Hello I have recently bought a olds that shakes under light load as in
when it shifts into its highest possable gear in driveat the 35 to 45
range.  It can also have some although not as bad at 55 to 70 but not
sure if its the same thing or not. it shudders or shakes and seems to
be in the forward direction the lower speeds..I have replaced a lot of
stuff like wires plugs, junkyard ignition module with coil pace(the
last one cured the backfire and stumble rev out the intake) cam sensor,
o2 sensor, tps sensor.  I had a transmission guy drive it and he said
the tranny was fine so he says....and that the engine has a miss at a
stop sign and this is magnified when the tranny goes into lockup so
hence I unplugged the electrical connector(4t60 tranny I assume since
it has a tv cable) and it did not vibrate or shake shudder at
all........I can only detect a slight miss in neutral stopped.  The
exhaust has a hole in the aftermarket catalytic converter and somewhere
around the muffler but not enough to be loud yet, just a little hissing
typicial of small exhaust holes.  If you punch the throttle it screams
up to speed with loads of power.  Car has 117,000 on it.  I did notice
that the tranny has been replaced at some time(says right on it service
replacement transmission assembly, gm remanufactured transmission)
right on it.  Charged battery for 3 days to get green eye indicator to
show green................now it stays green.  Replace harmonic
balancer because of cracks........rubs on sensor a little so I screwed
with the reluctor fins until it is almost quiet(still thinking I should
take the reluctor off the old balancer and put it on the new one).
dont know how to adjust crank sensor and would like to in detail but
havnt seen any tricks in detail how to.  checked injector resistance
hot five minutes after shut off>>>>>15.3to6 ohms on all.  dont know how
to check for leaky injectors.  Replace IAC and air filter. tapped on
maf(no change)..........at any rate the miss is not a dead miss, its a
very light miss at idle in park..  Turned front rotors because car sat
for a while and rotors when hot pulsated car at 50 mph badly.  Balanced
tires at wal mart.  tires are almost new........checked for some vaccum
leaks havnt found any so far but cant hear any......I did replace the
fuel canister vaccum line dry rotted and cracked but not sure it was
leaking.......any typicial vaccum leak area suggestions are
welcome....as far as manipulating the shake..........its as soon as it
has done all its shifting in drive or over drive(doesnt make much
difference) it vibrates at a 4hz frequency felt through the car seat
and floor like someone is varying the gas pedal 4 times a second....and
when at steady 35 to 45 speed, if I press on the gas, it will get
worseand  at the same time accelerating unless I press far enough to
get the tranny to downshift.  Wouldnt that be amazing to find a vaccum
leak that was affecting the vaccum modulator in the
tranny....................tranny guy said the modulator affects
pressure, not shifting and if it had a vaccum leak to it, the tranny
would shift hard.....sorry for the lengthy write up but the more info
the better so someone will be able to see and give advice based on
accurate info