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Old 05-04-2019, 08:29 PM   #1
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Slow up hills

As a newbie I have no idea how fast (slow) my bus should go.

I have a few more weeks of work on my interior conversion, then heading to Alaska with 3 of my kids for the summer

When I bought it last fall I drove it home 150 miles but encountered no hills till 12 miles from home. I drove 60 on the interstate (first bus drive ever...), then hit hills in western mass/southern vermont. 30 up one hill on a state highway (that has a truck climbing lane), and 15-20 up the steep 2 mile dirt road up to my house (about 850 foot climb).

Had a full $39.95 oil change look over service at Fleetpride, and asked them if thats all she had in her. They weren't wonderful but... (opps, did I put a . in that price quote), but they made me calm and changed air dryer and some big space ship looking brake component underneath and freed up a frozen shackle...)

Anyway had a nice drive today to get more used to her. A 2 mile 8% climb on a state highway with a climbing lane got me down to 22mph. On the flats she drive the speed limits easy.

My LIMITED knowledge of diesel engines is that not much can be done (ie no timing...) and this MAY be all I get. (Full disclosure, my summer car, a 74 vw thing gets up those same hills at 40 when fully loaded with my family).

I dont mind going slow and feel the bus is rolling and performing well for what it is. And then I think WTF what if I was going up the Rockies? (which I am not...this year).

Does this sound like an issue? It was built as an urban city bus. Is a CAT 3126 210 hp underpowered for my vehicle?

Would LOVE your experienced comments on my ride, and if you guys think I should search for a repair or service...thanks
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Old 05-04-2019, 08:35 PM   #2
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Correct me if I'm wrong, but it's probably your rear end ratio. If you switch the gearing out for higher gears, you'll probably go faster up the hills.

Mine will go 55 no problem, all day on the flats. Hit a step climb in Texas, 25 mph, towing the car.

It is what it is. You can change out the rear end. For my bus, I've seen them online for as little as $500 used. I'm sure if I had an experienced person to guide me, I could swap it with help.

I feel like you'd be looking at $2000-$3000 to have a shop do it. I think my mechanic would do it for less, but he's done it a couple times.
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Old 05-04-2019, 09:12 PM   #3
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I put the bus in gears 1 or 2 as it got down to 25. In 2nd gear rpm was 2200-2500 which I believe is MAX rpm, in first it went slower if anything.

I am aware with my tranny a 6th gear is possible with software, thats on my to do list.

I am still learning the diesel torque thing but in automatic it still slowed down/

BTW no tractor trailers running then to compare speed too...
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Old 05-04-2019, 11:24 PM   #4
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I have the same drivetrain. Ninja kitty is talking about the rear end gears, not the transmission gears. I have a 6ish:1 rear end which gives me a top speed of 70 or so at redline in 6th gear.

I think I would prefer a rear end ratio in the fives. My bus is geared for power, but still takes patience on the hills. I towed a Jeep all over the country last summer. Heat makes it worse because the fan is a horsepower hog.

On the coastal range in CA I maxed out at 9mph on one road. Tight, hot and steep.

Expect to cruise at decent highways speeds when on relatively flat ground. On a good day I can pull 3-5% grades without losing much steam. 6 plus and I start to slow down.

Steepest Iíve driven is a 16% grade. Went up in first gear no problem. Came down in first as well with pulse braking.

Youíll get where you are going. Just be patient going up and coming down. Make sure to start descents slow because once youíre committed it is hard to get slowed down.

Iíve researched replacing the 210hp with a 330hp 3126 from a motorhome if I ever blow mine up. Looks feasible, but must make sure cooling system is up to it.
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Old 05-05-2019, 04:36 AM   #5
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Originally Posted by matthews2001 View Post
I put the bus in gears 1 or 2 as it got down to 25. In 2nd gear rpm was 2200-2500 which I believe is MAX rpm, in first it went slower if anything.
I have been informed that a CAT 3126 will purr all day long at 2250 RPM and be fine with it. While you can push it higher, it is best to let the transmission do such things when shifting from a lower gear to a higher gear to place the engine RPMs at a better place when first in the higher gear ... instead of YOU keeping it in a lower gear and allowing it to wind up for a long time.


