47RE lockup

Sounds like either the solenoids are confused and not working correctly when the mode changes, OR, the PCM gets confused. Could this be a result of "interference" in the shift control circuit caused by the alternator wire? The cure for this was wrapping the wire in aluminum foil or something odd like that.

this is just my personal experience; I have a TC lockup switch, when I turn on the OD with the switch "off" (50 to 55mph) I experience the same as you are describing. with the switch "on" it shifts very fast and firm. if you go with a lockup switch, please not the following:

the TC will not lock in 1st gear.

the Trans will NOT downshift while the switch is on. in a breaking maneuver this helps slow down. the flip to that is the truck will not stop in safe manner. at 25 mph the engine is at idel in 4th gear, slower than that (if this is a Cummins) the truck will fight the breaks.

I thought shielding the alternator ground wire was to prevent the torque converter from cycling in and out of lockup at cruise speeds. I'm not sure it will help but it's easy enough to find out. The only time I have problems is when initially turning OD back on at speeds above the normal 3-4 shift. If I turn OD back on at speeds below the normal 3-4 shift it's fine. If I leave OD turned on it works perfectly. If it's interference I would expect it to happen during the normal automatic 3-4 shift as well. I'll try it and let you know.

Thanks Billy. It is a Cummins. I am aware that it will stay in gear when coming to a complete stop if the torque converter is manually locked. That's the only reason I haven't wired a switch yet. I've been rolling the idea around that the pulse signal from the VSS could be used somehow to disable manual lockup at low speeds but I haven't got that ironed out yet. I believe the VSS gives 8,000 pulses per mile so 25 mph is about 55 pulses per second. If I can find a control circuit that switches a relay at 55 pulses per second it would be simple to implement that as a low speed override.

What year is the truck? Have you checked for codes?

There are a couple of TSB's in the late 90's/early 00's dealing with converters dropping out of lockup and delaying lockup due to insufficient fluid flow.

Your problem might be a case of the converter dropping out of lockup due to the fluid demand caused by the engagement of the OD, this would explain the perceived "neutral" condition as the shift event occurs. If the vehicle speed exceeds the throttle setting when the converter unlocks it seems like it goes into Neutral then as the OD engages and the converter delays re-engaging it would seem like a double-shift.

I wrapped the alternator ground cable in foil and taped it up. That didn't seem to help. Thanks anyway.

It's a '99. I had it scanned today and it showed no codes.

This TSB?

That sounds like it may be what is causing the condition. Can I replace the separator plate myself? I've done shift kits before on C-6 automatics but I've never done anything more than filter changes and band adjustments on any Chrysler automatics. Will a shift kit help with this problem instead of changing out the separator plate? Would it be a good idea to change the separator plate and do a shift kit?

Thanks for the help.

A shift kit will necessitate opening up the valve body anyway, and would either include a new separator plate, or would have instructions to modify the existing plate. Either way, you'd be touching the plate.

Removal of the valve body, and the rest of the work to install the shift kit, is very simple and straight-forward. Just keep track of which bolt came from which hole, and pay attention to the torque specs. when re-installing.

If it were me, I'd probably just go ahead and modify the stock separator plate to open up that passage, as well as install a shift kit (might as well - the VB's apart). And while you're at it, install a drain plug in the pan - it will make any future fluid/filter changes a lot less messier :)

Thanks Tom. I'll look into the shift kits. I haven't had much luck with add-on drain plugs. They always seem to leak for me. I use a vacuum tank to pull the fluid out through the dipstick tube. It doesn't get every drop but it keeps it from spilling all over the place when dropping the pan.

Just as good... anything to avoid the otherwise-inevitable ATF shower :)

Be aware that the term "shift kit" is somewhat generic, there are cheap shift kits that can actually cause more harm than they help. Look for a reprogramming kit like the Transgo TFOD-HD2.

Thanks John. What do you think of the Transgo TFOD-Diesel?

Same thing only specifically for diesels. I recommend it. Best prices I've found are at bulkpart.com

Thanks again.