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GM 10L80: A new kind of pump noise

Shift-Pointers-August-Figure-1

How quickly time passes by. The GM 10L80/90 transmissions began production in 2017, meaning that we’re closing in on six years of this transmission being on the road.

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Many who work in the dealerships have become privy to the immediate failures that occur in this unit. And now, with some of these transmissions coming out of warranty, the aftermarket will soon begin to see issues that occur with them beyond their first years of life during their aging process.

Brian at Tommy Boys Performance, however, has the opportunity to work with a local dealership assisting them when their workload gets heavy. This allows him to see what kinds of issues some of these transmissions come back to the dealer with while under warranty.

Recently, they received a 2021 GMC Yukon with a very unusual sound coming from the front of its 10L80 transmission. They dealership gave Brian their opinion of what was making the noise. But the cause he discovered was related to the pump. The stator shaft support housing is fitted with a converter drive gear and idler gear. The idler gear is what drives the pump’s driven gear. This idler gear and ball bearing assembly is mounted to the stator shaft support housing. The idler gear itself has two threaded holes opposite each other for the use of a puller (see figure 1, above). 

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This suggests that the idler gear and ball bearing assembly has a tight interference fit to the stator shaft support housing. During the inspection of the transmission, Brain noticed that the idler gear could be easily lifted off of the bearing with just the use of his fingers (see figures 2 and 3).

Shift-Pointers-August-Figure-2
Figure 2.
Shift-Pointers-August-Figure-3
Figure 3.

The ball bearing remained tight on the stator shaft support housing. The drive gear and idler gear with the bearing are not sold separately. The stator shaft support housing comes with these gears as one assembly. The dealership was able to provide this part rather quickly. But the replacement of this assembly requires new bolts. This took the dealership a much longer period of time in acquiring these bolts for Brian to complete the job. But once he had the parts and the job was complete, the noise issue was resolved, confirming the cause to be the idler gear spinning around the ball bearing’s outer race.

Interestingly enough, it was not long after this that Brian received another 10L80 with the same issue to resolve. This seems to indicate that there will be other 10L80 transmissions that will be experiencing this same “new” kind of pump noise condition.   

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