The Newman Skoolie!

[Jolly Roger]

I ain't stalking you or your thread but you have some of the same questions I have been through and am trying to work through myself?
I would like to say that the mechanic or whoever made that statement without your entire power train in mind? The bus barn I bought my bus from told me that I could adjust the governor's but I would burn up my rear end if I did and after many discussions and research I would agree. My rear gears at 6.50 were not made for anymore power from my engine? Regardless of motor tranny and rear end combo?
Everything has to be synced together or one is going to hurt the other?
I can only reccomend that you figure out your rear gear ratio before you go any farther.
I have gone out of my way to keep my governors where the factory set them at because that is the sweet spot for my engine and tranny combo without changing factory settings.
My problem is my rear gears. Right now I can pull tree stumps but I can't get above 49-mph. Everything works like the well oiled machine it was meant to be.
My first option until I can find a different rear end is to change my tire size from 9r20 tubed de mountable (Dayton split ring rims ) to 10r22.5 non tubed Dayton de mountable rims which should get me to at least 55-mph downhill anyway. I am happy with the back roads the H??l with anyone behind me.
Engine sweet spot,tranny sweet spot converted to you rear gear ratio is what you need to figure out before any governor change.
My governors are set below the engine and tranny max but it was to save the rear gears?
If I ever do a rear gear change then maybe I will bump my governors up but in my mind the closer I am to factory settings the longer I don't have to worry about my powerhouse failing?
Food for thought?

[Jman6631]

Thanks a lot Jolly Roger,

That all makes perfect sense, and without articulating it so well I think (hope?!) these trade-offs were rattling around in my head. Nothing could be that simple, eh? I will figure out my rear gears but in the end were you suggesting that a pumpkin swap is feasible with the governors left as-is?

[Jolly Roger]

Yes, if you can find the correct one.

[Jman6631]

Is there a way to find out what's in the pumpkin from the outside? Would there normally be a p/n or s/n that I could investigate?

[Tango]

The ratio of any axle can be determined by doing the following:

1. Block front tires and jack up driver side rear with the vehicle in neutral
2. Put matching marks on the ground and driver side tire
3. Put a mark on the drive shaft
4. Rotate the driver side tire one full revolution while counting the number of turns on the driveshaft

That is your ratio

[Jman6631]

Hey thanks Tango!

[cadillackid]

I used the shop vac blower on one of the lines under the hood.. I dosconnected both lines at the pump and also removed the valves (as I was installing the electronic ones).. I blew air through and a lot more coolant came out.. the issue on a conventional bus (at least mine).. is that the coolant lines for the heaters are downlow going to the rear.. and then go up high to exit the firewall, so just draining it under the hood was still going to leave a lot in the interior loops...

the air pressure created enough of a siphon that most of the remaining coolant pushed out.. I ran it until I just heard air coming out..

when I pulled the whole driver side heater box out I still had a little in the rear lines but nothing so big a towel wouldnt sop it up...

not all busses have the extra boost pump.. not sure why mine does when its a short bus that didnt have the 'Mid' heater .. maybe because it was northern?

I just got it in May so ive only run the heat a little bit to know whether I need that pump on or not but with my electronic heater valves it will run now..

I do know you dont want to get rid of the heater valves.. those heater cores add a ton of heat to the bus on a summer day even with the fans off.. so you will want to keep the valves to kill the coolant flow in warm weather..

-Christopher

[Jman6631]

Thanks Chris, I don't know if I have a booster or not. I haven't seen one referenced in the manuals I have and I haven't seen one yet. Where are they usually located?

[Oldmopars]

Originally Posted by Tango

The ratio of any axle can be determined by doing the following:

1. Block front tires and jack up driver side rear with the vehicle in neutral
2. Put matching marks on the ground and driver side tire
3. Put a mark on the drive shaft
4. Rotate the driver side tire one full revolution while counting the number of turns on the driveshaft

That is your ratio

I hate to disagree with you, but I do not want someone using this method and assuming they have the wrong gear ratio.
If you only jack up one wheel, you will be driving the wheel through the spider gears, this is a second set of gears in the diff that will give a faults ratio.
See this web site:How does a Differential work ? ~ Learn Engineering
As you can see from this page, the Side gears are blue and the spiders are yellow. When you rotate the drive shaft it turn the carrier, this drives the spider gears, but if one side gear is held still(I.E. being on the ground) the other wheel(Side gear) is driven by the spiders rotating around the fixed side gear and rotating the free side gear(wheel in the air). Often times at a rate of 2:1, thus giving you a wrong ratio.
So to use your method, you need to have both wheels off the ground so that the only gears involved are the pinion and the ring.
Just want to make it clear for all in the future who may want to use this method.

