1992 Isuzu Rodeo 2WD trans trouble

I have a 1992 Rodeo 2wd with the GM 3.1 in it. It has 89,000 miles on it. It has been slow to go into drive for a while now.(auto trans) When you shift into reverse it goes right away, but when you place the shifter into D it takes a 2-3 seconds before it actually goes into D. I dropped the pan and changed fluid and filter and it did not seem to help. Now it is starting to go into N when taking off from a stop. It only does it when cold...About 15 degrees here now. If you stop at a stop sign and then go to take off, it is like it is in N and then pops into gear hard.. I dod't know much about tranny internals..I was thinking possibly a low band adjustment problem or I have heard of a "front pump" causing no go problems when cold... Any band-aid ideas..or what I looking at...BTW is this the same trans as the