No overdrive, please help!
 

I did a bunch of reading, thought I had a way to diagnose but now I can't find the topic again. Anyway: trans started dropping out of OD, then wouldn't go in at all. The TC has been slipping for months, got so bad I couldn't pull a trailer. Just got a new 47RE, billet TC, servos, hogged out VB, etc. Very reputable builder who dyno tested it before shipping and made sure everything worked properly.

Put the new trans in, everything works nice and smooth, but still no OD. TPS voltage is .80, which isn't great, but I've seen it as low as .60 and still have OD. Batteries, battery wiring and terminals are all recently new and clean. The tach works, speedo works. Top speed of about 65mph @2600rpm. I installed a TC lockup switch to see if I could narrow it down. TC will lock with the switch at any speed, but still no 4th gear. I'm just praying it isn't the PCM, and I can't remember if the TC locking only on the lockup switch rules that out or not. I really don't think it's the trans or anything internal because the old one did the same thing. I need this truck for work every day, I'm at my wits end. Anyone know what it could be?

Hows the throttle position sensor look?

I think its the TPS sensor. I would start by changing that. New tranny and all, that's what I would check, unless it your OD switch that is causing this issue. The PCM doesn't really control the tranny. Are you sure that you TL Switch is properly wired? All you need is a good ground.

Check the wires at the connector for the TPS, might have a bad connection or broken wire.

I had the same problem on my 47 RH stock transmission. I changed out the TPS; first one I bought didn't help I pulled my hair out; kicked around checked wires; checked everything I knew to check!!!!
Went back to Oreileys & got another one the next day.
That one fixed it!!!! It's been in here for 4 years now.
That taught me that just because its new don't mean it's fixed & you can rule it out....

Hope it helps!!!!

Don't change it. Check it. The tps and throttle valve both effect lockup and od. Both are computer controlled functions. Check the voltage of the signal wire at the tps.

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What is the TL switch? You mean the lockup switch? I only put that in to see if it would lockup even though it won't shift into overdrive, and it does. The problem was around before I put the switch in, but it won't lockup without it.

I checked the TPS according to the directions at Dodge Diesel Maintenance Tips. The only thing that didn't necessarily check out was probing the connector with the key on/engine off, the black and purple wires are supposed to read 5 volts, and I only got 5 at one of them. I forget which, I believe purple. The other read nothing. I've done this test quite a few times over the years, but I can't remember if it's always been this way or not.

Also, the OD switch on the gear selector appears to work, at least, the light in the dash comes on when I push it. Doesn't really matter though, because turning the OD on doesn't mean I have OD since I don't.
Also, there is no trans temp light on in the dash either. I did get locked out of OD once while plowing several years (and three transmissions) ago, and the light came on first. Eventually it cooled down and worked again, but that's not the problem here. Could be a bad temp sensor though, if I knew where to look for it.

temp sensor is in the vb also known as the gov. press. sensor. I would surely hope it would be new along with the gov. press. solenoid. considering you just had it rebuilt. You can check temp with a scan tool any reading 275* and up o/d will be inhibited. Ive seen trans temps show almost 300 with a bad sensor and no codes or light set for trans temp. The bad sensors would show around 160* or more with a cold engine and trans.

Hmm. Well, I probably shouldn't, but right now I'm trying to rule out everything internal. Since the transmission is all new, and this problem was present before I put it in.

I feel pretty confident you have a tps issue. Its very common to have bell crank wear which causes erratic tps voltages.

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If you want to find out if it is the trans or not you could use a jumper wire. Going to need a Wiring diagram so you know what wiring are grounds and voltage.

I just did a search for "bell crank", and found that you've been answering these questions for quite awhile! I think I found more questions than answers though, as I'm still not sure what a bell crank is or where to find/check it. And now I want to know what a POT is too, which is of course unsearchable like all three letter words. My main concern is that if two of the wires going to the TPS are supposed to show 5V and one of them is by all indication dead, what does that say about whatever that wire is coming from? That's an issue going into the TPS, not coming out of it. Unless I'm just misunderstanding the directions for checking the TPS.

