O/D Off button dead

[zap_ingo]

Hey guys
I have yet another question about overdrive problems, some days ago my transmission got stuck (96 XLT, 4R55 I believe) It wouldn't move at all, with the engine started if I switched to R or D the engine just suddenly died like the tranny was stuck or something. After a few attempts it start moving and I could get the truck back home but it couldn't barely move. After that I've had some problems like delay shifting and not engaging properly. The overdrive works sometimes only, sometimes it just won't go into overdrive, the O/D Off button does nothing when you press it, no light no downshifting. After more than a week of reading several posts of similar problems I decided to do some work myself and go ahead and replace the EPC solenoid, went to the dealer and bought one, remove the pan and notice the parts were not the same!!! Well' I ended up just changing the ATF and filter since they recognized they sold me the wrong part and they don't have the right part in stock, it will take a week and it's $250 CDN.

After th ATF change the truck shifts just fine, right in time and the tranny seems pretty smooth. The O/D fuse in the driver's panel was blown, I replace it but I still have the same problem with the O/D Off, not working, no O/D Off light and not going into 4th gear. Could this be be something electrical or there's a problem inside the tranny? I notice that the O/D light starts to blink 5min aprox after I press the O/D Off button while driving. If I don't press the button the light stays off all the time and doesn't blink.

Any ideas where to check?

regards

 

[zap_ingo]

I just thought I'm missing some info about the problem, the car has 190000km (118000 miles) After going to and back from work now I feel like the transmission is cavitating when you first start moving the truck, at very low speed, or when cornering and accelerating at the same time, you can feel some king of vibration coming. It shifts fine into 2nd and so on, mostly in time when it needs to, still the O/D Off button does nothing and sometimes it won't go into overdrive, light is flashing after the car warms up.
You think it could be the EPC solenoid? Or it's a more serious problem like a valve body rebuild or maybe the torque converter?
When I changed the fluid it was brown, but no visible bits of metal in the pan, just a coat of dark grey around, very fine, seems normal to me.
Also, when I removed the EPC solenoid, which I had to put it back in again, I test it with 12v and I can feel thuds, instead of clicks compared to the new one I had, but you can see it was moving inside through the filter screens.
If the fix is most probable the solenoid only I'll fix it myself.

Any help is very appreciated

 

[410Fortune]

if the OD button is not working you likely have a loose wiring connector on the tranmission. this could be causing all of your problems.

The OD wire goes directly to the switch from the trucks computer, then from the switch to the trans through the main trans wiring harness.

I would get under the truck and start checking the harness where it plugs into the trans (on both sides of the trans, the digital transmission range sensor on the shift arm, into the shift solenoids on the pass side, etc) and also where the main wiring harness plugs into the trans harness (big square connector with 10mm bolt)

You may have moisture, or a loose connector, broken/melted wires, or something else (simply not plugged in all the way) causing these issues.

Do you have a Check Engine Light??? Usually if the PCM (computer) is not talking to the transmission sensors/solenoids it would tell you via the CEL.

 

[zap_ingo]

Check Engine Light

The Check Engine Light came on only the day it started doing this, it was only that day and hasn't been on since. I'll check all connectors as soon as I can.
Also, any other fuse or relay that is part of the O/D aside from the fuse in the fuse box that I should check?

thanks for your help!!!

JR

 

[410Fortune]

I do not believe there is a fuse on the OD circuit, most of the signal wires from the PCM to the trans rely on the computers fuse if something should go wrong.

Your check engine light is telling you that there is a problem, by hooking the trucks computer up to a code reader you can pull the codes and find out what it is saying is wrong. Here in th eUS we would go to Autozone for a free diagnosis of the codes. You can buy a simple OBD-2 code reader and get them yourself ($40+) or pay a shop to pull the codes for you (mine as well buy the scanner)

 

[zap_ingo]

Code Reading

Thanks!
I'll get the codes readed, I'll either go to a shop or get the scanner and see what code it is. I first took it to a tranny shop to get it inspected and they said that might be a bad EPC and a valve body gasket blown, but it was too costly to fix it so I started looking for info here. I don't want to spend $1500 replacing all that to find out it was a loose connector
Anyways, I'll pull the codes as soon as I can and let you know, I'm glad to find out that it can be an electrical problem instead of having to rebuild the trans.

Thanks again!!!
JR

 

[zap_ingo]

Codes Read

I got the codes pulled today, here's the list:

741 TCC
701 EPC
749 Reverse Engage

They said I might need a new EPC and valve body, but is that has to be with the "O/D Off" not working at all? I suspect there's a wiring problem also, or the computer maybe? Anyways I'll check all harnesses weather permitting, it's a bit cold here. I won't be able to read the forums for the next 15 days at least so please if I don't reply just excuse me.

thanks
JR

 

[roby02]

I have a similliar prob and after reading that it may be a wiring prob just wanted to pose this question as i found a wiring connector (aussie version) passenger side hangs from the top of tranny down around 1-2 feet of cable but cant see where it would connect to any ideas

 

[zap_ingo]

Problems solved?
Now everything is working almost perfectly, I was away for 15 days and the truck was sitting on my driveway all that time, by the time I got back winter was over and temps are above cero now, to my surprise the slipping and shifting problems are gone, the truck is smoother than ever and is really smooth to drive. The only thing I notice is after a cold start it gets a bit of delay engaging into R or D, just once, that's it, after that is just perfect. I thought it could be a connector that was dirty or frozen by the winter but the thing that in the morning sometimes it lags to shift I have no idea what the problem could be. Winter allergic maybe?

I solved the O/D Off problem, I thought I would post this so in case someone has the same problem, the thin cables comming from the button in the shift lever were cut right at the lever base, I noticed only by coincidence two days ago when I saw a bit of smoke coming from the steering column so I disasambled averything.

Any ideas of the shifting delay when is cold?

great thanks to the forums and all people who participate!
JR