1999 3500 auto with TC lock/unlock problem

[DonFitzwater]

99 3500, 4x4 auto with 60k miles. Truck runs well and drives ok until it's time for overdrive/lockup. The trans will continuously hunt back and forth, in and out of lockup and will never maintain lockup. We checked the usual suspects like grounds, alternator (disconnected and test drove), replaced apps (no change), replaced output speed sensor (no change). The PCM was sent to a repair center in Iowa and they replaced the torque converter lockup circuit driver and the problem persists.

I wanted to verify that the problem isn't internal to the trans so I wired up a mystery switch and she locks up and drives great for as long as I manually ground that circuit.

I've been running my little scanner on it (a smaller Mac tools unit) but it's doesn't sample well or fast enough to see any real anomalies other than it's been graphing the heck out of the lockup circuit cutting in and out. I finally got it hooked up to a Solus by Snap-on and it showed up a whole bunch of really strange signals that all drop in and out with the same frequency of the lockup circuit going in and out. The voltage out of the TPS/APPS is rock steady to the engine but the voltage to the PCM seems to be erratic. The charging system voltage seems erratic also but the symptoms still persist even with the alternator totally disconnected while driving (didn't use the solus when running without the alternator so don't know what the voltage signal looks like while not charging).

Can I install an "overlay" wire from the APPS directly to the input at the PCM in an effort to rule out a potential harness issue and does that sound like the proper direction to be heading? Is this the classic example of needing the filter for the charging circuit?

 

[DonFitzwater]

Today I followed the instructions laid out by Suncoast and split the ground wire from the TPS and ran multiple grounds from the tps to the battery and from the PCM to the battery. The truck ran great and shifted as designed for nearly one hour. After an extended test drive, just when I though it was good to go, it started locking and unlocking again................

 

[JR]

The cause is almost always due to faulty diodes in the altenator sending dirty AC voltage through the system, the noise filters and splitting up the harness are usually just band aids to fixing the real problem. I know you mentioned disconnecting the altenator but did you test for AC voltage by chance? It takes very little AC noise to cause a problem. Should be under 0.1 VAC.

 

[Regcabguy]

The noise filter killed it for my '98.5 for years until I sold it.

 

[DonFitzwater]

The cause is almost always due to faulty diodes in the altenator sending dirty AC voltage through the system, the noise filters and splitting up the harness are usually just band aids to fixing the real problem. I know you mentioned disconnecting the altenator but did you test for AC voltage by chance? It takes very little AC noise to cause a problem. Should be under 0.1 VAC.

Yes, alternator was tested while running with a dvm and it registered .015 volts a/c at all speeds.

 

[AKGriz]

Installed the DTT filter, results were similar. Ran perfectly for about 2 hours of running time, and then the Schwarzenegger Gremlin reared its ugly head again. I was able to get it to drop out of lock and back in simply by turning the headlights on and off, and did it a few times by using the turn signal.

Don has done just about everything humanly possible with every conceivable fix, and it's still happening. I'm wondering if the problem lies in the alternator, even tho it tests fine (Don tracked steady voltage at all speeds, and the AC current is well below the 0.1 threshold (as previously noted). Truck was run on battery power only and the surge still happened.

Anyone have any ideas?

 

[JR]

Pull the fuses/relays for those systems and go for a ride.

Wow! What a mess!

 

[AKGriz]

Pull the fuses/relays for those systems and go for a ride.

Wow! What a mess!

Really! It seems to be intermittent, and involves more than the lights/turn signals. Vent fan and power windows cause it to act up as well, as I discovered on the test drive.

I'm not the smart guy here, but it seems to me it's getting dirty juice somewhere. I guess I'll start cleaning connectors one at a time.

Anyone got any ideas for a source of a good, clean alternator? Searching the forum it seems the rebuilds can be problematic. RockAuto has a couple of "new" ones listed, anyone have experience with them?

 

[BMelhuish]

The alternator diodes seem to go bad on a fairly frequent basis. I've replaced 2 alternators in about 5 years to solve the issue. I finally went with a new Autozone simply because of the life time warranty. When and if that one goes bad, Autozone will replace it free. As an aside the AC voltage that you are reading was enough to cause the issue in my truck. After replacing the alternator, mine read 0 AC. There is a TSB on the issue. I believe that Geno's has it.

 

[cerberusiam]

Alternators are rarely the problem, the system will work fine if the correct wires are isolated. Cut the charge wire where it enters the harness on the passenger side, reroute it across the top of the radiator support and connect where the old one in the harness did. Cut the passenger side battery ground wire that is in the harness and route it across the firewall keeping it away from other harnesses. Would be a good idea to use shielded wire for the power and ground both at this juncture.

