My Eaton 8LL is not going into high range.

[sonoran rock trucks]

I purchased the truck this past October drove it home no problem the truck sat for five months and now it doesn’t want to go into high range. I have change the air filter valve in the back of the transmission. I also  changed the range selector valve “slave valve” I currently do not hear any leaks in the shifter nor any of the valves. The transmission is still not going into high range. It was running perfectly fine before I parked it five months ago. Any suggestions would be greatly appreciated thanks

Edited May 5, 2020 by sonoran rock trucks

[alex g]

I had same problem. I tapped range selector air valve with a hammer and it worked. Not sure since you changed valve if your issue is the same. 

[sonoran rock trucks]

I did check the transmission fluid and the oil Looks like hair gel

[j hancock]

Hair gel?

Hmmmm..... should look like 50 W oil.  Eaton PS-321 or PS-386 synthetic or equivalent.

[sonoran rock trucks]

On 5/7/2020 at 2:31 PM, j hancock said:

Hair gel?

Hmmmm..... should look like 50 W oil.  Eaton PS-321 or PS-386 synthetic or equivalent.

ya man it was thick and looked like water got in there 

[david wild]

Oil the cheapest thing to keep shit running but the most overlooked, amazed every day.

[ultratruck]

Check and drain air tanks. If you have crud or if you dont check air pressure at lines into hi lo valve on the back if you have 60 or more put shop air in back and forth to where the high lo lines go on the valve. if you can not hear it shift pull the bolts out and remove the cover put a vise gripe on the nut you see and try to push it in and out. If air is leaking into the transmission it can be hard to hear  you would need to monitor loss of air with button up and down. It can be the syncro is gone if the trans made any kind of noise before you parked in on the high to lo or the low to high shift it uses to different pads. 

[sonoran rock trucks]

On 5/12/2020 at 8:05 AM, ultratruck said:

Check and drain air tanks. If you have crud or if you dont check air pressure at lines into hi lo valve on the back if you have 60 or more put shop air in back and forth to where the high lo lines go on the valve. if you can not hear it shift pull the bolts out and remove the cover put a vise gripe on the nut you see and try to push it in and out. If air is leaking into the transmission it can be hard to hear  you would need to monitor loss of air with button up and down. It can be the syncro is gone if the trans made any kind of noise before you parked in on the high to lo or the low to high shift it uses to different pads. 

So we found what the problem was. In the deep reduction cylinder the thumb button cylinder was getting stuck. A new O-ring kit for the high and low did the trick. The truck now shift into high gear is no problem.Thanks again for the help I’m sure somebody will learn from this

[sonoran rock trucks]

 

[j hancock]

Thanks for posting info on the resolution to the issue.