Bad throttle valve cable

[PPeters]

During my latest repair (rear main seal), the garage had to drop the transmission. After reinstall, my 3-4 shift has been screwed. Can't get it to upshift to OD. Adjusted the cable several times, every time it would work until I came to a stop, then on restart it would not shift up. Got under the truck and found that the TVC was not properly installed in the bracket at the transmission so that it pulled through after I would adjust it. So I'm thinking "AHAH", gotcha. Turn the cable 90* and get it to snap in place, now all is secure. Go back and readjust the cable (per spec's in shop manual). Make sure my TPS (which is new) is still adjusted to my desired setting (. 75v), breakover spring is cool, everything on the stops. Take it for a run, shifts great. Come to a stop, start again, no 3-4 upshift Check my TVC gap, and it appears to be out again. I'm beginning to wonder if the TVC is shot. When I cycle the throttle, the cable doesn't return like I would expect it to. So I went to NAPA and got a replacement TVC spring (heavier version than the stock) and tried running with it. Started out OK, but during my morning run to work (30 miles) the truck downshifted to 3rd. Stopped and examined the TVC gap, it had shifted to no gap. Whaddaya think? Cable pawl worn out? TIA



Pat

 

[dpuckett]

ANother reason to do your own work guys; most shops care about $$$ and no more. Every time I take something to a shop, I have to fix up something they f***ed up Plus, they see "diesel" and think you have all kinds of money to p!$$ into it.



Just had to rant. I thought the kickdown cable (TVS?- what is that, exactly? I'm IGNORANT when it comes to gassers- just know they are terribly inefficient) was only for the 1-3 shifts, and the TPS was the sole OD operative. I could be wrong, though. WHen I had a temporary lapse of judgement, and had an auto for 9 mo, I just unhooked the cable, and cured my early down/ late up shifting.



Daniel

 

[PPeters]

Same problem on the way home last night. Prior to leaving work had switched back to the original return spring, and set gap. No shift. Ran about 5 miles and pulled over to readjust. Released the locking pawl and cycled the cable through the travel range, reset the gap, and relocked the pawl. Then watched the cable slip right back to the stop. Did it twice. Sooooo..... I gather my guess that the cable is shot is right.



Daniel, I think that the TVC in conjunction with the TPS voltage will control the shift point on 3-4. As long as the fluid temp is high enough to satify the 3-4 shift solinoid. At least that's what I gather from reading the shop manual. But, hey, I could be wrong. Just waiting for someone with experience to correct me (where is the pastor, methinks my last post threatening to go 3gen has put me in the penalty box)



Pat

 

[Philip]

I just unhooked the cable, and cured my early down/ late up shifting.

This is the fastest way of killing a Dodge automatic trans that I know of. The TV cable controlls all the line presures in the transmission.



Unhook the cable from both ends and see if the cable slides freely in and out by hand. If it does not. Replace the cable. There have been a couple of people on here that has had them go bad over the years. Another symptom of this is the throttle getting hard to operate or sticking.

 

[PPeters]

Thanks Phillip, I'll look into that. Can you tell me if the gap setting should hold after adjustment? My read on it is it should. If it slips after relocking the cable, must be the pawl is worn enough to not hold.



Pat

 

[Philip]

If it isn't holding a setting then something is slipping somewhere. The hard part is finding what is moving or not returning properly.

 

[dpuckett]

Philip- it worked as long as I had it; looked like a kickdown linkage to me; maybe we are referring to different things? (I'm referring to the one next to the throttle and cruise cables on the throttle bracket) Anyway, Mom took it to the Almighty Transmission Shop (who cant even adjust a TPS) here in the swamp and they hooked it back up. Been fine ever since. I think it could use a line pressure adjustment, but that is just my opinion. Maybe 20K w/ the cable unhooked headed it south.



PPeters- how high should the fluid temp be? Mom's will go into OD at 35 right out of the driveway. Should it be this way? I mean, start it up on a 20 deg morning, let it idle 10 sec to get the engine oil pressure up, and go (easy, though). It will shift to OD at about 35, maybe 38mph out on the gravel road under light throttle.



I've never thought much of the transmission; it's sluggish off the line- give it fuel, and it catches up about 3 seconds later; shifts whenever the heck it feels like it. That's why I traded it for a 5 speed. They stay in gear for the most part.