The dirty signals that cause the lockup mode to drop in and out come from the charge and ground wires setting up a magnetic field and inducing garbage signals in the rest of the harness. Age and deterioration of the wires just make it worse. Rerouting those 2 wires should solve 99% of the issues, given everything else is relatively good. Random problems after that frequently end up being the VP44, the electronics are crap and after a time they are causing garbage voltage to feed the PCM because the whole works is in the same harness bundle.

 

[DonFitzwater]

We left the charge wire alone.........pulled the passenger battery small ground (ties into a bunch of smaller engine grounds directly forward of the injection pump area) apart and started working backwards on the wires. At the drivers side forward corner of the block, we cut open a large splice area. What I found inside made me more angry than any other stupid ***** I've seen dodge do over the years. There were at least four sensor grounds simply laying on top of the large ground wire and heat shrinked in place. No solder, no crimp connector......no nothing. This was factory!!! Total BS.

We removed the **** poor splice and installed some heat shrink butt connectors and added a small length of ancor brand marine battery cable to the passenger battery connection. The truck has performed flawlessly for about a month now.

This has been one of the worst torque converter lock/unlock problems I've ever had to fight. The clue in all of this came when I test drove the truck while using the scope screen on a Snapon Solus and voltage readings for every sensor on the engine and transmission were very erratic and what you could call "dirty". I wanted to update anyone interested and Dave (Akgriz) will probably post some photos later. We may even do a quick write up as this is something you can bet should be looked at on other rigs with persistent lock unlock gremlins.

 

[AKGriz]

Pix of Factory Ground wire heat shrinked--this fixed TC Lock/Unlock

We left the charge wire alone.........pulled the passenger battery small ground (ties into a bunch of smaller engine grounds directly forward of the injection pump area) apart and started working backwards on the wires. At the drivers side forward corner of the block, we cut open a large splice area. What I found inside made me more angry than any other stupid ***** I've seen dodge do over the years. There were at least four sensor grounds simply laying on top of the large ground wire and heat shrinked in place. No solder, no crimp connector......no nothing. This was factory!!! Total BS.

We removed the **** poor splice and installed some heat shrink butt connectors and added a small length of ancor brand marine battery cable to the passenger battery connection. The truck has performed flawlessly for about a month now.

This has been one of the worst torque converter lock/unlock problems I've ever had to fight. The clue in all of this came when I test drove the truck while using the scope screen on a Snapon Solus and voltage readings for every sensor on the engine and transmission were very erratic and what you could call "dirty". I wanted to update anyone interested and Dave (Akgriz) will probably post some photos later. We may even do a quick write up as this is something you can bet should be looked at on other rigs with persistent lock unlock gremlins.

 

[JMLambert]

When you say you added a small length of battery cable to the passenger battery does that mean you just added another ground at the battery? Thank you in advance as I am going to try this on mine. John

 

[AKGriz]

When you say you added a small length of battery cable to the passenger battery does that mean you just added another ground at the battery? Thank you in advance as I am going to try this on mine. John

No, we actually lengthened the ground wire that runs across the alternator to the passenger battery--the splice is at the driver's side of the engine. See http://www.kentsoil.com/dodgebug1.htm Fix number 1, the difference is instead of pulling the ground wire away from the passenger battery and alternator and running it to the middle of the radiator, we traced the ground wire all the way back to the messed-up splice on the driver's side, made good clean connections on all four ground wires (part of the factory splice), put in about an additional foot of ground wire, and ran it straight to the radiator's left (driver) side, across the top and off the right (passenger) side and were able to use the factory mount for the cable on the base of the battery box.

Hope this is not too verbose. I'll add some more pix in a couple of minutes. All I'll say is she runs better than ever, the T/C shift is so smooth that often you can't even tell you're in overdrive until you look at the tach....

 

[AKGriz]

One pix shows the driver's side splice (finger points at the splice), one the passenger battery, and one with the ground cable on top of the radiator with the alternator safely in the background.

 

[REdmon]

My 99' 2500 has the same problem and ended up putting aluminum foil around the ground cable from the alternator to passenger battery (have to do it about once a year). I guess I should go a little further and check what you found as factory splices.

 

[AKGriz]

Yes, I highly recommend this solution. 18 months post-fix, 25,000 more miles including a run from Fairbanks to Tennessee and back, and not one time has the problem resurfaced.

 

[BoeingDiesel]

Skip the foil and the noise filter, it's temporary at best. Do the Sun Coast Apps rewire. It's been several years since my '99 had this problem. Keep the battery terminals clean, etc.