings recieved, wrong part number

-->Come share my Addiction<--

 

If your towing heavy and pulling a grade in 2nd for any lenght of time, the TC will also lock up in 2nd gear. This only happens when the PCM determines your pulling heavy on a long climb. It is used to reduce transmission temps. I know the 4R70W does this, but I do not think (or at least know) that the 4R100 does.

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2001 Ford F150 Supercab 4.6L
Airlift Rear Suspention with onboard compressor