I dropping this blurb here because I had a heck of a time finding information on how to service this thing. All that came up with the google goggles were were parts suppliers and some Youtube videos that were WAY too long.
So, the long story first is I have a 2016 Cadillac CTS-4, the AWD version of the car with the 3.6L naturally aspirated engine. It developed a shudder and some odd shifting behavior and threw a couple of codes, P0711 among them, indicating the temp sensor inside the transmission was having problems.
On this transmission, that temp sensor is integrated into the transmission’s internal wiring harness. That part is readily available for about forty bucks.
These instructions may work on the 6NDL found in other cars, like many GM trucks and full-sized passenger cars like the CTS and CT6, but this article is about the 2016 CTS-4.
Stuff you need:
- New harness
- New filter
- New pan gasket
- Six and two thirds quarts of the appropriate transmission fluid.
- All the fasteners for this job are 10mm hex head.
Replacing the harness in 24 simple steps:
- Get the car in the air.
- Support the transfer case with a jack
- Remove the transmission crossmember
- Remove the level check bolt in the front left of the pan. Once it stops draining,
- Remove the pan, taking care to spill as much of the fluid in it on yourself as possible, like I did.
- Pull the filter down. You’ll see the harness.
- Detach the three built-in squeeze thingies with some needle nose pliers (look at your new harness, you’ll see)
- Carefully disconnect the connectors
- Remove the harness
- Plug the new harness in and secure it
- Put a new filter back
- IMPORTANT! At this point, push the filler plug on the passenger side of the transmission out from the bottom! It is nearly impossible to remove it from the top with the front propshaft in place, and we don’t want to remove that thing.
- Clean out the pan and put it back with a fresh gasket. The pan bolts are 20-80in-lbs, I found varying values. Don’t over tighten them or it’ll leak.
- Put the crossmember back on. The center bolt is 60 ft-lbs, the four bolts that attach the crossmember to the car body are 38 ft-lbs. Remove the jack.
- Use some right angle long pliers and a lot of cuss words to get the outlet of a fluid transfer pump into the fill hole.
- Start pumping fluid into the transmission until it comes out of the level check hole. It’ll be about five and half quarts. Go slow. This fluid is fourteen bucks a quart, you don’t want to waste any.
- Once the fluid starts dripping from the level check hole, start the engine and with the car still off the ground, move the transmission through all the gears.
- Now, wait for the transmission to get to ~110 degrees F (50C). You can check this with the now working transmission sensor and a scan tool, or use one of those IR thermometer thingies against the pan. Do not just top it off immediately. ATF expands quite a bit when it gets warm, and if you top it off cold you’ll end up overfilling it. Overfilling an automatic transmission is really bad. If the fluid level makes it to the planetaries it turns the whole mess to foam, pressurizes the case, and it’ll start spewing fluid out of the vent. Big mess. Let’s not do that.
- Once it’s up to temp, carefully pump more fluid in until the fluid starts coming out of the level check hole again.
- Replace the level check hole bolt and seal. Snug it.
- Remove the pump hose from the fill hole.
- Replace the fill hole plug. I used a right-angle plastic interior panel doohickey to do it.
- If you haven’t cleared the codes, go ahead and do that now.
- Test drive and check for leaks.
Voila! You serviced the transmission without removing the front propshaft, and you did it without having to sit through some Youtuber run his mouth for thirty minutes to drive up his watch time. You’re welcome!