Changing Gears

[rdbishop]

Has anyone changed the gears in their bus rear end. I wanted to go to 336 from 370 and have been told it can't be done. They said I would have to change the whole diff. Need some input please.

Richard

[edroelle]

I did replace my gears, but did not change the ratio.  During the investigation, I found that both those gears would fit that casting.  There should be a tag on the axle rear side right side.  Get that number and call ROCKWELL/MERITOR, 888-725-9355, (possibly Ext. 5, Bill or Mike in 2001).  They should be able to confirm and give you ID numbers.

I bought my rebuilt gear assembly from Valley Truck in Michigan, 616-241-5431.  In 2001 it cost $1350.

Ed Roelle
Flint, MI

[TomC]

Most T drive differentials are just truck rear ends rotated 180 degrees around.  I know Meritor (old Rockwell) makes ratios to 2.65 for the 23,000lb axle.  Good Luck, TomC

[luvrbus]

Richard, have you tried Sam Cayor the MCI guy in Kansas or Ed at Jefferson in OKC OK Jefferson sales parts for buses other than Eagles.I would do like ED and just get the assembly most of the time it cheaper and you have it out already to change the gears and bearings

[luvrbus]

Richard, have you had any luck on your gear change yet

[rdbishop]

Hi luvrbus,

No luck as of yet. spent all day today calling and discussing options. I found out no other gears will fit, so I can have this one repaired and have what I have, or I'll have to change to a eaton with 336 truck rear end. That gonna take a lot of cutting and welding, but I've just about decided to do it. Tomorrow I have to find the rear end and try to get it altogether by this weekend so I can go to the TEXAS ROUNDUP!!

Richard

[buswarrior]

For the novices, when Tom says "rotated 180 degrees around, he means rolled over, upside down, not side to side.

The right wheel on the truck has to stay the right wheel on the bus, only point the yoke backwards....

Otherwise, your bus will go backwards when you put it in drive!

There are a number of busnuts on here who have made modifications and rolled a truck axle over for their bus.

happy coaching!
buswarrior

[rdbishop]

buswarrior,

I knew about the flip over. I was just wondering if there was anything special I needed to do with the cutting and welding of the air suspension to the truck axle, and or the brakes. I have a mc-7 that weighs 35000 lbs fully loaded so I wanted to get an axle at least 38000 lbs.  I'll start calling in about an hour so I can get it done...

Richard

[RJ]

I have a mc-7 that weighs 35000 lbs fully loaded so I wanted to get an axle at least 38000 lbs.

Richard -

You're going to have a real problem trying to find a 38,000 lb rated rear axle.  Most are in the 20K - 25K range.

Granted, your MC-7 weighs in at nearly 35K, but remember, that's spread between three axles, not just on the drivers.

IIRC, the MCI data plate says 12K on the front, 20K on the drives, and 6K on the tags GAW, for a total GVW of 38K.  Since you're at 35K, sticking to a stock axle will be fine - it still leaves you with 3K for "stuff".  A 23K axle would work, too, but anything beyond that would be overkill.

It's entirely possible that MCI changed axle suppliers when they started offering the 336 ratios. 

Have you checked with Caylor or Jefferson Bus?  They're the closest to you.  Luke might have what you're looking for, also, 1-888-262-2434.

Anyway you look at it, I'd suggest you NOT rush this project just to make the Texas Roundup.  There will be another rally somewhere, there usually is.  And you'd also be welcome if you took some other vehicle.  But to rush the job and maybe "forget" something, only to have the repair come apart on the road, well. . . 'nuff said.

FWIW & HTH. . .

[buswarrior]

On the topic of axle changing...

One of the weaknesses of our buses is getting stuck out on the lawn at a rally. All wheels are only just settled in a half inch, the soil is a little damp under the wheels, maybe the slightest of rise in the land in front of you to the roadway, then the peg-leg differential spins that one set of duals and then it's over.

Or the unexpected rain storm turns what appeared to be a solid base into a muddy quagmire.

Never mind a slight rise in a snow and ice covered parking lot for those of us with more northern operating ranges!

Yes, many of us lay boards out under the wheels as a defensive move, but we still have to negotiate the lawn between boards and the road.

The tractor trailer folks have locking differentials that make these adventures a complete non-event. Flick the air control as a matter of course, and drive out with all 4 duals turning as one.

Coupled with the tag unloading valve, a locking differential would be a very convenient functional upgrade.

So, is there a locking differential out there with the yoke centred in the housing that will withstand a busnut putting it upside down and still function and lube itself as intended?

I smell a tutorial in the making...

happy coaching!
buswarrior

[H3Jim]

Buswarrior - The scenario you have spoken of where the tires sink in just a little and there is just a little extra resistance and ypou ad a little spin from one set of wheels and you're done - that has happened to me more than once.  Positraction would be a great addition!

[Stan]

Maybe there is a reason the manufacturers call them 'highway coaches'.

[H3Jim]

That's true, althoguh it still might help in inclement weather too.  I'm sure its just a cost tradeoff issue.

[rayshound]

I am in the process of installing a series 60 with an Atec transmission in a Mci-8. I went to a truck rear end & suspension shop in Houston. This shop repairs HD truck rearends. They cut off tubes repair & replace etc.  I gave them my mci 8 banjo housing and a rearend out of a late model truck with a 2.69 ratio. They cut off the mounting flange for the center piece, welded it to the mci housing, found metric splined axle's to fit the new center chunk and modified my existing hubs to accept 8 bolt instead of 10 bolt axle flanges. So I basically have a mci housing with a meritor 2.69 center piece & axles with all the standard mci stuff, brakes, hubs etc. Looks normal & the axles are common & so is the center chunk. The mci housing is highly modified but done by pros with a warranty and was I believe around $1500. worth of machine work + the cost of the meritor rear end. Bus not complete yet but have all the drive train, wiring etc.  Ray

[TomC]

You can get either positraction, that has the clutches inside and works automatically, but I'd suggest using a manual lockup diff with the air switch on the dash.  Because of the distance from the drivers compartment to the rear axle, a electric over air solenoid could be used-much like your engine shut off, but in reverse.  You want a normally closed solenoid that opens when charged.  Good Luck, TomC