TheFrench

Hello,

I have a problem with my automatic transmission.
All gears rise effortlessly from the first to the fourth gear and then in the overdrive, without problems.

But if I want to accelerate on the highway, the fourth gear (or the third?) want not to engage, the car has no drive and the engine goes high rpm.

My SS is Trifecta tuned, to test if it is the cause I reflashed the stock tune with no changes.

What can you recommend how I should proceed to fix it?

firemangeorge

Pull the codes and see if there is a hidden one that didn't trigger the CEL =Check Engine Light

( I am assuming that you don't have a Check Engine Light since you didn't mention it. )

Oldblue

Shift solenoids weak . Burnt connections.

donbrew

4th gear is overdrive at cruising the torque converter locks.

Are you saying that when you stomp on the gas from cruising speed the transmission seems to go to neutral instead of downshifting to 3rd?

If there is an electro-mechanical problem there should be some codes, maybe hidden. It is electronically controlled unlike older cars with a downshift linkage.

TheFrench

I took my scanner this morning, there are 4 error codes stored
from earlier issues concerning passenger presence module and Airbag but for

TCM and ECM no codes are stored, the CEL is off.

@donbrew I thought the 4t45 have a physical overdrive with a specific gear ratio on top of the 4 gears. Do I misunderstood this?
Yes, the TCC is locked and not slipping at cruising, when I stomp the gas it´s going to neutral instead of a gear, I dont know if 3rd or 4th.

@Oldblue I really hope it's a leaking, obstructed or hanging solenoid,
better than a worn band or disc. I dare to replace the solenoids, but not to disassemble the gearbox.
Dont think about electric problem because of no error codes are set, but who knows...

Thanks for helping.

More advices?

donbrew

just 4 gears plus locking torque converter. 4th is 0.681:1 overdrive, 3rd is 1.000:1

Down shift from 4 to 3 involves the 1-2 solenoid switching off. so that might be the prob.
Have you tried shifting into "I" that effectively turns 4th off. No matter what you may hear you can manually shift the automatic, you just have to do it at the right times. And you can turn overdrive off, just no button.

Check your PM.

TheFrench

Yes donbrew, I have tested to drive on "I" mode and all works fine also from cruising to accelerating
the automatic goes from locked TCC to 3rd gear without slipping nor going to neutral.

I read that the 1-2 solenoid is switched on/off in gear variations. I also read that this 1-2 solenoid is often bad because outer oil level.
As I say, I hope it is a bad solenoid. My intention is to replace all 4 solenoids and the plate as offered in a kit by many shops.

PM check: many thanks @donbrew

What do mean about the converter? How to test and what are the typical symptoms of a bad TC?

RJ_RS_SS_350

You said there were 4 error codes, what are they?

TheFrench

2 for passenger presence module, 1 for passenger airbag in the dashboard and 1 for rollover sensor.
The codes were never deleted, they came for years with a drained battery, airbag light is off and I think they have nothing to do with trans issue.

donbrew

Testing the converter involves sticking your finger in the center and seeing if you can turn it in both directions; not for the casual mechanic.
That is all in the book. As well as the solenoid sequencing. Could be the 1-2 is not going all the way off for some reason.