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Discussion Starter #1
Okay a little back story, I have a 2000 Ford Ranger 4.0 4x4. It has the 5r55e transmission. The transmission was recently rebuilt with the upgraded valve body. However, the truck will not shift from 2-3 under acceleration. If I let off the throttle, the truck will shift and continue on.

The interesting thing is, it only happens when the engine and transmission are warmed up.

I originally thought that the mechanic that rebuilt the transmission failed to use Mercon V transmission fluid. I assumed that the cheaper fluid was foaming or breaking down when it heats up. Therefore, I added some Lubeguard© additive that was supposed to turn it into Mercon V. I had little faith in this but it did seem to work for about two weeks. Now the problem is back.

Now for the kicker. I swore once I got this transmission working right I would sell the truck as fast as they could drive away with it. So I listed it on Ebay. The auction has 3 days left. Therefore I have 3 days to come up with a solution or I can take a loss on the auction. Clearly I don't want to lose money.

I will take any suggestions. At this point a blind guess is better than nothing. I'm between a rock and a hard place here and whole heartedly appreciate all the help I can get.
 

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I know next to nothing about transmissions. They are however computer controlled, and the computer relies on info from some sensors to set shift patterns.

The TPS, VSS and load sensors. Do you have any other issues? Is your CEL on? Can't the guy who did the work troubleshoot it?
 

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I'm no trans expert but.........It could be programming or a shift solenoid hanging. Sometimes disconnecting the battery will fix stuff like this. Allow about 30 minutes then re-connect.

Did the trans ever shift correctly? Take it to the trans shop that rebuilt it for a computer re-flash...at least have it scanned for codes......even if the CEL is off.
 

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A problem with the transmission may be cause by the emission control system, the electronic control system, the hydraulic control system, oe by powertrain components.Therefore when troubleshooting,begin with these.
  1. Check for codes with a scan tool'
  2. Check signals from the sensors with a breakout box
  3. Check control line pressure
Try reinstalling the original valve body back into the trans and see if it helps. Isn't the person that rebuilt the trans standing behind his work?:nono:
 

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What's a breakout box?
 

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A breakout box is just that. It is a box that has a large expanded version of the PCM connector in it. You hook the PCM to the box and then the box to the PCM and inside is a board with all the circuits so you can do tests on them without damaging the wires or contact pins. It is also much larger so instead of trying to get on the pin in a cramped space you know for sure you have not crossed a wire. They are very helpful.
 

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Thanks for that explanation Caunck623, I guess this is not a tool the typical shadetree mechanic has, probably not one I'll see added to my collection anytime soon, but great to know that it exists!
 

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Discussion Starter #8
I'm sure that the mechanic that did the work on the transmission will stand behind it but I wanted to see if I could get it fixed before the auction on ebay ended. I've suspected for a while that a computer reflash might help, but I don't know. I will have this done and then post my results. Thanks for helping guys. I really appreciate it.
 

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Discussion Starter #9
So I had the computer flashed and it seems better but I'm not 100% sure it's fixed. I'll drive it some more and see what happens. The mechanic at the dealership said that sometimes the Mass Air Flow sensor can malfunction and cause shifting problems.
 

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Considering that it worked for 2 weeks after adding the Lubegaurd, I'd say drain it and use the correct Mercon V.

Lots of people underestimate the importance of the right fluid. If it's engineered to run on Mercon V, and you're using something else, then you may as well just use water. Sounds like the fluid is getting to thin when it gets warmed up.

I'm just going to assume that the trans was shifting fine before the rebuild. It shouldn't be a sensor unless he changed some and got a bad one, or damaged one.

Try cleaning the MAF with alcohol. But definitely get with the guy that did the work. Could be a sticky 2-3 shift valve in the valve body. He should be the one handling this ass pain, not you.
 

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Discussion Starter #11
I suspected that the fluid might be the wrong type myself, so last friday I flushed it and refilled it with Mercon V. I replaced the filter also.

The truck has had this problem since I've owned it and I've literally spent a year trying to figure it out. I've only seen a few people online that had the same problem, but no one seems to know the solution.

The transmission was rebuilt in 2008 and then again about 3 weeks ago. The valve body has been replaced twice and I even tried the transgo shift correction kit, which only made it worse.

The IAC is new, the MAF is new, all the shift solenoids are new, the valve body and separator plate is new, all the clutches and bands are new.

The only thing that I'm not sure about is the servos.
 

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I'm pretty sure anyone that builds a trans will replace the servo seals, pretty sure.
 

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If they don't they shouldn't be in the business.
 
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