2008 Merc 5R55s 3-4 Hard Shift

[Bigskypc50mt]

Been plugging away on my 08 Merc I got from copart.

My 3-4 shift is sometimes really violent, after a 200 mile round trip drive on the interstate, the 3-4 shift felt like I was rear ended and shook/shudder the entire rig. I discovered a leaking trans cooler fitting, that lead to having to replace the radiator. (Maybe slightly low fluid level). So after the new rad I pulled the drain plug and refilled with new fluid and a bottle of lubeguard red. When cold the shifts are fine, but on my way back from a 60 mile round trip drive on the interstate, the harsh shifting from 3-4 is back, but not nearly as bad, its a hard shift (like the line pressure is jacked up) with a slight shudder.

The engagement to R is harsh when it's warmed up, I can get it to slam into R if I move it back and forth from R to D a few times.

How do I address this or am I ready for a rebuilt or used trans?

 

[dacaur2]

Is the wrench light on? if no, does it come on (with all the other lights) when you first turn the key before you start it? Does the OD/off light come on when you push the button to turn off overdrive? The hard 3-4 shift is definetly symptom of the transmiission about to gernade. How many miles are on it? This transmission is pretty famous for needing a rebuild around 90k-120k. Mine went at 112k and I had it rebuilt. I had hard 3-4 shifting, and a clunk when putting it into reverse, but my wrench light was on. When I got the truck at about 90k, I would have a weird/violent 3-4 shift every once in a while, but otherwise fine. then one day I had a REALLY violent shift, the wench light came on, and after that every 3-4 shift was hard.

 

[Bigskypc50mt]

The wrench light does not come on and the O/D light works and kicks out of O/D. The wrench light will show on the dashboard with the orthers. The rig has 158k miles on it.

Not good news wondering if it’s worth putting a trans into. Is it a DIY task?

 

[Bigskypc50mt]

Would the shifting get worse while it is re-leaning? I cleared the PCM by touching the two cables together for like 10 mins, drove it under light throttle though all the gears including OD, and then drove it that 60 mile trip again and it seems to shift a bit better and it is intermitting with the hard shift it's a different kind of shift each time. How long will the relearn take? When I first drove it after reconnecting the battery the 3-4 shift I could hardly feel it, felt nice smooth and crisp.


I have a hard time believing there is something major wrong with the trans it shift all other gears nice and floats down the road at 75-80MPH

 

[gdgiordano]

Would the shifting get worse while it is re-leaning? I cleared the PCM by touching the two cables together for like 10 mins, drove it under light throttle though all the gears including OD, and then drove it that 60 mile trip again and it seems to shift a bit better and it is intermitting with the hard shift it's a different kind of shift each time. How long will the relearn take? When I first drove it after reconnecting the battery the 3-4 shift I could hardly feel it, felt nice smooth and crisp.


I have a hard time believing there is something major wrong with the trans it shift all other gears nice and floats down the road at 75-80MPH

I don’t know if it would get worse per se but when I reset my computer the shift points were very distant after 3rd. They tightened up after relearning.

 

[Mitchs07explorer]

Ive been doing a lot of research on these transmissions lately because of a 2-3 shift flare I've been battling for a while now. It appears through the years as though the issues with these transmissions mostly seem to be with the valve bodies and solenoids. I just ordered a rebuilt valve body with the upgraded transgo shift kit and OEM solenoids and am doing the r&r this weekend, the job is very easy I've already taken all those components out but the re torquing takes time because of the number of bolts for the valve body and doing it in sequence. I am watching fordtechmakuloco's videos on YouTube for the how to do it, that guy is awesome and makes things really easy to understand. I've fixed several issues on my car thanks to him.

Anyway, from the things ive been researching it sounds like you need to replace your valve body and solenoids. Look up valve body problems and it'll describe the same symptoms you have.

 

[Tech By Trade]

Could try a fluid and filter followed by a band adjustment.