No overdrive - any ideas?

[ISh]

I have a 1992 ctd 4x4 automatic - the transmission does not shift into overdrive. I checked the wiring and it looks ok. The transmission was rebuilt by the previous owner and it shows that only 20k miles are on it. The speedometer also does not work but it looks like it is electronic vs. cable when I looked at the connection on the back of the NP205. One other thing is wrong also, when I am in two wheel drive the t-case is making a noise that sounds like a coupler is trying to engage. I can get the noise to go away if I shift into 4wd. While in 4wd there is not a problem to be heard or felt. I have only had the truck for about 500 miles.

 

[KSommer]

you need the speedo to work, it is one of the sensors that tells the truck when to shift into OD. don't ask me how, i swaped in an older cluster with a cable drive speedo and have a lighted toggle for OD.

kent

 

[TomThomas]

I had the same problem, caused by speedo not working like KS said. A new speedo drive unit cured it (the electonic thingy on the t/c)

 

[CumminsKid]

ISh-



The guys are right if the spedo is not sening a signal of how fast you are going to the computer if will not engage into OD. One way to get by until you can afford a new one is to mounta toggle switch to activate the overdrive sylinoid on the trans. you should have a 2 wire connector going into the top of the trans, it is kind of an oval shape and one of the wires should be orange with a green tracer. in order to activate via switch the orange with green tracer will need to be sliced and go to one side of the switch the other side will need to be grounded ( - on battery,or frame ground). hope this makes sense to you do noth ground the other wire in that connector it is +12V. By the way the connector is on the drivers side it is toward the frontbut on drivers side and is above the trans pan and virticle

Good Luck

 

[TomThomas]

Cumminskid, don't mean to steal this thread, but is that how people manually control the o/d?

 

[CumminsKid]

Yes, that is how people manualy engauge the overdrive or lock-up sylinoids in the trans. I used a weather-proof electrical box and put two switches and two lights, (red for lock-up, you can't forget to shut this one off, and green for overdrive), in a stainless steel cover. You do not need dummy lights to make the system work It was nice to know if the switches were on or off in the dark. With this box on some 14-4 S. O. cord I can put the box behind the seat when I don't use it. By doing this I have the ability to Lock the sylinoids up manually which means I can make lock-up engauge in 2nd. gear ( no torque convertor slip) andthe truck will cycle through all gears including overdrive or I can engauge over-drive sooner or make lock-up engauge after over-drive as normal. Keep in mind however The trans in my truck is out of a '95 CTD (47rh) and it was built by a local trans guy with a pro-torque convertor. However you can still do the same you just won't have lock-up. I love going up or down the hills and hearing the engine locked to the trans. as a manual would be. Plus the truck makes enough power that I can leave it in over-drive and lock-up from 40mph to speed limit and it doesn't need to shift.

 

[TomThomas]

Nice! Wish I knew about the lockup converter in later model trannys. Had mine rebuilt when maybe I should've switched out. I'm gonna do the o/d switch though, seems like my o/d cycles in and out at 50mph when I know the engine is producing enough power. So all locked up you could use an exhaust brake on an auto trannyd truck, right?

 

[BWatson]

A buddy of mine had this same problem in his 91. 5. No speedo, no cruise-control, and no overdrive. Turned out to be a bad computer. I guess the only thing the computer on that truck controlled was the speedo and OD. He changed that out and everything worked great. If that is what it is, he checked around and I believe O'Reilly's had the best price on a new computer.

Good luck.

 

[JStraw]

First, get some electrical contact cleaner and use it on the plug at the transfer case. Mine cruds up every now and then and I get the same symptoms. Heck, I've also used a can of carb cleaner with good results.



If the speedo then works but the overdrive doesn't, you may have a bad TPS. They can be cleaned and adjusted also. Mine started to consistently shift in and out around 47-55 mph before finally going completely out. I now use a separate switch as the other gentlemen have posted.



That's a dang good idea about the 'red,green' lights I need to do that.



Always remember to try the simplist fix first before shelling out the bigger dollars.

