4-low problem fixed!

rich said:

Posting just in case this encourages someone else to tackle theirs. I know this is a common illness with the electric T-case shifter.

96 Ranger, 4.0L, AT, electric T-case shift, manual hubs.

Bought this truck exactly one year ago this week. Shift from 2WD to 4 high always fine, shift from 4 high to 4 low was iffy. Sometimes worked, sometimes didn't. Shifting back from 4 low to 4 high was also a hold-your-breath-and-hope exercise. About 6 months ago, 4 low quit working completely. Just couldn't get to it using the knob on the dash. 4 high continued to work perfectly. No DTC codes that my reader could find.

Pulled the shift motor and cleaned everything up as shown here on TRS. It was pretty clean already, but I did what I could and put the motor back together. Verified that the T-case worked in 4 low by turning the shifter shaft manually when the motor was off. Put the shift motor back on, still no worky. I'm much more comfortable with mechanical problems than electrical ones, and this one must be something electrical. Better ignore it for a while. Maybe it will heal itself.

Waited a couple months. Pulled the shift motor off again, cleaned all connections, checked all wires underneath for fraying, found nothing. Verified once more that shifing t-case by hand was easy to do. Still no worky. Seriously considering throwing shift motor away and replacing with a pair of vise grips.

Waited a couple months. Bought a CD off Ebay with Ford repair manuals. Looked promising; lots of pinpoint tests and such. Also subscribed for a month at "eAutoRepair.net" for $15. Looked like pretty much the same info as the CD manual, but it was laid out better, easier to follow and easier to print series of tests and diagrams.

Today in the garage. Tried to shift to 4-low, knowing it wouldn't work. Checked for DTC codes, found none. Worked through the series of pinpoint tests listed under "T-case/Can't Change Gears in 4WD" (or something like that). Had to pull radio for access, disconnect and test 4WD switch for resistance in each position, disconnect GEM in dash, test several wires for continuity and voltage, disconnect and test "T-case shift relay module" behind GEM. Relay module was supposed to show 80-140 ohms between two pins, showed zero.

Drove to the Ford stealer with my radio and various pieces of dashboard laying on the passenger seat, while the 4WD lights flashed at me. Arrived 10 minutes befor parts department closes. Plunked down $71 for new T-case relay module and the governor's cut. Might have been cheaper at NAPA, but no time to check if they had one.

Walk outside with new module as they lock the door behind me. Sit in the parking lot and install new module, reconnect 4WD switch. Start truck, shift to 4 high. Works fine. Put it in neutral with foot on brake. Hold breath. Pray to God. Pray to Allah, just in case. Shift to 4 low. IT F'N WORKS!!!!!!! yahoo.gif

Drive across parking lot in low range (hubs unlocked). Yup, that's low range. Welcome back, old friend. Shift back to 2WD. No problems. Drive home. Test again. Still works. Reassemble. Test again. Still works. Pop a cold one. Rejoice beer.gif

Think I'll go 4-wheelin' tomorrow. Maybe I can break something else.

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jeebuzzin said:

rich, is this the same module you found? Mounted to the driver side of the radio bay.

I'm trying to fix the 4x4 problem on my 96 ranger. You mentioned a thread that listed test points for certain circuts on the gem? I've searched for that but can't seem to find any info thus far. Could you point me to it or do you remember what they were? Also, where was the "T-case shift relay module" mounted at? I don't see anything else mounted any where near the pictured module.

Thanks

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rich said:

QUOTE(jeebuzzin @ Sep 28 2006, 01:55 PM) *

rich, is this the same module you found? Mounted to the driver side of the radio bay.

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That looks like the GEM (generic electric module). The 4x4 relay module is behind that (closer to the firewall) and is much smaller. It's more of a cube, maybe 3 inches on a side. I haven't seen it for a while so don't hold me to those measurements. As I recall, the GEM was mounted just to the left of the radio location, and the relay module was at the same height and within about 6 or 8 inches of the GEM. It only has a few wires running to it. I took a couple of photos, but just deleted them about a week ago while doing some computer maintenance. banghead.gif

QUOTE
You mentioned a thread that listed test points for certain circuts on the gem? I've searched for that but can't seem to find any info thus far. Could you point me to it or do you remember what they were?

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The pinpoint tests weren't here on TRS, they were in the repair software. The online subscription http://www.eautorepair.net/ had good detail. I'll may still have the printout of the procedure; I'll have to check at home tonight.

Unfortunately, mine now has the same problem as before. The new module only lasted about 4 weeks. So the blown relay module was a symptom of some other problem in my case.

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jeebuzzin said:

Thanks for replying and for the help Rich. Sorry to hear your problem is back.

Sounds right, here is exactly where my GEM was so others can see as well. (the radio bay may look different, I actually have an 8" lcd screen mounted in my center console and had to trim some pieces out of the way rolleyes.gif )

BUT, as you can kind of see, there isn't much anything around that. I did find on the other side of the bracket that held the GEM there was a "cube", but a Little bigger than you described. After taking the cover off I seen it actually housed 3 relays, so I'm guessing that is not it? Was it just one single relay?

This was the relay block I'm referring to (red socket with 3 black relays)... picture taken looking up from the floorboard under the steering column.

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rich said:

It's not the same as the block in your second photo. On mine, it was right behind the GEM. In your first photo, you'd have to remove the GEM and then you'd be looking right at it on the firewall. You'd think it would be in the same place on yours. Mines an auto, but I wouldn't expect that to matter.

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jeebuzzin said:

I guess it isn't, there isn't anything behind the GEM but the metal bracket and the air duct you see in the picture. I went ahead and subscribed to that auto repair site and in the wiring diagram it lists having relays for the 4x4 system in Relay Box #1 to the right of the steering column. So I guess that block are those. I will post the part I'm referring to later, I don't have time right now. My bet is there are other ppl trying to figure this out too!

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