About a week ago, I bought a used 1993 Dodge Dakota Club Cab LE as a towing / hauling / beat around vehicle. It has a 3.9L v6 with 4 speed automatic transmission. It has 168,000 miles; however, based on VIN, CARFAX says it is a one-owner vehicle, with proper mileage increments, all in Southern California, with no salvage / damage / flood / lemon issues…so I took the chance on this high-mileage vehicle. Visual inspection indicated that the machine was well cared-for.

The transmission seems to shift fine from 1-2, and 2-3 (and on downshifting), and goes into reverse fine; however, the transmission will make no attempt whatsoever to go into overdrive. This problem will severely increase operating costs, as I estimate the truck will get 12 to13 miles per gallon in this condition. It turns about 2700-2800 rpm at 55 mph, and about 3000-3100 rpm at 65 mph.

I live in San Diego, so there is certainly no issue with extreme cold; even so, before engaging the transmission, I always let the truck idle for at least 2 minutes on first startup in morning, and at least 20 seconds for any subsequent daily restart. No dashboard warning lamps light up during operation.

In lurking forum boards, I have made a list of possible checks / problem areas, from what I believe will be easiest to hardest to diagnose / repair:
1) Battery ground
2) Battery
3) Computer (may need reset)
4) Transmission fluid (could be wrong kind)
5) Vehicle speed sensor (VSS)
6) Throttle position sensor (TPS)
7) Transmission temperature sensor
8) Transmission input and/or output sensor
9) Governor pressure solenoid and/or sensor (GPS???)
10) Transmission control module (TCM)

Here are some additional symptoms / problems that may or may not be related to the lack of overdrive:
1) Cruise control does not work at all
2) A slight whining sound from transmission during acceleration through first gear
3) Idle speed is high (950-1000, instead of 750 as stated in Chilton manual); also, it never goes down, even after letting idle for a few minutes to fully warm up.
4) Tachometer wavers up and down by about 50 rpm
5) Fuel gauge reads near empty when tank still almost half full

Also, the truck has a “Viper” anti-theft device, if this could be causing and/or hiding some sort of electrical problem.

I learned the trick for using the check engine light to read the diagnostic trouble codes. The only DTC I get are: 12 (battery disconnected within last 50 starts), 55 (end of reading).

Questions:
1) Am I leaving anything off my list of checks / problem areas? Should I go through them in a different order?
2) Do any of the other symptoms help narrow down the problem area? Are there any other, perhaps subtle, symptoms I should look for?
3) How exactly do I reset the computer?
4) Is Valvoline ATF+3 OK for this transmission (it is the only brand of ATF+3 stocked at the nearby auto parts store)?
5) I have definitely visually located the VSS and TPS, and I think I have located the transmission temperature sensor; however, I cannot find the transmission input and/or output sensors. Does this year / equipment vehicle have these sensors? If so, exactly where are they located?
6) What is the GPS? Where exactly is it located and what does it look like? How do I test it?
7) If my TCM is bad, would I get any DTC at all from it? Wouldn’t the transmission go into “limp” mode?

 

Replace the speed sensor first to get your speedometer and cruise control working and your trans might shift into OD
ATF4 will give you better shifts and make your tranny last longer, you can mix ATF3 with ATF4 so top off with ATF4!!!
I mostly work on newer vehicles so pardon my.......nevermind..... Is there a button at the tip of your shifter for turning O/D on and off??? If so they fail..... If pushing that button doesn't make a light go off and on in your cluster it has failed!!!

