During cold weather, a small,
red fluid leak may be noticed on some 2001-2010 Silverado and Sierra
2500HD-3500HD series models equipped with the Allison LCT1000 transmission (RPO
M74, MW7). The fluid leak may be at the back of the transmission by the vent.
This condition may be caused
by fluid being discharged out of the transmission vent during extreme cold
weather (approximately -15°F or -25°C or colder), at which point DEXRON®
VI and other conventional transmission fluids become extremely viscous.
When the viscous fluid is
circulated into the vent area, it becomes trapped and is not able to drain back
to the pan. As the transmission warms up, the expansion of the air inside the
transmission can force the trapped fluid out of the vent, leading to small
drops of fluid being discharged.
To correct this condition, remove the stock vent assembly and run an external tube (Fig. 2, A) and vent (remove the top of the vent assembly) (Fig. 1) up to the front of the transmission to a mounting bracket. (Fig. 2, B)
The extra length of the tube
will allow the expelled fluid to be trapped and later drain back into the
transmission.
In addition, on 2001-2004
models, replace the transmission fluid indicator (dipstick) with a new vented
indicator.
Refer to bulletin
#10-07-30-001A for additional information and installation procedures.
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