Technically Speaking
- Author: Mike Riley, Technical Editor
- Subject Matter: Automatic transmission
- Unit: 6L80
- Vehicle Application: 2010 Cadillac Escalade
- Issue: Underhood rattle
Complaint/concern:
A 2010 Cadillac Escalade equipped with a 6.2L engine and 6L80 transmission arrived with a somewhat erratic rattle noise from under the hood. At first glance (or sound, actually), there was not a particular condition that would trigger the noise. And noises being what they are, this made for a tough diagnosis.
There was, however, one condition that occurred which seemed to set off the rattle. There is a feature on many newer vehicles today called active fuel management (AFM), which is responsible for improved fuel economy. When the engine would cycle in and out of AFM, the rattle noise would come and go, but as stated not always.
Cause/condition:
After the technician popped the hood and poked around the engine compartment for a bit, one odd issue came to light. The transmission fill tube would move around as if it were disconnected. Upon further inspection, the tube was not found disconnected but rather broken at the hold-down bracket.
Correction/modification:
Failure of the fill-tube bracket has not been much of an issue over the years, although it does happen from time to time. Most tube brackets are merely spot welded in place, and sometimes the weld does not penetrate too well.
Apparently there were enough GM vehicles that have had fill-tube-bracket failures for GM to issue a TSB (technical-service bulletin) and a recall. The TSB/recall number is 12138, and it refers to 2010/2011 Escalade, Avalanche, Silverado, Suburban, Tahoe and Yukon.
There are actually two different fixes/preventions for this problem. The bullet-proof approach is to change the tube, which can be a little difficult because of the tight space (Figure 1).
Some technicians have cut off a piece of the tube below the seal surface to make it easier to reinstall (Figure 2).
Even if the filler tube happens to be in good shape during a transmission repair, it would be advisable to replace it anyway, just to be on the safe side. The part number of the filler tube is 24260606.
The second option for addressing this issue is a foam sleeve that slides over the end of the filler tube (Figure 3). Placing the foam sleeve over a good tube reduces vibration and minimizes the risk of the tube and bracket separation. So, it is a call shot whether to install just the foam sleeve over a good tube or just replace the tube itself. All new tubes come with the foam sleeve already attached and held in place with a plastic tie strap. The part number of just the foam sleeve is 24262134.
In addition to the rattle noise, there have been reports of water leaking into the transmission because of the broken tube, under certain conditions.
Faced with a potential annoying rattle or, worse yet, water in the transmission, it would make good sense to replace the tube whenever possible, especially because it’s cheap.
