ECU/PCM or Tranny Problem ? 95 Ford Explorer

[naturlm]

Hi:

I have a 95 Ford Explorer, 4.0L, 2wd, with 4R55E tranny, with non reprogramable EEC-IV computer part number F5TF-12A650-ARC having calibration code 5-58B-R10. I am getting a delayed tranny shift from 1st to 2nd and no engine braking when in manual 2nd. 3/4 Od light flashes and error code readout with analog vom gives me a code 646 (2nd gear ratio problem). I did a stall test per ATSG and it passed the required spec rpm range (not over speeding or going under) in all shift lever positions. Figuring the intermediate servo band is not being properly applied I have replaced a hard rubber seal intermediate servo piston and seal but it has not helped.

I downloaded a couple Ford TSB's off the adddata website and am a bit confused regarding the Ford TSB article 98-5-1 dtd 03/16/98. Is says it might be possible to fix my tranny problem and eliminate the blinking light error code by replacing my F5TF-ARC computer with a later design, model F5PF-BRA. Both old and new computers have same recomended calibration code.

I have been unable to locate any low cost (junkyard) F5PF-BRA's for my trial use in my vehicle. No trouble at all finding the ARC's. All the local tranny shops, with exception of Ford Dealer's shop, say they have never heard of a computer causing a tranny shifting problem. However the local Ford dealer tech manager, after I showed him the TSB, says I should first change the computer before starting to look for problems inside the tranny. Ford wants $ 275 for the BRA computer. Sure wish I could find a used one for $ 75 or so.

Does anyone have any technical details on what could be occuring that the model F5PF-BRA (I am assuming it may be a later design) may or may not solve my tranny problem ? I would like more info / knowledge before I under expense of having the tranny torn down or ordering a rebuilt tranny.

And that brings up another question, if I put in a rebuilt tranny and the problem is in the old design ARC computer, will I have to get the latest design BRA computer to make a rebuilt tranny work ?

Comments appreciated....

Mark

 

[1Bluegrass]

Here is what your dealing with on a 5R55E transmission.
The trans has a turbine sensor.
The actual gear ratio can be computed anytime the trans is not shifting properly. An actual gear ratio is computed in each gear and compaired to the predicted gear ratio in order to determine the actual gear pattern obtained during an upshift sequence.
This information is then used to determined which shift solenoid is malfunctioning by the responses from voltage and current monitors.
For example if SS1(shift solinoid 1) is shorted to power or is hydraulically stuck in that position, the 1-2-3-4-5 commanded shifts will actually result is a 2-2-4-4-5 pattern.
This unique pattern will set a code that is indicitive of what SS is malfunctioning.
This should give you an idea that a shift solenoid or it's circuit is in trouble and not a very serious internal transmission fault, hopefully.
Droping the pan and/or testing the solenoids has a high probability of finding the problem.
This use of logic is used throughout all the different transmission models to different degrees as well as in engine control.
I had to dig it out from Ford discriptions of operation.
Hope it is your answer.

 

[naturlm]

Bluegrass1: (in Engine & Fuel Enginnering Forum)

Great response !

I now much better understand this particuliar control mechanism and what is actually setting off the 646 error code in my 4R55E transmission. I note my vehicles computer is also set up to issue an error code 622 if the SS2 solenoid circuit fails to provide the proper voltage drop across the solenoid. I am not getting the code 622, so I think the electrical signal to the solenoid coil is likely OK and solenoid coil is OK, but I am guessing the solenoid is not moving because the solenoid piston or valve is mechanically stuck in place in its casing and will not move. Does this make sense ? To find out for sure, I guess for sure the tranny pan needs to be dropped/removed and the actual valve mechanism examined / cleaned to be sure SS2 piston/valve is free to move.

The tranny had 150,000 trouble free miles on it until this problem occured. About 7500 miles of the last 50,000 miles was done towing a 3300 lb boat/trailor combo.

All the shop mechanics I talk to say I am very lucky this particuliar model tranny lasted this long, and it is very likely that other than this specific current SS2 solenoid or valve problem, the whole control valve assembly has several worn internal valve parts, worn valve casing parts, deteriating valve rubber O rings and seals etc......... all of which could give me trouble in next 10,000 plus miles if I keep this vehicle. Anyone agree or disagree ?

So ......., maybe I should listen to the tranny repair techs and shops, and put in a rebuilt tranny to renew all the worn parts at this point, with the idea I will keep the vehicle another 5 years plus to get my money out of the rebuilt tranny.

I have found a rebuilt or remanufactured tranny at an out of state tranny repair shop. Seller says it was rebuilt by Ford's inhouse rebuilder, Fred Jones Enterprises. Seller says he can let me have it at a good price with a 12,000 mile warranty because he got it at a good price from a Ford dealer who was going out of business. I am thinking maybe this is best way to go, especially if the rebuild was done by Fred Jones.

Wondering if there is someway I can easily verify this rebuilt is actually is a Fred Jones rebuild by looking at the tranny ? Are they special stamped some way or tagged some way ? Guess I should contact Fred Jones to find out.

Note: Parts of this particuliar post, at least those parts asking for comments on long term wear/reliability at 150,000 miles etc. belongs over in the driveline forum. So I will post it there also.

 

[1Bluegrass]

I can't help you on the new unit you have a lead on but, I do think besides the wear in the valve body bores, the valve body and all the SSs are exposed when the pan is removed.
If you are going to keep the vehicle another 5 years, I think another trans is in order or have yours rebuilt so the thoughts of failure are removed from everyday concern.
Locally, I am lucky to have a fine shop that does quality work. They done 4 different Ford units for me, over the years.