Quote:
Originally Posted by BrandinoBeatz
Just sucks cuz about 2600 rpm for me is like 53 mph smh and I know I shouldn’t take it that high of revs
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you likely have a 6.50 or 7.17 rear end.. if your bus came from north carolina this was spec...
the extra low ratio means very low top speed and a lot of heat for your engine as navistar engines hate nbeing run at their RPM limiter.. they will do it all day long and you dont shorten their life doing so but they lose fuel economy doing it.
the low ratio is also EASIER on your transmission than a Taller (say 4.78 rear) gear... essentially its easier for the transmission to turn the wheels..
if you think about it like a 10 speed bicycle.. when you climb a hill you are in a low gear and the bike is easy to pedal but even pedaling as fast as you can , the bike doesnt go very fast,, shuft to a high gear and the bike will go fast (if you can pedal it.. because its hard to pedal)...
your bus is geared to go slow but standas a halfway decent chance at climbing hills.. while I dont drive fast in my busses.. 53 top speed would be unaceptable to me on freeways and barely acceptable on backroads..
if you re-gear the rear you could get higher top speed but just like a bike, the transmission would work harder.. not just from the ratio but from higher wind resistance created at higher speeds..
if you drive in 2nd gear at 15 MPH up the mountain grades you can probably keep the trans cool.. you'll have good engine braking downhill with the low ratio and again going very slow..
I darn near Burned up the AT540 in my Superior bus climbing mountains out west when I first got it.. that bus has a Gasoline engine with a carb so not near the torque of a diesel.. was empty except for seats(35 foot bus)
11R22.5 tires and a 6.50 gear ratio it had and I got the trans so hot I boiled the fluid out climbing a grade in wyoming..
it was about 65f outside.. that engine has a straight fan so the fan was roaring as i climbed the grade in 3rd gear.. engine temp was at 190 so my trans cooler in the radiator had a lot of room to work...
the rest of the trip i climbed the grades in 2nd gear at 15-20 MPH and I could keep the trans under 220 or right around...
ive regeared that bus to a 4.78 now, and on flat ground itll run 65 all day that 392 just purring away but climb a hill and the trans temp wants to climb right with me...
that Superior bus will never go in the mountains or if it does it will just be the low-grade east mountains.. ( like I-75 between ohio and florida.. nothing big).