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Hello! So, today my cousin took the Packard (48 super eight LWB) for its first test drive. Happy to say it made it home safely, but there was some weirdness! Apparently, when they were trying to engine brake down a hill, the engine freewheeled instead of braking. The car has an electromatic clutch, and I'm wondering if this is normal behavior, or a failure state? Please and thanks in advance!

Edit note: the problem has been localized to the overdrive module, which is freewheeling but not engaging the actual overdrive gear itself.

It's the overdrive that allows freewheeling, not the Electromatic clutch. The two are almost always found as a package though I believe it was possible to optionally have either one individually, I'd have to check Neal's book for confirmation.

How do I disable the freewheeling? Is it a feature of the solenoid, is there a switch on the dash?

Lock out the overdrive with the overdrive control just to the right of the steering column at the base of the dash. Ivory-colored knob. Do NOT lock it out while driving in OD!

Don't you have an Owner's Manual to read for such info? If not, highly recommended. I'm sure its available here in the Literature Archive to browse. Or buy a reprint from the Packard Club.

It seems the entire system needs going through, because the transmission is freewheeling at *all* speeds and conditions! I'm gonna tear into the solenoids and connections and see if cleaning things up helps; it seems like the OD is stuck on.

Depends on conditions or speed the car was going but it is possible the clutch disengaged. If the car was going below the overdrive engagement speed of approximately 20-25mph the governor would have the AD contact disconnected and EC contact going to ground. As soon as the accelerator was completely released the accelerator switch would have made contact and with the governor also making contact the Electromatic Clutch on/off solenoid would get ground and turn on to allow vacuum into the system. With the accelerator relaxed and vacuum available the control valve would disengage the clutch. If the car was going faster than 25 the EC should still be inactive electrically unless the gear shift lever was moved. As soon as the lever is moved from third another switch is made to admit vacuum and irregardless of speed, if the accelerator is in the right position EC could have been made active.

If the car has overdrive and that was engaged it is possible the overdrive and the probability it went into freewheeling was the actual culprit to disconnect from the engine.

Packard recommended locking out both EC and OD when under certain conditions including when descending a hill.

Attach file:

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  OD_EC.jpg (126.80 KB)

Due to it's age, I suspect there's some malfunction(s) coupled with lack of operating knowledge newness, but since you're in the "exploring" phase, try to downshift to a lower gear going down and see if it freewheels or not. That way you can eliminate some items. Guessing what might happen won't solve the nor diagnose.
Electromechanical systems in the day weren't totally robust. And depending on the condition the wiring would be expected to be more than aged past useful life and prone to faults.
Selling points more than needed. A mad dash to avoid the automatic transmission invasion of the co

So, I've determined several faults (via a game of telephone bomb defusal with my cousin):

1) the overdrive solenoid is not functioning, either because the governor is non-functional (contact is apparently normally open), or because the solenoid itself has open windings.

2) the electromatic clutch is *fully* functional. There's no significant vacuum problem, the solenoid is engaging and disengaging correctly, and the dash button cutout is still properly working.

3) the car is still freewheeling in all gears, *but* it can still be shifted into reverse, which according to the OD service manual means it's not stuck active.

4) the manual cutout knob is frozen (and my uncle broke the knob off trying to get it moving). However, my impression from the schematic is that this isn't actually a serious issue; that is, so long as it's not stuck in cutout, it should function.

It seems the electronics controlling the overdrive have died, though it's also possible there's an internal issue with the unit (the pawl could be worn, etc). I'll try to source new ones, but frankly after looking at a few pictures of their internals, I'm pretty sure I can rebuild whats in there. Winding the solenoid looks pretty easy.