Transgo Kit, Superior Kit, Sonnax Boost Valve, new EPC and still have shift flare | Ford Explorer Forums - Serious Explorations

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Transgo Kit, Superior Kit, Sonnax Boost Valve, new EPC and still have shift flare


October 4, 2005
Reaction score
City, State
Corning, NY
Year, Model & Trim Level
99 Explorer Sport
99 explorer sport, 5r55e tranny. i have done the following and STILL have a 3-4 shift flare:mad:

-Transgo Kit (currently using red spring on forward mod valve. orange spring caused a harsh 3-2 coast downshifting clunk)
-Superior Kit (steps 1,2,6,7,9. took out step 3 cause with that mod, i again had a harsh 3-2 clunk)
-Sonnax Boost Valve (increased ratio)
-New EPC
-New VB gaskets
-Adjusted bands (tightened to 120 in. lbs., backed off 2 turns on both)
-Changed fluid and filter with Mercon V

the flare is intermittent, usually happens when i'm a little harder on the throttle. if anyone has a idea where to turn now, i'd really appreciate it, thanks

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Increased Ration Boost Valve, I wonder if the upgraded Servo Pistons would help?

3-4 flare, instead of 2-3 ?

yep 3-4. its done this ever since i bought the truck about a year ago. 1-2 and 2-3 are nice, solid shifts. other than this 3-4 issue, the tranny seems to be fine.

Did you click test the solenoids? I'm thinking maybe SS1 may be a possiblity? If SS1 failed Failed ON (it is ON for 1st-3rd gears and switches OFF for 4th along with SS2) then that might cause a 3-4 shift issue?

just a thought.

Ok well let's first look at the 3-4 shift, and go from there.

In the 3-4 shift, the intermediate band releases, and the direct clutch applies.

Shift solenoids SSA and SSB are ON in 3rd and OFF in 4th. The Coast Clutch Solenoid may be on in 4th.

Knowing this, let's see what the FORD factory manual says and contrast what you have already done. Maybe we can isolate something from there.

As we look at the rundown on a soft/slipping 3-4 shift, we start, as always with electronic trannies, with a check of general system inputs, wiring etc. Absent codes you are probably ok here. Pinpoint tests recommended are those that check the shift solenoids (remember the change in SSA and SSB?) and the EPC (which you replaced).

Next we look to the Main control assembly (Valve body). We look for screws out of torque spec... a damaged gasket or sep plate, or a bad epc. You pretty much covered all this.

In the VB we look at 3-4 shift valve (bore 215 and not a big problem child) the forward modulator valve/EPC boost valve (bore 207 and SOMEWHAT of a problem child) and the EPC blowoff valve (which you replaced with your FORD MOD - so not an issue.)

Your center support sealing rings can be a problem (teardown) or your direct clutch can be leaking , either because of seals or checkball issues (teardown). You COULD have burnt frictions in the direct clutch (teardown). You COULD have some intermediate Servo issues, but I doubt this because you have a solid and good 2-3.

So non teardown items include internal spools in the VB and the shift solenoids A and B.

Hope this is of some help. I hate to say but I lean towards direct clutch issues.

ps. I can send ya some shift solenoids to try out.

You might also look at the Sonnax "Reconditioning" kit for this tranny. It mainly consists of O-ringed bore end plugs, a boost valve (which you alredy have) and an upgraded pressure control spool.

BillJ, I'm not exatly sure what you mean by click testing. I did test the resistance of the solenoids and they were all within specs if that helps any. What is click testing and can I do it with basic tools?

Glacier, I may take you up on that offer with the solenoids. At one point, I did swap around solenoid 2 and 4 but unfortunately made no difference so I swapped them back. It seems that would rule out solenoid 2 but maybe not. Let me know about prices and all that on the solenoids. One thing that comes to mind....and keep in mind that i'm no tranny expert but since the flare is intermittent (like all other flares i've read about in this forum), wouldn't that lead more towards an electrical issure rather than a mechanical issue?

Try a click test with a can of pressurized fluid such as WD-40, or brake cleaner. If you see that these solenoids behave like a valve, then they might still be good. Either way the cleaner will clean out anything which is clogging them.

i'm going to give that a shot, probably won't get to it till this weekend. i'll let you guys know the results. thanks for the ideas