2000 Limited gets confused shifting from 4th to 3rd

[Mark_BC]

I've had this issue ever since I owned the car. When I'm cruising along the highway in 4th and I encounter an uphill, it naturally wants to shift down. But it gets confused and seems to be stuck in a half way land where it shudders violently and I don't let it stay there long enough to see what will eventually happen. I either turn off overdrive which then shifts it down or I put the pedal to the metal to do the same. Any idea what this is? I'm hoping it's something simple like adjusting some linkage. Otherwise the transmission is fine.

 

[RandyBobandy]

Mine used to do the exact same thing when it was still an auto but it was pretty intermittent, ended up being a misfire that only happened under load in fairly specific conditions. Does it always do this or is it intermittent?

 

[Mark_BC]

It always does it when I'm cruising on the freeway in 4th and I hit a hill where it needs to downshift.

 

[brillo_76]

I have Randy's old transmission in our 97 limited. Its perfectly fine so it wasn't his auto transmission..

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[brillo_76]

Will see if [MENTION=8262]badluck[/MENTION] has any ideas. As it kinda sounds the the Tc is not locking unlocking properly or maybe a solenoid malfunction.

Very possible misadjustment on the kickdown cable itself.

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[Bad Luck]

It always does it when I'm cruising on the freeway in 4th and I hit a hill where it needs to downshift.

So here’s what is supposed to occur when you apply more throttle when going highway speeds. You are in 4th with the torque converter clutch engaged, more throttle is applied so the ecm commands the torque converter to unlock (this is where your shutter is occurring), when you hit overdrive off it shifts down to 3rd and will engage the torque converter clutch again.

Assuming that it is torque converter shudder and not a load related misfire then I would suspect a problem with the torque converter clutch shift solenoid, valve body, or even the torque converter itself. When torque converter clutches fail they typically shudder in 4th gear with the clutch engaged (or whatever the highest gear available is depending on the transmission). What are your engine rpms before, during, and after the increased throttle and shuddering?

 

[GunslingerT4R]

Not saying it will fix your issue, but when I first got my 97 SR5 I replaced the transmission solenoids and it fixed my issue. Just something to think about.


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[Mark_BC]

Thanks everyone, I will start with the solenoids. I need to learn more about how those work and which one to suspect.

I'm in the city now so don't have the rpm's available but I'll be cruising at 55 mph and then I hit the hill and it wants to shift down but has trouble. Whatever rpm that is in 4th.

 

[phattyduck]

As brillo said, pay attention to 4th with torque converter locked, vs. 4th with torque converter unlcocked, vs. 3rd with torque converter locked, vs. 3rd with torque converter unlocked. Those 4 different modes almost feel like 4 different gears.

You can tell if the converter is locked or unlocked by varying throttle input and seeing if the RPMs are locked to road speed or vary a bit with throttle application.

It does sound more like a torque converter issue than a shifting issue. Especially at lower highway speeds (say 55mph, like mentioned) the torque converter will unlock really easily. RPMs should just jump up a few hundred and that's about it.

-Charlie

 

[Mark_BC]

I got up to 55 for a short while today. 1800 rpm (32" tires, 4.30 diff). I could push the pedal down and rpm's didn't change at all which tells me it was locked. Then I pushed it down harder and it "decided" to shift but got confused, and then pushing it down further at a hill forced it to downshift.

 

[brillo_76]

Do you happen to know how old your fluid is and the condition of the screen filter? As this is an odd issue. The confused state.

Does it seem to be going form one gear to lower gear then back to the higher gear?

As I believe the solenoids control the gear shifting. Sending transmission fluid through different paths.

I am also wondering if someone before you put the wrong atf in it thus causing this issue as well. Puzzling in deed.

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[Mark_BC]

I did a complete change last year as per Timmy's video with the same stuff he used. Previous fluid was good.

When it gets confused it's like it gets halfway to shifting but doesn't complete and as a result the power from the engine just leads to a lot banging and thumping and shuddering since it isn't going into a gear properly.

Shifts between 1, 2 and 3 are perfectly normal. I'm guessing it's a problem with the solenoid that controls that gear shift, but I know nothing about about transmission solenoids.

 

[19963.4lsr5]

Is it a missfire at those higher rpm’s that makes it feel like it’s the trans screwing up?

Does your year trans have a kick down cable? If it does not what is your tps reading in that zone of screwing up?


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[Bad Luck]

I got up to 55 for a short while today. 1800 rpm (32" tires, 4.30 diff). I could push the pedal down and rpm's didn't change at all which tells me it was locked. Then I pushed it down harder and it "decided" to shift but got confused, and then pushing it down further at a hill forced it to downshift.

The first “shift” is the torque converter clutch unlocking. The second shift is going from 4th to 3rd.

Does it happen if you have overdrive turned off and the torque converter clutch unlocks when more throttle is applied in 3rd?