 

[CumminsKid]

TomThomas-

Yes, you could use an exhaust brake on a truck equipped with a lock-up convertor as long as you can control the engagement of the convertor so that it doesn't un-lock when using the engine brake. In fact I was reading the dodge and Cummins along with Jacobs Brake will be the first light-duty truck to offer an engine brake from the factory, pretty cool.



JStraw-

I bought my indicator lights at Napa auto for about $2-$3 a piece and you can get them in any color. Mine are just 3/8" incandecents but you may even be able to get them in an L. E. D. form of light. Any Auto store should sell them.



ISh-

I don't Know how familiar you are with the TPS. It is located on top of the injection pump, is a square box with two screws holding it in place. Some times the get dirty and need cleaned, I 've also got ticked of and beat them with screwdrivers (on the side of the road). Here is how to check and adjust the TPS (throttle position switch) http://www.piersdiesel.com/Tech1GTPS.htm

But my suspicion is that it has something to do with your speedometer not reading. Could be a bad connection or defective part. A few weeks ago my speedometer was not working and either was my overdrive engaging automatically. Turns out that the unit on the transfer case popped out enough so that it would not spline with the drive inside of the Transfer case

 

[ISh]

I replaced the speed sensor on the t-case and it still does not function.



DOES that mean the only thing left to replcace is the main computer?

 

[cerberusiam]

What does not function? The speedo? The OD? Odometer?



You must have a speed sensor signal for the speedometer, odometer, and the OD to function. First question is do the speedo and odometer function?



If they function and still no OD it could be the PCM, TPS, OD solenoid in the trans, or a mechanical failure in the trans.



First wire in a mystery switch and verify the OD will mechanically function when engaged then backtrack from there.



Next would be to test the TPS and verify you are getting a good clean signal at the correct voltage output to the PCM.

 

[ISh]

The speedometer, odometer, OD, and cruise control all do not work.

 

[DPetrey]

same here

well here it is guys i have od sometimes not all the time my speedo works and so does the odometer now is it the tps or the cluster to me it seams these are all tps problem's with bad conections what do you all think

 

[BWatson]

Sounds just like what happened to my buddy. He replaced his TPS and still nothing, only a new computer fixed it. And I finally got my GPS back that he was using for a speedo. :-laf I hope for your sake it is something cheaper but it sounds the same.



To the last guy - If you get it sometimes and not all the times, sounds like a sensor (TPS) going bad or the connections are loose or dirty. My $0. 02.

 

[cerberusiam]

Ish, check and make sure the gears in the adapter on the t-case are not stripped and the output shaft is spinning. That screwy gear reducer can be the source of a lot of problems. Then check your wiring to the PCM and make sure you don't have a broken wire somewhere.



Dpetrey, check your output of the TPS first and make sure it is within spec. You need to read the voltage on the center wire of the TPS connection. It should be around 1 volt at reat and move smoothly to about 3. 5 volts at WOT. If there are any fluctuations in the movement range that is likely the problem. That said I had to replace both my TPS and PCM to get the OD finction to work correctly even though they were within spec.

 

[ISh]

Ish, check and make sure the gears in the adapter on the t-case are not stripped and the output shaft is spinning. That screwy gear reducer can be the source of a lot of problems. Then check your wiring to the PCM and make sure you don't have a broken wire somewhere.

Will do. Thank you.

 

[dadmagoo1]

Does anyone know where to find this speed sensor unit that fits into the transfer case???

 

[dadmagoo1]

The part that I had to replace was actually called a transducer and the way to find it is there is a number on the transducer that matches the part number at Dodge

 

[Jacob1993]

Removing

ISh-



The guys are right if the spedo is not sening a signal of how fast you are going to the computer if will not engage into OD. One way to get by until you can afford a new one is to mounta toggle switch to activate the overdrive sylinoid on the trans. you should have a 2 wire connector going into the top of the trans, it is kind of an oval shape and one of the wires should be orange with a green tracer. in order to activate via switch the orange with green tracer will need to be sliced and go to one side of the switch the other side will need to be grounded ( - on battery,or frame ground). hope this makes sense to you do noth ground the other wire in that connector it is +12V. By the way the connector is on the drivers side it is toward the frontbut on drivers side and is above the trans pan and virticle

Good Luck

How do you remove sensor?