I think it was someone who worked on transmissions that went by “Transman” here. The car had about 100k on it at the time and the fluid was likely never changed.Īnyway, someone here suggested that she pour a can of Berryman B12 into the transmission a few days before having the fluid changed. The basic problem they were having were rough shifts at part throttle and shuddering like it wasn’t fully engaging before it finally caught and held. I was helping someone with one several years back and posted here for advice. I am not an automatic transmission guy and have never actually owned one. So maybe just doing it a few more times will fix the problem, knock on wood. You can only get about 30% of the fluid out each drain and fill. And sieve the contents of the bottom of the pan & old fluid you drain out for signs of metal debris. You might want to purchase the fluid at a Chevy dealership so you can make sure it meets the required specs. One idea, if you feel lucky, do the transmission service a couple more times. You may indeed need a rebuild, but it could also be just a bad solenoid. First thing I’d do is ask a shop to measure the pump pressure. It also needs to be able to adjust its decision for what gear to use for engine load, so there’s a method inside the transmission to do that, either with a vacuum modulator (as on my Ford truck) or a throttle position modulator (common to GM I think), or on most modern vehicles there’s computer involvement, often using electrical solenoid valves. So the transmission uses the pump pressure to decide – this is done with a part called the valve body – what each of the gear set’s inputs should be. The pressure comes from a pump inside the transmission, the pump pressure tends to be proportional to the vehicle speed. So off/off might be neutral for that gearset, and on/on might be a 1.3:1 ratio, and on/off might be direct drive, a 1:1 ratio. The pressure for a logic “on” might be between 10 and 15 psi, and for logic “off” might be between 2 and 8 psi, that’s the idea anyway. Each input to a gear set is a hydraulic fluid pressures, and are either on or off. The one for the drum operates what is is called a “band”. Each gear set has two inputs, one for the clutches, and one for the drum. But unlikely, like I say, if the service was done correctly, probably just a coincidence.Īutomatics are configured with 3 or 4 gadgets called “gear sets”. The only thing that could possibly affect the transmission adversely is if the fluid change somehow stirred up some gunk which is now blocking some port or another. A proper transmission service can only help. I don’t think the transmission service you did is the cause of your symptoms.
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