Gearing for 80 MPH

[WARGEAR]

Doesn’t surprise me a bus doing 80mph in Jerz! Every time I go back driving gives me anxiety haha.

[Buzz Nichols]

Here in Utah (and plenty of plaes out West), there are lots of stretches of highway that have a posted speed limit of 80 mph. The busses I drive, though, are mostly governored for 75 (poor man's cruise control), and I'm real content to stick with that. It's an awful lot of vehicle, and the diminishing returns in mpg at those speeds worry me almost as much as the prospect of an accident.

[Rogue1bus]

Originally Posted by EastCoastCB

My bus will do a little over 80.
Its got 3.42 gearing in the rear and 1:1 4th gear in the Allison 545.

Its happiest at 1800 rpm cruising at 65mph.

I'm getting good fuel economy. Better than any bus I've owned.

The school set the bus up for high speeds, so I haven't done anything to it.

How big is your bus? GVW? Engine?

[EastCoastCB]

Originally Posted by Rogue1bus

How big is your bus? GVW? Engine?

5 window Thomas with a 3126 and a 545.

[Dragonpop]

1996 Bluebird AARE 8.3 L 300hp MD3060 transmission.75 fifth gear overdrive sixth gear locked out. 12R22.5 tires governed speed 2400 rpm top speed 85 mph. Safety factors transmission retarder slows bus like power brakes in a car. Safety-Plus unit
On front, steers like power steering with one hand.

[cowlitzcoach]

I feel like I am coming in during the middle of the movie so I don't know how my comments might be productive.


It has already been mentioned about gradability with gear ratios. Gear it fast enough it won't have power for the hills. Gear so it has power for the hills and you lose your top speed.



There is no free lunch when it comes to speed in a bus. Many times the HP will be your limiting factor for going fast. It takes a HUGE amount of HP to push/pull the brick shaped body through the air. It take exponentially more HP to go faster. Increasing HP requires increasing cooling capacity--easy to do in a front engine bus, difficult to do in a rear engine bus.


If you feel the need for speed, find a bus that is already set up to go fast. A bus with a factory designed power package to go fast might cost more initially but it will cost a fraction of what it will cost to upgrade gears, engine, and cooling systems of a lower HP/slower geared bus.


One of the reasons why the Crown and Gillig buses are preferred by so many people is a large percentage of them were designed to go fast. I have seen more than a couple that were powered and geared to move a full load at 80 MPH. I know of a few that could cruise well excess of 80 MPH. But those buses were turning more than 350 HP, they had 9" wide front brakes, and 13" wide brakes in the back--they not only could go fast but they had the braking capability to stop the fully loaded bus from those speeds without experiencing dangerous brake fade. They also had from the factory cooling systems that could cool down a hot engine like that while going through the desert of CA and NV.


It is possible to turn a regular route bus that never went over 40 MPH during the total service life into a bus that can cruise at 80 MPH. But it isn't going to be cheap or easy.


Good luck.

[somewhereinusa]

Originally Posted by cowlitzcoach

I feel like I am coming in during the middle of the movie so I don't know how my comments might be productive.


It has already been mentioned about gradability with gear ratios. Gear it fast enough it won't have power for the hills. Gear so it has power for the hills and you lose your top speed.



There is no free lunch when it comes to speed in a bus. Many times the HP will be your limiting factor for going fast. It takes a HUGE amount of HP to push/pull the brick shaped body through the air. It take exponentially more HP to go faster. Increasing HP requires increasing cooling capacity--easy to do in a front engine bus, difficult to do in a rear engine bus.


If you feel the need for speed, find a bus that is already set up to go fast. A bus with a factory designed power package to go fast might cost more initially but it will cost a fraction of what it will cost to upgrade gears, engine, and cooling systems of a lower HP/slower geared bus.


One of the reasons why the Crown and Gillig buses are preferred by so many people is a large percentage of them were designed to go fast. I have seen more than a couple that were powered and geared to move a full load at 80 MPH. I know of a few that could cruise well excess of 80 MPH. But those buses were turning more than 350 HP, they had 9" wide front brakes, and 13" wide brakes in the back--they not only could go fast but they had the braking capability to stop the fully loaded bus from those speeds without experiencing dangerous brake fade. They also had from the factory cooling systems that could cool down a hot engine like that while going through the desert of CA and NV.


It is possible to turn a regular route bus that never went over 40 MPH during the total service life into a bus that can cruise at 80 MPH. But it isn't going to be cheap or easy.


Good luck.

Well said. Quote from my racing days "Speed costs money, how fast do you want to go?"