Daniel

 

[Philip]

looked like a kickdown linkage to me

That is part of its usage. About the last 1/8" of movement in the cable assy. The rest of the movement is controlling line pressures which in turn delay the shift points from 1st to 2nd and 2nd to 3rd. On the later trucks with OD. OD is controled by the TPS and RPM sensor for the shift to OD.



You are very lucky for that trans to last that long with the cable unhooked and in the low pressure setting. The lever is spring loaded. It goes to low pressure whenever the cable is unhooked. Most Dodge auto's don't last a month with it unhooked. Less if it has a high performance engine and a lead foot behind it.

 

[PPeters]

Thanks for the reply's guys, been home sick and have too much time on my hands so...



Daniel, quoting from the bible ('92 service manual)...



"Fourth gear operation in the diesel is also controlled by two temperature sensitive thermo-switches.



The first thermo-switch is the engine coolant temperature switch. This switch prevents overdrive fourth gear operation when engine coolant temperature is below approximately 65F.



The second thermo-switch directly monitors transmission fluid temperature. The switch will either downshift the transmission to third gear, or prevent a 3-4 upshift when fluid temperature exceeds 270-275F.



The fluid temperature switch is located in a boss built into the cooler outlet line. The boss and switch are located approximately 2-3 inches from the outlet line fitting in the transmission case.



The engine coolant and fluid temperature switches are in circuit with the overdrive control switch in the instrument panel. "



Now all of this suggests that the TVC may not have a bearing on the 3-4 shift, but like Phillip said, the movement controls line pressure. A little further on in the manual, it states that ...



"Line pressure acting on the 3-4 shift valve overcomes valve spring tension moving the valve to the upshift position. This action exposes the feed passages to the 3-4 timing valve, 3-4 shuttle valve, 3-4 accumulator and ultimately to the overdrive piston. "



So I'm inclined to believe that the cable is still causing the trouble. Just need to get better and crawl under the truck again and examine the cable before buying.



Pat

 

[cerberusiam]

The kickdown cable controls throttle pressure not line pressure. Line pressure is set internally and driven by the pump speed and pressure bleed off switchs. Throttle pressure is controlled by the position of the TV cable and pump rpm. The more the cable moves the later the 1-2 and 2-3 upshifts occur. The OD upshift is controlled by the OD solenoid via an electric signal from the PCM which uses the 2 temp sensors, TPS voltage and speed sensor input to determine the shift point. There is also a pressure adjustment for the OD on the front corner of the valve body that will control the OD shift.



Readjusting the cable and making the OD shift work seems to indicate the pressure adjustment for the OD solenoid is dependent on throttle pressure not line pressure. It could be the pressure is set high enough that misadjustment of the TV cable is causing low throttle pressure and not allowing an OD shift.



Adjusting my TV cable high or low made no difference on the OD shift point at all. Set high the trans would shift to drive at 50 and into OD at 52, set low it would go to drive at 40 and OD at 52. That was with stock settings. Modifying the shift pressure and TPS allows me to tune to different speeds and the TV cable still has no effect on OD shift.



You might try the mystery switch and overide the PCM and see if it will shift into OD even with the cable misadjusted. If it shifts into OD its not the cable but probably an electrical component not functioning correctly.

 

[PPeters]

So what I want to examine is the two temp sensors and wiring for damage? I'll do a search for the "mystery switch". I assume that is some form of a manual OD switch, right? Thanks again guys, I'm still learning



Pat

 

[cerberusiam]

Since the trans was out I would start by checking all the connections and using dielectric grease on them. The trans temp switch is normally closed and I believe the water temp switch is the same so jumping them for a test would be easy. The speed sensor is problematic. It will work and the speedo will work but OD shifts will be unreliable. If you can't clean it and its connections and make it work all you can do is replace it. The mystery switch is wired to the orange/black wire (I believe) on the trans harness and run back to a SPDP center open switch mounted in cab. In one position it works normally, in the center there is no OD, to the other side OD is manual.

 

[phillips5]

I have my tps turned upside down and bolted back on upsidedown. The drum in it I have pined in a fixed position so it never changes. when I drive light footed it hits od at 38 mph. When I mash the pedal it holds out till 65 mph. I think that the tps and engine temp and maby another sensor or 2 tell the trans that it can chose od if it would like to. But the cable between the pump and left side of the trans ( that I awalys called throtle pressure cable) and ground speed and maby another sensor or 2 in the trans are used by the trans personaly to deside if it wants to shift or not into od. If this were not so than why does my truck shift in the way discribed above with a fixed tps.

