Re: Governed Speed, Vocational, Over Rev
Reply #5 –
Yes, this is what it is supposed to do. Both models (3060 and 4060) work the same way. They are wonderful transmissions and have a lot of built in safety features to prevent the operator from doing something that should not happen. I am fairly sure that when the transmission is mated with the engine at the factory it is programmed for the max engine rpm for that engine. Even though you may have selected a lower gear like 4 or 5 normally it will not up shift past that gear. It engine rpm does get too high though it will up shift in an attempt to lower engine rpm. Like you said it will come as a big surprise as the higher gear is a loss of braking effect. The only thing the driver can do is hit the brakes and slow down until the transmission selects a lower gear. Another safety feature is that even though the driver selects a lower gear the transmission will not shift into that gear if doing so would over rev the engine. Again brakes must be used to reduce speed before the downshift will happen.
I know the theory about using the same gear going down and coming up the grade, but usually I have not come up that way, so what would that gear be? I have found that selecting anything above 3 on the retarder on a descent will overtemp the transmission after a few minutes. So I select 2 or 3 and a gear that will keep the speed and rpm under control. I don't select a gear that is so low that I never have to hit the brakes. A few intermittent brake applications to reduce speed should not be a problem. I just don't ride the brakes, and that seems to work well for me. Foretravel has installed disk brakes which have less brake fade than drum brakes, don't be afraid to use them. At the same time we are much heavier than a car, so we can't drive like we are in a car. I think you will find the happen medium very soon.
Topic: Governed Speed, Vocational, Over Rev