Hey guys! Lost reverse with the 4R75E (2007) here. I've have read a lot of forum threads and watched some youtube videos before coming here.

So what's going on: I tried to reverse one day and it didn't work. SOMETIMES it does work, I would say, 30% of the tries I could reverse, even though it seems very "weak". All other gears are working normally.

What I've already done: Step 0 - Checked for fault codes and fuses. No codes e faulty fuses. Checked the fluid, it was at correct level and not dark or smelly. Step 1 - Opened the pan, it was not durty, didn't find anything suspecious. Changed the filter, flushed the rest of the fluid throght the return line and added Mercon V to level. Drove about 30miles, no reverse ever since.

I've watched 5 guys solving this issue on youtube, and for all of them, the problem was a broken reverse band.

I was about to take the trasmission off, but then I realized I had to answer a decisive question: Is it possible to reverse 30% of the times with a broken reverse band? Or with a broken reverse band, I would have lost the reverse forever?

If the answer is "with a broken reverse band, you can't reverse whatsoever", so the problem is elsewhere (maybe the servo?) and I don't have to take the transmission off for now. Thank you guys!

 

Your logic makes sense, "Most of the time" Just like we say, never say never !

Hind sight can be 20/20 .
If you had some idea of what to look for with the pan down you might have spotted the problem with the servo or if the band had a problem.
You just might try taking the pan down again , but make sure you know where the band and servo are located so you know where to look. If the band appears sloppy , it is probably broken at one end. If so, the entire trans has to come apart to replace it and this is best left to a trans shop that has the equip.
Depending on your capability, you might be able to save some $$$ by removing the trans yourself and having a shop repair it. Again, if mileage is pretty high a rebuild might be in order. If you choose to install a remanufactured trans , you will get no warranty unless the cooler is flushed and you are not equipped to do that.

 

Hey hanky thanks for your reply! The 1st time I took the pan off, I didn't know exactly what to look for. I didn't take the valve body off and didn't open the filter to inspect. In the pan itself, I found no clue.

Now I know where the reverse servo is, what to look for, and how to remove it for inspection. Is it possible to know for sure if the band is broken without taking the whole transmission off?

I was making a plan to rent some tools and take it off myself, but it would be muuuuuuuch better if I could fix this without doing it, or at least make sure that it is the band and go forth with my plan.

 

There are check ***** under that valve body and when you remove it they can fall out ,and now the can of worms has been opened.

 

It was interesting for you to mention that, since it was the last and only service done to this transmission (per last owner, check ***** were changed)

 

If you had the picture of where those check ***** go you might be able to stick them back in their place using something like trans assembly lube or a sticky grease to hold them in place while you get the valve body back up there, There are like 5-6 of them not positive, but sometimes you can see where they go and sometimes a passage doesn't appear to look the same as the others and that could cause problems.