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Mypopslou

Transmission Shift Seems Off

6 posts in this topic

My 2006 Tuscany has a Allison MH-3000 6 speed transmission that does not seem to be shifting correctly. By the time I reach 40 miles per hour I am already in 5th gear and it will not go into 6th gear until I hit 55 mph. When decelerating it is slow to downshift but coach does not seem to be dragging.

I almost feel like it is in an economy mode and is shifting quickly but I am not sure.

Anyone have any suggestions, taking it to Freightliner tomorrow for Oil Change, Filter change and PA state inspection and thought I would ask them about it, the problem is every time I ask them about something it always ends up costing me big time.

Thanks in advance for your advice.

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Mypopslou,

When the engine is not getting enough fuel or when the turbo pressure is low, can cause the problem. Also the valve tappet setting out of adjustment can have the same affect.

When did you have the fuel filters changed last, number of miles? and how many miles on the coach? Have you ever changed the fuel lift pump or had the fuel pressure tested?

Rich.

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I have 24,000 miles on the coach and have had the fuel filters changed at least once, and it is at Freightliner as we speak with instructions for an oil change and all new filters as well as PA inspection. The main fuel filter that is accessible through the trap door in the bedroom of the coach I am not sure has been changed but I specifically asked them to make sure they did it this time. I have had the oil changes with new filter on the average of once a year. When the coach had 5000 miles on it I also took it to have the transmission serviced as recommended in the manual.

I have never had the fuel lift pump or the fuel pressure tested.

Hopefully it is just the filters

Just out of curiosity with a 6 speed transmission, when should it be shifting?

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Just out of curiosity with a 6 speed transmission, when should it be shifting?

That is kind of a loaded question. :rolleyes:

There a a number of variables the Engine and Transmission Control modules are looking at to allow them to shift.

The software set up, The load on the engine / transmission, elevation and throttle position are the key factors.

Rich.

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Conceptually, at light throttle, the upshift should occur as soon as RPM in the next higher gear is not below PEAK TORQUE RPM. In reality, because the gears are not evenly spaced, some are a little higher than that.

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Well, the service tech who I was dealing with it at Freightliner checked with their Allison guy and he said it was normal, so I guess I an good to go...I think?

Went back and checked my service records and have had all fuel filters changed 5000 miles ago and just did it again as that was 2 years ago.

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