96 k1500-4l60e no 1st or od after warmup

[fupidstumbducker]

truck just started messing up.works great for about the first 4 miles then I lose od.once I stop I lose first gear also.i then have to manually shift to 2nd and it hits hard.i can let it sit for 5 minutes and it will work fine the first time I take off then back to 2nd and 3rd.reverse works fine at all times.someone said maybe fluid in vacuum modulator.didnt know it had one.any help would be greatly appreciated.thanks

 

[WorkinMan]

I had an issue once while driving down the highway that my truck kicked out of OD and the check engine light came on. Turned out to be a shift solenoid. There are two solenoids one is for first and fourth gear, the other for second and third. If that is the case you'll have to remove the pan to get to it, but it is a very quick and easy fix once you pull the pan. I can't really remember if I had to remove the trans filter as well, but if this is your problem you might as well get a new one since you'll be in there anyway. I don't think the solenoid was very expensive either.

Just thought this might be worth a look. Sounded kinda similar.