Hello and welcome to just answer. Let me see if I can help you with this. The whine sound and slipping out of gear is indicative of a front transmission pump and failing torque converter. The whine is coming from the torque converter. The burnt smell is from failing clutches in the torque converter itself. If you want to keep the van for a few more years, then I really recommend having the trans and torque converter replaced with a re manufactured unit, or have the existing transmission overhauled and a new or re manufactured torque converter installed. Have the transmission's oil cooler flushed out with mineral spirits at that same time, because clutch material is probably in the cooler, and if you do not flush it, you risk the chance of damaging the new transmission.
I hope this information helps, and let me know if you need further assistance with this.
Well after you telling me this, I am thinking that maybe the transmission's filter is getting plugged up with debris. What you may want to try before purchasing a new trans and torque converter is to have the transmission's oil pan removed and the filter replaced. Now this may help, but if the filter is really plugged up with debris and clutch material, you need to think that this plugging up is being caused by excessive clutch material and that means that clutches in the torque converter are coming apart. So this may help for a while, but the transmission may eventually fail completely. I do not think that this is a sensor issue at this point.
Actually flushing the trans does not ensure that the filter will be cleaned, so yes I do recommend at least trying a new filter before going with a new transmission. Flushing the trans does replace the old dirty fluid with fresh clean fluid, but does not clean the filter.
Well it is not that difficult, but can be messy. You will need to get the van up on jack stands and get yourself a large drain pan placed under the transmission's oil pan. Then you will remove all of the pan bolts except for a couple. Then loosen the last 2 bolts a few turns, and take a flat bladed screw driver and a hammer, place the screw driver between the pan and the trans housing. Tap on the edge of the screw driver to separate the pan SLOWLY from the trans housing. Fluid will start to leak out. Then slowly remove those last 2 bolts and let more fluid drain out. Then while holding the pan, pull it off completely. You will then see the filter ( a flat looking filter mounted to the bottom of the valve body). Simply pull the filter off and then let the rest of the fluid drain for a few minutes. Place the new filter in place and tap it up to secure it. Be sure that you remove the old o ring and install a new o ring onto the new filter. Clean off the old RTV sealant from the pan with a razor blade. Clean/wipe out the pan's sealing surface. and clean off the old RTV sealant from the trans housing. Apply a fresh bead of RTV sealant (use RTV sealant that is designed for transmissions). Pick off the old sealant from the bolts. Set the pan into position and install the bolts. Tighten them to about 35 ft lbs. Refill the trans with about 4 quarts of ATF 4 transmission fluid. Shift the trans through all gears, and recheck the fluid with the engine idling and in park. Be sure that the van is on a level surface when checking the fluid.
Yes those are transmission related codes, and it may just be a sensor problem, so have the codes diagnosed properly. If it does end up needing a trans, expect about 2 days to have this repair performed.
I am sorry, but I got your question mixed up with another. It does sound like you need a transmission, and it is not a sensor issue (sorry).