Rear Axle Ratio thoughts---

[PorchDog]

Well, I have already been down this path, but watching Check Cassidy on YouTube swap his rear end has me scratching my head again.

My bus is short, 6 windows, and has a DT466 rated at 175 HP and 430 Ft Lbs of Torque. Lowest horsepower of all the DT 466 variants-- as far as I know.

It has a manual 5 speed transmission, which is direct in fifth, and a granny low gear. It came with a 4.78 axle from the factory. I have swapped in a 4.10 which puts me at 2150 RPM at 60 MPH.

Chuck has a midsize bus with a mechanical DT466-- I am sure it is higher horsepower than mine-- and an AT545. On his YouTube show he has swapped in a 3.73. So-- with direct drive (says he intends to install an MT643 in the future) that will put his 60 MPH RPM at 1960. (Assuming he has 265/75R22.5 tires like mine...)

So-- my swap from a 4.78 to a 4.10 is a 14% change.
Chuck's swap is from a 4.44 to 3.73 which is a 15% change.

Should I have gone lower-- maybe 3.91, or even 3.73 like Chuck?

[Ronnie]

I guess what I have to ask is are you happy with what you have? As you get steeper in the gears the it will feel sluggish especailly on hills. If you up the horsepower then going lower would be nice. That engine should be happy around 2000.

[cadillackid]

so i have too steep of gear in my red bus.. even withy my engine cranked up to close to 350 HP (6 window short bus).. it hauls ass for sure but my EGTs go up real quick when I get on it and the RPMs are a bit low.. technically not lugging because it is gaining speed and RPM but I really need to gear down.. so there is definitely a sweet spot you want to stay.. for a low horsepower DT, 2200 RPM isnt bad for highway cruise.. you go taller and you will be shifting a lot.. now if you plan to Orion the engine or god-mode service maxx it up to a higher HP then a 3.90 would be a good choice for the rear end as the DT in higher HP forms will take quite a bit of fuel and not hate life. . (id still put a Pyro on it)...

[Booyah45828]

This is kind of an apples to oranges comparison. Chuck's automatic will mask any issues he might have with acceleration and grade climbing. You on the other hand having a 5 speed and granny low(really only 4 gears), will have a much harder time with it compared to him IMO. He will have to watch his 545, though, until he swaps to the 643.

On the other hand, you being lighter/shorter should make it easier for you grade climbing/accelerating, so it might all be a wash......

I think 2150 RPM at 60 MPH gives you a good all around gear. With the 4.10's, If you wanted to push 70mph/2600rpm, you can. But with a stick and city/highway driving I'd likely rather have 4.10's over 3.73's. Unless this will be solely an interstate cruiser, then the 3.73's would be preferable.

Truthfully, I'd keep what gears you have, and if you want to make a change, go with a different trans with more gears and an overdrive. Then you'd have the better rig all around. Maybe something like a super 10? It'd give you a lot of overlap being light as you are, but they're common to find and have some pretty good ratios.

[PorchDog]

Thanks very much for this input.

I have spent the last year fixing minor issues and replacing 28 year old rubber hoses, and a whole lot of other parts in an effort to make the bus as reliable as possible. I do NOT want to have to be towed. My bus drove home to Alabama from Kentucky with no issues-- as people will often say. But the reality is there needed to be a lot of things done. All new brake calipers, brake pads, all new rubber brake hoses, three or four hoses around the fuel system that were darn expensive, a rebuilt brake booster that was leaking-- and a leak between the rear main seal carrier and the engine block-- bolts were loose. New clutch, pressure plate, throw out bearing, and flywheel(deep grooves). Driveshaft carrier bearing-- the rubber had deteriorated. Driver seat pedestal was broken, and the drivers seat needed reupholstered. My point is this has been a long fun process, and I have not even started the conversion. (well-- it's gutted, and the floor painted...)

The video by Chuck just made me question my previous choice of ratio. My calculation of the percentage change sort of answered my own question-- I was within 1% of the change that he made. Also-- it is sort of apples and oranges-- with the automatic versus a manual-- my goal is to be able to cruise at 60MPH on long stretches, and be able to climb minor grades without shifting-- so I will probably just stick with the 4.10.

One interesting thing I noticed was that the spacing of ratios-- 3.73, 3.91.and 4.10 each result in an approximately 100 engine RPM change at 60 MPH.

I love driving the thing. It's a hoot!

[Omnibot2000]

Leave it. You made a call, it works, run it.

I've seen some of chucks videos, he has some good information but he contradicts himself to much for my liking.

You are talking about 2 different transmissions. An automatic converter makes torque at the expense of speed. Hence the name. You can go with taller gears and the engine will multiple torque through the converter to get a tall geared bus moving.

