4L60E No 4th Gear

[ChevyCowboy22]

I have a 1994 Chevy K1500 5.7/ 4L60E. trans was rebuilt 12000 miles ago with all new raysbestos clutches, electronics, and even an aftermarket cooler half the size of my radiator. Since the rebuil the trans has worked flawlessly. i havent pulled anything in OD just in 3rd. But to the point i was driving down the road and the truck downshifted to 3rd coming up a hill and it never went back into 4th gear. I let it sit overnight got in it and it drove great all gears and tc lockup. Got in it the next day and no 4th again and havent had 4th since. I checked the brake swith just in case and ive also drained the pan to look for debris and examined and cleaned the servo. But i still dont know whats wrong with it. If anyone has any ideas please let me know? I miss driving my truck

 

[ndians68]

sounds like maybe a broke band, our cousin's cummins that he just got broke the band from 1-2 and it would only shift out of first some times, and when it did it would shift hard, and then it would act like it didn't know to up shift or down shift for a bit, then go into 2nd. Or you would have to let off and let it shift then get back on it.

 

[ChevyCowboy22]

there's only one band in the trans and its for 2nd and 4th if it was bad i dont think id have 2nd gear. thanks though. so here's an update. i went to take my truck to a buddy's house and now i dont have 1st gear also. So now i dont have 1st or 4th. if you leave the trans in OD it seems to try to shift into 4th but it never does. any help?

 

[ccreddell]

if you let it get low on fluid, its most likely fried. Takes about 20 seconds of low fluid to kill one of these. Time for another rebuild....

 

[rhino]

Have you checked for codes? Some codes will set and not turn on the check engine light. That's where I would start. Loosing 4th gear is not a very common problem. In second gear as you already stated the band is on. Then in third it releases, and on come the 3/4 clutches. You have 3rd so they are good. Then comes on the band again for 4th, while the 3/4 clutches are still applied. So... the piston in the servo cap, is the 4th gear servo apply, you already looked at that. Next is a valve body or solenoid. Thats where I would look. Check them codes, I bet that will tell you where to go. Keep us updated...

 

[rhino]

You find anything out on this?

 

[ChevyCowboy22]

well i finally figured it out a few days ago. There wasnt any codes but once i realized i didnt have 1st or 4th i did a little more research and found that it was either the 1-2 solenoid or bad wiring from pcm or bad pcm. I unplugged the trans and found the pin for the 1-2 solenoid and had a buddy pull the truck down into first so i could check for power. I had power so that ruled out the wiring from pcm or a bad pcm. so i went and got a new solenoid changed it out and it runs like a dream again.

 

[ChevyCowboy22]

o and also what i thought was it trying to go into 4th gear was the torque converter locking up.