Dear All,


An update: the failure is when the truck is running at normal temperature (warm/hot), the first 5-8 minutes after it is turned on the transmission/truck works perfect!, but when it is at normal temperature the fail appears..., what can be the cause?


I really need help to identify what could be the problem on my transmission (2006 CrewCab Lariat 5.4L 4x4). The problem has just started, let me explain it: when the truck is running at normal temp and it starts to move after a total stop when the throttle pedal is pressed the first gear feel like it canīt be engaged at the normal way, so the tranny has a small "slipping" and the truck "jumps" 2 or 3 times then start to run as the normal way (the jumps are wild). After it is angaged the nexts gears change up or down fine. But when it is running at the last gear (65 mph) and the throttle pedal is unpressed the truck starts to change down the gears by itself so the truck reduce the velocity suddenly. At that time, when the throttle pedal is pressed again the transmission jerks one or two times during acceleration.

I canīt hear any strange sound neither metal noise, my mechanic said he canīt identify what can be wrong or damaged, his scanner didnīt collect any code. No "check engine" or message appears on my truck. I checked the ATF fluid level, it is OK. The mechanic verified all the connectors (from computer to tranny) and all are cleaned and OK.

Could be a damaged sensor?, or damaged solenoid valve?, how can I find the problem/root cause?

All your comments and advices will be more tha welcome!

Thank you in advance for your help.

J. Leal

 

How many miles are on this particular truck?

Have the plugs been changed?

 

Thank you for your answer, here is the info:

The truck has 100k miles but the plugs were changed 10k miles ago. The coils are the originals that came from factory.

Should I be focused on "combustion" issue instead of transmission?

Thank you in advance!

 

No, this is a transmission issue.

 

Thank you for your response. I have to said that I washed the engine after a hunting trip (because was stuck in a muddy field) two weeks ago; and just the day before it started to fail were installed a new amplifier/subwoofer/speakers/head unit by a professional installer.

However, my mechanic cleaned all the wiring connectors from the battery, computer, etc., to discard any bad connection, the problem remains the same.

Can any of these events cause this failure ??

Thank you!

 

Washing the engine can cause coil failure, it's also possible water got past the coil boots into the spark plug wells. By the description of your symptoms, I think it's more than that.

 

Thank you GLC, all the coils were removed and cleaned by the mechanic but the fail remains the same, as you said it is more than that.

Any ideas/suggestion what could be damaged? Or why the truck fails on this way?

Thank you!

 

I'm wondering (wild guessing) if the cause of the problem could be the filter in the transmission fell off???

 

Thank you Roadie for your answer; ...Do you think a fell off filter can cause the symptoms my truck has?, if it is the cause then is easy/cheap to fix (no major damage) crossfingers!

 

As updated of my problem, the fail is when the truck is warm at normal temp ONLY!, ...the first 5-8 minutes when the transmission is cold works perfect (did the same the past two days), hope this can help to identify the cause ??

Please suggestion? ?

Thank you in adavnce!

 

When the fluid is cold it is thicker. This will allow a transmission that is failing due to a sealing issue to sometimes operate normally until it heats up.

Unfortunately hard to diagnose over the internet.

D