With yours being a standard with to tall of a final gear, while you can select the appropriate gear like an automatic, you loose that torque multiplication in turn causing acceleration issues.

[PorchDog]

4.10 it is. Thanks guys for helping me think through this.

[EastCoastCB]

4.10 is good- no sense in changing it up.

[Flying I 365]

In your application I would stick with the 4.10 gears. Though I would be curious as to what ratios you have in the transmission. For allround use of your bus, 2150 at 60mph is a good speed setup with the manual. Continuous Interstate usage would deem a lower gearing but if it will be primarily a city/highway cruiser then the current 4.10 gearing is sufficient.

I myself was thinking about changing rear end gears on my CE200 from the 6.17 gears equipped to something lower like 5.57 or 4.88, given the VT365 in it. My reasoning was primarily to bring the RPMs on the engine down so the VT365 isn’t screaming along at 60mph. With the current 6.17 gears, 60mph puts me at 2200 RPM. Though I did see a few CE200s with the VT365 have different gearing to where the engine at 60mph was screaming along just about at redline.

[Omnibot2000]

Originally Posted by Flying I 365

In your application I would stick with the 4.10 gears. Though I would be curious as to what ratios you have in the transmission. For allround use of your bus, 2150 at 60mph is a good speed setup with the manual. Continuous Interstate usage would deem a lower gearing but if it will be primarily a city/highway cruiser then the current 4.10 gearing is sufficient.

I myself was thinking about changing rear end gears on my CE200 from the 6.17 gears equipped to something lower like 5.57 or 4.88, given the VT365 in it. My reasoning was primarily to bring the RPMs on the engine down so the VT365 isn’t screaming along at 60mph. With the current 6.17 gears, 60mph puts me at 2200 RPM. Though I did see a few CE200s with the VT365 have different gearing to where the engine at 60mph was screaming along just about at redline.

2200RPM is not that bad. Those VT365's I believe have a 3300RPM red line I thought. My T444e with the 5 speed runs just over 2000rpm at 60MPH. At 100kph speed limit where I am its 2100rpm if not less. I think that's 63MPH. I'm going to ditch the 10 inch tires, get the 11's for next summer and live with it. I would imagine your engine would be not as noisy with the taller gears.

[Flying I 365]

Originally Posted by Omnibot2000

2200RPM is not that bad. Those VT365's I believe have a 3300RPM red line I thought. My T444e with the 5 speed runs just over 2000rpm at 60MPH. At 100kph speed limit where I am its 2100rpm if not less. I think that's 63MPH. I'm going to ditch the 10 inch tires, get the 11's for next summer and live with it. I would imagine your engine would be not as noisy with the taller gears.

I think the VT365 has a redline around 2500 or 2600 (at least that’s what the build sheet states for mine) so the engine is just about at the redline for highway cruising, hence why I wanted to lower the rear end gearing from 6.17 down to 5.57 or 4.88 to get the engine lower in the RPM range. I wanted to do that anyway to also bring the engine temperature down so I don’t want to overheat the engine. Sabrina (the bus) is quite old (built in 2005) and has dealt with 14 years (if not more) of school service. She’s not exactly a “spring chicken”

100kmh is the same as 62mph for reference.

[s2mikon]

I have to agree with what Booyah said, 4.10 gears and a super 10 transmission would be the cats hind end. You can drive it as a wide ratio 5 speed or a close ratio 10 speed or any combination you need. Lower first gear and taller top gear.

[Omnibot2000]

Originally Posted by Flying I 365

I think the VT365 has a redline around 2500 or 2600 (at least that’s what the build sheet states for mine) so the engine is just about at the redline for highway cruising, hence why I wanted to lower the rear end gearing from 6.17 down to 5.57 or 4.88 to get the engine lower in the RPM range. I wanted to do that anyway to also bring the engine temperature down so I don’t want to overheat the engine. Sabrina (the bus) is quite old (built in 2005) and has dealt with 14 years (if not more) of school service. She’s not exactly a “spring chicken”

100kmh is the same as 62mph for reference.

2600 RPM is your rated hp I believe. Example. 195 hp@2600 rpm. Governed if I remember is 2800 RPM. However redline is higher. On the 6.0 powerstroke. Governed it around 4000. The 3300 RPM figure I gave is the rated hp for the powerstroke. 325 up at 3300 RPM.

[Flying I 365]

Originally Posted by Omnibot2000

2600 RPM is your rated hp I believe. Example. 195 hp@2600 rpm. Governed if I remember is 2800 RPM. However redline is higher. On the 6.0 powerstroke. Governed it around 4000. The 3300 RPM figure I gave is the rated hp for the powerstroke. 325 up at 3300 RPM.

