Shifting issues 4l65e - SOLVED

[srcmull]

Hello,
I have a 2003 Yukon Denali LQ4 with 4l65e transmission. 89k miles on the vehicle.
A couple of weeks ago I was out driving. As I went to pull out from a gas station the car felt like it was in 3rd gear. I down shifted manually and was able to get moving, shortly after this the check engine light came on with these codes.
P0758
P0740
P0753
P0785
P1860
On my drive home the check engine light went off and the vehicle shifted fine. The next day the same thing happed.
After a little research I ordered a new solenoid kit (all solenoids and the loom)
The engine codes were now gone but the vehicle won't shift past 2nd gear. There is no 3rd when I shift manually either. One weird thing I noticed is if I take my door off the gas and coast, I noticed a drop in rpm as though it were shifting to 3rd.
So I called a mechanic, they suggested it was either a TCM issue or something internal. I decided to swap out the TCM to see if that fixed it. No luck.
Please help

Steve

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

@NickTransmissions is our resident transmission expert, and he will chime in with his thoughts and perspectives.

 

[NickTransmissions]

Hello,
I have a 2003 Yukon Denali LQ4 with 4l65e transmission. 89k miles on the vehicle.
A couple of weeks ago I was out driving. As I went to pull out from a gas station the car felt like it was in 3rd gear. I down shifted manually and was able to get moving, shortly after this the check engine light came on with these codes.
P0758
P0740
P0753
P0785
P1860
On my drive home the check engine light went off and the vehicle shifted fine. The next day the same thing happed.
After a little research I ordered a new solenoid kit (all solenoids and the loom)
The engine codes were now gone but the vehicle won't shift past 2nd gear. There is no 3rd when I shift manually either. One weird thing I noticed is if I take my door off the gas and coast, I noticed a drop in rpm as though it were shifting to 3rd.
So I called a mechanic, they suggested it was either a TCM issue or something internal. I decided to swap out the TCM to see if that fixed it. No luck.
Please help

Steve

Does it stay in 2nd gear or does it shift from 2nd gear but feel like it's in neutral after shifting from 2nd?

 

[srcmull]

Stays in 2nd. It's feels like it shifts if I take my foot of the gas, I see a drop in rpm.
Could it be a stuck valve?

 

[srcmull]

Does it stay in 2nd gear or does it shift from 2nd gear but feel like it's in neutral after shifting from 2nd?

srcmull​

TYF Newbie​

Stays in 2nd. It's feels like it shifts if I take my foot of the gas, I see a drop in rpm.
Could it be a stuck valve?

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[NickTransmissions]

Could it be a stuck valve?

Quote Reply
Report •••

Maybe, maybe not. Grab a bidirectional scan tool, plug it in and take it for a test drive. See what gears are being commanded. If a 2-3 upshift is being commanded by the PCM but it's not happening (or if it's not happening even when you command a shift) then the cause is either shift sol B is stuck on, stuck 2-3 shift valve/shuttle valve or something else...Let us know what the data tells you and we can go from there.

 

[srcmull]

Maybe, maybe not. Grab a bidirectional scan tool, plug it in and take it for a test drive. See what gears are being commanded. If a 2-3 upshift is being commanded by the PCM but it's not happening (or if it's not happening even when you command a shift) then the cause is either shift sol B is stuck on, stuck 2-3 shift valve/shuttle valve or something else...Let us know what the data tells you and we can go from there.

Ok,
So the PCM is commanding a shift but not shifting. I pulled the VB to take a look at the valves. The shuttle valve moves freely but the shift valve does not. I managed to get it out and I am attempting to clean the bore. Is there anything I should look for or would it just be gunked up?

 

[NickTransmissions]

Is there anything I should look for or would it just be gunked up?

You already found it. Now it's time to fix it...

Completely clean the bore, removing all traces of fluid and other contaminant. Then reinsert the valves dry. Conduct a vacuum test. If your reading is higher than 22Hg, the valve is a bit too tight in the bore. Polish the bore with a bench buddy using your drill and WD40. Do short bursts (15 sec or so) at moderately high speeds then check for freedom of movement. Do this until the valve isn't dragging.

Then completely clean the casting to remove all of the WD 40 plus all other residue and then reinsert your 2-3 shift valve, shuttle valve and solenoid B...Once done, vacuum test the 2-3 shift and shuttle valve to ensure you still have good sealing integrity. 15-22Hg is ideal. Any less, you took off too much...Any higher (23hg-25Hg) you still have some work to do.

I would vac test the entire valve body at this point - see my video here for reference.

Let us know how it goes.

 

[srcmull]

You already found it. Now it's time to fix it...

Completely clean the bore, removing all traces of fluid and other contaminant. Then reinsert the valves dry. Conduct a vacuum test. If your reading is higher than 22Hg, the valve is a bit too tight in the bore. Polish the bore with a bench buddy using your drill and WD40. Do short bursts (15 sec or so) at moderately high speeds then check for freedom of movement. Do this until the valve isn't dragging.

Then completely clean the casting to remove all of the WD 40 plus all other residue and then reinsert your 2-3 shift valve, shuttle valve and solenoid B...Once done, vacuum test the 2-3 shift and shuttle valve to ensure you still have good sealing integrity. 15-22Hg is ideal. Any less, you took off too much...Any higher (23hg-25Hg) you still have some work to do.

I would vac test the entire valve body at this point - see my video here for reference.

Let us know how it goes.

It worked!!!
She shifts great now.
Thank you for your help Nick.

 

[NickTransmissions]

It worked!!!
She shifts great now.
Thank you for your help Nick.

You're welcome!