A tps is a variable resistor or some might call it a potentiometer. All tps sensors are a 3 wire sensor. One hot (in this case 5v vref) one ground and a signal. The signal is connected to a "sweep" which is turned by the tab on the end of the bell crank. As the throttle is applied the sweep moves closer to the hot side of the resistor therefore increasing the voltage. The pcm uses this voltage in a map or chart (easiest way I can explain it) to calculate throttle angle which is in turn used to make of and lockup adjustments. Its only other use on 12v trucks is freeze frame data. The computer looks for a starting voltage of around 1v and hits full throttle around 4.89-5.00 volts. Its very simple to determine without a wiring diagram which wire is which. With the connector plugged in you should have one 5v wire, one wire with .5-.1v and one wire with 0v. 5v is your 5v vref. The low voltage wire is your signal and you 0v is your ground. To verify, unplug the connector. Vref will remain 5v, signal will come up to around 5v (the signal circuit uses a bias voltage to verify the circuit is working, the bias voltage is supplied by a very high impedance resistor, in some cases a meter may pull this voltage below 5v and in all cases a test light would be capable of pulling the bias to ground therefore it won't light) and your ground will remain at 0. To test the tps output determine your signal wire, make sure it starts at around 1v and smoothly climbs to 4.59 + (hopefully 5v because this particular pcm sees 5v as 100% throttle)
Do this a few times to verify that the numbers remain consistent. Wiggle the bell crank (the bell crank is the portion of the pump linkage which engages the tps and attaches the throttle cables and the pump linkage. The most common wear is up and down or back and forth toward the pump. Often we find the plastic bushings have worn allowing the linkage to move which effect the tps voltage. In some cases the wear is severe and wears into the bell cranks rod or bore which would require replacement. A pot is basically a used controlled variable resistor which allows you to trick the pcm into commanding lockup and od via a knob in the cab. I would recommend fixing the tps system but if funds are limited the pot will do the trick.

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This video is by one of the best diagnosticians and instructors I've ever seen:

This is by Dave Goerend and is an excellent visual representation of what I've explained

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i have the tps deletes on my site. the name of it is dnr customs. :hellox:

I keep them on the shelf but their extremely easy to build yourself. About $5.00 in parts max.

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So, POT is short for potentiometer? I've only heard them called TPS deletes. I put one in last year, hated it. Took it out. I'll never do it again. I really prefer to have it all work properly, as Dodge intended- which is to say I like it being variable, not locked into shifting at whatever it's set at. I realize it's still technically variable, but I don't feel like messing with it every time I accelerate under different loads/conditions than the time before. It also had other issues, wasn't working right, although I don't remember what they were. I just remember they went away when I went back to the stock/TPS arrangement.

Regardless, those videos were both great. And wow, I want a Verus. (while I'm dreaming, I'd also like this problem to fix itself, but I digress). So, the bell crank is the throttle linkage under the TPS? That makes sense. While I was messing with it to test the voltage, I don't recall there being any play or looseness in it one way or the other, I believe it worked very smoothly, but I wasn't looking for this so I will check it again when I get back to the shop where I left the truck. Thank you very much for all your time on this!

So, trying to diagnose this was pretty frustrating, until we realized that the point of the frustration led straight to the problem- which was actually pretty stupid. Voltage readings on the TPS both for idle and sweep were erratic, getting the same reading twice was almost impossible. Turns out, this was because (even though everything looked fine on the outside) the wires were actually loose inside the plug on the pigtail side.
And come to find out, this pigtail isn't available from Chrysler anymore, and I didn't have any more luck at the local chain parts stores. A buddy of mine works for a Cummins distributor, and he wasn't able to come up with anything either, but when I took a picture of the plug he was able to dig through the inventory and find one that matched. All fixed, and the world is right again. Now if I could just get it to the body shop...

OK, all was supposedly right. Overdrive works fine, but now it's stuttering on the 1-2 upshift. Bad. :argh: