Rebuild the Clutch or put a rebuilt MT644 in?

[Fredward]

OK guys/gals you've heard me nashing my teeth over this topic this fall already. In my MC-5 the clutch is in need of work and appears to be about to the end of its adjustment (might still go 20,000 miles; you never know). But the knob is about two turns from the end of its travel. Seeing as I'll have to take the clutch out of it eventually maybe I should take the plunge and put an auto in it. I've got jacks and blocks and lots of concrete so I should be able to jack the bus high enough do it without pulling the engine.

The question in my mind is: with a rebuilt clutch and linkage, etc. how much easier will it be to drive than it is now? I've got it figured out how to drive it, without even clutching anymore but nobody else seems to be able to drive it. Is it hard to drive and shift because the clutch is about shot or because its a four speed spicer? My local bus garage confirms that the clutch is going to need work sooner or later. THey think its hard to drive. I inspected and removed the air assist cylinder and it seems to work but not sure there is enough travel in the linkage for it to get full mechanical advantage. Maybe a rebuilt clutch would work better because the air assist would kick in and the linkage geometry would be correct.

It looks like I can find a transmission here locally or in MAK so all I'd have to buy would be the adapter kit flex plate or whatever, and put in a cooler over on the curb side where the compressor used to sit. Of course get a new drive shaft built. What other considerations are there? How do you mate up an auto trans to an 871 mechanical engine? If the tranny has pushbutton control does that mean it needs a DDEC engine? How does one of these transmissions sense throttle position? Would the tranny and accessories cost more than $5,000.00? Our bus is a real nice utilitarian conversion; not fancy and I know an MC5 isn't worth investing much in. We'll run it a few more seasons but then will be looking for an MC9 with two bunks on one side.

Winter's cold here in Minnesota and it fits in my shop so we've got three or four months to do the project. We've got lots of trips planned for the warmer months so I'd like to figure out something. Either way fixing it or converting it seems like a fairly doable project?
Fred

[Tenor]

I don't want to sound discouraging or negative, but maybe you should ask yourself "how serious am I about getting another bus?"  The work would be serious.  Maybe best to leave it alone and invest the money in a new bus.  $5,000 goes a long way in getting a new bus especially if you plan to sell the old one (5k plus income from old bus).  If you LOVE what you have, go for the repairs/modifications.

Glenn

[makemineatwostroke]

Fredward, you may can find a 6v92 and a 740 takeout for less than the parts to do a 644 and its not that hard of a swap ,set the engine on around 300 hp or less and you will not have that much of a heating problem.Not trying to start a debate just 1 more option for you but you are going to lose some fuel mileage with any automatic and there is always a market for a good 8v71

[Tom Y]

Fred, If I were doing a clutch I would pull the motor. With the slide its not a bad job. If you go auto stay with a non electronic trans, much easier. I but a cable shift in mine. I don't know much but I think 644 is only going to be non electronic. If you go auto you can call me about mine if I can help.  Tom Y

[Ncbob]

Fred, you and I have compared notes on our buses and problems from time to time and since I've been where you are I feel qualified to offer my .02.

When I picked up my bus the clutch was known to be a 'slipper' but I nursed it home. At the first opportunity I sent it to a reliable mechanic to have the engine pulled and a clutch installed.  Two problems were uncovered. A) the clowns who replaced the clutch previously didn't install the blue springs in the pressure plate...yellow is too weak. B) the Transmission input shaft was seriously scored necessitating replacement and had lots of shake rattle and roll....it can be replaced without tearing the whole tranny apart.

With that solved I asked him to install Jakes.  I don't know about Jakes with an auto...but with the Spicer it gives me about a half a hole more on the downhill runs. Meaning instead of having to descend a 7% grade in 2nd...I can do it in 3rd with the Jakes...or in 2nd and no brakes at all.

Me?  I like to stir well while driving and as long as that left puppy is able...you won't find me shiftless!

Bob

[Lin]

I am still giving my Spicer time to get used to me and then see if we get along.  I have also looked into a change to automatic.  Someone I spoke to today said that a ZF 590 would work well in the MC-5a with the 8v71.  He also said that, if one wanted to changed engines also, the ZF and a Cummins L10 are a good combo.  They claim that even though the horsepower is less, the increased torque will let you drive higher gears giving better speed and mileage.  Sounds good anyway.

