I have a 1998 Dodge Caravan with a 3.0 liter motor and 3 speed automatic transmission. we recently installed a junkyard transmission, and we put a new filter and the correct fluid in it. It worked just fine for a couple weeks and now it does not want to shift into 3rd gear when it is warmed up. It shifts just fine when it is cold, no slipping or anything like that. It has gone into 3rd a couple times when warm, but it downshifts into second gear as soon as you touch the gas pedal. It has no codes come up and the check engine light did not come on. I have a strong feeling that it is something electrical, but I don't know where to start, and I don't want to just start replacing things until I get it right. Any help will be greatly appreciated.

Those Chrsylers have had a problem with their shift solenoid packs. It's mounted externally on the left side (facing the radiator). If you still have your old tranny, take if off & try it on the new one. Just make sure everything is very clean around it (especially bewteen the pack & tranny case) before you remove it.Get dirt into the valve body & you will be creating more problems that you are trying to solve. You might want to also replace the gasket, it is also common for them to leak from this area as well.

From the dealer they are around $300 so I probably wouldn't go out get one with out making sure that is the problem.....

No shift solonoid on the three speed trans, Except t conv clutch. This trans is controlled by mecanical linkage from throttle to lever on trans, try disonnect linkage and see if it shifts? Drive easy! adjustment may be out at the linkage on top of the trans
Bob

The problem ended up being the return spring and adjustment on the kick-down linkage. I replaced the spring and then adjusted the linkage in so that it kicks down later and now it works like it is supposed to.

sounds like superbob had the right diagnosis!

Good call Bob.....

I'm sure Tom, Loren or HT will be forecoming with a star that is redeemable at starbucks.......

For Bob! Good call.
Loren
SW Washington