Transmission is slipping

GATEWAYSPARKY

MEMBER
2002 FORD E-SERIES VAN
5.5L
V8
2WD
AUTOMATIC
56,000 MILES

The van is a cargo van with a 5.4 liter engine and 4R70W transmission. Transmission code is "U". The PCM is setting codes P1747. The overdrive light on the stalk will flash. In gear, a grinding or whine can be heard coming from the front of the transmission with the engine cover off. A bit like something is not engaging. The transmission fluid is full and pink with little to no burnt smell. I have not dropped the pan (transmission fluid is expensive) just to look for metal in the bottom.
History: Before I bought the van it had sat in the same place for about six years and never ran or operated. The former owner thought a new transmission would be too expensive. I got it home via tow truck, started it after a new battery and fuel pump, and took it for a short drive. To my surprise it shifted and performed fine through all gears. Then the codes started and I assume it is now in limp home mode. I pulled the transmission connector and it had transmission fluid leaking up into it (passenger side of transmission). The harness looked good other than the fluid which I thought could be causing a short out. No dice after cleaning it and putting dielectric grease in it. Still p1747 and noise. It is at the point where I will not drive it for fear of destroying the clutches.
Could the computer be killing its own transmission?

3 Replies

HMAC300

MECHANIC
48,601 POSTS

This is a code for electrical pressure solenoid problem or bad connection as you have /had fluid at electrical connection you will need to drop the pan and replace the solenoid or check for bad wiring. A transmission shop cold probably do this in about two hours and tell you if anything else is wrong, but you can attempt it yourself. It does have a molded lead frame which connects to solenoid so you have to check that as well. If bad replace it, but you need a tool to check it. I can send stuff if you want to do it.

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Saturday, December 10th, 2016 AT 10:37 AM

GATEWAYSPARKY

MEMBER
3 POSTS

I am not sure what a lead frame is, to tell the truth. The factory drawings are"sketchy" and I haven't seen one in color. I know there is some sort of tool that you stick in holes in the lead frame to see if it is bad? Furthermore the factory manual assumes you have a Ford test equipment that commands solenoids on and off. Trannies are my weakness. I'm afraid a trans shop will want to change the trans whether it will solve the problem or not. I see that a lot. It's unbelievable that the tranny has 56000 miles on it and it has already failed. There is no hitch or towing ever done with it, either. What can you send me?
A lot of guys also say that bad coil packs can cause this, too. But I don't see where that could be the problem because it idles just fine, and I'd think it would generate a code for a miss.

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Sunday, December 11th, 2016 AT 5:54 PM

HMAC300

MECHANIC
48,601 POSTS

It's the pressure solenoid not the trans. They will probably give you an estimate without looking at it see pics for testing on out tips area some guys have replaced lead frame and solenoid and still had problem and others found it was a bad pcm. Here is how to check with volt meter. Last pic pin on right is 4 and left 5. Evidently the pins break. Most of us mechanics are not familiar at all with trans like you as we have to much other stuff to learn/diagnose and or fix. That's why we send people to trans shops who specialize in that sort of stuff.

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