multiple codes..0753, 0758, 1864 and sometimes 1886..ugh!!

[96ls]

FIRST OFF, Hello and thank you in advance for any assistance anyone can give me on solving this dilemna..I have a '96 tahoe 4wd w/ 248k on ..runs great but recently has developed some issues w/ showing me some codes..it is usually just 0753/0758 and 1864 but sometimes 1886 likes to visit. It goes like this sometimes while driving at a steady pace on a smooth road at steady rpm's the speedo jumps briefly and/or freezes, followed by the shift indicator light going out, and the tach drops to 0 and then the service engine soon light comes on, sometimes the check gauges light comes on but not always..I pulled over the first time it did it and when I went to shift it into 1, the shift indicator light came on and then went out as if something was loose but nothing changed as far as 'limp' mode in the trans ..where it was in 3rd, I shut it off, started it up w/out any problems, codes are stored and service engine light is on but drives w/ no problems...clear codes and sometimes it is ok for some time and sometimes it comes back on ????? It is becoming more frequent lately and it actually went into the limp mode and speedo/tach inop after just starting it up ..shifting into drive on a initial start and moving 80 feet

what I have done so far...
checked all my connections on trans and pcm/ecm
no evidence of chafing/rubbing wires or harness
fluid is good, not discolored or burnt
trans has NO issues w/ slipping or shifting hard
vss was changed previously,..2 + yrs prior, when that went speedo just quit

sorry for the lengthy post..thanks again

[777stickman]

My 1st thought would be the ignition switch. There are 5-6 contacts in it, one of which is dedicated to the tranny.

[96ls]

are you talking about the switch on the lower part of the column?