2007 Yukon Transmission Clunk Noise

First, the clunk you heard is the problem that sent our Yukon into limp-home mode. A longtime feature in vehicle transmission, limp-home mode is there to provide two things. The first is that your SUV can remain rolling long enough for you to get home — or your destination. Once you are there, you can then call a ramp trunk and have the Yukon brought into the shop for service. The second reason limp-home mode is there is so you can slowly (the gears you have available don’t answer the “need for speed.”) drive your car to the shop for repair. If you opt for this method, you are saving the cost of a tow-in to the dealership.

With that said, though, there are several problems that can put your SUV into limp-home. I’ll list them out for you (they are in no particular order of importance):

*** One or more of the solenoids that designate the gear your truck should be in have failed. Hopefully, this is the problem — it’s tough to say without seeing and tearing down the transmission — because it is one of the least expensive fixes. There are two solenoids located on the valve body of the transmission. One of them is external and sits on the jacket, while the other only requires the drain and removal of the transmission case to access. Each one will cost about $175 to replace. What may have happened here is that a solenoid failed, throwing you Yukon rather violently into limp-home (the thud). With labor, replacing both solenoids is a $650 job.

*** One control module or another has failed, again, rather aggressively — the thud which is more than likely when it jarred out of top gear. Just afterward, an error code was thrown to the engine control module and/or the transmission control module. The code shows what electronic part of parts failed. Since there are possibly 16 or more control modules (computers) or sensors that are used to keep things working correctly in the transmission, there are many failure candidates. However, if this is the area of failure, then your technician should be able to pinpoint the error quickly enough by using an OBD-II diagnostic scanner and reading the error codes. The issue with an electronic error is reaching the sensor or module that may have failed. The cost of your tranny fix depends on how much of the transmission has to be torn down to access the electronic device. I can only guesstimate the cost at this point, but it can be anything from $675 for an easily accessible device to upwards of $2,000, if the device is inside. The cost is mostly labor.

*** This problem might be a band or clutch failure. Either one of them can cause the type of failure you described and then can send your transmission into limp home mode. The fix here is replacing the clutches and/or bands. The cost will be between $2,450 and $3,000. The caveat with this fix is that there might be other damage to the transmission that has occurred, as well. If there is then it is a good idea to drop in a rebuilt, rather than trying to find each and every issue. Doing a piecemeal repair is a guarantee that you will overpay by several thousand dollars and there is no guarantee that the transmission won’t fail again.

*** The torque converter may have failed. A torque converter failure can easily cause the type of transmission behavior that you have described. Because of the importance of the torque converter and due to its complexity, it might be a good idea to drop in a rebuilt. It will save you lots of time and aggravation.

The four suggestions that I have listed here are the tip of the iceberg. There could easily be multiple problems involving electronic and mechanical systems that will cause the problem you describe. My thought here is that it’s time to cut to the chase, replace the transmission with a rebuilt and enjoy your Yukon this summer.

Let me know what happens, please. I’d like to know the results. You can also contact me with more questions if you would like. I’m around most of the time, except this week when a brief trip took me away from the keyboard.