Sounds like that for the grade you were on, 25 is a relative MAX speed.


By the way, unlocking the 6th gear will gain you a second over-drive gear and can help in the top-end or cruising at better fuel economy. It will not help with low-end pull (i.e. climbing hills and taking grades).
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Old 05-05-2019, 07:37 AM   #6
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Originally Posted by matthews2001 View Post
I put the bus in gears 1 or 2 as it got down to 25. In 2nd gear rpm was 2200-2500 which I believe is MAX rpm, in first it went slower if anything.

I am aware with my tranny a 6th gear is possible with software, thats on my to do list.

I am still learning the diesel torque thing but in automatic it still slowed down/

BTW no tractor trailers running then to compare speed too...
OD and high gearing won't help you in hills. You need HP/TQ for that.
2400 is redline for your 3126.
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Old 05-05-2019, 08:14 AM   #7
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"hill" is such a relative term.. what kind of grade is it? if its an 8 or 9% or higher grade then its expected most anythin g large is going to slow down.. (think about carrying 6 bags of groceries up a wheelchair ramp vs up the steps).. I dont know the particular road you were on but i do know there are some STEEP inclines in the area you are.. and 15-20 MPH isnt unreasonable on some of those..



now if you are dropping Way down in speed just to climb the inclines to over-passes on the freeway then yes maybe a gear change is in the cards..



unlocking 6th gear will lower your RPMs at any given speed.. it is a 0.65 OD ratio vs 5th which is 0.75.. you could then gear down your rear end a bit to have the same current highway RPMs you do now.. however in your lower gears you woukd then have a bit more torque for hill climbing.. as ECCB mentioned.. you need Torque on the ground to climb hills.. if your desired cruising speed is 65 then i'd should to have your CAT-3126 at about 2000 RPM in 6th gear at 65 MPH.. 5th downshift on small inclines will put you right in the top HP band of that engine.. and slowing down a bit sllows you to drop to 4th. I have no idea what your RPMs are now at any given speed.


and finally, it may be possible to have the CAT dealer pump up the HP on your engine.. I havent yet figured out how to hack the CAT engines to do it yet..



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Old 05-05-2019, 10:45 AM   #8
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If you are at 210 there is no way to increase HP with CATís blessing. It requires pistons, injectors and a few other things to get past 210 safely and they are very tight with their authorizations for re rating their engines. Motorhomes and some other applications used the 330HP variant.

Thatís why I have looked at an engine swap as likely being the cheapest way to get big HP out of a 3126 powered bus.

It has even occurred to me that rebuilding a high HP 3126 could be a good winter project.

What you are describing sounds more or less normal, but make sure you have fresh fuel filters. Also my 3126 is gutless until it is warmed up. That may be part of it as well in some cases.
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Old 05-05-2019, 11:21 AM   #9
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You can fuel it heavier with bigger injectors and bigger turbo, the bottom end on those 3126s are much beefier than 210hp. They are all built way under powered for busses.. navistar is the same way. In fact your stock turbo is actually pretty good on yours. If you have the wastegated model you can turn the gate up a few psi and go with stage 1 or stage 2 injectors. The computer will already be set to fuel it with similar logic to the smaller injectors so it will be fueling heavier.. add to than an ICP and maybe boost cooler and you are going to be pushing 300 and from what I can tell of the components the stock bottom end should take 300 no issues. No you won’t get half a million miles on it like you easily can on a 210 hp cat or a fully built 300hp model but I venture to say most wont put even 100k on their busses additional unless they are one of the few on this board that run their busses all over a lot.
Even an ICP cooler can net you 30-40 hp without any other mods.. which for most is the difference between slowing down on every small hill and holding speed on moderates.

