I know I'm new here, but PLEASE HELP. I'M GETTING DESPARATE.

Either my 2003 AWD Astro with 124,000 miles is suffering from major multi-organ failure and needs to be taken off the road until I can do a lot of major repairs, or there is likely a single underlying cause to all of this. Many of you know some of my troubles from earlier posts. I'd appreciate any input you have for troubleshooting or from others who have gone through some of this. Here goes:

Major Symptom: Van continually upshifts going up hill, getting into 2nd gear and staying there. Stomp the accelerator, whatch your engine RPM and speed drop.

Other Symptoms: Transfer case rattle, what sounds like a minor gear whine? (rear differential I think). Generally, if you stomp the accelerator the van will hang in second gear rather than slamming through. But speed drops after too long in second gear. If it drops and hangs in 2nd gear at higher RPM, you get treated to hearing a rattle.

The Engine Codes:
* PO101 (cleared it, didn't see for months after changing MAF and now one pending)
* PO420 (cleared it a few weeks ago and haven't seen again)

Most Recent Event: While going up the mountain the van went to second and hung. Out of curiousity I tried upshifting manually and slowly through 3 2 and 1. When it when into 1, it wasn't going all that fast, so I'm certain I wouldn't have killed a healthy transmission with this provided you don't do this often. Then I went back to OD and pulled over. When I put in park, the engine was running really rough. I shut off and turned back on, engine was then okay, but no real power to climb the hill. It got home, but barely, and van prefered to shift to easier gears at every opportunity. I thought for sure I was going to end up getting towed.

Transmission Fluid Condition: Pinkish Red. It does not smell burnt. When wiped on a rag, you can see some blackish dirt--it does not feel gritty to me.

Engine Oil Condition: Unusually and abnormally low, but not burnt or gritty. I figure either I'm either burning oil or I've caused an oil leak with some of these high RPM going up hills.

Things I've done or replace so far:
*Air Filters--of course
* Differential (rear) rebuilt 2 years ago. Fluids for both changed and on schedule at the moment.
* Engine oil regularly changed with 2 prolonged, but not recent, excursions from scheduled milage.
* Front and Rear Differential Fluids changed
* Fuel Pump
* Fuel Filter
* Ignition Coil
* Mass Air Flow Sensor
* Oil Cooler Lines
* Spark plugs and wires
* Transmission fluid and filter (20K miles ago, dropped pan, changed filter and gasket, cleaned magnet, and refilled with fresh).
* Transfer Case Service (GM's Auto Trak II Fluid--the magic blue fluid)

What would you suggest I do next to troubleshoot this?

Any thoughts on a some of the issues or a single underlying issue?

 

My initial thought also before I even read this post. Un bolt the front pipe from the manifolds and see how it drives