2005 4.8is transmission shifting / slipping issue

[desertfire]

So…. I must admit that it is weird to feel comfortable about draining and disassembling a transmission as a “routine” weekend thing to do… but it has become fun.

I ordered the set of replacement solenoids and the Torx bolts for mounting the Mechatronic valve body to the transmission main body from thectsc .com . The Torx bolts were not listed so I reached out to them via email from their site and got a response from them and they processed the order directly to me via P**pal and the products were delivered promptly. Excellent service I must admit. And, it looks like the product was drop shipped directly to me from a ZF distribution point, which means that surely if there is anything I could POSSIBLY need I could get it from them, which is good.

I pulled the car into the garage and had the transmission drained and valve body out in about 45 minutes. 10 minutes later had the electronic unit removed from the valve assembly and proceeded to replace the solenoids. The original solenoid bodies were colored yellow, green, and one black. The new solenoids are yellow, BLUE, and one black. After comparing them I went on the assumption that the blue ones replaced the green ones and that the yellow ones were a direct replacement. The new solenoid set also came with a foam strip to insulate the connectors.

I replaced the solenoids one at a time, starting from left to right of the valve assembly, making sure to number and place the old unit into an egg crate that I used as a tray and taking a new solenoid from the package. Can never be too safe when doing these things so I made sure to absolutely isolate the old from the new. After replacing the solenoids I then placed the foam strip onto the connector array on the electronic module and mounted the module to the valve body. Immediately following I mounted the valve body to the transmission and closed up the transmission.

Total time was 2 hours, and I took my time. Not sure if this should be disturbing, but it was effortless.

I forgot to mention earlier that the Mercon SP fluid that I drained had about 1000 miles on it, which really isn’t much, but it drained out relatively clean and the viscosity was not changed, adding that the fluid is perfectly compatible.

Before refilling the transmission I took the time to reset the transmission “adaptions” by using the BMW INPA software and a USB cable that connected the vehicle to my laptop. Purchased it on Amazon for about $30 and is VERY MUCH WORTH every penny. Got in and reset the adaption, cleared any errors, and also configured the door auto-lock feature to automatically lock the doors when the car reaches 15 MPH, which was annoying me that it didn’t do it in the first place.

After doing the reconfiguration I pumped the fluid back in and topped it off with an extra half quart that I had lost during the drain/disassembly. I made sure to fill the transmission cold, start the engine and continue filling until it started streaming from the drain plug, and jumped in while it was running to flip through the gears and then went back under to continue filling. I did the gear shift flip three times to make sure that there was nothing left to fill, and then plugged the fill hole.

I drove the car around our subdivision, literally, and it felt like an ENTIRELY DIFFERENT VEHICLE!! Being late in the evening I decided to take it out the next day.
Took it out the next day and… Wait for it…… THE PROBLEM IS SOLVED !!!!!!!!!!! (I think I even cried for a second...)

The car shifted like it is brand new, can’t even feel the gears as they go through. Took it easy though as the ECU needs to re-learn the mechanics, so drove it easy and coming to steady full stops and not gunning at all for about 50 miles or so.. a good weekend’s running of errands and stuff…
The following week I decided that the vehicle needed “pressure testing” so I decided to go “Russian submarine testing” style and see how far I could push it to see at what point I’d start hearing noises so went for a 1400 mile weekend road trip through the southwest… a true pass/fail scenario ;-). Hills, declines, long grades, winding roads…

The vehicle performed flawlessly… winding up through the hills, especially in sport mode, was the most refreshing experience after all the troubles. It appears that the mileage has even gotten better… averaged 25 MPG on the freeways and 19 in town… made the trip on a little over 3 tanks, which was also nice.

I have a few more road trips planned and will post the progress as things move forward, but if there is anything I can recommend to anyone that has a vehicle with a ZF 6hp series transmission with about 100k miles on it since it’s last service is to replace the solenoids, rebuild the valve assembly with the Sonnax kit, replace the bridge seals between the mechatronic and the transmission body. Not sure whether the Ford Mercon SP fluid is any better than the ZF branded one, but I have an absolutely positive experience with the Ford Mercon SP fluid that I can vouch for as a testimonial

The PTSD from having dealt with the transmission issue hasn’t worn away yet and I’m still weary that the issue will come back, but after taking the “girl in a red dress” out for a weekend and clearing the 193k mile mark, I feel that the issue is completely solved.

For those that are out there and are having transmission issues, I truly hope that this “adventure” helps you in solving the problems you are experiencing.

Safe travels!