Engine tag on the passenger side valve cover has my engine as an A200 variant and the tag reads 200bhp @ 2600rpm and 520lb-ft @ 1400. I don’t think the VT365 could rev that high to 4,000. Governed might be at 2800 (no idea why the sheet would say 2600 then) so I think you’re right on that one. I know that firsthand experience the engine struggles to keep up at highway speeds. Once at highway speeds (2,000 and above in 5th gear final drive) the engine is screaming and struggles to keep speed (and it doesn’t even hit the 60mph governor), and the engine temperature starts climbing to the 200 degree mark (doesn’t go beyond that, but still)

[Omnibot2000]

Originally Posted by Flying I 365

Engine tag on the passenger side valve cover has my engine as an A200 variant and the tag reads 200bhp @ 2600rpm and 520lb-ft @ 1400. I don’t think the VT365 could rev that high to 4,000. Governed might be at 2800 (no idea why the sheet would say 2600 then) so I think you’re right on that one. I know that firsthand experience the engine struggles to keep up at highway speeds. Once at highway speeds (2,000 and above in 5th gear final drive) the engine is screaming and struggles to keep speed (and it doesn’t even hit the 60mph governor), and the engine temperature starts climbing to the 200 degree mark (doesn’t go beyond that, but still)

Sounds like your Turbo veins are stuck to me. If it's struggling at 60 mph with high engine temps and a slug in the city, I don't think your making the boost required to make your HP. It's not a really big job. Pull the turbo and remove the clamp on the exhaust housing. Clean the uni ring and free up the veins. They say if there is deep rust pitting it needs to be replaced. I never have and works good. Might loose a tiny bit of efficeincy. I personally spray every thing down with graphite lube and reassemble.

You have a boost gauge?

[Omnibot2000]

Originally Posted by Flying I 365

Engine tag on the passenger side valve cover has my engine as an A200 variant and the tag reads 200bhp @ 2600rpm and 520lb-ft @ 1400. I don’t think the VT365 could rev that high to 4,000. Governed might be at 2800 (no idea why the sheet would say 2600 then) so I think you’re right on that one. I know that firsthand experience the engine struggles to keep up at highway speeds. Once at highway speeds (2,000 and above in 5th gear final drive) the engine is screaming and struggles to keep speed (and it doesn’t even hit the 60mph governor), and the engine temperature starts climbing to the 200 degree mark (doesn’t go beyond that, but still)

Just got back from my trip. I know we have different engines but mine is rated at 195hp and I was wrong on the cruising RPM. I'm running about 2200RPM at 100kph. Regardless. If I step on the fuel at that speed I will easily accelerate with no issues. Engine running at 180 degree.

Here is a link for prechecks for low power that you list. It should be similar to your engine

https://www.powerstrokehub.com/servi...vgt-clean.html

[Hooker]

Originally Posted by PorchDog

Well, I have already been down this path, but watching Check Cassidy on YouTube swap his rear end has me scratching my head again.

My bus is short, 6 windows, and has a DT466 rated at 175 HP and 430 Ft Lbs of Torque. Lowest horsepower of all the DT 466 variants-- as far as I know.

It has a manual 5 speed transmission, which is direct in fifth, and a granny low gear. It came with a 4.78 axle from the factory. I have swapped in a 4.10 which puts me at 2150 RPM at 60 MPH.

Chuck has a midsize bus with a mechanical DT466-- I am sure it is higher horsepower than mine-- and an AT545. On his YouTube show he has swapped in a 3.73. So-- with direct drive (says he intends to install an MT643 in the future) that will put his 60 MPH RPM at 1960. (Assuming he has 265/75R22.5 tires like mine...)

So-- my swap from a 4.78 to a 4.10 is a 14% change.
Chuck's swap is from a 4.44 to 3.73 which is a 15% change.

Should I have gone lower-- maybe 3.91, or even 3.73 like Chuck?

JMO, but Chuck was way wrong to swap to a 3.73 in a school bus, especially with 22.5 tires. Sure he'll get more mph out of it on flat land with the wind behind him, and he has a big roof raise too, that thing isn't going to pick up any speed at all on hill and against the wind. In fact, he's going to lose speed because he denutted the torque multiplication to the wheels on the ground and the engine is now going to bog and not have enough torque to pull a wet string out of a goats butt let alone climb a hill or drive into a headwind. He should have kept the 4.44's and being he intends to upgrade to the MT643, just upgrade to the 2000,2500 or MD3060 using a stand alone controller and have OD with converter lock up. Keep those low gears, you'll need them. Best bang for the buck IMO, is upgrade your transmission even if it does require an expensive stand alone controller or a retune of your current ECM. Just my 2 cents for whatever that's worth.

