Alright guys, need some serious troubleshooting tips here.
Guy that I work with has a 98.5 24v 4x4. Approximately 1 year ago, he purchased a fully built Suncoast tranny with as much billet as you could get. We installed the tranny, along with a set of twins and some injectors. Head gasket blew shortly after the combo, which we expected because he opted not to do head studs or rings at the time. Had the truck O-ringed and studded, went to pick it up and after picking it up the tranny has never been right since. The truck was bucking like crazy, converter locking in and out in and out.......... We have done everything imaginable to try and cure this, and it seems that every time we try something, it temporarily fixes it and then goes back to the converter locking in and out. We have isolated wires, checked our grounds, installed a DTT noise filter, even tried the hooptie aluminum foil around the alternator wires. Suncoast does not seem to know anything either except for their jumper wire fix, or setting the APPS which we tried and is kind of a bummer since he spent so much $ with them. We installed some battery cable ends that gave us extra posts to put his aux electrical stuff on (electric fan for tranny and engine, fog lights, driving lights, etc.) which seemed to temporarily fix the issue. What gives? This thing has been to a respectable mechanic around our area multiple times that we both trust and he seems to come up short every time. Any help would be greatly appreciated.

Also a note is that the truck sets lift pump failure codes, but truck has an AirDog on it.

 

Did you try updating PCM yet? Try running ground wire to pcm and grounding to battery negative also.

NO: 18-02-99
SUBJECT: Erratic Torque Converter Clutch (TCC) Operation (5.9L Diesel Applications)
DATE: Feb. 19, 1999
OVERVIEW:
This bulletin involves selectively erasing and reprogramming the Powertrain Control Module (PCM) with new software (calibration changes 98cal12 & 99cal14).

NOTE: THIS INFORMATION APPLIES TO VEHICLES EQUIPPED WITH A 5.9L 24 VALVE DIESEL ENGINE AND AUTOMATIC TRANSMISSION BUILT BETWEEN JAN. 1, 1998 AND DEC. 18, 1998 (MDH 0101XX & 1218XX).

SYMPTOM/CONDITION:
Some vehicles may experience a surge like condition while in 4th gear. This may be caused by the Torque Converter Clutch (TCC) unlocking and locking when it should be consistently locked. The cause of this erratic operation has been identified as electrical noise from the Throttle Position Sensor (TPS) or Alternator.

DIAGNOSIS:
Using the Mopar Diagnostic System (MDS/MDS2) and or the Diagnostic Scan Tool (DRB III®) with the appropriate Diagnostic Procedures Manual, verify all engine/transmission systems are functioning as designed. If Diagnostic Trouble Codes (DTC's) are present, record them on the repair order and repair as necessary before proceeding further with this bulletin.

Verify the condition by creating a custom display in the DRB III® and include the following: SENSORS (Output Shaft Speed, TPS Volts, Trans Temp Degree) & INPUTS/OUTPUTS (Brake Switch, Park/Neutral, ASD Relay Sense, Desired TC Clutch).

Drive the vehicle with a helper monitoring the DRB III®. Warm the engine and verify the transmission fluid temperature is greater than 32F and consistent. Operate the vehicle with an output shaft speed greater than 2200 rpm. Verify that the brake switch shows a released status that is consistent and verify the park/neutral status reads D/R and is consistent. While keeping the output shaft speed above 2200 rpm, hold the throttle so the TPS reads 1 volt. Monitor the TC clutch status, it should be consistently locked. If the TC clutch status shows unlocking/locking, look to see if the TPS volts are fluctuating by 0.2 volts or more. If the conditions are met, perform the Repair Procedure. If a surge like condition is felt but the above test does not confirm the TCC unlocking/locking occurrence, further diagnosis and testing will be required.

 

Have you done any good old fashioned pressure checks on it yet?

 

To eliminate alt noise, Just disconnect the two smaller wires to alternator. You can easily drive for an hour and see if continues.

 

x2 on updating the PCM. Might as well do the ECM (is it needs it) while its in the shop. You have done all the right things. Have you ran a ground wire from the PCM to the firewall? talking abou the corner bolt on the PCM closet to the engine. I had to do this one my old 98.5 and it worked after all else falied. Also check your body grounds. I pulled all mine off and cleaned them up and reinstalled. Did you by chance check and adjust the kickdown cable a little back and forth to see if it helps?

 

Big Iron - We did ground the PCM - that was Suncoast's suggestion. We did not monitor the DRB III though.

McMopar - negative on the pressure checks

Dozer - we discovered it was the alternator itself (this time)

Fox - we did ground the PCM as you suggested. We did adjust the kickdown cable and it did not fix the problem. We cleaned as many grounds as we could find on the whole truck, but we may have missed one somewhere along the way??

As of yesterday - we put a new alternator on the truck, which was done in the past 9 months. (We thought this may have been the culprit when we replaced it back then). The diodes were bad in the alternator and it was giving us some reverse feedback, causing the surging. I believe that we have done so much tweaking on this thing that we forget the simple things. I believe that when we put the DTT noise filter on, we may have actually needed a new alternator, but it was overlooked since it was only 9 mos old. I appreciate everyones help and suggestions and as of three days of driving, we have had no issues, (other than the starter going out on us yesterday! So thanks again to all you DTRers who have helped whether it be a direct post or something I searched.