1995 jimmy problems all at once

first of all sorry to make a new thread but i couldnt find much of what i needed to fix my problems. i have had a 95 jimmy for about 4 years now and havent had many problems until lately. all kind of at once and got me boggled. however these are the problems in short..
1-abs light on all the time-brakes pulsate like they are grabbing and releasing. just replaced brakes and rotors/ drums all the way around. probably the speed sensor nor brake booster, but wanted to see what others thought.
2-clunking sound heard only when tranny shifts to overdrive-other gears fine. drive shaft and u joints seem to be ok. maybe tranny mounts or rear diff possibility?
3-has a hard skip/pause when idling intermittently, at the same time the oil pressure drops to 0 and comes back up to about 40-45. average idle for most of the time at idle is about 25-30( i need to change to 30 weight oil- i live in the southeast) maybe oil cooler line leak? but wouldnt that make it happen more regularly than intermittently?

all i know is that this thing has been a good truck for the most part but difficult to fix in certain circumstances. any help i can get is hugely appreciated. there are not many mechanics around here that are reliable to fix it right the first time. thanks for any help.usaxray25

My oil pressure jumped on my 93 jimmy. Ended up being my oil pressure switch, about 35.00. Also, you might try cleaning the sensors on your abs. Over time they get brake dust build up on them and can give your abs comp wrong readings. Also, if your rear brake shoes are wore out, that will cause your front end to shimmy while the brakes are applied. The front brakes end up doing to much work. Sometimes if one of your rear brakes grabs more than the other side, will cause the same effect also. Hope that helps a little.

Thanks for the advice. Gives me a little more confidence with this thing. Any idea about the tranny only shifting hard when it goes into overdrive? It makes a clunk sound almost like the u joint going out. Any ideas?

It's been my experience that when a U-joint goes bad I feel a shimmy( usually towards the rear of the vehicle) upon acceleration or deceleration. Check your u-joints, you don't want a drive shaft falling out while your going down the road. Can make for a wild ride.