Won't downshift??

[operatorTRP]

OK, So I searched a little but am pinched for time.
'97 LX450 Supercharged. Farkled to the hilt. TRD SC.

Driving up the big hill to my house (don't now the grade but pretty steep and about 500'? elevation change?)
Tranny seems like it is stuck in high gear? needing to downshift to make power?
When running right the truck will pull all the way to the top downshifting to 2nd? revving to 3500ish, pulling 6-7psi boost. and holding speed 65-70 mph.
Now it looses speed and tops out at 45 and nothing left? sitting at 5PSI.Holding in high gear?

Is there a common problem/ easy fix? I recently washed the engine bay? maybe a vacc line got blown loose? point me to a thread or give me the answer!

GO!

And THAnks!

 

[operatorTRP]

Nothing?

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[Offroads4x4]

Sounds like your kick down cable needs to be adjusted.
Is it adjusted correctly?
Did your shift cable brake to the trans?
Start with the cable it controls the kick down timing.

 

[Nemo]

Ditto the above on the Shift Cable.

Might make sense to check your wiring harness along the fuel rail line and make sure the clip hasn't broken and made it's way onto the EGR Valve. I found this to be my problem immediately after washing my engine bay as well resulting in the problems you describe.

 

[operatorTRP]

Thanks for the direction!!

I had to leave town, I'll check the cable and wiring when I get home.

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[CJF]

Start with the cable it controls the kick down timing.

Supposedly only on a 91-92 (hydraulically controlled A440F).

Hey OP: You know about the "PWR" button?

 

[Offroads4x4]

Supposedly only on a 91-92 (hydraulically controlled A440F).

Hey OP: You know about the "PWR" button?

FYI:

My 94 has a trans kick down cable and the ECT (PWR) button for the trans.

 

[CJF]

FYI:

My 94 has a trans kick down cable...

I know.

Tools R Us has said (on pretty good authority) that on a 93-97 the cable only affects line pressure (and hence how smooth or "snappy" the shifts are) and not shift points.

I don't have any direct experience with that though...

 

[operatorTRP]

Is there something special about the power button?
I have it, but it has never been on? The change in performance was with it off?

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[Offroads4x4]

Power button (PWR or ECT) when engaged holds the trans in the lower gear longer before the up shift. This allows the engine to be at a higher RPM giving you an extended power band sort of speak.

 

[Offroads4x4]

....Tools R Us has said (on pretty good authority) that on a 93-97 the cable only affects line pressure (and hence how smooth or "snappy" the shifts are) and not shift points.

I don't have any direct experience with that though...

Correct but it acts just like a kick down when adjusted correctly. With it adjusted as you describe "snappy" ( more line pressure ) that will make it shift sooner as well as stronger.

The OP issue he wanted to resolve was faster kick down and or more power before up shift.

I should of just said adjust the trans cable correctly Instead of kick down cable.

 

[Tools R Us]

Correct but it acts just like a kick down when adjusted correctly. With it adjusted as you describe "snappy" ( more line pressure ) that will make it shift sooner

Nope.

... stronger. ...

Yep.

On the later rigs the trans cable has nothing to do with when the trans shifts, it only adjusts the firmness.

On the solenoid shifted units, the shift points are purely controlled by the ECU. It uses inputs like RPM, load, throttle position, temp, etc and compares them to a map, the map varies depending, button pushed, power, 2nd start, trans and transfer shifter position, etc, this determines when shifts happen.

 

[operatorTRP]

So my problem of it not downshifting when revs get too low, like going up a hill is most likely something not communicating to the ECU. I need to chase wiring and make sure nothing has come loose. Also set correct tension on kdc..
Is there any sensor that would typically go bad and cause these symptoms?

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[Offroads4x4]

Water in connections can cause grief. Corrosion and electrical current don't mix well.
Be sure as you check and clean your connections with CRS Electrical Contact cleaner or alike.
Make sure you use dielectric grease in them to help them make better contact and protect them in the future.

JM2C

 

[operatorTRP]

So I got home last night.
Today I started looking around the engine, nothing looked out of order. No loose connections, burned wires, nothing?
I take it for a test drive and everything is fine, back to normal, perfect.
I guess some water got somewhere and took several days to evap? A little un nerving not knowing exactly what caused it, but thankful it is working fine now!

Thanks all for the ideas.

I'll still go over all the connections and DI-electric grease after cleaning with contact cleaner.

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