ive got a 99 4t65eHD.
the 1-2 shift is slow. with a lot of throttle it doesnt want to shift at all and it feels like being in 3rd gear in a manual, reaching for 4th and accidentally shifting into 2nd and letting out the clutch. theres that same... yank. the RPM's drop quite a bit when this happens, even at WOT.
doesnt do it in any other gear and for the most part all other gears are quick, while downshifts are instantaneous.

i took the filter apart and ive got no metal bits and its pretty clean. theres no clutch mud/muck. i dont think its a clutch issue. im leaning towards a valvebody issue or a 1-2 shift solenoid issue.
anyone familiar with these valve bodies? could it possibly be a 1-2 accumulator valve, a boost valve, or a pressure regulator valve.
i had issues earlier in the year with a bad EPC solenoid. i think most of the damage was done when i went to long before replacing it.


UPDATE* the problem has progressed to identical symptoms on the 2-1 shift, and symptoms while in gear.
under WOT, while in first gear the transmission will slip right out of first, almost as if its going into nuetral. let off the throttle and it shifts into second.

im starting to suspect a failed pump. ive previously inspected the teeth on the pump shaft and they were fine.

bumpity bump bump.

If it's ONLY the 1-2 shift then it's probably a shift solenoid. That's my guess.

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98 GTP (RIP 11-5-09); 73 Z28 Camaro (350, TKO 600);01 Monte Carlo SS (L36, L67/L32 hybrid in the future)
"Death smiles at us all; all a man can do is smile back"

i thought that as well, but from googling shift solenoid issues, when the 1-2 fails you usually end up with no 1st or no 2nd gear.

Could be the PCS...Pressure Control Solenoid. It causes a soft 1-2 upshift. Do you have a check engine light on?

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One Big Ass Mistake America

no, and no.
ive already replaced the PCS with an OEM unit, and no check engine light. although i was getting some codes from the snap on scanner.

P1571: TCS PWM circuit no frequency
P1689: TCS delivered torque circuit fault.
P1811 (the infamous) Maximum Adapt Long Shift.

i think that the TCS issues are from the failsafe mode. it shuts TCC off in failsafe.
not sure though, but i definately dont have TCC issues.

The P1811 is caused by the PCS. If that code is gone now, then that is good. If not, then you still have a problem in that circuit.

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One Big Ass Mistake America

i dont think its caused by a failed EPC solenoid. i do know that if you have a bad EPC solenoid, then youll surely have that code.

like i said, ive replaced it twice. the code persists. which has got me thinking its the regulator valve underneath the EPCS.

http://tripleedgeperformance.com/Harsh_ ... P1811.html

that will give you some ideas what to look at

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92 LeBaron Convert: Turbo 3L 97 Grand Prix GT 4dr "Frankenstein": L67 4t65 swap
97 Grand Marquis: Summer DD 99 Grand Prix GTP: Top Swap Beater

that post makes me think its gonna be a bad 1-2 shift accumulator valve.

UPDATE* the problem has progressed to identical symptoms on the 2-1 shift, and symptoms while in gear.
under WOT, while in first gear the transmission will slip right out of first, almost as if its going into nuetral. let off the throttle and it shifts into second.

im starting to suspect a failed pump. ive previously inspected the teeth on the pump shaft and they were fine.

it's at the point for me i would need the car in front of me. internet diagnosing trans issues is hard lol

i wounder what the line pressure is

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92 LeBaron Convert: Turbo 3L 97 Grand Prix GT 4dr "Frankenstein": L67 4t65 swap
97 Grand Marquis: Summer DD 99 Grand Prix GTP: Top Swap Beater

im pretty sure i figured out whats wrong with it. ill have to pull apart the old clutch packs to be sure, and see if theyre bruned.

im thinking its a broken or badly burned forward apply band. Boosting the line pressure doesnt help much, or very little.
it explains the RPM's tendancy to stay steady, as opposed to maxing out at WOT when the issue occurs. it explains all the slippage issues under heavy throttle, WOT, or downshifting and upshifting when the RPM's are very high when the selected gear is engaged.

the only thing it doesnt explain is the slow shifts. which leads me back to the idea that the original damage was all caused by a failed EPC solenoid that i neglected for too long.

Wow i noticed this today as well seems like the car just goes to second could it be the EPC it takes a Looong first shift to 2nd seems like a power loss is that what u also had ?

once again, ive replaced the EPC, many times. along with the clutches.