i started having this problem right after i broke my built motor in (around 1200mi)i was crusin down the hwy doin bout 75 then the speedo died and the truck i guess went into safe mode and shifted itself into neutral. i let go of the throttle and the speedo came back up and the truck shifted back into gear. it happened a couple more times within the next few days until it left me stranded on the hwy. im reading a po340 code which is a camshaft sensor i changed that still the same problem. i had a po722,po720 code come up also which is the oss sensor which i changed also, still same problem.
i checked all fuses,o2 sensor wires,o2 heater sensor wires,all connectors,all grounds,wire harness from the pcm back to the trans and everything looks good. what gets me is i was told by numerous people that the code im getting has nothing to do w/the problem at hand. i even tried putting the pcm back to stock and took it for a ride still the same thing.
any info will be appreciated.
thanks
jay

 

Sorry, I don't know, I'm a Rookie..There's some nice folks on here who can help you out..

 

Your intermediate sprag died on you. The OSS (output speed sensor) code is because the computer expects a certain output speed for a given RPM and you aren't getting it. The sensor is fine, the reading t's giving isn't. The tranny needs to be rebuilt. Is this by chance a 2001 Model with a J1 Transmission (code on the ID tag forward of the extension housing)


G

 

I would say you have your answer, lol. Gregg knows his chit. Sucks about the rebuilding of the tranny though. Good luck with that.

-Kimball

 

My 2001 was a J1 tranny and **** the bed @ 60000...it was the
test tranny for a different...uh...****in'....

 

na man its a '00 and the trans showed no signs of having to be rebuilt. the only addition to the trans is the factory tech valve body, could it be possible that some dirt blew into the internals of the trans while installing it (i picked the nicest day to do this but who knows i did do it outside) the truck has only 31000 on it. what happens if the valve body loosens up from the main internals of the trans, would this loose pressure and cause it not to shift?
whats a intermediate sprag? and why would i be getting a camshaft sensor code if its the trans??? i am totally stumped and pissed off
thanks jay

 

I have changed my camshaft sensor but don't recall having shifting problems. Could be a failsafe not allowing it to shift.
The sensors are not too costly..under 20 bucks if I remember. I would check the tranny wiring harness if changing the sensor and resetting the ecu doesn't work. I had a couple wires melted on mine near the passenger side exhaust once and it would set codes...OSS on the tailshaft. Repaired the wiring..two were fused together and everything went back to normal. This wiring damage was ,in my judgement, caused by not hanging the wire back in place correctly after a tranny install..You have to get up close with the harness...chances are you'll find a glob of melted wire conduit if this is your problem...good luck. Damn..I guess I should have read your post better...Ok...I even changed the VSS...on the differential housing. I'm still thinking bout it...Has it been shifting ok consistently after the valve body install ? Maybe stuff the stock valve body back in if you haven't sent it in for credit...My FTVB has lots of miles on it and works like a charm.

OK..my speedo would bounce and set codes...then it would run fine for a while and the speedo would die..
I changed the OSS and VSS...without noticing the wiring problem. Maybe double check the wiring on the tranny...mine was obvious once I started really snooping...My guess is the motor work and or tranny removal has done some wiring damage..if not melted..possibly crushed..maybe borrow a harness or ohm it out. Hey remember I could be wrong and your mileage may vary.. I think Factory Tech is saying the computer tables indicate a certain OSS input for a given Cam Position Sensore input..if they are out of tolerance or considerably off..then it sets the CPS fault.
When the intermidiate sprag/clutch went in mine it did not want to shift out of 1st. If you lifted...it would shift into second and then the rest of the gears were fine. Have you been hammering it pretty good? Maybe you have a 2000 with a J1 prefix...should be on the tranny tag. Mine ran ok for a while as long as I remembered to lift my left foot every time it wanted to shift to 2nd.

 

Also check your TPS. It can have an affect on shifting.

 

twisted, i had the truck at my local dealer and they tested the harness from the pcm back to the tranny and they said it read ok. i wasnt hammering it at all because i was just breaking the new motor in. as for the valve body i just put it in while i was installing the motor so i dont know much about that. i tried lifting no dice! well my only next move would have to be dropping the trans pan and swap the valve body out

gregg, would the intermediate sprag give some kind of sign that it was on its way out, instead of just becoming dead??

silver, ill take a look at that tomorrow!! and cross my fingers, hoping thats it!
thanks jay

 

No, when the sprag dies, it just dies. It's much more common on the early 2001 models (they had a different design one way clutch, the dreaded mechanical diode) but the dogbone style does grenade sometimes.

G

 

Try this, do a normal slow and steady acceleration with it in Manual 1, and shift to manual 2 at about 20 MPH, do you get second gfear that way?

G

 

I just had to have my J1 transmission rebuilt, mine would shift into 2nd and bog down and wouldnt shift into third. If i remember correctly it was a 2nd intermedial clutch that broke in two.

 

I think the technical name is the intermediate one way clutch.

G

 

gregg, just got back from a ride around the block and the truck will shift into 2nd manually, but will not shift into 3rd?? does this help narrow it down to the problem at hand?? still getting the 340 code on the programmer.
thanks jay

 

u out there gregg