[Fredward]

All good thoughts. I figure the bus is worth $20,000.00. To find another bus worth upgrading to it would be a lot more than $5,000.00 more than this one is worth. Plus who knows how long it would take to sell it. I do have access to an Eagle 05 seated bus with 692/740 that probably wouldn't cost much. My 871 runs so nice and the mechanicals on the bus otherwise are really good so I kind of hate to buy a bunch of someone else's troubles. On a limited budget right now.

Bob, how's that clutch pedal work now that you've gotten it all rebuilt? How much force does it take to disengage?

I still haven't heard anybody say that the spicer with a properly adjusted clutch is a breeze to drive; anybody can drive it. Like I said, I can drive anything growing up on the farm, but nobody else can drive it. Which means it will be harder to sell-won't it?

One answer would be to just replace the clutch and then work on selling it. I'm not just looking for a project; I would be doing the work to save money and end up with a more driveable/sellable unit. I believe in doing just as much as I have to. Not any more.

[TomC]

Of all the swaps listed here, changing to the MT644 will be the easiest.  Mind you the 8V-71N with 65 injectors will be at the top of the torque limited for that transmission, so if you want to turbo the 8V-71 later, you will be able to do the turboing, just not increase the injector size (this is sometimes called a smoke turbo, to cut down smoke at higher altitudes and for a bit better power).  You'll have to change the bell housing, flywheel, transmission mounts, drive shaft, add a trans cooler, add the shifter with throttle sensor.  If it were me, I'd do it and turbo the engine-I can tell you from experience that turboing the 8V-71 REALLY wakes it up.
If you have a bit more money and time, changing to the 6V-92TA and HT740 will make a real sports car out of the 5.  But it is a serious change-you have to get bigger radiators on top of changing all mounts and such.  Good Luck, TomC

[Fredward]

Tom,
Do you know which 600 series Allison is the right one for me? 644? 645? As metioned earlier in the thread, should it be electrically controlled or cable controlled? What do you think the adapter parts and tranny would cost? 

Did you have a shop turbo your 871? I don't think there is room in the 5a engine compartment to fit a turbo. But what would it cost in 2007 dollars to have someone turbo one?

The easy thing to do is just put a clutch in it I suppose but it doesn't seem like that much more of a project to put an auto in there.

Thanks for sharing your expertise.

Fred

[tekebird]

Problem with a Turbo on a 5 if you can fit it is the lack of room to put larger radiators.

[makemineatwostroke]

Fred, I did the 644 change over on my 5 in 1990 and the adapter rings, flex plate, new drive shaft,stone benett shifter ,and machine work the 1990 prices were as the following

adapter rings
flex plate
new drive shaft

   1928.57 dollars    Arizona Transmission  1-888-395-1392 ( KIM) 

644  rebuilt Allision transmission
    1500.00 dollars core charge (did not have a core)
    2000.00 dollars transmission charge
    1238.00 dollars New Stone Bennett shifter
      275.00 dollars for machine work on spacer
      410.00 dollars freight
      215.00 dollars misc. oil and bolts,filters (etc.)
      412.00 dollars for cooler, hoses and fan

    7978.57 total with no labor this is the invoices that I have

If you can shop around and buy a used 644 tranny with out the core charge and a used Bennett shifter you could probably do it for 5000.00 dollars.I help a friend install a 6v92 and a 740 in his 5 several years ago it wasn't that hard to do, he installed differnet size belt drives on the fan blower and crankshaft drive never knew of any heating problems for him. Good luck on what ever you do.P.S the sad part i traded this bus in on a Bluebird Conversion 1 year later (dumbest thing i ever did) well almost

[Fredward]

Wow. Thanks for the reality check! A new clutch looks pretty attractive now. $5K I could handle but not more than that.
Thanks.

[TomCat]

If a MT643 shifter will work for you, you can save $1000 right off the top.
http://cgi.ebay.com/ebaymotors/Automatic-control-shifter-for-Allison-MT643_W0QQcmdZViewItemQQ_trksidZp1638Q2em118QQcategoryZ50466QQihZ005QQitemZ150018410260QQrdZ1QQsspagenameZWD1V

Jay
87 SaftLiner

[Lin]

Most of these parts are pretty reasonable at places like Nimco.  I think they sell the MT644 for about $2000. and can supply all other parts.  I think they say that one of the only parts to get new in the shifter cable.  I am considering the same switch and would seriously consider it at under $5000.  But I will not do it myself, so it remains to be seen what will happen.  Maybe in the meantime I will come to realize that a Spicer holds the secret of true happiness.