[Flying I 365]

Originally Posted by Omnibot2000

Sounds like your Turbo veins are stuck to me. If it's struggling at 60 mph with high engine temps and a slug in the city, I don't think your making the boost required to make your HP. It's not a really big job. Pull the turbo and remove the clamp on the exhaust housing. Clean the uni ring and free up the veins. They say if there is deep rust pitting it needs to be replaced. I never have and works good. Might loose a tiny bit of efficeincy. I personally spray every thing down with graphite lube and reassemble.

You have a boost gauge?

Apologies for the late reply. You may be onto something with the stuck vanes. The bus (being essentially bone stock beyond the options FS had ordered for Illinois) doesn’t have a boost gauge equipped. Instruments onboard only show RPM, MPH, Water Temp, Oil pressure, Battery Volts, Amps, and Fuel. The stuck vanes might also explain some of the issue of the bus smoking a bit on acceleration. The turbo I know hasn’t been off (at least not in a good long while) so there may be carbon on the vanes that inhibit some of the movement.

Originally Posted by Omnibot2000

Just got back from my trip. I know we have different engines but mine is rated at 195hp and I was wrong on the cruising RPM. I'm running about 2200RPM at 100kph. Regardless. If I step on the fuel at that speed I will easily accelerate with no issues. Engine running at 180 degree.

Here is a link for prechecks for low power that you list. It should be similar to your engine

https://www.powerstrokehub.com/servi...vgt-clean.html

Mine being the VT365, it isn’t exactly as reliable as the T444E. The engine does accelerate up to the 55mph mark with little difficulty (though it is sluggish on accelerating)

[La Camioneta]

Originally Posted by Hooker

JMO, but Chuck was way wrong to swap to a 3.73 in a school bus, especially with 22.5 tires. Sure he'll get more mph out of it on flat land with the wind behind him, and he has a big roof raise too, that thing isn't going to pick up any speed at all on hill and against the wind. In fact, he's going to lose speed because he denutted the torque multiplication to the wheels on the ground and the engine is now going to bog and not have enough torque to pull a wet string out of a goats butt let alone climb a hill or drive into a headwind. He should have kept the 4.44's and being he intends to upgrade to the MT643, just upgrade to the 2000,2500 or MD3060 using a stand alone controller and have OD with converter lock up. Keep those low gears, you'll need them. Best bang for the buck IMO, is upgrade your transmission even if it does require an expensive stand alone controller or a retune of your current ECM. Just my 2 cents for whatever that's worth.

Agree 1000%
Swapped 545 to 5 speed Allison and it drives like an entirely different bus.

Use a gear ratio chart for your application to see where the rpms are at speed. Or take your current top speed at top rpm and divide by .71 for your potential top speed in gear 5. 60mph in 1:1 = 84mph in .71:1

IMO gear 6 is unnecessary unless you're over 400hp as there isn't enough horsepower to push the bus at high speeds. https://www.rvtechlibrary.com/engine...erformance.pdf Is a great tutorial on rv power and aerodynamics.

My B700 with 5.9 12v with timing and fuel plate mods now keeps up with or passes semis on the interstate and can do over 80 on the flats with good EGTs.
You might luck into the entire swap combo from a scrapped VT365 bus, would be some minor tuning required but much less work than a 12 valve swap.

[Hooker]

Originally Posted by La Camioneta

Agree 1000%
Swapped 545 to 5 speed Allison and it drives like an entirely different bus.

Use a gear ratio chart for your application to see where the rpms are at speed. Or take your current top speed at top rpm and divide by .71 for your potential top speed in gear 5. 60mph in 1:1 = 84mph in .71:1

IMO gear 6 is unnecessary unless you're over 400hp as there isn't enough horsepower to push the bus at high speeds. https://www.rvtechlibrary.com/engine...erformance.pdf Is a great tutorial on rv power and aerodynamics.

My B700 with 5.9 12v with timing and fuel plate mods now keeps up with or passes semis on the interstate and can do over 80 on the flats with good EGTs.
You might luck into the entire swap combo from a scrapped VT365 bus, would be some minor tuning required but much less work than a 12 valve swap.

You totally get it. I'm with you on the 6th gear too. And what can happen with all the "gear huntin" back and forth,5th 6th, 5th 6th up and down, converter unlock up and down, etc, that's all wear BS. Just put in OD, and cruise and it stay right there in the 5th with the converter locked up and your golden. Only way I'd want 6th would be if my rear gears were into the 6's and that's just awfully low geared and not necessary at all in any skoolie or bus. But lower RPMS are NOT always better. What matters is keeping your RPMS in that sweet spot for mpg and max performance. You get to low in the rpm band, you can be straining the engine making it work harder and there goes your mpg.