Don't beleive there is a one fix cures all repair. Suggest starting with grounds and power connections. Clean rust and seal with grease.
Next have batteries individually tested at parts store and have alternator bench tested. A inspection of brushes for grease on slip rings would be in order while off.
Try shielding the wiring at alternator. Wrap aluminim foil around wiring for 18 inches of so, back toward engine. Taking tape and couvlute off and wraping alternator wires (3)with very small wire for 18 inches or so and then ground this shielding wire. Do Not short the shielding wire to alternator wiring. You can now rewap the convlute for nice apperance.
Some other items of intrest. APPS reset mayh be of benefit. Killing memory by disconneting all battery terminals and toughing a positive lead to a negative. You are shorting the wiring, NOT the batteries. This kills memories and fault codes.
A poorly adjsusted brake switch or erratic speed sensor need mentioning as a possibility.
A condenser (radio supression condenser from old Chrysler ignition coil) housing mounted to alternator frame with the lead connected to alt. output terminal is effective in reducing alternator stator wiring imbalance and internal condenser issues.
These are very low cost repairs and have been effective. The tranny specialist also offer various supression fixes and rewiring kits, but are expensive in most cases. Some have success with kits and some don't seem to, is my take on them.
A worn out torque converter may be the culprit also.
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2000 Big Blue Beast 3500 SLT 2WD heavy hauling auto, stage 1 injectors, 242K miles and still growing.
Toys include 1248 ci D8H dozer, 743 ci WABCO grader, track hoe and more. Wanna play!