[EastCoastCB]

I feel like the highway gearing is probably the most underrated upgrade one can make. I've got 80+ mph capability and I'm getting fantastic fuel economy.
Before owning this bus I'd have thought 3.42 gearing was too high.
The best part of having an 80 mph bus is that at normal speeds its a real pleasure to drive. No yelling to have conversations with passengers. Its the quietest bus I've been in.

[Ab01ns]

Originally Posted by EastCoastCB

I feel like the highway gearing is probably the most underrated upgrade one can make. I've got 80+ mph capability and I'm getting fantastic fuel economy.
Before owning this bus I'd have thought 3.42 gearing was too high.
The best part of having an 80 mph bus is that at normal speeds its a real pleasure to drive. No yelling to have conversations with passengers. Its the quietest bus I've been in.

Still trying to figure out what I should move my rear to.

I have a md3060 (0.75 od final), 5.57 rear with 10r22.5 tires but will be unlocking 6th gear for a 0.65 OD.

I don't want to cruise much faster than 65mph cause fuel, but I also don't want to put the engine

You have a 3126, what does Cat recommend ideal fuel economy rpm at?

Thinking

[o1marc]

Originally Posted by Ab01ns

Still trying to figure out what I should move my rear to.

I have a md3060 (0.75 od final), 5.57 rear with 10r22.5 tires but will be unlocking 6th gear for a 0.65 OD.

I don't want to cruise much faster than 65mph cause fuel, but I also don't want to put the engine

You have a 3126, what does Cat recommend ideal fuel economy rpm at?

Thinking

How are you unlocking the 6th gear?

[Ab01ns]

Originally Posted by o1marc

How are you unlocking the 6th gear?

Sending the letter to Thomas to start. I found a shop that will do the programming

[o1marc]

Originally Posted by Ab01ns

Sending the letter to Thomas to start. I found a shop that will do the programming

The only one that can authorize the release is Allison. They will notify the service center to allow it if they decide to allow it. So far I don't believe anyone has been successful getting Allison to cooperate.

[Ab01ns]

Originally Posted by o1marc

The only one that can authorize the release is Allison. They will notify the service center to allow it if they decide to allow it. So far I don't believe anyone has been successful getting Allison to cooperate.

I thought that a few Thomas owners had been. The issues seem to be rear end ratio, has to be numerically higher than 4.5 or so(mines 5.57) and a 75mph speed limiter. Mine is set at 65. As soon as I get the bus plated I'm moving forward on this

[o1marc]

Originally Posted by Ab01ns

I thought that a few Thomas owners had been. The issues seem to be rear end ratio, has to be numerically higher than 4.5 or so(mines 5.57) and a 75mph speed limiter. Mine is set at 65. As soon as I get the bus plated I'm moving forward on this

As soon as Allison gets the request they will deny it for being too old. My 99 Genesis cruises easily at 85mph in 5th. I requested the gear open for better fuel economy, Allison said it was too old. Which makes absolutely no sense whatsoever.

[Ab01ns]

Originally Posted by o1marc

As soon as Allison gets the request they will deny it for being too old. My 99 Genesis cruises easily at 85mph in 5th. I requested the gear open for better fuel economy, Allison said it was too old. Which makes absolutely no sense whatsoever.

Mine is an 02. Might be new enough...

[PNW_Steve]

I have seen a handful of posts here from members that have successfully had Allison unlock 6th gear.

They have been Thomas and (I think) International.

Unfortunately no Bluebirds. Allison requires a letter from the bus manufacturer authorizing the change and Bluebird won't play ball.

[o1marc]

Originally Posted by PNW_Steve

I have seen a handful of posts here from members that have successfully had Allison unlock 6th gear.

They have been Thomas and (I think) International.

Unfortunately no Bluebirds. Allison requires a letter from the bus manufacturer authorizing the change and Bluebird won't play ball.

I can't agree. I found a Navistar dealer willing to make the change but Allison told them no. Some may have had luck unlocking them in the past, but I haven't seen any unlocked since I've been into buses. I don't understand why they play hardball on something they have no liability to.

[weboughtabus]

Originally Posted by o1marc

I can't agree. I found a Navistar dealer willing to make the change but Allison told them no. Some may have had luck unlocking them in the past, but I haven't seen any unlocked since I've been into buses. I don't understand why they play hardball on something they have no liability to.

http://www.skoolie.net/forums/f10/al...ial-21661.html

[PNW_Steve]

Looks like Porkchop and Backwoods Wanderer are among those that have been successful in getting Allison to unlock 6th.

[Ciscokid]

My bus is happy at 62 great gas mileage and things dont go flying around all over the place. I also have a 545 behind a DT466. Seen many mods to do to the engine but why? It runs great and good fuel mileage. Guess this is a sign of old age too