Cat c7 speed

[Peterjk]

Hey everyone, first post.
We just purchased a 2005 Thomas HDX 25 seater with a C7 and Allison. . Does anyone here own one and what can we expect to be the cruising speed, 55? I haven't taken delivery yet, we're having a mechanic go thru the engine first.
Is it worth regearing the rear end.

[EastCoastCB]

Cruising speed is 100% determined by the rear axle ratio which isn't a standard. Could be anywhere from 3.27 to 6.50. Also there is an option to limit the top speed in the ECU.

[Peterjk]

Thanks, I'll get the ratio, it's stock most likely. So to rephrase, given a stock rear end and no governor or Ecu limitation. I'm assuming that limitation can be removed from the Ecu or at least set at a more appropriate level to highway cruising?

[EastCoastCB]

Originally Posted by Peterjk

Thanks, I'll get the ratio, it's stock most likely. So to rephrase, given a stock rear end and no governor or Ecu limitation. I'm assuming that limitation can be removed from the Ecu or at least set at a more appropriate level to highway cruising?

what I'm saying is there's not a "stock" ratio. My bus came from the bus yard with a 3.27. Its the only one like that I've ever heard of. Every bus is built to order. IF you call the manufacturer with the VIN they can likely tell you what it has. Or there's usually a tag on the axle housing.
Changing the electronic speed limit is easy if you have the software and the connector.

Seems most buses I've had came set to go about 55-65 tops. I got lucky mine will do 80+ and it came that way.

[Peterjk]

Perfect, that gets me started , thanks!!
Peter

[concrete]

Another factor in top speed is transmission. Which Allison do you have? If it’s a 4-speed (AT545 or MT643) then final ratio is standard 1:1. If you have the MD3060, it is a 6-speed double overdrive. 5th is .75:1, 6th is .65:1, granting 35% more speed potential (or lower rpm’s at a given speed). Unfortunately these trannies are often electronically limited to 5 speeds, but 6th gear can be unlocked.
The dealer can use your VIN to tell you what tranny you have. Or your mechanic can crawl under and take a look; there is a tag on the tranny that identifies the model.

[Peterjk]

Thanks concrete, I'm still on vacation so cell range is sometimes weak. It's a 5 speed for sure, I explained the above posts to the bus sales place I'm buying the bus from as they have mechanics, they said they don't have the Allison software needed to unlock 6th. Any ideas how to unlock 6th?

[concrete]

There is an extensive thread on this subject.

https://www.skoolie.net/forums/f10/allison-md3060-unlock-tutorial-21661-20.html

Unlocking 6th is a paperwork dance between you, the vehicle manufacturer (via a dealer) and Allison transmissions.
Start with your bus manufacturer’s local dealer. Tell them you want to unlock 6th and they should produce some paperwork for you to fill out. The Bus dealer submits the request for 6th to the bus manufacturer who has to approve; this approval and request for 6th gear is sent to Allison by the dealer/manufacturer; Allison releases the necessary programming to a local Allison dealer (some bus/truck dealers are also Allison dealers); the local Allison dealer has you bring in your bus and installs the new software. Boom. 6 gears.
This process generally runs between $150-$350, based primarily on how much of your money the dealer wants today. .

(If your Bus dealer says you have to go directly to Allison, they’re wrong. Allison IS the one to supply the new programming, but they will ONLY do so WITH APPROVAL FROM THE VEHICLE MANUFACTURER! Liability issues no doubt. Calmly explain this to your bus dealer’s service rep. If he won’t budge, find a better dealer/service center.)

Thomas seems very cooperative in allowing 6th, but does so in batches a few times a year; so start the process now or you may miss this round and be delayed some months
IH/Navistar apparently only approves vehicles made in the last 10years (counting from the moment you ask them).
BB has been uncooperative for most on this forum, but it may depend on bus model

Since you have a Thomas I would recommend getting the ball rolling now...

Best wishes!!

[cadillackid]

or use the 3rd party to do it like brokedown and others have done.. a few hundred bucks and a few minutes and done is what it soumnded like for those guys..

[concrete]

Originally Posted by cadillackid

or use the 3rd party to do it like brokedown and others have done.. a few hundred bucks and a few minutes and done is what it soumnded like for those guys..

Come on, Chris... that’s so quick and easy

[Ronnie]

Yes it is. Brokedown was at the Skoolie Swarm, running around with his laptop unlocking 6th gear and resetting governors.

[cadillackid]

brokedown's guy was awesome!!

[FreebirdTheBus]

By doing this, what is the benefit vs. time and effort? Worthwhile to get it unlocked?

[cadillackid]

depends on what you want.. it takes the final trans ratio from 0.75 and to 0.65 so even if you dont want to go faster you can lower your engine RPM for quieter and possibly more efficient cruising... and of course it does increase top speed if you are geared low in the rear it can mean thye difference between going well slower than you want and being at a comfortable speed..



-Christopher

[CHEESE_WAGON]

Originally Posted by concrete

There is an extensive thread on this subject.

https://www.skoolie.net/forums/f10/a...-21661-20.html

Not to sound like a Nazi, folks, but links don't create themselves, ya gotta highlight it, click the icon of a chain link and globe, then paste it in the window that pops up... NO WORRY, PEDRO FEEX!

[concrete]

Originally Posted by CHEESE_WAGON

Not to sound like a Nazi, folks, but links don't create themselves, ya gotta highlight it, click the icon of a chain link and globe, then paste it in the window that pops up... NO WORRY, PEDRO FEEX!

Thanks, I didn’t know.
I pour concrete for a living, and am daft with this computer stuff. So thanks for helping out!

Now if only I remember this in 3 months when I want to include a link to something...