Went to lunch today and when I left I noticed truck seemed as if not shifting out of 1st until high RPMs. Then noticed on a hill when truck kicked down to second the transmission was like it was in neutral and revved to the rev limiter. I tapped the brake to kill the cruise and then transmission seemed to go back to third. 1st, 3rd & 4th all seem fine and it is like 2nd is slipping or not there at all. After doing some research it seems to me like this is a candidate for the Sonnax 7778702K Servo Pin Kit to buy a little time for a possible worn band. Does this problem usually seem to come on that fast that it just starts randomly one day when you just drove the truck 30 minutes ago and it was fine? Only reason I'm hesitant to assume this is I've never seen someone reference the trans kicking down to what seems like no second gear, it's always just complaining of skipping 2nd gear when shifting.

04 Silverado 4l60E

 

Are you certain that Reverse and Over-Drive are operating?

 

Yeah i was going to say it sounds like a sunshell issue, but then he wouldn't have R or OD either.

If it was the band you would likely have issues with OD as well.

Low/reverse or reverse input clutches maybe??

1-2 shift solenoid? Damn we could sit here playing guessing games all day. Pull it apart and let us know.

 

Yes, reverse and OD are confirmed working. I will try and get it it up in the air tomorrow so I can check the travel on the servo cover.

 

Checking servo travel and doing a basic line pressure test are the most basic and effective places to start.
Sounds like you're on the right track if you do both of those.
Let us know what you find.

 

Wouldn't 2-4 servo/band issues cause loss/issues with OD as well?

 

Not always.
There are two separate pistons for 2nd and 4th...they can both apply slightly different strokes.
LOTS of documented cases where you'll lose one of them (2nd or 4th) and the fix is to lengthen the pin...then you get both.
The funny part is...sometimes it's 2nd that goes first...sometimes it's 4th.
in my personal experience it's 4th that goes first MOST of the time...but not every time.

 

Interesting, are the two pistons both in the 2-4 servo?

Still learning heaps, love working on transmissions

 

Realistically the transmission has one bore for both servos that share a common apply pin.

But they work as if they are two different servos all together...

The small piston directly under the cover is for forth gear.
Then you have a circuit separator.
Then a larger piston for second gear.

 

Interesting, thanks for sharing.

What is the purpose of a separate piston to apply the same pin? wouldn't it have been simpler to just have the same piston apply for both 2 and OD? Forgive my ignorance, just learning.

 

2nd piston applies 2nd...3rd gear actually acts on the back side of that same piston to push against it and release the band.
4th comes on to push back and re-apply the pin.

I'm not going to speculate on what would have been simpler or more complicated...The valve body and sequencing of valves worked for the 700r4 when it was designed...that's what the engineers chose...and that's what stuck as the years went on.

 

Have you tried manually shifting it? that would rule out a shift solenoid.