The reason my bus hauls ass is because it doesn’t weigh much. A little 6 window shorty 3800 on the 17500 gvwr class is the lightest duty full chassis navistar made in that year. Coupled with the fact it’s all stock means I’m running with little weight except my luggage and tools means it goes.. and I’ve got the motor turned up.. which I’m sure means it’s life is shortened.. the navistar books for my older dta360 even talk on that engine about how the engine is safe to turn the rpm up to 3200 and the fuel up but at the cost of longevity

I wouldn’t expect a fully converted full size bus to move out.. not with medium duty engines. The big coaches like prevost mci etc are running class 8 semi truck engines that are built for 400-450 hp with class 8 transmissions and drivelines ..
I spent many years driving a new prevost to ft Myers and Ohio and back that had a 450 hp engine. That bus never broke a sweat anywhere on I75 or 77.. but it was built for it.. it also had the jake brake, a retarder, and upgraded abs air brakes to handle slowing itself down on the down grades.. school busses don’t..
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Old 05-05-2019, 06:32 PM   #10
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I am surprized this buses are so underpowered.

I dont really care, going slow and seeing more and being more relaxed.

HOWEVER aren't people and truckers pissed off? I mean 9 -20 mph up hills? I'd hate to be behind one if I was on my way to work, or pulling a load as a truck driver.

Some highways have minimum speeds, I dont think I can reach them!!


Anyone go up a hill and not reach the top? I remember in my hippie days my vw van was f ed up and wouldnt get over the berkshires, we had to get out and push once or twice!!
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Old 05-05-2019, 07:07 PM   #11
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Quote:
Originally Posted by matthews2001 View Post
I am surprized this buses are so underpowered.

I dont really care, going slow and seeing more and being more relaxed.

HOWEVER aren't people and truckers pissed off? I mean 9 -20 mph up hills? I'd hate to be behind one if I was on my way to work, or pulling a load as a truck driver.

Some highways have minimum speeds, I dont think I can reach them!!


Anyone go up a hill and not reach the top? I remember in my hippie days my vw van was f ed up and wouldnt get over the berkshires, we had to get out and push once or twice!!
You mean all the trucks that piss off the drivers because the semi is going so slow up the hill. Screw em, we have as much right to that lane as anyone.
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Old 05-05-2019, 09:08 PM   #12
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minimum speeds dont apply on grades... esp in truck lanes... the only time drivers really get pissed off at truckers is when they LogJam... ie take up all the lanes even lanes that state "no trucks" on an uphill grade... otherwise when they obey the no-trucks signage for usually the left lane people just run right by that want to go faster
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Old 05-05-2019, 09:49 PM   #13
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minimum speeds dont apply on grades... esp in truck lanes... the only time drivers really get pissed off at truckers is when they LogJam... ie take up all the lanes even lanes that state "no trucks" on an uphill grade... otherwise when they obey the no-trucks signage for usually the left lane people just run right by that want to go faster
The ones that piss me off are the semi's that use the #2 lane and get right next to another truck and then does the same speed, for 10 miles, MFer's
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Old 05-06-2019, 08:41 AM   #14
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The ones that piss me off are the semi's that use the #2 lane and get right next to another truck and then does the same speed, for 10 miles, MFer's
Many's the time I wished I had missile launchers mounted...
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Old 05-06-2019, 11:27 AM   #15
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There are times that I am right in line with trucks going up hills - sometimes I have a little more power, but not enough to pass, and sometimes I am the slow poke. I have had good CB conversations with some of the truckers up hills - and I am always respectful. They are mostly really great people / drivers. But they are generally on the road a lot more than I am - and time is money for them. I'm never in a rush.
I have not really met up with truckers out on the road who were not nice. They are out there - and some are likely downright miserable SOBs - but overall, it's the many frantic, high-strung, stressed out, daily car drivers who have short fuses that create a hazard out on the road.
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Old 05-06-2019, 10:43 PM   #16
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Turnouts are good for being kind to those behind when on rural routes. Got pretty good at this on the PCH last summer.
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Old 05-06-2019, 10:44 PM   #17
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You can fuel it heavier with bigger injectors and bigger turbo, the bottom end on those 3126s are much beefier than 210hp. They are all built way under powered for busses.. navistar is the same way. In fact your stock turbo is actually pretty good on yours. If you have the wastegated model you can turn the gate up a few psi and go with stage 1 or stage 2 injectors. The computer will already be set to fuel it with similar logic to the smaller injectors so it will be fueling heavier.. add to than an ICP and maybe boost cooler and you are going to be pushing 300 and from what I can tell of the components the stock bottom end should take 300 no issues. No you wonít get half a million miles on it like you easily can on a 210 hp cat or a fully built 300hp model but I venture to say most wont put even 100k on their busses additional unless they are one of the few on this board that run their busses all over a lot.
Even an ICP cooler can net you 30-40 hp without any other mods.. which for most is the difference between slowing down on every small hill and holding speed on moderates.

