My van won't shift out of 1st gear, rev, neu, works but 3rd and low won't engage when physically shifted.
There are a couple of obvious possibilities. Linkage and/or the bands need adjusting. Both require a certain amount of expertise. The linkage get old, stretch and no longer engage when the shift knob is moved. If you have a couple hundred thousand miles on your van it could be the bands are out of adjustment. If you can find an honest transmission shop they could inspect it and make the determination. Unfortunately most transmission places will put it on the lift, drain the fluid out and show you all the metal fillings that have collected for the last month and tell you your tranny is shot. They do have to pay the rent after all. Depending on the make and model sometimes low fluid can cause strange behavior as well. But low fluid indicates a leak and to replace seals involves tearing the transmission out and apart.. Again they have to pay the rent. To do that they rebuild transmissions. If you need a seal they will want to rebuild your transmission. Fact is the kits to rebuild most transmissions cost under $100.00. Pulling them out and tearing them down takes hours and skill. So, they charge you $2500.00 labor and $500.00 in parts. Which is why so many folks buy used transmissions and have any ol mechanic swap them. You can often buy a whole running car with a good transmission for a fraction of rebuilding one. Swapping them is a serious repair but any mechanic can do it. Good luck and HAPPY MOTORING!
You vehicle has no adjustments for the bands or much of anything else. You are probably stuck in 'Limp Home' mode which means it's time to pull the unit and rebuild it. Any reputable shop would recognize the symptoms instantly and offer to rebuild it. Unfortunately this is not considered as a very robust unit and what you're experiencing is normal for most owners although there are some that get surprising mileage out of them. Since this is such a weak unit and you now have a decision to make, adding to your grief by purchasing a used unit is rife with potential nightmares, as you already have a used unit; why buy another unknown and used unit? If you don't mind taking the used unit out for another used unit you get from a junkyard - I guess you could eventually find a better (albeit used) unit that may or may not survive a day, a week or somewhat longer. FWIW: I owned a transmission shop, worked in others and did so for over 47 years before I retired a couple of years ago. Send from my Nexus7.
Before you go into a costly repair, you might try replacing your INPUT SPEED SENSOR which tells your van when to shift. It costs around $20 and is easy to replace.