hi i am having problems with my alli tranny. when i am in D cruising down the road my tranny all of a sudden will just fall out of gear and the rpms shoot up. it does this mostly when i am in high gear and when my tranny guy scanned it there were no codes. i dont think it is slipping because wot it grabs good in every gear. so now i drive around in third and it does the same thing but not even close in frequency as when i am in high gear. also when in third at 3000 rpm there is a feeling like a off and on clunking or like its wanting to shift in a higher gear. when in D after it falls out of gear i just let the throttle go and it catches gear right away. then i can punch it and the tranny holds really well. then all of a sudden it will fall out of gear periodicly.also sometimes after coming to a stop it will do a banging clunking in gear at take off (not slip yoke) feel it right underneath you.i dont know if this is a t case or tranny issue as i did run my t case dry after pump rub issue a few months ago. any help on this would be great thank you. my truck is not modded for power but it may have been in the past

what does the shift indicator do when this is happening ? is it off or flashing ? coulb just be the switch on the slector (NSBU switch) some times they get water in them and cause issues.

no the gear indicator does not start flashing when it does this. but once a month or so when i put it in reverse it starts flashing R and it is not in gear. then i have to put it in park, then back into gear and everything is fine. also the truck has had this reverse issue well before i had the forward gear problem. thanks for the help

I would suggest to put a Prindle switch on and see what happens. Without any codes it is hard to say what it is for sure.

by prindle switch do you mean nsbu switch. thanks for the advice i will have to come by your shop when i get more money to upgrade my truck

It is the switch on the side of the trans that tells the PCM what gear is selected. If there is a problem with the switch the computer may think it is in a different gear then what is selected. See alot of them go bad. Sometimes it will set a code and other times the trans just act funny. Dirt and water collects behind the switch and eventually gets inside the switch and takes it out. Alot of the times the DIC will flash, go blank, say range shift inhibited, or just the line on the DIC saying what gear you have selected will dissappear.

so is this prindle switch you reffered to the nsbu switch? and do you recomend changing this first before doing anything else. i still dont know if this is a tranny or tranfercase problem. truck is parked for now as i dont want to hurt anything further. i work with this truck and it cant be down for long but taking it to the stealership is not an option. any help or recomendations would be greatly aprieciated thanks

Prindle switch/usbu switch is the same thing. Changing the switch is just something you could try. You should also remove the speed sensor on the back half of the transfer case. I have seen a couple of them leak atf into the sensor connector a screw up the reading. If the PCM sees a change in vehicle speed it may take it to a lower gear.

It costs more to have the NSBU switch diagnosed than the price of a new switch.

well i put the new nsbu switch and external filter on today. when i went on a test drive,it did the same thing but this time it threw a code p0700,p0735,p0736.now it is making weird grinding noises in all gears and the truck doesnt move. the reverse only works sometimes and it has a pretty bad burning smell. i know it is cooked but what options do i have now. i plan to add a ppe accelerator hot +2 so what upgrades do i need. will a sc 3 a 1057 plus replace the burnt clutches be ok with the highest setting. i got a good tranny guy so what will these parts cost. thanks for the help.

I don't want to hijack here, but I have the same type of situation. Truck is doing the same thing but is throwing:

P0734 Incorrect 4th gear ratio
P0735 Incorrect 5th gear ratio
P1720 Soleniod A controlled clutch stuck off

Any ideas??? Thanks