Clutch, Transmission, Differential, Axle & Transfer CaseSPONSORED BY:
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I don't have direct access to the transmission in question, because I'm only considering a purchase of the truck above, but it seems like a good deal except for the ONLY issue the current owner says it has. It appears 1st gear doesn't work/engage if the lever is in the "D" position (revs up, but goes nowhere), but works fine if it's in the "1" position. All other gears work including reverse. There is no slipping, no hard shifts, no noises or smells. For all intents and purposes, everything works perfectly except it won't start from a stop in Drive.
My question is...what are the most likely causes of this scenario?
From some reading I've been doing, I may be describing the problem wrong, and I may have missed something.
1st is available in the L/1 position, 2nd in the 2 position, and every gear including OD works in drive except whatever gear Drive likes to start in normally. Reverse works fine also. I've been assuming 1st gear is the gear Drive normally uses for starts, but if Drive normally starts with 2nd gear, then that's the gear which isn't working in Drive. Again though, 2nd is available in the 2 position.
I didn't find anything specific about a "low reverse one way clutch" for the 4r44e, but I found plenty about it for a 5r55s, and other 5 speed trannys; however, I did find a few articles concerning the "one way clutch" (perhaps the same thing really), and if I understand it correctly, the 1-way clutch is what I've previously heard called a sprag, and it's used in drive for the lower gear, while manual low uses bands/clutches. If so, the lack of a low in drive makes sense.
I also read where this clutch "overruns" in all but 1st gear on a 4 speed, and 1st and 2nd in a 5 speed.
I'm not sure what "overruns" means with respect to this 1-way clutch, but I suppose out of curiosity my question becomes:
Is there any way to mitigate the situation (i.e. start from 2nd, and avoid LowDrive) for an extended period of time until a repair or swap can be performed, or is an imminent failure at hand regardless what one does to avoid use of that 1-way clutch?
BTW...thanks to both of you for pointing me in the same direction. This is starting to make sense...
P.S. How is reverse working if this 1-way clutch is used for both gears (or am I not understanding some more of what I've read)?
UPDATE: Ahh...never mind. It appears the Low-Reverse Band holds during reverse operation in the 4R44E, and the one-way clutch isn't used. Correct me if I'm wrong, because I'm really wanting to understand more about these things.
As for what overrunning means, have you ever ridden a bicycle? When you pedal, it moves the bicycle. You can also stop pedaling and coast. When you are coasting there is a one way clutch in the rear wheel hub that is overrunning. The one way clutch in your transmission is the same, just larger. If there was no one way clutch in the hub you would have to pedal all the time, but you could resist the pedals turning to help slow the bicycle.
In your truck you could always start in manual 1 or 2. Usually, but not always, no additional damage will occur. The one way clutch is failed, but probably won't damage anything more than it already has.
__________________ Mark Former Ford Automatic Transmission Engineer
“The good thing about science is that it's true whether or not you believe in it.” ― Neil deGrasse Tyson
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