 

Update on my Dodge diagnostic nightmare:

Here is what I have done so far:
1) Checked out battery; OK
2) Cleaned and retightened all battery leads/ground wires.
3) Not knowing what the previous owner used, changed out fluids, going with:
3a) Mobil 1 10W-30 synthetic and Mobil 1 filter
3b) Mobil 1 75W-90 synthetic transaxle gear lube
3c) Mobil 1 synthetic front wheel bearing grease pack
3d) Valvoline Red Moly chassis lube on all steering joints/ball joints
3e) Valvoline ATF +3 transmission fluid

Note: with Tranny fluid change, I:
a) Dropped the pan and cleaned out about a ¼” layer of gray sludge from bottom of pan. There were a very few small metal particles on magnet.
b) Drained 5 qts (out of 10 qt total capacity)
c) Rebolted pan, drove 20 miles
d) Dropped pan again and drained 6 qts
e) Replaced filter and gasket; rebolted pan
I figure this gave me at least 80% new ATF +3 in transmission.

After all this, I now had: smoother 1-2, 2-3 shifting, less engine noise, less 1st gear whine, no transaxle chatter, and idle at 750 rpm, turning 2500 rpm at 55mph and 2900 rpm at 65mph (these rpm’s should improve overall mileage 10%-15%); however, still had no O/D or C/C. So, I moved to looking at sensors:
4) Checked out VSS:
4a) Unhooked VSS; threw NO codes…figured that since this is a 2-wire sensor (whereas much later model VSS’s are three-wire), perhaps the TCM can’t monitor this sensor; however, this remained a possible problem area in my mind, so…
4b) Checked VSS with ohmmeter across the two leads…made 8 clicks per revolution, upon each click went from 0 ohms to infinite ohms…
4c) Ordered a new part from dealer…they gave me wrong part; it was a VSS from a later model vehicle with 2 leads but no mechanical speedometer cable hookup. Checked it with ohmmeter and acted exactly as current part…hooked up to vehicle anyway (just had no speedo) for quick test drive; still no O/D or C/C. Figured current part must be OK, and problem must be elsewhere (though still not exactly sure); returned part to dealer.
5) Checked out TPS:
5a) Unhooked TPS; threw DTC 24 (OK); rehooked TPS, cleared computer
5b) TPS voltages: throttle closed: 0.59v; WOT: 3.12V; OK, in specs
6) Decided to bite bullet and replace transmission temperature sensor/governor pressure solenoid/lockup solenoid assembly (all one unit); $60 from dealer. Although not throwing codes, I had no known way of testing this unit, and wanted the peace of mind. Noted that new unit had been totally redesigned, and had superceding part number. Had to drop transmission pan AGAIN to replace this. While unhooked, checked for DTC’s and got 45 and 37 (both as expected). After GPS hookup and TCM reset, got no codes (OK).
7) After much searching, I could find no “transmission input speed sensor” or “transmission output speed sensor.” I assume that this model year (1993) simply does not have these sensors.

Upon test drive, still no O/D or C/C!

Then I started thinking about the TCM. I checked for continuity between the wires going into the 60-pin connector and the female pins on the face of the connector…sure enough, there was only intermittent continuity between pin 47 and the white/orange wire leading to the VSS…and then, only with some serious “jiggling” of the wire. This got me thinking about “intermittent” symptoms…I recalled that on occasion (i.e., maybe one time out of 20), the power locks would lock on takeoff. I figured out that perhaps this was a symptom of intermittent VSS operation!

I spliced a wire into the white/orange wire, and wrapped it around to the face of the connector, jamming an exposed end of the wire into female pin 47, making a shunt that would ENSURE contact.

Upon test drive, still no O/D or C/C…and no automatic door locking, either! Of course I no longer had the new VSS part to test…DOH!

I now believe that I had ALL of the following problems:
1) Intermittent to bad VSS
2) Intermittent to bad VSS wiring connection at 60-pin connector
3) Broken spring in valve body
4) Bad GPS (maybe…)

Items 2), 3) and 4) are repaired. This can only leave ONE thing, and that IS that the VSS—while apparently OK—actually does need replacing. I will replace this with the correct part and provide an update.

BTW, truck does have an O/D off switch on dashboard, and it lights/unlights when pressed. Also, what I originally thought was the transmission temperature sensor is actually the shift position indicator sensor.