The vehicle is a 2001 Expedition AWD with a 5.4 engine. I believe that the transmission is a 4R100. The vehicle has 94K miles on it. When decending a hill we have no engine braking at all. With the cruise control set at 60MPH in OD the speed will increase to 75 MPH decending a moderate hill, then slow back to 60 on the flat ground. The engine idles while the truck seems to free roll. With or without the OD switched off the transmission seems to disengage when not under a load. The engine RPM will drop to idle speed. Second gear reacts the same as drive. The truck will pick up speed on a hill, while the engine idles. First gear will act like it wants to engage, but drops back to idle within a few seconds. As soon as the throttle is depressed the engine and transmission engages smoothly and firmly.

It has been suggested that the coast clutch may be worn or has failed completely. Does this sound like the issue? Is it possible that the coast clutch solonoid is bad? Can any of these parts be repaired without removal and disassembly of the transmission? Will this problem eventually cause the transmission to fail completely, or are the current problems all that will happen from this sort of failure. In other words is this an indicator of a complete pending failure? Can I continue to drive the vehicle like it is without fear of other problems other then the obvious increased brake wear?

Thanks in advance,

Charles

 

Yes, that's the issue
Yes, it could be bad, but it isn't causing this issue. The coast clutch solenoid is not used to engage the coast clutch with the shift lever in 1 or 2. The clutch is hydraulically applied in those two gears without using the solenoid.
No.
I've seen transmissions run a long, long time with a failed coast clutch.
Usually, yes. It is possible that a piece from the failed clutch could go and damage something else.

 

Thanks lots Mark, for answering all of my questions.

Since the truck has 94K miles on it, sounds like a rebuilt transmission is the only way to correct the problem.

Charles

 

If it had ten miles on it a rebuilt trans would be the only way to correct the problem.

 

Thanks Mark,

I discussed the problem again with our Ford dealer. They can install a Ford reman trans, however they also recommended a local shop in Franklin NC that does good work, if I want a modified unit built for the truck.

I spoke to the independent shop by phone. The service manager told me that the coast clutch has plastic parts in it, and that they frequently fail. He says the same thing as you did. It could run a while, however if pieces of damaged parts begin to break loose and flow down stream they will plug up the hydrolics and some other problem will develop. We live in the mountains, so driving it with a failed coast clutch is a little scary. Most of our roads are steep and winding.

He told me that he can rebuild the unit similar to OE for $1,700.00, or he can do a HD build for $2,700.00. The HD build will include all steel gears and steel instead of plastic parts. He said that most of the better parts are used in the 4R100's that are used with Superduty series trucks with diesel engines. Apparently the units in the Expy's and F-150 get aluminum and plastic internals.

I am begining to think that these things are just a total piece of junk.

If it would not be a major PIA, I would convert the vehicle to a six speed stick shift, but that would be a major undertaking.

Charles