The older Dexron VI fluid has issues being hygroscopic, allowing moisture to build up inside the transmission. This involves using a machine to flush the old transmission fluid out of the vehicle and then pumping in the newer fluid. The first attempt at fixing the unit issues with fluid chemistry involved replacing with a Mobil 1 “Black Label” synthetic fluid (GM part number 19355656), and later a “Blue Label” Mobil 1 LV ATF HP fluid (GM part number 19417577). In recent years, fluid complexity has increasingly become an area of attention to support the redesign of transmissions traditionally driven from hydraulic stimuli to electronic control. General Motors believes that the answer is to do a transmission fluid service to replace the original Dexron VI transmission fluid with a newer low viscosity fluid. In the meantime, General Motors has issued service bulletins to address the problem. Several class actions suits have been filed against GM in regard to the 8L90 and 8L45 transmissions. We are not lawyers, so it is unknown whether General Motors has a valid legal liability on its hands. Can a fluid exchange or redesign avoid a major liability for GM? These long term results have not been realized given most of the vehicles have yet to realize 100,000 miles in their lifetime. Premature wear of the unit due to added friction and added heat is a likely outcome. You can be sure the transmission’s failure to realize a smooth shift is not just uncomfortable for you, but also causing damage within a transmission. In all cases, the transmission is having problems properly shifting between gears and therefore gives a very erratic ride. In most cases the shudder is less abrupt and leads to a sound similar to driving over a “rumble strip” even though the vehicle is on smooth pavement. In some cases, this shudder is severe enough to cause hard shifting and violent jerking between shifts. Although a wide range, the intermittent and unpredictable transmission issue was a cause for concern for many buyers of these vehicles. These complaints have to do with the tendency to “shudder” during light throttle acceleration between 20 and 80 miles an hour. Since introduction, there have been a number of complaints about the 8L90 and 8L45 units. There’s probably a 15-20% improvement between the 8-speed transmissions and their 4-speed ancestors. Having eight speeds allows the transmission to stay in the “sweet spot” of the RPM power band and also gives 5% better gas mileage than the earlier 6-speed transmissions. The 8L45 is a lighter transmission introduced in 2016 for vehicles equipped with a V6 engine such as the Chevy Camaro, Cadillac CT6 and the Chevy Colorado pickups.The 8L90 was introduced in 2014 in vehicles like the Chevrolet Silverado / GMC Sierra pickups, the GMC Denali, the Corvette and Camaro, and several Cadillac applications.The GM 8L90 and 8L45 transmissions were developed to replace earlier 6-speed automatic transmissions in General Motors rear wheel drive vehicles. Some of the transmissions with 8-speeds were only integrated within the manufacturer’s lineup for a handful of years but it’s worth discussing given the millions of these units on the road. How did we go from 3 and 4-speed transmissions from the 1960s through 2000s to 11+ speeds in units today? The increase in gears within transmissions is tied to key objectives including (1) lowering vehicle emission standards and (2) maximizing driver comfort. General Motors has been a leader in pushing for additional gears in automatic transmissions and there has been both success and failure.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |