Used Seafoam to clean Intake --- Now transmission upshifts VERY slow with loud whine

Which intake hose did you feed this into? If you want to clean the intake/combustion chamber, there is a product, I believe it is by 3M, that attaches to the schrader valve on the fuel rail and does this, but it costs about 150 with the attachments and you have to disable the fuel pump. It runs on the contents of the pressure bottle and then stops. I have never done what you describe, but I don't think there is a direct link any more between vacuum and transmission operation, it is all computerized and based on engine speed, temp, etc. So the most likely thing that happened, if it did happen exactly when you did the Seafoam deal, is that the stuff ran down the line the wrong way and got into a sensor or something else and damaged it. I would trace that vac line backwards to what ever it goes to and see if that is it. If it runs fine on full throttle cold, it could be you damaged the 02 sensor with gunk gumming it up. There is so much tarry crud in the plenums now, I believe from ethanol induced breakdown products, that I would consider it dangerous to melt all that crud in a short time and try to shoot it down the exhaust. If you were going to do something like you propose, I would pull the intake plenum first and clean it with mineral spirits, put it back on and try cleaning the intake ports with some product. Sorry for the problem.

Engine now runs fantastic after changing plugs and wires.
The engine ran seemingly well until I used the Seafoam which caused the the misfire code/ hesitation because of original plugs still in use at 85k (gaps on all plugs were huge-about double)
Transmission use to run fantastic until I used Seafoam.
The vacuum hose was pulled off the intake manifold and I used a clean /new piece of hose from aut-parts store to connect the seafoam to the intake..then reattached vacuum hose.
I understand this is an electronic tranny and vacuum lines have nothing to do with the tranny??????
However, the tranny went from fine to to a royal pain after using Seafoam and I know it makes no sense.
I plan to change the tranny fluid/filter and throughly clean my battery contacts as soon as I can.
I am certainly open to more suggestions and will post the solution when I find it.
Does anyone think a Dealer reprogram/firmware update would work? -- I did replace the solenoid paack a few weeks back.

2003 t & C Limited AWD ( bought in 2008 for 7,000 with 64k miles --gas was 4.25 /gallon)
2001 T & C Limited AWD (bought in 2005 for 6,500 with 120,000miles--- still going strong with 165k on the original transmission)
1999 Lxi AWD
1996 T&C
1986 caravan

If your transmission is still working, immediately backflush the trans oil cooler and clean it out. Then drop the pan and check the pan and filter for crud. Replace gasket with a NAPA rubber one that can be reused. There is one possible connection between your problems that I can think of. If your engine was missing excessively, for whatever reason, and you were driving it around (sometimes people try to "blow them out" when they are running bad) or if you had mountains in your route, a missing engine causes the torque converter to be slammed, and it can shred pieces of the clutch material, throwing it to the cooler, clogging it and burning up the tranny when it finally seals shut. You may be able to flush it out and if it runs fine, it was the clog. If it still runs badly, it may only be the TC damaged by the above action. It is cheaper to replace the TC than the whole thing and it can save you having to replace the whole thing, if you can narrow it to the TC. I lost a tranny this way in the NC mountains from a single bad spark plug wire that I thought was a slipping transmission.

Proper simple maintenance is so important for these vans!!!!!!

Turns out my catalytic converter was getting glowing red hot and is very close to the tranny. Rebuild shop said the damage from the heat was "very excessive" and wanted to know why. Luckily they investigated before rebuilding the tranny and slapping it in. For $1850.00 the Tranny shop gave me a 3yr/36,000 mile warranty and 1 free fluid/filter change every year for three years. plus they installed the Cat converter for free--just charged me $300.00 for their cost of the converter. They seem to be an excellent family run shop (30 years) here in Buffalo, NY .

Furthermore, when I inquired about upgrades to the tranny over factory, the owner immediately listen many improvements like a better pump, better bands, brazened torque converter .......etc.

So what appears to have happened is my 3.8 awd needed new plugs long before 86,000 miles and was probably sending crap to the converter for some time. When I added the Seafoam to the intake directly, it really plugged up the converter and the tranny had no chance--Very costly mistake on my part!!!!!!!!!!! I will never make this mistake again.

PROPER SIMPLE MAINTENANCE IS SO IMPORTANT FOR THESE VANS!!!!!!!!!!!!!!!!!!!!!!!

You may interested to know that the 41TE (the transmission in your van) has no bands. Allpar.com has a nice writeup on the transmission: http://www.allpar.com/mopar/transmissions/41TE.html (Note: the 41TE is a descendant of the A604.) If your transmission shop rebuilt your unit, the rebuilt kit will contain the latest "spec" parts that are to be replaced. Also, sometimes skilled and experienced tranny rebuilders may have a couple tweaks they like, but mostly, it is simply the skill of the rebuilder that determines the quality of a rebuild. For example, I've been told that really good tranny rebuilders can often tell if the differential preload is right without measuring it. I would prefer they measure it, of course, but the point is that skilled guys really know what they're doing.

There is virtually maintenance you can do to the 41TE aside from changing its fluid regularly. (Solenoid pack replacement is a repair, not maintenance.) The *most* important thing to note is that you must, must, MUST always use ATF+4. You cannot use Dexron/Mercon, and you cannot use an additives package that is supposed to make Dexron "like" ATF+4. I encourage you to inquire as to which fluid your shop used in the rebuilt tranny. If the answer is anything other than an emphatic "ATF+4, of course!" then I'd immediately flush and refill the transmission.

I submit that there was already a problem with the transmission prior to a failed catalytic converter. The converter's distance from and orientation relative to the transmission makes excessive heat transfer difficult. If there was significant degradation of the fluid, or something other than ATF+4 had been added to it, perhaps heat from a catalytic converter could cook the transmission, but I'm pretty skeptical of that. My money goes on "pure coincidence".

Finally, the plugs in your 3.8L should still have been good at 86,000 miles unless there is some other problem that ruined them. They are double platinums from the factory, and double plats last a very long time indeed. I have yet to have a Mopar minivan reach 100,000 miles, but when it's time to change my plugs, I'll be installing factory-spec double plats.