clutch

[dreamweaver]

I'm in need of some advice. I have just drove down from Calgary Alberta to Yuma and have blown my clutch on my MC 7. Can anyone give me any advice on replacing it and where to find parts? Do I have to pull the motor or can I just move the tranny? I am in the foothills and can work on it right here since I will be here for a few months. Any advice would be appreciated, thanks Dave

[ol713]

Hi;
    I have gone thru two throw out bearings and both times the mechanic just slid the trans
    back. I also have an MC-7.  If you look in your manual in the trans section, It will show how
    to build a cradel that the trans will roll on.  When you say you have blown the trans,  what
    is the trans doing or not doing?
                                      Good luck,   Merle.

[TomC]

Merle- if you look closer, Dave said he blew the clutch.
Dave- Highly recommend that once you have the transmission moved back, you use only new quality name parts.  I would remove the flywheel and have it resurfaced.  New organic clutch lining (ceramic lasts longer, but is rough on engagement-you'll get alot of wear out of the organic), pressure plate, new throw out bearing, and also the pilot bearing.  Make sure all the clutch linkage is in good shape without alot of slop.  If you do a quality job, this should last many years of driving. 
Have you considered maybe changing the trans to a 7 speed overdrive?  If you have the four speed, you'll have one more top gear and two more gears on the lower end making the gear jumps closer with a lower 1st gear (that in itself will lengthen the life of the clutch).  Or- install a HT740 Allison automatic?  For about twice the cost of the clutch job, you could be sliding down the road without shifting!  And after 21 years of over the road truck driving 13 speeds, I thoroughly enjoy my automatic-plus it accelerates quite nicely from a start.  More importantly, it is ever so effortless starting on a hill-that's probably how you fried your clutch in the first place!  Good Luck, TomC

[buswarrior]

Hello.

Darn, Dave, this is a pain!!!

Swapping that clutch isn't as bad a job as some, bus drivers burned the clutches out all the time, and the shop patched it back up in record time. Tranny stayed up under the bus. I wish I had paid more attention back then!!!

As for the theoretical swapping:

I'd be curious about the gradeability in top gear of the 7 speed Spicer mated to an 8V71 in an MC7. Has anyone tired it?

Maybe not enough grunt at the RPM to pull that tall gear in a head wind or up any rise in the road?

And IIRC, the ratios aren't even steps, shift is in a different place for each gear. I've driven a couple, and it was not as much fun as it should have been.

If I was going through the effort to swap, I'd want the closer ratios at the top for highway use that a splitter gives. So realistically, a 13, and some careful thought as to overdrive vs direct for the differential gear, typically a 3.7:1 in an MC7.

Great ideas to chew on here Tom!

happy coaching!
buswarrior

 

[TomC]

The main reason I suggested the 7 spd, was it is the transmission with the most gears but still without any air shifters or splitters.  The 13 would be the best, but there are two air lines that have to run to the rear of the bus (one for the range shifter and the other for the overdrive splitter-air supply could be taken from the front tank).  I ran nothing but 13 spd when driving and they are the best.  Especially if you can get one of the new RTLO's that are the low enertia design.  Roadranger changed the rear overdrive section so you can make overdrive split and gear lever shifts at the same time without getting stuck between gears.  Good Luck, TomC

[dreamweaver]

Thanks for all the input on trannys but for now I think I will just change the clutch.I just built the tranny dolly showen in the book. When I get back homein the spring I will shop around for a tranny, I think I like the idea of a 13 speed. It's not a big deal to run air lines but what about the clutch linkage and shifter?

[TomC]

Clutch linkage should work with the 13spd. As to the shifter, you'll have to get the X shifter that reverses the shift pattern.  Otherwise you'd have to relearn to shift it with 1st in the upper right and reverse at the lower right, with 2nd in the middle bottom, 3rd at the middle top, 4th at the left bottom, 5th at the left top.  Anything can be learned.  Good Luck, TomC