Red's Cowboy

The rig below. Cold start (today was about 35). Idle a few minutes, then 1 1/2 miles to the highway rough road, so no hotrodding. Once on highway, run it up to 65 mph and set cruise. Tach is at 1800 +/-. 35 miles later the the truck begins to shudder and the tach goes from 1800 to 2000, then it shudders again and back down to 1800. Lately when it has been run for a while, an hour, or so, 65 mph is 2000 rpm, up from the 1800 when I start out cold.

What is up? What is flaky, or not working?

My assumption is that when the rpm is higher, the TC is not locking up, and the shuddering is the TC losing the lock, or trying to relock.

If so what is fix?

RCW

Check the throttle position sensor and make sure it is functioning properly, the symptoms sound like it is not functioning properly. If that is not the problem, check both ends and the cable housing locks on your throttle valve cable from the transmission to the fuel pump.

I would suspect the shudder is the overdrive when it happens at the speeds you list. It can be from the TPS or the throttle valve cable, or both, or from loose bands.

On these transmissions when the bands become excessively loose the oil pressure and volume is diminished and the clutches will not fully lock with the usual snap, and you get slippage and sometimes will fail to shift properly.

Red's Cowboy

I will check the TPS. A neighbor suggested it, too. It ran better yesterday, after dragging a trailer load of several power poles and railroad ties down the Intersate at 65 - 70 mph for 150 miles, or so.

Really loved the power. Once it got to speed, it dropped into OD and settled in for the run at about 2000 rpm for about 70 mph. My former gasser would not have gotten over 50 - 55 mph, and require that I lock out OD.

Now this morning, running empty, it is back to 2000 rpm is 65 mph again.

I don't think it is the OD because when I click the OD off switch the rpms go up to about 2800 at 65.

infidel

Check this out http://dodgeram.org/tech/transmissio...TPS_adjust.htm

Red's Cowboy

Infidel, Thanks for the link.

Last night, before I messed with the TPS below, it was not locking either, so I stopped by my mechanic. He got out his scanner and away we went down the road. Wouldn't you know the darn thing locked right away, and every time we stopped and started again it worked perfectly! I had a meeting and on my way it worked great until I slowed down to go through a little town. When I go back out into the country and accelerated, no TC lockup.

It was that way all day today.

Tonight:

TPS was at .8v on idle, and is now set at 1.4v, after a couple of intermediate settings. It has smooth voltage increase to about 4.3 to 4.5 on the high end.

It is still the same, the TC will not lock.

I guess next is the cable. According to my Hayes manual, it looks to be set correctly. If I mess with it should I make it a few clicks shorter, or longer?

OR should I look somewhere else????

berner

Check your brake switch and also the VSS (vehicle speed sensor) at the back of the tranny on the driver's side. I had TPS trouble in November and ended up replacing it. If you have to go that route, try a Cummins dealer before you go to DC. It's a Cummins part.

I seem to remember somebody removing the TPS wiring from the harness and running them on their own. I can't recall the post but it was sometime within the last four years. Maybe someone will chime in.

Red's Cowboy

Appreciate the comment, but need more information.

The item you replaced was the VSS? How did you figure out that it was the problem?

Define "check," please. What and how?

As far as the brake switch, the brake lights work OK, and the cruise works OK. Are these all on the same connection, or is there one for each?

Last night I stopped to help get a neighbor out of the ditch. Her truck was in too far for me to get it out without a winch, but I was able to give her and her babies a warm spot to wait for the wrecker. After sitting and idling for over an hour, I'll be darned if the thing didn't take of and shift perfectly into lockup at a little over 45 mph. It worked fine all of the way home.

This here little snafu is really getting on my nerve.

berner

Sorry I didn't make myself clear. I replaced the TPS. The old one "seemed" to have a smooth voltage increase when I checked it but it was definately shot.

The VSS should read about 5 volts, I think (don't have a manual at work). I'm not sure if the brake switch has a separte circuit for the TC lock/unlock, but I seem to remember checking 3 circuits (again no manual). There's some decent instructions in your Haynes book on checking these. BTW, did you try to clean the TPS with electrical cleaner?

Don't ya just love intermittent electrical problems?

Red's Cowboy

Berner,

I really thought the brake switch was it. I adjusted it, and VIOLA! Everything worked fine for about a day, and then right back to the same old same old. That section of the switch is also connected to the ABS and "Brake" lights. If it does not work properly, the dash lights for those items is illuminated.

I am going to try the electrical cleaner, and check VSS right after it quits raining.

The next step in the Hayes Manual says "Take to professional transmission shop"


So, how did you know, or figure it out? I hate to drop $200, and it not be the trouble.

This is getting on my last nerve

ticki2

If you do need a TPS , try NAPA , best price I've found

berner

Well, after I checked every other possibility, I was pretty sure that was what was wrong. Every symptom pointed to it. It was so bad that it would lock/unlock at about 30mph with the O/D off.
Did you try to pull the TPS wires out of the harness? Maybe you're getting some electrical interference.

Red's Cowboy

So you finally said, "Screw it" and bit the bullet?
It rained until dark, so I did not get to try the electrical cleaner, or check VSS.

About the VSS, doesn't it also contol the speedometer? So if it is flaky, the speedo will malfunction, too??

I had not thought of unlacing the wires from the harness. I'll put that on the list, too.

With a little luck, I can get home early enough to have the mechanic put his scanner on it again, and see if anything has changed.

dave0415

The VSS is seperate from the speedometer feed and will cause flakey shifting problems. I took mine out and cleaned the crud off of it. this cured the problem for a couple of weeks till I got my new sensor in. Also I've had a bad wire from my CPS causing problems like what you have described with the added symptom of the tach jumps upward with no change in engine speed. (bad wire caused by a serpintine belt failure)

marine4life

when i thought my tps was going out i change mine with out checking anything else, turn out that all i had to do was clean it, too late, already bought and installed a new one, if you'd like i can send you my old tps, no charge maybe it would work for you, no promises tho. pm if you'd like.

chop342

[QUOTE=Red's Cowboy] That sounds to me like you have a bad trans temp sensor, which on your truck being likely a 47RE is located in the trans instead of in the cooler line. but next time you get your mechanic in the truck with his scanner have him check the voltage and temp readings coming from the trans temp sensor. after sitting and idleing for a while like you were the trans heats up enough to get the sensor to read high enough for the ecm to allow lockup.
my truck did that for a while, i could drive about 10 miles in the cold and never shift overdrive or lockup, sensor voltage was eratic and a new one fixed it.

Chris