changing gear ratios

[Kubla]

18 bolts is to keep the gasket from leaking, have to have the bolts close enough together on the flange to keep it from warping under load

[Brewerbob]

Originally Posted by Kubla

18 bolts is to keep the gasket from leaking, have to have the bolts close enough together on the flange to keep it from warping under load

Yeah I know. Oil pans too. Doesn't mean I have to like it tho.

[SCARECROW]

To Anyone, please supply the RESULTS;
Of the gears You started with.
Of the gears You changed to.
Your THOUGHTS of the results of Your
gear change. RPM at a given speed in
say fourth gear. Would like to know
the "meat" of the components and if
you are "satisfied. Thank You all
Sincerely, SCARECROW.

[cowlitzcoach]

Our church bus is a 1995 Thomas Saf-T-Liner MVP EF that has a 5.9L and AT540.

Finding a serviceable used gear set that would fit our pumpkin was a bit of a challenge. Not all gear sets will fit all pumpkins. Among other things to be concerned about the splines on the axles have to be able to slip into the new gear set.

We went from about 5.65 to about 4.25.

All in it cost us about $2K to have it all done--parts and labor.

Top speed went from 50-55 to 70-75. It will cruise very easily now at 60-65 without the engine screaming at you.

It used to be almost against the governor in 3rd gear at 40 MPH. Now you can hit 40 MPH in second gear.

With a full load on the bus acceleration is a bit leisurely. Most of the drivers prefer to be able to cruise at highway speed with pedal left than to cruise the highway below highway speed with your foot flat on the floor.

[SCARECROW]

Dear Cowlitz, Thank You for the
reply. What would You say the
RPM is when under NORMAL
driveing, 3rd gear & speed also
4th gear & speed. Where is the
"sweet spot" torque of Your 5.9
Cummins engine. Thank You.
Sincerely, SCARECROW.

[cowlitzcoach]

60 MPH is about 2200 RPM in 4th gear.

35-40 MPH about 2200 RPM in 3rd gear.

[SCARECROW]

Dear Cowlitzcoach, Thank You for the reply. Perhaps
You may have been able to drop another ratio ? If
the torque pull begins around 1800 RPM? I don't
Know the torque curve of the Cummins. Maybe You
are satisfied at 2200 RPM? Thank you for the real
world knowledge.
Sincerely, SCARECROW.

[cowlitzcoach]

I would have appreciated a little lower numerically gear set to lower engine RPM's at speed. The problem we ran into was in order to go any faster it would have required changing the rear axle housing, axles, etc. On a bus with less than 14K miles that didn't make a lot of sense.

[SCARECROW]

Dear Cowlitzcoach, Thank You. maybe I miss read,
You really purchased a '95 with only 14K miles?
That had to be very lucky. Nice bus We do suppose.
Thank You for all Your assistance. Good luck on
the build.
Sincerely, Kathleen.

[cowlitzcoach]

Originally Posted by SCARECROW

Dear Cowlitzcoach, Thank You. maybe I miss read,
You really purchased a '95 with only 14K miles?
That had to be very lucky. Nice bus We do suppose.
Thank You for all Your assistance. Good luck on
the build.
Sincerely, Kathleen.

When the church purchased the bus it was 11-years old and had just over 10K miles.

When you consider the bus was purchased by a transit agency in AK and the bus was built in NC it is obvious that the bus was not used very much. So little in fact more than half the seats still were wrapped in their shipping plastic.

I think what happened is someone who didn't know buses purchased a bus without really knowing anything about buses. Anyone who has ever driven a Type 'D' FE bus in the ice and snow know how impossible they are to drive when the roads get slick. They also didn't realize how physically large a Type 'D' FE bus is even though it isn't a long bus.

As a consequence the bus got parked and was never used. It was then sent to the Thomas dealer in Portland, OR where they tried to sell it for over six years where we were able to purchase it.

Part of the reason why it took so long to sell was the transit agency wanted near new price for a really oddly spe'c'ed bus. I am sure that if it had adult passenger seating it would have sold sooner. But school bus seating in a non-school bus is not a real positive when selling in the used market if you are trying to sell the bus to a senior center or church.

[SCARECROW]

Dear Kotflb, We realize this is
a old discussion. We are curious as
how the "gear change" worked out
if You did it. Thank You.
Sincerely, SCARECROW.

[Sundowner]

This is the formula I used when figuring my gearing.

With 1 to 1 tranny gear ratio in high gear:

RPM x 60 (eg. 2600 rpm x 60 =156000
________ = MPH
R x M ( R= 4.11 x M= 486 = 1997.46

156000 divided by 1997.46 = 78.09 mph at 2600 rpm

With different tranny ratio ( eg. .73 overdrive )

RPM divided by tranny ratio x 60
____________________________ = MPH
R x M

R = rearend ratio
M = tire revolutions per mile

[Tango]

That math is over my head. Does it take into account the tire diameter? (not sure what R & M are?)

[SCARECROW]

Dear Sundowner, Thank You for
Your reply. The math is somewhat
confusing, but I believe My helper
may understand it better. Did You
accomplish some satisfactory
"gear change" with Your project ?
Thank You again for Your help. We
sure do find this difficult to under-
stand for some reason. Wonder
what the engineers are thinking.
Sincerely, SCARECROW.

[SCARECROW]

Dear Mr. Tango, We saw a video
about Your bus awhile back on
youtube. What happen on the
driveline of Your bus. Has it been
what You figured on ? Thanks.
Sincerely, SCARECROW.

[Tango]

Hmmmm...no videos of my rig that I am aware of. Must be someone else. Have not run mine over the road yet but did run all the numbers through an online calculator and then confirmed them with a driveline tech so I hope it is very close to what has been planned.

The gear/rpm/speed calculator is at the bottom of the page below...

Engine RPM Calculator

[SCARECROW]

Dear Mr. Tango, a person with the name
of ........- d redmond - showed a interview
with You, in Your garage, on February of
2016. We do really believe the '46 bus
and garage is Your. Perhaps We are not
correct but My Friend thinks it's You. Maybe
You could "set us straight". Thank You for
the reply.