Re: [AMC-list] Testing an Overdrive Solenoid

[Frank Swygert <farna@xxxxxxx>]

People who actually HAVE and USE one of those units know better than to split-shift it! The gears just aren't far enough apart to make it worthwhile. I set one up like that once. 1+OD is about the same as 2nd, 2+OD is about the same as 3rd. No point in split shifting. I suppose it would be handy if you needed to pull something and weren't using OD as 4th gear -- 2+OD then down-shift by flooring it, shift back up by letting off the throttle. But I don't see that as being very useful either. That's why the Twin-Stick trans had a big gap between 2nd and 3rd gears -- so 2+OD would be somewhat useful. As Tom found out, that can be a hassle shifting! 

The governor is set kind of low, but the way it's made there's not much you can do about it. It could be taken apart and stronger springs put in, but that would be quite a chore because of the way it's made. I don't think I'd attempt it. Besides, it only shifts when you let off the throttle. To delay shifting into OD just hold the gas down a bit longer. As soon as you let up for any reason though, it will slip into OD. 

You can engage OD in 2nd, then just shift normally into 3rd (remember 2+OD is about the same as 3rd). I found that with just slightly aggressive driving that was the best thing to do -- it would slip into OD when I let off the gas to shift into 3rd. So I'd let off and go into 2nd, then shift when needed. 

The funny "ratcheting" double-pole kick-down switch is a MUST!! If you wire a standard momentary switch in you'll have to use the clutch when disengaging OD. One set of poles (top -- closest to plunger) is normally closed. Power for the solenoid goes through those. The other set is normally open. Those ground the coil when engaged, killing the engine for one or two beats. When the switch is pushed in it momentarily bottoms out and closes the NO set of contacts, then immediately pops back up, opening the lower contacts. If it didn't the engine would die. If the coil weren't grounded out power would still be applied and the OD would eventually blow from the stress on the planetary gear shafts, which are small. I've "blown" one by NOT having that switch. It lasted 2-3 months of normal driving. All I had was a toggle switch to the solenoid. Works fine for shifting into OD, would have been fine if I'd used the clutch when dropping out! I'm sure Tom could figure out some logic circ
uit that would do the same thing along with a momentary switch though. 

When I used one with my EFI I used a relay powering the ignition module instead of grounding the coil. Wasn't sure how the computer (or coil) would like grounding! That will probably work with a coil -- relay in the power wire instead of grounding it. Not sure though, might need the relay between the coil and dizzy. The coil charges then discharges, so it might have a beat left in it when the power is dropped, and that could be enough to eventually damage the OD. Grounding it out discharges, so that's probably the best thing! Won't hurt a Pertronix unit, and probably wouldn't have hurt the EFI coil. Not sure if the computer would have reacted though, so better safe than sorry! 

Part of the convenience of OD is having a mini auto trans. You can do most driving in 3rd and OD (or 2nd and OD). Before autos were economically feasible in most cars that's the way it was done. First was only used for complete stops, and many of the old 30s cars would chug off from a level stop in 2nd. Driving was way different back then than it is now!! 


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Date: Sun, 18 Oct 2009 14:45:53 -0700
From: tom jennings <tomj@xxxxxxx>

I like my electric OD. Works great. Most people who even know of them all
say to disconnect/jumper out the governor so it'll work in all gears, but
I'm very happy with mine. Kicks out of OD instantly with a push of the
button, and 1st-OD doesn't sound too useful to me.

The governor is set to engage at 28mph, which is about 1 - 2 mph above lazy
shift-to-3rd, so it's 1, 2, 3 upshift normal, let off, 3rd-OD. On those rare
times I am pulling faster, and shift 2 to 3 above the OD cut-in speed, I
just hold the button in, it's right under my hand (Twin Stick).

My Classic wagon had the regular OD with the under-dash cable and the
throttle kickdown switch. If I recall it was somewhat of a pain to adjust
that switch right. Unfortunately the switch is a double-pole funny switch so
it would not be completely trivial to add a second dash mounted kickdown
switch. The Twin Stick gets different wiring that allows for a single
short-to-ground to do the kickdown function. It takes an additional or
different relay I think. Might not be worth the effort to adapt.

--
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)


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