1995 Trans Stuck In First

I have a 1995 Chevrolet 1-ton diesel 4 door with a 6.5 t.d. in it. On our way to church tonight I slowed to exit the highway, as I poured the coals to it to merge onto another highway it revved way up. I looked to make sure I didnt knock it into first some how. It was still in overdrive. I pulled over and checked the fluids, all were good and didnt smell burnt. I then shut it off and restarted it, still stuck in first. I checked all the other gears, goes into park just fine, goes into reverse perfect but no 2nd, 3rd, or O.D. Any Ideas on what it could be? Ive lost transmissions in other vehicles in the past and there was definitively signs to tell the tranny was gone, but this was different. Any help would be greatly appreciated....

P.S. The Truck was warm, the wife had driven it all day. I did not head to church with a cold pickup. No check engine light, Im going back out to see if it will throw one after it cools.

In all my Google searching tonight Im leaning towards "Shift Selonoids" does this sound like a good starting point?

Get a jumper wire or something and check it for stored codes. Trans codes normally will not turn on the check engine light for a 6.5 OBD1. Sounds to me like either a shift solonoid(but this normally gives you 2nd only), or a bad speed sensor.

Thank you THEFERMANATOR, I do believe it is stuck in 2nd gear after all. There is no gear switch between first and second from the column and I limped it home at 25 mph.

Im gonna go ahead and replace the shift solonoide but the local parts guy says there's tons to choose from, does anyone know what one I need when the trans won't shift outta second?

My ABS light has been on for 6 months or so but it never has been an issue with me and my speedometer works fine. Could it be that the vss just decided to quit work alltogether and make it so the tranny won't up shift? And if the vss is bad would my speedometer still work? Getting ready to drop the pan tonight and don't want to replace the shift solonoid if my problem could be the vss. I'll pull the codes in an hour or so when I'm off the clock.

Does your gear selection indicator blink at all? '95 trucks have always been notorious for faulty ignition switches.

I had a '95 Tahoe that wound up stuck in 2nd, and a new ignition switch solved it.

No gear select blink, but every now and then I would have to cycle the key once or twice to get the starter to turn over. I just figured I had a short somewhere, it never bothered me and would eventually turn the starter over so I left it alone. I never thought to look into the ignition switch..

Disconnected the batteries tonight then drove it around the block, checked the obd1 codes again and got. DTC 87, DTC 92, DTC 91, DTC 89. I cant find 89 on any obd1 list, and the dtc 87 has me stumped. Still not shifting at all

got the truck scanned by someone with a much nicer obd1 scanner than my 25 dollar cheapo....he came up with DTC 78,81,82,83. He also thought I may be dealing with a bad ignition switch because of all the tranny fault codes.. any ideas??