Silverado bad 1-2 shift

[GarrettM]

I have an 06 silverado vortec max. Under wide open throttle, the shift between 1 and 2 is not like it should be. I'm not exactly sure how to describe it, but it's almost as if it tries to shift but it takes it about a half second. The rpms come down to about 4 grand when it shifts and then it revs up a few hundred rpms past that and then I can feel it finally complete the shift and it gets pulled back down to about 4 grand. All under wide open throttle. It should be a quick firm shift but it is definitely not

[Sierra Boy]

When was the last time you changed your fluid and or filter? Your trans needs maintenance to live a long life. How many miles on the truck/trans?

 

Sierra Boy

[GarrettM]

Less than 2,000 miles ago it was flushed with filter change. I believe about 147,000 miles

[00Silverado4x4]

I'd get it to a shop for diagnosis. Save you time and money vs guessing.

[02suburbanZ71]

I'd get it to a shop for diagnosis. Save you time and money vs guessing.

An LQ9 with a 70e and 150K miles i think we know what the problem is

[Chris]

An LQ9 with a 70e and 150K miles i think we know what the problem is

Not necessarily. Im pushing the limits of the stock 160k 60e that came in it from the assembly line with a tuned LQ9. Just because you had problems doesnt mean they all do

[02suburbanZ71]

Not necessarily. Im pushing the limits of the stock 160k 60e that came in it from the assembly line with a tuned LQ9. Just because you had problems doesnt mean they all do

I never had problems and i just hit 124K it was called torque management and now i had 75% removed

[Chris]

I never had problems and i just hit 124K it was called torque management and now i had 75% removed

I had a lot more than that removed 80,000 miles ago. The past 50,000 with the LQ9.

[02suburbanZ71]

I had a lot more than that removed 80,000 miles ago. The past 50,000 with the LQ9.

What percentage did you remove 100?

[Chris]

With the 1-2 shift being the issue it could need a rebuild, but it could also be something as simple as the 1-2 servo

[Chris]

What percentage did you remove 100?

85% with the 4.8, 100% with dyno tune and 6.0, it probably has about 90% removed now. Tow/haul dials it way back down so i can tow without hurting anything

[02suburbanZ71]

85% with the 4.8, 100% with dyno tune and 6.0, it probably has about 90% removed now. Tow/haul dials it way back down so i can tow without hurting anything

I have all my TM in normal driving then tow/haul turns down 75% i noticed with Tow haul on i dont have the clunk when slowing or accelerating around town [emoji4]

[GarrettM]

What makes you say that? 150k miles should be fine on a vehicle that has been taken care of which mine has

[GarrettM]

An LQ9 with a 70e and 150K miles i think we know what the problem is

What makes you say that? 150k miles should be fine on a vehicle that has been taken care of which mine has

[PJB1972]

Under wide open throttle, the shift between 1 and 2 is not like it should be. I'm not exactly sure how to describe it, but it's almost as if it tries to shift but it takes it about a half second. The rpms come down to about 4 grand when it shifts and then it revs up a few hundred rpms past that and then I can feel it finally complete the shift and it gets pulled back down to about 4 grand. All under wide open throttle. It should be a quick firm shift but it is definitely not

 

My guess, and it's ONLY a guess...

A delayed or abnormal 1-2 shift under WOT (If there's a problem ONLY on the 1-2 shift) could be caused by the 1-2 accumulator piston being cracked or stuck cocked inside the bore.

Check the yellow spring inside the accumulator housing for breakage. Also, if the accumulator housing walls are scored, the housing must be replaced.

 

Additionally, IF the 1-2 shift does not happen at WOT until you let off the gas:

Best case: Try replacing the TPS.

Middle case: Possible leak in the 2nd gear apply circuit (servo assembly or 1-2 accumulator). Double check by using a pressure gauge and watch for a big drop when the PCM commands 2nd gear.

Worst case: Poor line pressure rise (Cracked 1-2 accumulator)

 

Either of these will allow the transmission to run "normally" during regular driving but would reveal themselves under WOT.

I would consult a REPUTABLE transmission shop and/or baby it until you can have it rebuilt...

There's my 2 pennies...