Is there a usual place where the (88)240 DL overdrive circuit grounds out against the chasis and causes thsi problem repetitively. If so where ? I had a smiliar problem once in my 87 and the mechanic told me the wires were grounding out on the bell housing and he rerouted them .

 

First look under the car. The sheilding is known to fall off the wires. If all is good there it might be where it goes through the shifter bucket.