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03 4.0 4x4 Automatic Transmission in trouble


03ranger4x4

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Okay, so my dad just called me and said while driving his truck today he barely made it block before as he described it, the truck seemed to "jump out of gear" when he hit the gas. Following this, he explained the "O/D OFF" light started to flash. Doesn't sound good :sad:

So, I know its not much for you guys to go on....but its all I know right now.

He did check the fluid, and he said it looks clear and it is filled within spec...not low or anything. I have a scan tool so im going to use that tomorrow to see what trans code pops up.


I read somewhere that there is a "servo o-ring" that sometimes fails and isn't too involved to replace? Also saw another article about the valve body gasket going?

Im leaning towards something like that, the transmission never seemed slip before this, it sorta just gave out according to him, leading my to believe a part just failed and the transmission is not actually worn out beyond its life. It has only about 120,000 miles on it, I would assume it should have a good 40,000 left. It was occasionally abused when it was my truck....some harsh sand romping from time to time But I kept on the maintenance on it and always changed the fluid every 30,000-40,000 miles.
 
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96firephoenix

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the light blinking is a notice that the ECU has found something electronically fubar with the trans control and can no longer consistently control the trans.

probably a solenoid
 

03ranger4x4

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Well, I scanned it today and got a pending code for P0720

Which is for "output shaft speed sensor"...

Also took note of symptoms. It has no 1st gear, and no reverse. I would put it into either drive or reverse and the RPMS would drop slightly as if it engaged that gear, but you hit the gas and it pretty much just revs up and slowly coasts. Put into "2nd" and it shifts right in, doesnt slip or anything. I would able to floor it and it didnt pop out of 2nd or slip. Didnt drive it far enough to see if I could pop it over to drive at speed and see if the other forward gears worked or not.

I have no idea how the speed sensor would prevent 1st and reverse from working, so im going on a limb and saying that sensor probably isnt actually bad, and that whatever let go in the transmission is making the computer see the signal from that speed sensor as faulty and setting that code.

I took the valve body off today as well as the low/reverse servo. O-ring on the servo looks fine, valve body gasket didnt look bad, but one part looked like it "may" have been leaking. Who knows....got new o-rings for the servo and new valve body gasket on the way. Gonna put it back together, torque everything to spec and see if it goes away.

I might pull the speed sensor too, just to see if maybe something let go so bad in the trans that it chewed up the speed sensor and thats why that code was reported....

Other then that, idk....pretty much need to pull the trans to do anything else, and if thats the case then we might aswell put a re-manufactured one in with a good warranty
 

96firephoenix

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i suppose it is possible that if the output sensor is bad, it is limiting the transmission's efforts... :dunno:

Google "GM Limp Home mode" and you'll see that you aren't the only one with similar issues...
 

03ranger4x4

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i suppose it is possible that if the output sensor is bad, it is limiting the transmission's efforts... :dunno:

Google "GM Limp Home mode" and you'll see that you aren't the only one with similar issues...
I don't think so, I mean the "O/D OFF" light doesn't even start flashing until you start moving in second gear, which it what led me to believe that the sensor code was caused because of something mechanically going wrong in the transmission. If the sensor was just straight up bad, you would think it would set the code the second the key was on, i mean thats how ever other sensor works.

Besides, in limp mode, Both "D" and "R" should still work. In limp mode D locks the trans is second gear. And reverse should also still work....

Anyways, new gasket and 0-ring is at my dads house, going to put it back together tomorrow. If it doesn't work, then I guess its going to a shop. Seems to be some promising ads on craigslist by non-franchise offering 5r55e rebuilds for around 500$, and around $1200 installed with new convertor.
 

03ranger4x4

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Well, the gasket and servo o ring didnt help. Though I am proud i was able to put it back together and it at least still drove lol.

Did some further symptom analysis. Turns out, if I run the truck up to 50-55mph in second, I can click it over into drive and it shifts into overdrive no problem. So my guess is something quit near the low/reverse drum. maybe the band broke, also read somewhere someone with similar symptoms had thier 5r55e torn apart and there was a thrust bearing that went bad.

Anyways, its going to the shop to get fixed. Going to run around 11-1200 bucks.

Not like this truck doesnt have enough problems....passenger CV boot is torn, from that stupid splash sheild that fell down and rubbed against it.

Also had a coolant leak i need to find

And listening to the motor today im pretty sure i hear faint timing chain rattle...even though 2003 should have the stronger chain guides, i guess its somthing thats inevitable. Its needs an oil change, so ill probably put 10-40w in it from now on.
 
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