need help diagnosing problem with 545RFE transmission

[theksmith 3,828]

2003 grand cherokee, 4.7 HO with the 545RFE tranny...

 

symptoms: MIL on, transmission in limp mode, scan tool reports P0734 GEAR RATIO ERROR IN 4TH. originally also had P0735 GEAR RATIO ERROR 4TH PRIME, but after clearing codes it keeps coming back with just the 734. seems to be hesitating or slipping when it tries to shift into 4th, then downshifts hard, then upon trying to accelerate again it will sometimes rev 2K RPM without any change in speed for just a second, then hard shift and the jeep starts speeding up. then after that it goes into limp mode, and will still randomly shift hard or slip while shifting.

 

troubleshooting done so far: checked fluid levels. had tranny flushed. checked input and output speed sensors which seem ok based on the resistance reading. cleared codes to get out of limp mode and drove it again, same result each time.

 

history: last week i noticed it shift kinda erratically, like it was hunting for the correct gear a couple times, but no MIL. also noticed the fan running full speed at idle even though the engine coolant temp was fine. i had it flushed on friday, it drove fine to and from Superior area for the trail run Saturday. then Saturday night getting on the freeway it started the really hard shift and MIL came on and that was when it went into limp mode.

 

any ideas what else to troubleshoot? i don't want to throw any money at shotgun fixes since a whole salvage tranny is under $500 - of course i don't want to swap the darn thing if there's an easy fix either! thanks in advance.

 

EDIT - forgot to mention i did swap the TPS while troubleshooting too.

[kaspily 2]

Sounds a lot like what we just went through. We replaced all the sensors first and then the solenoid pack. This didn't help. We tried a salavge tranny and this turned out to fix the overdrive transmission issue but then resulted in us not being able to go into reverse. We didn't want to go through having to take out this tranismisson (super heavy and a pain in the butt) and return it to the salvage yard. So we paid a shop to rebuild it. So sorry you are going through this. Hope it turns out better than ours did.

[Bradywgn71 710]

Like Sarah said, this is exactly what mine was doing. Come to think of it, I had the fan speed thing happen too. Don't bother spending a bunch of money on this trans. Just get another one. The dealer checked mine out and said that mine was toast. They made a passing mention of a snap ring that fails inside. My code was P0734 too. It would attempt to shift into 4th then downshift into 2nd, back and forth until it would go into limp mode. while researching, I found out that 4th and second prime are the same set of planetary gears so it's losing pressure in that area due to the failed snap ring. I was able to drive mine by clearing the code then turning off OD as soon as I started it. That way it won't attempt the 4th shift. It would still slip a bit occasionally, but I was able to get it to the dealer and back home by driving it that way.

 

Let me know if you need any help! Good luck, Dood!

 

[theksmith 3,828]

yeah i agree about not messing around with it. i called http://www.precisionteam.com a little bit ago and they have one with 19k miles ready for me to pick up tomorrow for $425. i got my 242HD tcase from them a few years ago and they were easy to deal with.

 

at least my driveway isn't on as much of an incline as the last house!

[johnpa 745]

This would be a great time to convert to a manual transmission.

[theksmith 3,828]

This would be a great time to convert to a manual transmission.

 

nice one

[91AzXJ 2]

Wow, three WJ's with similar issues in a short time span, sounds like a virus hit the herd, Glad the XJ's are immune! Seriously though, hope the new to you granny fixes the problem. Supposed to be nice and cool this weekend so good time to switch it out. Holler if you need a hand.

[LO PHAT 1]

had tranny flushed

 

This is pretty much the worst thing that can be done to a higher mileage transmission.

[theksmith 3,828]

This is pretty much the worst thing that can be done to a higher mileage transmission.

 

only if you haven't done it in a long time, i do mine every year or 2

[LO PHAT 1]

only if you haven't done it in a long time, i do mine every year or 2

 

In that case it shouldn't have hurt anything.

 

Great job swapping the TPS, by the way. That was my first thought when I started reading your post.