Re: [DML] Auto trans governor problems

["Mark Hershey" <dmcinfo@xxxx>]

Matthew, one of the new transistors could be bad and replacing the originals
may do the trick. But the solenoid current isn't all that high and I'd be
surprised if the TIP42 is thermaling on you. Especially since they are both
biased off in 3rd gear (when it's working right) and should generate little
heat of their own when you're crusing down a long stretch of highway and not
changing gears often. Still possible of course; the transmission generates a
lot of heat on it's own.

Did you add the .1 microfarad caps across pins 3 and 4 of the 6-pin
comparator chips? Greatly improved overall stability. Could have cold solder
joint somewhere on the board that opens up with heat. Most likely spot is
where the inter-board jumpers solder on the boards. Been suspicious of
several but never proved a bad one for sure. Nearly all of 'em have solder
pads that look bad and could use a touchup just on principle. I've always
just resolderd everything on he ones I've fixed for friends so we may have
covered over a few problems without knowing...Recently found one unit that
had badly nicked wires where the jumper ribbon's insulation was removed at
the factory Two of the leads were broken. Made intermittent contact--tough
to find! Really ambitious: replace the solid-wire multi-lead interboard
jumper with individual flexible, stranded wires.

Several folks have suggested adding some antispiking diodes; that's
certainly good engineering practice but I removed mine years ago while
trying to isolate other problems (and to prove the diodes help) and never
put them back. Haven't had any problems without them but if something else
is marginal they could help.

Another possibility: downshift circuit is getting set when it shouldn't.
Look for the two little white throttle microswitches that engage only at
full throttle (near the throttle spool) One of 'em forces a downshift to
second and can even downshift to first if it is closing at lower than full
throttle (like if the switch is bad). Bit of a long shot, but try
disconnecting them at the inline black connector a few inches downstream
from the switch body, drive for awhile, and see if it makes a difference.
Grounding that wire anywhere on it's length would cause a downshift, so look
for burns and abrasions. Incidentally, the other companion white switch just
cuts out the A/C compressor on wide-open throttle so leaving both
disconnected while you test won't hurt anything.

I suggest you lavish paste flux (non-acid of course) on all the interboard
jumpers and resolder them and the cable leads where they solder on the
boards. Might as well flux all of both boards and resolder everything.
Usually you can pull the boards out just far enough from the plastic cable
strain relief to butterfly them out for access. I sent some pics showing the
.1 cap solder location for the DMCNEWS technical section and moderator Dave
Swingle kindly offered to process 'em into a useable and smaller file size
format. Watch for them at http://www.dmcnews.com/techmain.htm#index
\\Mark