4L60E Won't Downshift

[CHEVY_1999_K1500]

1999 K1500 5.7L V8 w/4L60E Won't Downshift to 1st

First shop replaced all solenoids and it did not fix anything. ($1000)

2nd Shop ran a new wire for the downshift solenoid and it didn't fix. They then ordered a new ECM. It changed nothing.

I'm back to fixing it myself and was hoping somebody had some experience troubleshooting it versus swapping parts.

 

[1997]

any codes?
how many miles? any other symtoms? other gears work? downshift manually?
sounds like it's in limp mode ....
do you have a scanner?

 

[sprite]

I had an issue where my truck wouldn't shift out of first gear and it was because my throttle position sensor had gone bad. Might be worth a shot

 

[tayto]

4L60E doesn't have a downshift solenoid. are you saying it won't shift out of 1st gear?

 

[CHEVY_1999_K1500]

PO785

It won't downshift to 1st from 2nd upon coming to a stop. You can manually shift into first and it then upshifts fine.

Transmission is a Monster 4L60E I had a shop install back in 2019. Tranmission has about 60K. Suburban has almost 400k.

I did find a couple of you tube videos I need to review but wanted to see if anybody had any direct experience.

 

[df2x4]

Transmission is a Monster

Uh oh...

I know this doesn't help you now, but in the future I'd stay far away from Monster Transmission. I've been reading horror stories about them on the internet for years.

 

[tayto]

i think time for a scantool to see what gear it is commanding. have you had the vehicle tuned at all?

 

[CHEVY_1999_K1500]

No, have not tuned anything. Factory Stock. I do have a low end Autel bluetooth scan tool but it does have any command modes - Read only. Can anybody suggest a budget scan tool that can perform all the tests required to troublehshoot a 4L60E.

 

[CHEVY_1999_K1500]

Reading more about limp mode.

Need to check power to transmission

 

[tayto]

limp home mode is 3rd gear all the time