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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 1639
Experience:  Owner at DJ Wilson
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Have an Allison at 545 in a 1990 gmc topkick. It was a spade

Customer Question

Have an Allison at 545 in a 1990 gmc topkick. It was a spade truck, only has 20k miles on it. Max speed is 55mph, what can I do
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Curtis B. replied 1 year ago.
The transmission shifts ok? Transmission does not have anything to do with top speed.
Expert:  Curtis B. replied 1 year ago.
Engine rpm. or the rear end ratio is what determines speed.
Expert:  Curtis B. replied 1 year ago.
Easiest is to change the rearend ratio!
Customer: replied 1 year ago.
Done that, still the same the acceleration is better but still tops out at 55mph.
Expert:  Curtis B. replied 1 year ago.
Is engine stalling out? What ratio did you have and what did you add?
Customer: replied 1 year ago.
Engine doesn't stall out.
Expert:  Curtis B. replied 1 year ago.
Transmission has no way to add speed. Only engine rpm or rear end ratio does that, unless you have a speed limiter in the governor setting of the truck! Is this old rental truck? May need to be reprogrammed.

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