MC5

[artvonne]

Short answer - Maybe, but probably not.

Have we driven you crazy yet??   

  Nahhh, I was already crazy, lol. I think you have to be crazy to consider a Bus as private transportation.

  I assume the 6V92 over the 6V71, because the 6V71 is not so great, anemic, etc. ?

  This off setting the turbo on a 6V92, does this use standard Detroit pieces, or all custom made stuff?

  Are mci-8 radiators big enough to cool a -5 with a 6V92T?

  Thanks for answering all my dumb questions RJ, and everyone else as well, it means a lot.

[Fredward]

Art,
I have an MC-5A. I've pulled the 8V71 out; replaced the clutch; I've removed the dropbox to replace seals. Its all doable. The drop box project was a bugger because its cast iron full of gears and weighs about 200 pounds. Yes the engine is at an angle because the driveshaft shoots up over the drivers side top of the axle to the input of the dropbox. The axle faces forward as if the engine were up in front. Transmission options are the spicer or a 640 series Allison as long as you don't beat on it. Gearing on the spicer is really high; thats what I have. I think you'd like the automatic a lot better because of your driveway. Before you buy the coach you can check the oil in the rear end/drop box quite easily. If its got oil in it its probably OK. If it doesn't then you might be buying a case of troubles. I can tell you how to check that - real easy.

Regarding rust I don't think you have to worry about an MC-5 rusting and falling apart on the way to your favorite place to go. Rust around windows and back by the radiators is annoying but the wheels don't fall off. I guess the engine rails can be an issue but usually there is so much oil back there that the engines don't usually fall out of them. Its a great coach and the 35 ft length is kind of nice although I think turning radius on 7,8 9 is about the same; just a longer overhang front and rear.

If you pm me your email address I can send you pictures of the engine project and the drop box project or my phone number to discuss details.

Fred

[RJ]

Paul -

6V71 only pumps out 238 hp.  6V92TA can reliably put out 350.  Your choice!

Some plumbing for the off-set is stock DD parts, some custom.  Depends on where you put it.  Most that I've seen have been on the driver's side.

Best to go with the MC-9's optional 8V92 radiators.  Plenty of capacity in a 5.

For all this work to convert/upgrade, better to buy one already equipped.

FWIW & HTH. . .

[Barn Owl]

For all this work to convert/upgrade, better to buy one already equipped.

Unless there is something that makes that bus outstanding then RJ is right. Money holes and headaches come with owning a bus as is. Making big changes to one only compounds the issue. If a 5 with an auto is what you would really like, wait it out, and you will find one cheaper than you can make one. Be careful not to get tunnel vision, it might cause you to jump to early.

[artvonne]

For all this work to convert/upgrade, better to buy one already equipped.

  Where would the fun be in that?

  Really just trying to see what my options are.

[Gary '79 5C]

Fred,
When removing the dropbox, did you have a pit while doing this job ? Beyond the 200#, the box is sizable to remove. I looked at this and would have needed to remove the garage door opener drive/track to allow for the height the bus being jacked up to facilitate DB removal.

If you did this yourself, You da man ! I went to Luke & Bill for my DB rebuild.

[buswarrior]

Gotta save up for a set of those used hoists that grab each wheel, and then a set of jackstands...

for instance:

http://www.mohawklifts.com/wp/consumer/browse-lifts/mobile-column-lifts/mp_series/

Check with the garage supply company in your neighbourhood for good used trade-ins.

And they'll pick up your car too!

The easier you make doing maintenance, the more likely it will get done...

happy coaching!
buswarrior

[artvonne]

For all this work to convert/upgrade, better to buy one already equipped.

Unless there is something that makes that bus outstanding then RJ is right.

  Okay, heres the deal. A GMC probably wouldnt make it up here, and the upgrades to make it do it are exceeding expensive and kill any fuel economy it had. We can argue about fuel economy, but its important to me. That leaves MCI's and Eagles. I want to utilise the air ride to create a leveling system, so Eagles are out. That leaves MCI's. I am fairly confident a 7, 8, or 9 would crank up here easily with a 5 or 7 speed box, and they are easy to find as well as affordable, but I really dont want that huge of a Bus. Sure, extra room is nice, but so is passing truck stops, carrying 2 less tires, and being able to turn it around. So ive been looking for a -5.