[Jman6631]

Thanks Oldmopars,

Great video. So I'm back to my original question, short of lifting both wheels now, is there another way for me to accurately determine my diff gears? Is there no make/model marking on the casing? What about researching at Freightliner on the original build with the VIN or other s/n?

[Tango]

Yes...Thanks...my bad. I should have said both rear wheels.

[Oldmopars]

So, the only way to do this without lifting both rear wheels off the ground it to roll it.
So, find a SAFE place to do this like a parking lot or very quite dead end road.
Mark a line on your tire where it contacts the ground.
Put a large Zip Tie on the drive shaft pointing in the 6'O clock position.
Now have someone drive the bus VERY SLOWLY and have someone count the times the Zip Tie passes the 6"O Clock position. This will be 4 times plus some.
When the mark on the tire returns to the bottom where it started, stop the bus.
Now look to see where the zip tie is pointing in relation to the start position(6'O Clock), this will give you your ratio.
Keep in mind you need to drive in a straight line, and you need to be careful, the driver can't see you.
A quiet area, or walkie-Talkies help.
This is the only way you can do it if you have no tags and no way to lift the bus.
Also, it is not going to tell you if you have a 4:11 vs. a 4:10, you just be able to see that you have about a 4:10 and will need to look up what was available and match it to what you found.
Hope this helps.

[Jman6631]

Hey thanks Oldmopars, that makes sense and I could probably actually pull that off (!).

So, getting back to Jolly Roger's point, once I've done that and I know my diff gears, what next? How do I know if it's safe/advisable to change or bypass the governor and/or the gears to give me more speed and most importantly better milage? Or am I most likely stuck with what I have?

[Oldmopars]

That is where you start to get into Black Magic and it's hard to answer. However if you find out you have, say 4.78:1, going to 4.11:1 would be an improvement. But too big of jump and you could end up with a gutless bus that won't climb a hill.
You will also need to recalibrate your speedometer.

[Jman6631]

Ok, I'm going to do this this weekend and will report findings.

Assuming there is room for "reasonable" improvement in swapping out the gears that won't diminish its overall abilities, how much improvement in performance and milage can I reasonably expect...e.g., is it really worth it and can I measure the expected gain at least roughly?

[Tango]

Really no way to precisely calculate MPG, but you can nail the numbers as far as RPM at a given speed. Use the calculator below...

Engine RPM CalculatorEngine RPM Calculator

[Jman6631]

Very interesting, thanks Tango! And I do know my question doesn't really have an answer, I'm just trying to get some idea of a benefit I MAY get if I decide to make the change.

[Tango]

It is worth running the numbers. It doesn't take much of a reduction in RPM's to create pretty substantial fuel savings. Like backing off from 70mph to 65, if you can get your RPM's down near the sweet spot by cutting down on revs, the difference can be surprising.

That said, unless you spend a fair amount of time at highway speeds...the difference may not be worth the effort.

[Jman6631]

Right...I do expect many miles will be highway miles, not all but a fair amount but of course I won't know that until I do it. Until then I'll make whatever study of it I can and see if something significant reveals itself enough to push me to do it.

[cadillackid]

heres my experience..

7 row carpenter, 27500 GVWR, high top
DT-360 AT545 trans flat ground

running 65 - 68 engine pegs on rev limiter 2700-2800 constantly. MPG 6-6.5
running 60 - engine occasionally hits the rev limiter.. usually stays at 2500-2600. MPG 7.5 or so

running 55 - engine never hits rev limiter.. usually at 2200-2400 RPM on average. 10-11 MPG. (I got 11.5 on a couple tanks of fuel)

my bus is running 11R22.5 tires and a 4.78 rear.. my RPMs vary because of no lockup in the AT545 trans...

these numbers were measured making Long rides of 500 miles or more.. i typically took the MPG numbers when i had been on flat ground.. up and down hills lowered it.. im guessing because of the AT545...

-Christopher