TPS revisited

[walmor]

BushWakr, I tried everything you suggested including checking the lever on the transmission. I now am of the opinion that it is not the TPS. No matter where I set the voltage it shifts exactly the same. It will shift into OD if I let up on the accelerator over 35, but if I maintain a constant acceleration with out lifting it won't shift until 60 mph.

Something that does puzzle me is when I set it at say 1. 0 volts and then work the throttle to WOT, it goes up to something like 3. 29 which seems a lot higher than the recommended 2. 25. There is no way to adjust the upper end without changing the lower end that I can see. Regardless nothing I do with the voltage makes a difference with the OD performance.

The lever on the Transmission is all the way forward when at idle position.

 

[BushWakr - RIP]

If I remember right the total increase over 'at rest voltage' should range between 2. 25vdc and 2. 75vdc. If you're in that range it's working properly.

Have you confirmed the proper gap on the throttel governor cable at the linkage connector? I am not positive, but if I remember right that gap should be approx . 180"



The next items in question would be the speed sensor mounted on the transmission transfer case. The crank position sensor or engine speed sensor is located on the front of the engine, and there is a wire w/harness running down behind the fan pulley. It is a bit tough to reach but if the connector down there gets gummed up, it can cause problems too.

The sensor head is positioned over the harmonic balancer. The gap setting is between . 049" and . 051". You must use a non-magnetic feeler gauge to set it, and make sure that the head is not near any slots in the balancer when you set it.



Any other thoughts on this one guys???? Jump in here... lets see if we can get this baby up and running properly. .



Bob.

 

[PPeters]

Bob, you have the correct numbers. All suggestions are what I would do (have done ).



Walmor, is this a "new" TPS, or one that has been cleaned? I went through the same problems as you, and the only thing that fixed it was buying a new TPS from Cummins (cost: $150). Definitly cheaper than stealer (at least in my area).



What I would suggest is clean all electrical contact points that Bob is referring to, dielectric grease on plugs, then check/set the gap on crank sensor, adjust the throttle cable linkage (be sure to check the breakover spring position for correct behavior), then check/adjust the TPS voltage. If the voltage goes up in excess of factory spec when performing WOT test, then perhaps TPS is NFG.



I tried all these before replacing TPS. Others have saved $$ by taking apart their TPS's and cleaning, then reassembling with RTV. If it works, you save the cost of new, if it doesn't, you still needed to buy one.



Pat



Found your earlier post

 

[dusthomps]

Just a little input that might help you guys out, on my 92, I have the TPS set at 2. 94vdc at WOT and . 37vdc at closed throttle. I know I'm out of the specified range, but the transmission shifts into OD when it should with those settings. When I get around 3. 25vdc at WOT, OD won't work properly. Hope this helps.



Dustin

 

[walmor]

BushWakr, PPeters, and Dusthomps, it looks like another day under the hood following up on these suggestions. The people along the route that I take to test drive surly think by now that I have a very UNRELIABLE (piece of crap) truck because they see me at every turn out in the road adjusting something under the hood.

PPeters, I have already sprung for a NEW TPS 175. 68 at the Dodge place and that is with a discount through a employee.

The suggestion from Dusthomps makes sense, if I go lower voltage at idle then it would not be so high at WOT. The only problem is that no matter what I have adjusted it so far it has no affect on the shifting. But I will try it a lower voltage like . 37 and see.

I will check on the sensor on the front pully. Since I have a Gear Vendors OD the "Speed sensor has been moved over to the frame rail and hooked up through a cable to the OD. That part works good in fact with the GV overdrive I hardley miss the transmission OD. But I still want it to work.

BushWakr, are you referring to the gap within the end of the Trans. cable and the pin in the slot?

 

[BushWakr - RIP]

Yes, that's the gap/spacing I'm referring to.

I'm a little suspicious of that cable from the speed sensor thingy you mention now though... ... maybe I'm just being anal here... (BCaldwell will confirm I'm sure )



Some guys have gone as low as what you are going to try, and had no problems with that as an "at rest" setting. Whatever works, right...



Bob.

 

[walmor]

TPS

BushWakr, Are you the "Night Shift Moderator"? I kinda thought that might create some concern when I mentioned the location of the Speed Sensor, but it has been in that location for about 6 years and performed perfectly. They plug the hole in the Transmission and hook it to the OD. I have had trouble with it once before I got the GV. At that time my speedo quit working and it wouldn't go into OD. I took it out and washed it out with solvent and that took care of it.

Walt

 

[PPeters]

Walmor, FWIW, before I replaced the TPS I was also adjusting the TPS lower to get OD shift. At one point it was set to . 25v at rest, anything more would delay shift of OD to what you are seeing. Then one day it started to hunt between 3-4 shift, or just drop out of OD while running at 65mph, and not upshift again. No amount of adjusting/cleaning corrected the problem. That's when I replaced the unit. Voltage setting after is now . 75v at rest, and shifts have been reliable since. I know you have bought new, so this is very puzzling



I'll dig into the manual tonight and look for some clues. If I recall, the throttle cable setting can be critical to the correct function of the TPS. I had trouble with mine returning correctly, seemed to have some crap in the jacket. Tried to work lube into the cable, after much effort it is better, but not perfect. Don't know if it is possible that you got a bad TPS from dealer?