[DMCForum] Automatic shifting troubles....
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[DMCForum] Automatic shifting troubles....



Hmmm...as much as I loath responding to people who refer to inanimate 
objects in the female vernacular, I'll make an exception.

The most common failure mode of the C/G are the capacitors. Certain 
capacitor types (in this case electrolytics) are notorious for 
exhibiting thermal related problems with age. This is because the  
electrolyte paste used in their manufacture drys out over time. Also, 
their working voltage is under rated in this application so you 
should replace then with tantalum caps of a higher rating. I refer 
you to the instructions available online by another D owner a few 
years back. That fellow knew his stuff and his mods are solid.

Since the solenoid output is readily available in the engine 
compartment, if you want to see if your C/G is operating correctly 
simply wire two test lights into it. Go to Radio Shack and get three 
banana plugs and two 12 volts lamp assemblies. Make up 4 feet of 
three wire cable and bring it into the car through the door seal. 
Or simply place these lights where you can see them in the mirror.

In first gear (or with the key turned on) both lights should be lit. 
Second gear will extinguish one light and in third both will be out. 
(The solenoids de-energize to change gears, it's why when the C/G 
fuse blows the car always starts off in third.)

If the lights behave as they should at the proper speeds then your 
C/G is functioning correctly and the problem is transmission related. 
Or it could simply be your soleniods are sticking or bad. (There are 
ways to electrically check them without removal.) Of course, this all 
assumes you've checked to be sure the C/G is getting power and there 
are no other wiring problems.

But as Walter points out, if your C/G is original in all likelyhood 
it's bad...or will become so at some point. You should replace the 
caps after stripping off the old conformal coating. Also while you're 
in there you should replace the driver transistors, add bypass 
filering caps to the op amps, and resolder the connections between 
the two boards. In fact, I'd replace those wires with ribbon cable 
and resolder every connection on the boards as the quality of it is 
atrocious. Often times just twisting the boards or stressing the 
connections will change the solenoid outputs.

Deflux and then recoat the PCBs with mil-spec acrylic conformal 
coating and reassemble the unit. Use fresh thermal grease and be sure 
the driver transistors are in contact with the cover, there is a wire 
spring in there to insure that. Clean and reseal with sealant, be 
careful about using RTV as it's corrosive. All these chemicals and 
components are available at any electronics store. If you're not 
comfortable doing all this then send it to someone who is. I'm sure 
John H can handle it but you'll save money by doing it yourself, 
learn new skills, and get more satisfaction. Or maybe you have a pal 
who's literate in electronics.

If you choose to relocate the C/G be sure you use high temp cable and 
keep it clear of the exhaust. If you do, be sure you connect the 
wiring correctly from the small alternator to the relocated 
electronics because the phasing is important. It'll work if you get 
the phasing wrong but will shift at slightly different points. It 
won't feel quite right so you'll know it. Besides, you don't want to 
remove this thing any more than neccessary. Install the electronics 
in a good project box and heat sinking on the solenoid transistors. 
Place it where it won't get wet with rain or when washing yet still 
be free from excessive heat.

Check the O ring on the alternator and use a new one if it looks 
flat. Install the C/G and rig the actuating cable as per the service 
manual. Save the test light harness, you can always use it to verify 
your C/G in the future. Also check the kickdown switch on the 
throttle and it's wiring, it must not be actuated at less than WOT. 
In fact, check that before you remove the C/G. Best to also check the 
multifunction switch when you have the C/G out. Btw, you don't need 
to remove the pan to remove the C/G, simply disconnect the solenoid 
wiring at the same terminal block you connected the test lights to. 
I'd still check all the wiring however, it runs near the crossover 
pipe and is subject to heat.

PS: Hi Bill, I see you're as witty as ever. You sure have a way of 
tuckering people out, you wouldn't believe the mail I get. Nice to 
see you went and bought some books, sounds like you're actually 
learning something. It's a start...

PPS: Hey Walt, quite the forum you've got here. What's it supposed to 
be about again? ;)

*********************************************************************

The first 10 minutes or so, she drives perfectly, shifting from 1st 
to 2nd to 3rd with no problem. However, once the car has had about 3 
miles down the road, I will have the car in 1st going down the road 
and it sticks in 1st.........




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