  I dont know for sure if a -5 can crawl up here either. On paper it appears to have enough torque (4.25 or 4.30:1 in first/3.70:1 final drive, 700 foot pounds from the engine), but you can probably wipe with that paper for all its worth, proof is in the pudding. But these -5's arent exactly growing on trees either. The ones that you do see for sale are either very expensive with big power upgrades and nice conversion work, which I cant afford, or old originals like this that need some Bus Nut like me to try and make it go. I am simply looking for the simplest and most cost effective options to give it a bit more oomph if I need it. A gearbox with a lower first, perhaps a smog turbo, maybe even a shot of propane, are all reasonable options, but what if thats not enough and I really need lower gears? If the engine has to come out to swap gearboxes, and if a V6 would give me better gearbox options, then thats something I would consider. If I can get the Bus cheap enough, those options could make a lot of sense. 

[Barn Owl]

Ok, getting a better idea of what the plan is. How many miles on average will you be traveling a year?

[RJ]

Paul -

Just an FYI. . . The overall gear ratios for a stock GMC PD4106, 4107 or 4108 with the manual gearbox are as follows:

First = 10.39:1
Second = 6.73:1
Third = 4.03:1
Fourth = 3.33:1
Reverse = 8.86:1

The venerable 4104's ratios (with the stock rear axle) are:

1 = 12.87:1
2 = 8.33:1
3 = 4.99:1
4 = 4.125:1
R = 10.97:1

FWIW & HTH. . .

[artvonne]

Ok, getting a better idea of what the plan is. How many miles on average will you be traveling a year?

  As far as I can afford to?  A lot will depend on the future economy and fuel prices, but by the looks of the news lately, probably not as much as I would like to,  if it goes back up over $4 this summer. less so if it really goes over $5 next year. Alaska someday? That would be cool. Over a 12000 mile trip to Alaska, a 2 mpg improvement could save between $2500, to $3500 at $6 gallon.

[Fredward]

Gary -
I did it on the floor in my shop. removed the wheels; jacked up the bus about six inches; blocked it and we took the drop box out by rigging up a cable and attaching it to one of the bolts on the top of the case. Also rigged up a cradle to stabilize it on the floor jack from below. It was not easy. Re-installing it was not easy either but once we got it back into place one of my neighbors who is stronger than I gave it the final shove after we jacked it back into place.

Bus garages have a bracket they attach to a floor jack that bolts on to the drop box. That would have made it much easier.

Fred

[artvonne]

Paul -

Just an FYI. . . The overall gear ratios for a stock GMC PD4106, 4107 or 4108 with the manual gearbox are as follows:

  Am I correct in believing a MC5 has 4.25:1, or 4.30:1 first, and 3.70 final drive, giving 15.75:1, or 15.91, respectively, overall?

[RJ]

Paul -

Yes

[rv_safetyman]

Gearing and startability is an area that I have limited knowledge, so take my comments for what they may be worth.

When you look at truck gearing, the typical 10 speed has a low gear of between roughly 11-13:1.  When you combine that with something like a 3.73 rear end, you can see that the overall gearing is over 40:1.  That is for an over-the-road truck that often is operated at 80K.  When you start talking about what I think they call vocational gearing (think dump trucks) the gearing can double that value.

Yes, we are half that weight, but something like 16:1 overall gearing is pretty marginal in my opinion.

Paul, your driveway is extremely steep and it sounds like you don't have a place to get a run at it.  I really doubt that stock bus manual gearing will do the job.

I did some searching to find the link that Tom C often sites when startability issues come up, but I can't seem to find it.  However, I did find two threads that might be of interest (one is one you started):

http://www.busconversions.com/bbs/index.php?topic=17432.0

http://www.busconversions.com/bbs/index.php?topic=16525.0

Jim