Hard Shift in 4th to 5th gear?

[Husam]

Gentlemen,

2015 v6 3.8L RWD Genesis: Condition:
- Mileage = 92,500 Miles which is about 149,000 KM.
- Location: Dubai
- Warranty: Expired
- Car very well maintained, regularly.
- All fluids changed (Engine Oil, Radiator fluid, Brake Fluid, Diff Fluid)
- All filters changed.
- Transmission fluid completely drained and filled 3 times in a few days in the dealership with new pan.
- Zero codes in scanner; system check: OK.

Situation:
- Hard shift or slam-like shift from 4th to 5th gear with more than gentle throttle applied. Hence I performed the above service.
- While pushing pedal with (let's say) 15% throttle, Hard Shift b/w 4th and 5th gear is very apparent.
- While changing throttle positions (i.e., very gentle acceleration, shifting is very smooth), or (i.e., more than 1/2 throttle, shifting is smooth too) between these two gears.

Action Taken:
- Transmission fluid completely drained and filled 3 times in a few days in the dealership with a new pan -- same issue persisted.
- Added a bottle of Lubegard Red into the ATF fluid -- same issue persisted.

My own analysis:
- A bad shift solenoid that is clogged or dirty.
- A bad throttle position sensor? (no codes in OBD scanner though)
- Speed sensor?
- Valve body?


What do you guys think the best course of action is? My last resort is to pay for a full Transmission replacement which I am trying to avoid by carefully eliminating the problem.

Let me know your thoughts.


Thanks,
Husam

 

[Kraig Wilkinson]

Gentlemen,

2015 v6 3.8L RWD Genesis: Condition:
- Mileage = 92,500 Miles which is about 149,000 KM.
- Location: Dubai
- Warranty: Expired
- Car very well maintained, regularly.
- All fluids changed (Engine Oil, Radiator fluid, Brake Fluid, Diff Fluid)
- All filters changed.
- Transmission fluid completely drained and filled 3 times in a few days in the dealership with new pan.
- Zero codes in scanner; system check: OK.

Situation:
- Hard shift or slam-like shift from 4th to 5th gear with more than gentle throttle applied. Hence I performed the above service.
- While pushing pedal with (let's say) 15% throttle, Hard Shift b/w 4th and 5th gear is very apparent.
- While changing throttle positions (i.e., very gentle acceleration, shifting is very smooth), or (i.e., more than 1/2 throttle, shifting is smooth too) between these two gears.

Action Taken:
- Transmission fluid completely drained and filled 3 times in a few days in the dealership with a new pan -- same issue persisted.
- Added a bottle of Lubegard Red into the ATF fluid -- same issue persisted.

My own analysis:
- A bad shift solenoid that is clogged or dirty.
- A bad throttle position sensor? (no codes in OBD scanner though)
- Speed sensor?
- Valve body?


What do you guys think the best course of action is? My last resort is to pay for a full Transmission replacement which I am trying to avoid by carefully eliminating the problem.

Let me know your thoughts.


Thanks,
Husam

If you have access to a good Snap on scanner you can maybe check live data on the trans an compare voltages between the solenoids and psi differences. With a Solaras scanner you can do a deep dive into what's actually going on in trans/engine.

 

[Husam]

I just did - i have a "Launch" Scanner with me anyway - I did a live stream on a few solenoids and here are the screenshots.

The culprit is Shift Control Solenoid Valve C (35R/C) which is responsible for 2nd to 3rd AND 4th to 5th shifts. I am not quite sure if the voltage is within standard limits but it seems that this specific solenoid's voltage is the least of all. Paying close attention to its behavior, I felt the downshift from 3rd to 2nd being a bit harsh too.

Please take a look at the attached images. (check the legend under each diagram as the color code changes from one image to the other)

What do you think?


Thank you,
Husam

 

[Husam]

If you have access to a good Snap on scanner you can maybe check live data on the trans an compare voltages between the solenoids and psi differences. With a Solaras scanner you can do a deep dive into what's actually going on in trans/engine.

Can you check my post / reply with the Scanner results? It seems one Solenoid's voltage is lower than the others.

Thank you

 

[Husam]

I discussed the issue with the dealership workshop, I agreed with them to order a solenoid to replace Shift Control Solenoid Valve C (35R/C) for now. Once they order the part, it will be replaced and will test the car; I shall keep you posted.

However, the HMC recommendation in such cases is to replace the transmission in full which I decided not to do; and only test a new solenoid.


Thanks,

 

[Husam]

UPDATE:

I replaced rear diff, all Transmission solenoids; flushed the ATF 3 or 4 times, replaced wiring harness b/w valve body and TCM; reset adaptive values and did a gear adaptation or re-learn.

Issue persists; and I still have hard shift from 4th to 5th gear while ATF is not so hot and it is still noticeable when ATF warms up. Then added Lubegard Instant Shudder Fixx but did not help.

What do you guys recommend? is it a Torque Converter issue? Are the clutch bands wearing out? Should I consider Lucas Transmission Fix to stop slip or improve the grip between the clutches? or am i looking at replacing the full transmission assembly?




Thanks,
Husam

 

[Jtc527]

You sure it’s a harsh shift or it’s coming from the rear differential

 

[Husam]

You sure it’s a harsh shift or it’s coming from the rear differential

Its a harsh shift; I forgot to mention that I already replaced the rear diff as well. (i'll update my post).

 

[Husam]

I had taken my car to the dealership, they checked it and although my TCM was having the latest software update, I asked them to reflash the TCM with the software and it worked! No more hard shifts 90% of the time!

 

[SixFootSix]

I had taken my car to the dealership, they checked it and although my TCM was having the latest software update, I asked them to reflash the TCM with the software and it worked! No more hard shifts 90% of the time!

I experienced the same hard shift and found that removing battery power for 15 minutes also resets the shift back to soft.
I have not replaced anything (yet) but the upshift and downshift now causes a loud click in the rear axle or differential. That’s not surprising since the hard shifts have at times chirped the tires at 40 MPH and that can’t be good for any powertrain.

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[Husam]

I experienced the same hard shift and found that removing battery power for 15 minutes also resets the shift back to soft.
I have not replaced anything (yet) but the upshift and downshift now causes a loud click in the rear axle or differential. That’s not surprising since the hard shifts have at times chirped the tires at 40 MPH and that can’t be good for any powertrain.

The clicks you experience, are they at specific speed always? I suggest you look into the propeller shaft potentially.