2004 Explorer drivability issue at highway speeds

[rodav8]

I have a 2004 Explorer 4wd 4.0L XLT with a 5r55S tranny. For the past two weeks when driving at highway speeds (above 50MPH) the vehicle seems like it is missing. It's kind of "clunks" rhythmically is the best I can describe it. There is no noticable drop in rpms on the gauge, the OD light is not lit and I have the same issue when I turn the OD off. I'm thinking it's something with the tranny and after reading hundreds of posts on here, I'm still at a loss. Only one other person had similar issues and he said he changed his plug wires and it fixed it...well...I tried that and it didn't fix my problem. I might also point out I have two additional issues with the tranny. One is the tranny is not engaging after applying the brakes really hard. It takes a few seconds of revving the engine to have the tranny engage. The second is when putting the tranny in reverse I get a hard bang when it engages. I've checked the fluid level thinking that was the problem, but it's full. Before you ask, I checked the fluid level by leveling the vehicle on jack stands with the engine running. After removing the center bolt on the pan, I had fluid trickling out.

Any help you guys could give me would be GREATLY appreciated.

 

[swetrid]

Ford had a tsb to replace the slonoid pack in the trans for banging in reverse.

 

[Miglater]

There was FSA released about some mercon V not having an additive in it thus creating the possibility of crystals forming in the valvebody of the trans. This would cause the checkballs in the valvebody not to operate properly. Dealers got sent cases of bottles containing the additive. This may not have anything to do with your problem. Just stating that the symptoms you describe are similar to those in the FSA. The trans may have an electrical issue or may simply just need mechanical repair.

For the missing/clunking, i would find a dirt road and drive it in 4 hi to see if the problem goes away, if it does it is most likely that your auto 4x4 is engaging to create this clunk. This could be due to an under or over inflated tire. I'm assuming the tires are all the same size and about the same tread depth.

Mig

 

[rodav8]

fixed it

Ok, the driveability at highway speeds issue ended up being the rear speed sensor?!?! Go figure. I'd like to know how THAT fixed it, but it did. Somehow the speed sensor was making the 4wd engage slightly causing the "surge" or "engine miss" feeling I was having at highway speeds. Anyway...thanks for any input I got from you guys. Oh, btw, the Ford dealer told me I had two codes for the speed sensor. They were C1165 & C1175.