The reason my bus hauls ass is because it doesnít weigh much. A little 6 window shorty 3800 on the 17500 gvwr class is the lightest duty full chassis navistar made in that year. Coupled with the fact itís all stock means Iím running with little weight except my luggage and tools means it goes.. and Iíve got the motor turned up.. which Iím sure means itís life is shortened.. the navistar books for my older dta360 even talk on that engine about how the engine is safe to turn the rpm up to 3200 and the fuel up but at the cost of longevity

I wouldnít expect a fully converted full size bus to move out.. not with medium duty engines. The big coaches like prevost mci etc are running class 8 semi truck engines that are built for 400-450 hp with class 8 transmissions and drivelines ..
I spent many years driving a new prevost to ft Myers and Ohio and back that had a 450 hp engine. That bus never broke a sweat anywhere on I75 or 77.. but it was built for it.. it also had the jake brake, a retarder, and upgraded abs air brakes to handle slowing itself down on the down grades.. school busses donít..


Lots of great knowledge here. Iíve got some studying to do! Having trouble finding what an ICP cooler is.
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Old 05-06-2019, 10:59 PM   #18
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i don't know if its relevant with an MD 3060, but adding a trans cooler to my 545 was like adding another turbo. powr that i lost on the hills to the transmission came back in spades and i no longer climb hills as the slowest vehicle out there.
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Old 05-16-2019, 01:39 PM   #19
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Originally Posted by matthews2001 View Post
I am surprized this buses are so underpowered.

I dont really care, going slow and seeing more and being more relaxed.

HOWEVER aren't people and truckers pissed off? I mean 9 -20 mph up hills? I'd hate to be behind one if I was on my way to work, or pulling a load as a truck driver.

Some highways have minimum speeds, I dont think I can reach them!!


Anyone go up a hill and not reach the top? I remember in my hippie days my vw van was f ed up and wouldnt get over the berkshires, we had to get out and push once or twice!!

One does have to remember that the vast majority of school buses spend 95%+ of their service life on route at speeds less than 35 MPH. One does not need every bus in a fleet capable of going highway speeds. It costs more $$$ to purchase buses that are capable of going highway speeds so most school buses are not ordered with the big HP engines and highway gearing.


One also needs to remember the hot rodders adage, "there is no replacement for displacement!" On a hill a 250 HP Cummins 6CT/ISC is going to walk away from a 250 HP Cummins 6BT/ISB. The bigger engine is going to have at least 30% more torque with the same HP.



If you have the need for speed you are going to need big HP. Big HP requires more cooling capacity and faster gearing. In order to not slow down on any hill you are going to have to have at least 50% more HP than what most school buses have.


If you have to go down into 2nd or even 1st gear to get up a hill, putting in a higher speed rear end is going to mean you will be shifting down into a lower gear sooner.
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Old 05-16-2019, 05:00 PM   #20
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I pass about 1 in 10 trucks that are climbing long interstate grades. Most of them are faster than me, but not all.
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