Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Hard downshifting transmission

I just replaced the AT filter and now the tranny is downshifting hard. It is perfect on the way up. It is an '03 grand caravan 3.8L with 105,000. I replaced the fluid that came out when I did the filter swap. I saw in a previous post that it may be caused by the input or output speed sensors. It was working fine until I replaced the filter. Anybody have a clue what could be causing this?

Thanks for any help you can give.

In a parking spot, put the shifter in all gears at least twice, then drive for 20 minutes to warm up the fluid, then check it. If it’s too high or too low, make it right. Then drive a few minutes and check again. My shop instructor would have asked if you put the filter in right or he would ask what we broke so as to save time looking for it.

Have the computer scanned and see if any codes have popped up.


I’ve been driving it for the last couple of days and it is no worse or better. I have checked to make sure fluid is correct a few times just to make sure I didn’t overlook the obvious. My main question is why after the filter/fluide change would this start happening. Transman what fault codes do you think I am most likely to see

There are a number of codes which would put the trans into limp mode causing what you feel. Couldnt tell you exactly.

Let us know what you find out.


I used the on board on/off/on/off/on method to get codes and the only one that came up was P1684–Battery disconnect. Would a scan tool show more codes or is that all the codes that are in the system. If there are no more codes does that make the diagnosis harder?

Was the correct fluid used???

ATF+4 used and fluid level is fine and the tran pan doesn’t leak

I want to throw this in because I don’t know if it could be related. The same day I changed the transmission filter I also changed the spark plugs and wire set. Like I stated before the only error code I got was the P 1684 (battery disconnect). It’s been a week and the problem is still there, no worse no better.

Any thoughts?

I don’t actually know enough to know whether or not it makes a difference, but when you installed the new filter did you get the new filter seal (gasket/o-ring or whatever) in place and seated properly?

I also don’t know what kinds (if any) of electronics are revealed on this van when the pan comes down, but did you perhaps knock an electrical connector?

The right scan tool will show you more codes if there are any. You’ll need to take it to a transmission shop and ask for a scan - its murky to me, but as I understand it there can be codes stored and don’t trigger the OBDII light and don’t show up on a typical OBDII scan.