e4od tranny not shifting

[bigfoot]

Hi - haven't been here for quite a while - my 93 NA 7.3 has been running great for a few years. Not now. last week - fired right up but no tach. reverse was fine. Put it into drive, and it only had fourth gear. O/D light on. Put it in first - but it was in second. drive off in second, move shifter to drive and it shifts into 4th. Drove it 30 miles in 4th, no O/D.

four years ago the tach started jumping around; a new sensor fixed it. Now, nothing - not a bump.

Thanks a bunch for any help.

2wd, E4od, NA, 138k miles, all original, in great shape overall.

 

[BeastMaster]

I just got through chasing down a similar issue in my van.

Before I go into a long winded diatribe, gotta ask you... Do you have an Android phone kicking around that you can sideload open source apps in?

You will need a signal generator app from F-Droid. "Bill the Farmer" has generously coded a fine one that is exactly what you will need to make your phone's earphone output look like a VR sensor. You will not need to run the engine during circuit tracing. The phone will provide the tach signal .

Second thing...can you fab up a test wire from headphone extension wire to feed the connector your tach sensor feeds? The other end plugs into the phone.

Third thing... Feel comfortable about using some "computer speakers" , you know, ones with adjustable volume, to aid you in circuit tracing? This also involves you making the necessary test cables, so you can listen in at various points.

During tracing, you will need key on to power your tach. But not run the engine.

And everything off while probing around the PCM. Is the tone getting there? Where did we lose it?

You mentioned your tach was dead. If we can first find out where we lost the signal, we will be that much closer. Your PCM can't do much if it has no idea of engine speed.

Be careful though of not ramming 12 volt power into the phone.

Personally, I use a 600 ohm audio line transformer to isolate the phone, but those things are hard to find these days .

 

[saburai]

Hi - haven't been here for quite a while - my 93 NA 7.3 has been running great for a few years. Not now. last week - fired right up but no tach. reverse was fine. Put it into drive, and it only had fourth gear. O/D light on. Put it in first - but it was in second. drive off in second, move shifter to drive and it shifts into 4th. Drove it 30 miles in 4th, no O/D.

four years ago the tach started jumping around; a new sensor fixed it. Now, nothing - not a bump.

Thanks a bunch for any help.

2wd, E4od, NA, 138k miles, all original, in great shape overall.

Good luck with the diagnosis, lots of knowledgeable help to be found here. I'm a relative idi e4od novice compared to many of the guys here, I'm sure that some of them will chime in. All I can add is to check all the plugs for a good clean connection and maybe pull the codes. Also, 4th is OD. You were in 3rd.

 

[LowTech]

I've had that "limp mode" issue and this was my fix.
https://www.oilburners.net/index.php?posts/1036853

 

[trackspeeder]

Hi - haven't been here for quite a while - my 93 NA 7.3 has been running great for a few years. Not now. last week - fired right up but no tach. reverse was fine. Put it into drive, and it only had fourth gear. O/D light on. Put it in first - but it was in second. drive off in second, move shifter to drive and it shifts into 4th. Drove it 30 miles in 4th, no O/D.

four years ago the tach started jumping around; a new sensor fixed it. Now, nothing - not a bump.

Thanks a bunch for any help.

2wd, E4od, NA, 138k miles, all original, in great shape overall.

4th is overdrive. Check the TCM relay for power.

 

[bigfoot]

Thanks to everyone for the great info. I'll let everyone know how it goes.

 

[Timm]

I had an od light flashing issue, limp home mode, full pressure shifts... three codes, one was my fault... ended up being the harness on the range sensor on the tranny just needed a wiggle..