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47re converter erratic lock/unlock in 3rd gear with OD off

13K views 40 replies 7 participants last post by  DanG144 
#1 ·
47re converter erratic unlock/lock in 3rd gear with OD off

As the title states, this lovely problem just started. Before I go any further I want it to be known that the brake switch is brand new, and I made sure to hold the pedal up with my foot to rule that out.

I can repeat the problem like clockwork if I turn OD off and go up a hill with medium to heavy throttle. It unlocks then locks quickly, repeatedly. I don't want to do it too often as it bangs pretty hard and I don't want to hurt the transmission. I do have a manual lockup switch and if I turn that on the issue completely goes away.

Knowing that a bad alternator can cause lockup issues, I tested my charging system. Both batteries were at 12.68 volts with the engine off, and when I start it it sits at 13.97 volts with the alternator charging. When the grid heaters cycle, the 13.97 volts drops to 12.68 then back up to 13.97. I am not sure if this is too low as some others report it is supposed to be over 14 when the grid heaters are not cycling, and shouldn't drop below 13 under load. It should also be known that I have an el cheapo Innova multimeter.

All the grounds are fine, and I checked the voltage drop with the multimeter and it was .04. All of that seems to check out, so my next course of action is to drive the truck to the hill where I can get it to do it every time, and then pull the fuse to the alternator and see if it still does it. If it does not, then I would think it is the alternator and perhaps a bad diode, but I'm not sure how unplugging the alternator (fuse) might affect other systems.

I know the TPS can affect lockup, too, but am unsure why it would only be in 3rd gear, not OD, when the throttle is in the same spot. I tried some heavy acceleration in OD and it never did it, but I can't find a steep hill where I can safely get enough speed in OD.

Suggestions appreciated. Will post more as I try to work my way through this. These are the kinds of annoyances which push me into brand new vehicles as I tire of the constant troubleshooting and tinkering. A G56 would be so nice...
 
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#32 ·
I have cleaned all grounds and inspected/exhausted all potential areas of failure. I can say with almost complete certainty that this is a TPS/linkage problem. Even though it tests fine, there's something going on there. I will be ordering the bushings for the linkage, then when they come in I will be taking it all completely apart, upgrading the bushings and inspecting all the linkage, then reassembling and testing again.

I found in my paperwork that the original owner had the throttle linkage replaced per TSB, but that TSB was only for manual trucks so the paperwork said they had to re-install the original parts. I measured from the back of the bracket to the center of the ball, which is supposed to be 5", and it appears to be shorter than that, somewhere in the 4 1/4" - 4 1/2" range, but I will have to remove a couple things to gain better access for an accurate measurement.

When I get everything put back together perfectly, I will test the TPS again, then drive the truck. If the issue persists, I will replace the TPS.
 
#33 ·
brownbear, I know you are against band-aids. When your truck was new it had many electrolytic capacitors in it. These were used to resist short term voltage transients - to smooth out the voltage signals.

The average lifetime of these electrolytic capacitors is somewhere between short and medium. In any case no one would be surprised by electrolytic capacitor failure on our trucks.

https://www.allaboutcircuits.com/ne...an-of-electrolytic-capacitors-with-de-rating/

The addition of a capacitor to the tps signal line is a very reasonable fix, it may very well be establishing the signal filter that used to be on our PCMs - so I don't see it as a bandaid but as a part of the life extension of my PCM.
 
#34 · (Edited)
I appreciate your suggestions in this thread, and will definitely consider that if I come up empty. But I agree with Mopar1973Man that if the system worked fine without it initially, it should never need it. Kind of like that BD noise isolator - it's masking a deeper issue which in many cases is leaking AC current from the alternator. Mine does not have that issue.

Does anybody know the OEM part# for the TPS? All I'm finding online are aftermarket units made by Standard Motor Products. Is this all that's available?

PS - Also found a Borg Warner (which is a subsidiary of SMP).

On edit, I found the Mopar #4874412 and the Cummins #3930318. There is quite a price range. The SMP parts can be had for as little as $88, and the BWD for $135. Not sure why there is a vast range there since they are essentially the same company. The Cummins can be had for $190, with the Mopar unit at $247. I am wondering if aftermarket is ok?
 
#35 ·
Yesterday I removed the bracket for the throttle controls and checked the bushings on the throttle arm. The play is minuscule so that's not my problem. I then did an ohm test on the tps. When I sweep it very slowly there's a dead spot where the reading zeros out every time. I verified it several times to make sure my probes were not losing contact. This is something I did not see when I initially tested it. I think it's bad.

I drove to O'Reilly's because they had a new Borg Warner EC3061 in stock. I bought it. I went out to the truck and decided to check it before I left the parking lot. Not only did I find a dead spot in it, there was also another spot where the reading would not increase, then it would jump up really high. It was bad out of the box. I took it back in and showed them. They agreed it's bad, and told me they had another guy in there with a Dodge who had returned one recently, bad out of the box. They refunded me.

I am going to contact Cummins tomorrow to check on prices, and also ask them if they can verify it's a good unit before I agree to drive all the way there to buy it.
 
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#36 ·
It looks like the genuine Cummins part is $203.69. They also only offer a 1 year warranty. The dealer wants $425. I can't believe how expensive these are. If I installed it and my problem persisted, I'd be terribly disappointed. My multimeter definitely showed a dead spot, but I am concerned that the new aftermarket one showed a dead spot in a similar location, up in the 3/4 throttle range. If the Cummins sensor showed similar, I'd be concerned that a multimeter OHM test is not a satisfactory test.

I have been researching the accuracy of digital multimeters for sweep tests and some say that an analog meter should be used. My analog broke years ago. I'm wondering if I should purchase one, or trust that my digital multimeter test was sound. I cannot stand throwing parts at problems, but I don't have an oscilloscope to do a proper test on it.
 
#38 ·
I installed my new Cummins TPS today. I am cautiously optimistic that the issue is fixed.
 
#39 ·
My tps delete works also, I had brake light switch problems at one time and holding up the pedal didn't help. There is a lot of small items that can cause the problem. Have fun as I have been there and done that. I have a lock up switch on the converter and I have to use it now and then to keep it locked until I have time to chase down the next issue. I can go months in between but I always comes back in one form or another. My brake light switch is doing it again but this time holding up the pedal is working. It isn't constant but intermittent.
 
#40 ·
I thought I would update this thread as it's been over a month with my new TPS. I have not had one single shifting issue. The transmission is shifting better than it ever has.
 
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