 

[PPeters]

Hey, anybody got a part number or know where to find the transmission line temp sensor? Checking my connections this weekend and the molded electrical connector on the sensor is cracked through (just came off in my hand). Went to the dealer and looked on their part computer, could not find the sensor. Just in case, I'm talking about the one closest to the engine, in the boss where the transmission line exits the transmission



Anyone? Anyone? Bueller? TIA



Pat

 

[cerberusiam]

Check a NAPA store. I think Echlin makes a replacemnt sensor for that but can't remeber for sure. They make the oil and water temp sensor so a good bet they would have a sensor to match the trans temp.



Phillips5, I believe the reason lies in the difference between throttle pressure and line pressure. If I understand the schematics correctly the solenoid that controls OD shift also has a pressure switch that will not allow shifts when the line pressure is to low. Under light throttle the line pressure builds past throttle pressure faster than under heavy throttle. By changing the pressure that is applied to the switch you can change shift points up or down. Have you tried disconnecting the speed control or trans temp sensor and checked what happens to the OD shift?

 

[Philip]

The kickdown cable controls throttle pressure not line pressure

The line pressures of the transmission are controled by the throttle valve. Look at the flow charts in any Dodge service manual. The flow that controls the delay shifts is diverted threw the throttle valve and then it flows to the pressure regulator to raise line pressures. If you wish to see it in writing. Go to page 21-76 of a 93 service manual. Lower right corner of the page look for "Pressure Regulation" .



Here is a copy of the test.





The pressure regulator valve maintains transmission line pressure. The amount of pressure developed is controlled by the throttle pressure. Throttle pressure is depented on the amount of throttle opening.



The throttle valve determines line pressure and shift speed. The throttle valve also controls upshift and downshift speeds by regulating pressure according to throttle position.





So like I stated in my earlyer post. The TVC adjustment controls transmission line pressure. BTW I had to do some reading up to backup my statement. If you knew how long it has been since I had a transmission class. This was some hard reading. LOL

 

[PPeters]

Hey Phillip, thanks for the research, I'm still trying to figure this out.



Cerberusiam, gonna try NAPA today at lunch for the sensor, then go back to the Dodge dealer to talk with the parts counter again. I need the cooler line that is attached to the back of the transmission oil cooler that is mounted below the turbo (side of motor). The front line is fine, but the rear line is all corroded, and appears to be leaking at the bend where it starts vertical to the cooler. Also, the engine coolant lines to the oil cooler are pretty rotten looking as well. Even the cooler is getting funky. I'll probably replace both transmission lines if the price is not too bad. Don't know about the cooler and other lines, have to see what mother mopar says.



BTW, that line is a cast iron ***** to get at. Anybody got a tip for making it easier? My guess is pull the passenger wheel and come in through the fenderwell.



Pat

 

[Philip]

One of the lines is not avable any more. I ran into this a while back. I am not sure which one it is. My lines have some compression fittings in them so I was going to replace them. I think the line with the temp sensor in it is the one N/A now. If memory serves me right someone posted a while back the 94 and up line with the sending unit is the same.

 

[PPeters]

That's great , thanks Phillip. This may be why when I went to the dealer last week they could not find the sensor for the transmission. I looked at the parts screen with the counter person, and you could not find any detail on the sensor. Maybe it's another "10 year old" part and they are no longer going to stock them. I'll let you all know after lunch today.



Pat

 

[cerberusiam]

The amount of pressure developed is controlled by the throttle pressure

Philip, I respectfully disagree with your assumption that the TV cable controls line pressure and the above statement is the proof. "The amount of pressure developed" is not the same thing as controlling line pressure. Line pressure at idle is not controlled by TV pressure but rather by the pressure regulator settings. The same is true for the pressure at WOT. What the throttle valve does is affect the amount of line pressure available depending on its position but it in no way controls the amount of line pressure that is developed at idle or WOT. The two systems are independent and a much clearer way to state it is "The TV affects the line pressure applied".



The point I was making is the OD shift can be controlled to a certain extent by changing the pressure applied to the OD solenoid. If you overide the PCM there is a way to modify the OD shift with small adjustments that do not entail tearing into the transmission.



Ppeters, if you can find a sensor with the right range and correct workings it really doesn't matter. That sensor is simply open or closed and the PCM acts on that basis. You might want to think about just foregoing the lines to the water cooler and that postage stamp sized thing at the front and look at an optional cooler under the bed. Depending on cost you may be farther ahead building some custom lines to an aftermarket cooler than trying to replace the factory system. Let us know what you find out for available pieces and prices.