The only change was that the diagnostics and picoscope analysis were no longer needed, and the work hours were reduced - which you can clearly see on the same pdf in the list of updates to 18-NA-355 at the bottom of the page. The final updates to 18-NA-355 were in July 2019, as described in your link to the pdf, using the same exact Mobil 1 blue label as it did in Jan 2019. Mine was flushed in Feb 2019 with the same, but was already available at my dealership in January. Blue label was already in use in Jan 2019 (the date of 18-NA-355 release), but not available at all dealerships until later that summer.
The black label was used in previous (different number) TSBs, and was never used under 18-NA-355. If you read carefully your own link to the most recent version of 18-NA-355 with the descriptions of updates at the bottom, and the link I provided from Jan 2019 (that you repeated) which refers the original version of 18-NA-355, they BOTH mention the new version (blue label) Mobil 1. Hopefully the new fluid swap will provide a lasting fix.Sorry, but this is incorrect. This is obviously a big deal for owners struggling with their vehicle’s eight-speed. Driving the vehicle for about a week or so improves shift quality even further as the new fluid cleans things up inside the transmission and the adaptive shift algorithms relearn various parameters. The issue seems to stem from “moisture content in the transmission fluid.” As such, the old GM transmission liquid is swapped for new Mobil 1 Synthetic LV ATF HP fluid. If the flush doesn’t fix the issue, the next step may be to replace the torque converter, which could be glazed. However, a new fluid flush appears to fix the issues, with some customers beginning to report a dramatic change in shift quality after swapping out the old juice.
#Tsb 18 na 355 full#
These conditions are most commonly observed under light and medium throttle applications, and as often during full throttle applications. Secondly, the shifts are very harsh between first to second, and then second down to first, especially when accelerating and the transmission is upshifting or decelerating and the transmission is downshifting. First, some customers report the transmission shuddering frequently. The issues with the 8-speed GM transmission are two-fold. Affected vehicles include Chevrolet, GMC and Cadillac vehicles, as follows.Ģ016 – 2019 Cadillac CTS (excluding V-Sport models)
#Tsb 18 na 355 update#
As of August 7th, GM dealers should also be flushing all potentially affected new vehicles on the lot.Īccording to TSB (Technical Service Bulletin) 18-NA-355, the latest update addresses “torque converter clutch (TCC) shudder conditions on 8L45 and 8L90” eight-speed automatic transmissions, RPO codes M5N, M5T, M5U, and M5X. Customers that complain of shuddering and harsh shifting characteristics in the 8-speed GM transmissions are recommended for a trans fluid flush. Now, GM Authority has learned that there’s a new fix that seems to be alleviating the eight-speed’s shifting woes outright.Īs of July 8th, 2019, GM began using a new type of Mobil 1 automatic transmission fluid for the troublesome transmissions. In fact, we cover a class action lawsuit brought against GM back in April, complaints from owners, and even a recommendation that GM replace the eight-speed altogether with a new unit as quickly as possible. We’ve covered the problems of the eight-speed GM transmission on numerous occasions. Directly from GM Authority, written by BY JONATHAN LOPEZ - AUG 13, 2019:
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