I have searched the threads but found nothing specific to my concern. So, to kick things off, the vehicle is a 2000
E250 5.4L. There is no Check Engine Light and no transmission codes present. When accelerating up to 45 to 50 mph the trans upshifts smoothly. However, a few seconds after the 3-4 shift is complete and the throttle is held steady, the trans starts shifting from 4 to 3 and 3 to 4, back and forth at a steady cycle of 1 to 2 seconds between the downshift and upshift. It is not TC shudder. I know what that feels like. I can slow the van to a stop with perfect downshifts to 1st gear, no jerking and the shifts are not noticeable. Reverse is fine too. Has anyone had this specific issue with their AODE/4R70 series tranny??

 

You'll need to look at live data to see if the computer is commanding these shifts or the transmission is doing it on it's own. If the computer is commanding the shifts you'll need to look at data for the inputs to see what's out of whack. It could be vehicle speed, engine RPM, throttle position, TRS input, OD switch problem, or a few others that I haven't thought of.

 

I am still troubleshooting the concern. I recorded trans data on several road tests for further review. The cruise was set to 49 mph in order to maintain a steady speed and consistent throttle angle on flat road. The PCM is commanding 4th gear at cruise when the "anomaly" presents itself. It appears right now that any change in throttle angle toward deceleration, however slight it may be, triggers the event. The commanded gear is still 4th, but it feels like it is downshifting to 3 due to the significant engine braking and rpm rise going on. The braking effect can actually move me forward in the seat at 50 mph. Then it will shift back into 4th/OD and do it all over again several times. One thing I noticed looking at the PIDS is the TCC solenoid modulating between off and 50% give or take, and coinciding with the change in shift feel. I should be coasting when coming off the throttle at 50 mph but instead it feels like it downshifts to 3rd (no command to go to 3 by the the PCM) - or maybe the converter clutch is applying when it should not be. I am studying the TCC pids more closely as it modulates from the OFF condition to see if it correlates to deceleration. Still no codes yet. I don't know, maybe a crossleak in the valve body or the OD servo piston fluid pressure is leaking down causing the OD band to lose grip on the low/reverse drum? I don't think that is the case. I don't feel any slipping nor is the trans neutraling out due to low apply pressures. It shifts great except for the dang OD issue.

 

This sounds like a engine miss, it is very common on this vehicle and can be deceiving because its more noticeable when in lock up. We have other shops send us vehicles like this and they are convinced its the transmission when in fact its a engine miss so its easy to overlook.

It can be caught in a scanner that is capable of recording engine misses in the generic section of the data menus.

 

Well it is possible of course, but I don't think that is the issue in this case. Believe me, I am trying my best to cover every base before considering removing the valve body or yanking out the trans, lol.. The pids show no misfire counts at idle or under any load condition on the road test. I gave it a major tune up recently. There is no timing correlation issue causing misfire after verifying with cam and crank waveform overlays and relative compression is very consistent. Power balance test is good. I did not capture any unusual waveforms on the primary (trigger) side of the COPs using an amp clamp and the secondary spark and dwell times look good. In other words, no indication of lean, rich or compression misfires. No primary or secondary fault codes pending or stored. The symptom is not a fuel or fire related stutter or misfire, or a converter shudder for that matter. The ecm will command all up and down shifts at the proper time right into 4th/OD, back down to 1st. Stall test is within prescribed rpm range for the 5.4L standard E-250 configuration, between 1768 and 2114 rpm in all gears so no clutches or OD or low/reverse band slipping. No shifts into neutral. They are nice and crisp, not harsh or too soft.
BUT, while holding steady throttle, light loading, on a flat road at any speed where 4th is commanded and the OD button is not lit, the TCC solenoid will modulate and the converter will indeed lock up....until I ease OFF the throttle. It is at this point that the trans feels to be downshifting to 3rd while 4th is still commanded, for two or three seconds and then back to 4th for a couple seconds, back down to 3rd for a couple seconds in a repeating cycle. Trans fluid and filter are new. SS1-SS2 solenoids are new along with the EPC solenoid. The OSS is new and the TPS has no linear drop out. I am thinking I need to look closely at the possibility of a weak or contaminated TCC solenoid and/or the VB circuit for OD and TCC control. I feel like I have eliminated most everything outside of the trans at this point.

 

If you are sure its not a engine miss and in fact the transmission is cycling in and out of forth gear this can be caused by a stuck or worn solenoid regulator valve.

The solenoid regulator valve is responsible for providing a proper amount of regulated line pressure for shift solenoid 1, shift solenoid 2 and the TCC solenoid to operate effectively. If the valve becomes stuck inward, or if the bore is worn, the solenoid regulator pressure will be limited and can cause the shift solenoids to not operate correctly, causing a number of shift issues, especially cycling of 4th gear apply and release over and over. The reason this typically occurs in 4th is because both shift solenoids are ON in 4th gear. In addition the TCC solenoid is also turned ON for converter clutch operation. So the number of solenoids that are competing for operating pressure is greater and a loss of available pressure can cause one of the solenoids to not function correctly.

 

Thanks for the reply and your info on the solenoid regulator valve, jk080.
I am confident it is not a misfire concern. I have been there a number of times with the 5.4 engine and their owners thinking it's a transmission issue. I am admittedly less proficient, however, in troubleshooting valve body symptoms, simply because I don't get into many of these units. So, after the series of tests performed outside of the transmission and no issues discovered, I will be pulling the VB for inspection, paying very close attention to the solenoid regulator valve and bore area as you suggested. I'll install a new TCC solenoid while in there since it is the original. I have not overhauled many 4r70w's, and among those, have not had any specific failures of the tcc solenoid but I always replaced them as part of the overhaul.
I have learned to check for worn epc regulator valves and bores, worn boost valves and sleeves, etc. that can cause pressure loss, but mainly, what I have experienced on these units amounts to broken accumulator springs, burned up direct clutch, Int clutch (pressure loss or overheating), broken stub shafts and reverse sun shell gear broken from the weld.
I will let you know what I discover once the VB is on the bench. I'll go ahead and stone the VB case and install new check ***** as well. Thanks again jk080. Your suggestion may prove to be the remedy.

 

Could also be a split checkball in the valvebody.

 

The VB is on the bench and I am going through it with a fine tooth comb. Verified no split check ball in any of the 8 locations. Condition of each check ball is good, but using new ones when going back together.

 

i have always found that a trans will start to "hunt" between direct and OD when it is in need of a service.
and after service the hunting always goes away.

 

Resolved! I just want to close this thread on a positive note. The 3-4 shift problem has been FIXED.
As some of you suspected, myself included, the source of the trouble was in the valve body, specifically, the 3-4 and Low Servo Capacity Modulator Valve circuits. I inadvertently swapped the springs between these two valves (thanks JK080 for the spring arrangement info) during the initial rebuild process. Having the lighter tension "white" spring behind the 3-4 modulator valve apparently created an imbalance in the 3-4 shift circuit. It should have had the "yellow" heavier tension spring installed with it and the white spring installed with the low servo valve. Now, although I did replace the TCC solenoid and the harness assembly with new ones this time around, I did so purely to extend the operational reliability of the transmission. There were no problems detected with either of these original components. Additionally, I replaced the solenoid regulator valve and spring, mainly as a precaution, but there was no indication of sticking and no wear on the valve or in the bore detected that might have caused sticking. To this end, the trans shifts beautifully and is silky smooth at the top end in OD, and perfect closed throttle coasting conditions without going into that rapid 4-3 shift cycle. Thanks to all those who offered their experience to get this one resolved!