1st to 3rd on upshift, 4l60e 1999 yukon, 144000 miles

[dsltrc]

I'm dealing with a gremlin.. At first I thought my truck was just shifting into 2nd after I let off the gas at 2500rpm. Changed the 1-2 accumulator and boost valve with no change.. Then realized that I was missing 2nd gear when the truck is up shifting but had 2nd when manually downshifting without giving it any gas.. Any help would be great...

 

[SunlitComet]

Do you have 4th and regardless of that can you select them manually and have each gear function correctly then?

 

[dsltrc]

I do have 4th gear when driving, I don't have 2nd gear when pressing the accelerator.. But when I am at speed and let my foot off the gas and down shift manually thru each gear I can feel the transmission down shift thru each gearing including 2nd but when I give it gas it goes back into 1st gear... I don't know but it sounds electrical to me..

 

[SunlitComet]

sounds like the sprag is goofed. Pull codes to see if anything pops up as some tranny issues will not trigger the light.

 

[dsltrc]

Ok so my check engine light came on read read the codes,
First one is B0226 left front speed signal..
Then P0751, shift solenoid A performance or stuck off, so I replaced both solenoids while I was in there took it for a drive and no change, unplugged the battery trying to reset the computer now... Hoping that works..

 

[dsltrc]

Ok.. I'm at wits end.... Still didn't fix the problem and now there are no codes...

 

[retorq]

It's not the sprag, if the "sprag was goofed" you would have no forward movement in D, only in the 3 2 1 position. Ask me how I know.

You may have a worn separator plate issue with 144K if it's stock. Those steel balls can blow thru the separator plate or become lodged in there blocking flow all the time. When you down shift you are engaging the overrun clutches and the transmission will function differently internally.

 

[dsltrc]

So Ill change the separator plate next and if that doesn't fix it I'll take it to a pro..

---------- Post added at 03:33 PM ---------- Previous post was at 03:02 PM ----------

What is the worst case senecio if the ball has gotten lodged in the separator plate?

 

[retorq]

Then you need a ball and a plate. I like the Trango plates with torlon balls.

 

[dsltrc]

So I tore into the tranny and this is what I found, got a transgo separator plate, gaskets and thorlin check balls. Put it all together tonight and will finish tomorrow and see if this fixes my problem, QUESTION; could this have damaged my transmission?