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The General Motors Turbo 350 transmission has been showing up at drag strips for over 30 years. The Turbo 350 has proven itself as a durable piece of equipment and has been in thousands of winner’s circles. We decided to take the Turbo 350 out of the “Olds-mobilology” Cutlass and have it checked out to make sure it was ready for another season of punishment dealt out by the torque from the 425-inch small block Olds and the impact of another 250 wheelstanding launches.
The Turbo 350 we are using is equipped with a transbrake, reverse pattern valve body. We try to always have some heat in the transmission before making a full pass. I try to get the transmission temperature up to at least 160 degrees before “dropping the hammer” on it. We use a lot of different launch rpms racing off the bottom bulb. I usually have between 3200 and 4000 in the two-step for launch rpm. We have come pretty close to figuring we pick up about .005 in reaction time for every 200 rpms in launch. It is not an exact science because my “personal reaction time” varies more than that, but overall that is a close assessment.
Nick Jeffrey, the owner of the Olds I have the pleasure to drive, had Coan Engineering build the Turbo 350 and the torque converter. That was five years and about 700 runs ago with no issues other than changing fluid twice a year.
Speaking of transmission fluid, Jason Coan recommends a quality “F-type” trans-fluid. Currently we are using Valvoline Type-F but when I change trans-fluid this week we will switch over to Amsoil Super-Shift synthetic trans-fluid. We enter this car in two classes and feel the synthetic trans-fluid will help control oil temperatures better and the friction additives in the Amsoil Super-Shift will maintain the aggressive shifting the F-type fluids provide.
Why did we want to take it apart if it was still working alright? Good question. I was hesitant to send it in, especially the torque converter, as it has been excellent. Coan Engineering assured me the converter would come back with identical stall speed and performance.
Once they opened it up, we found out WHY you need to have a professional check your transmission on a regular basis. We found some broken components and some obvious wear and tear that probably would have become a problem in the middle of this season.
The following photos and captions show the internal components and how Coan Engineering assures they are checked and ready to perform. Thanks to Jason Coan and Art at Coan Engineering for their technical insight to the Turbo 350 and sharing some of their knowledge with the readers of DRO.