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Author Topic: Clutch assist cylinder  (Read 2757 times)
Fredward
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MC-5A #5401 8" roof raise 8V71 with MT647




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« on: October 30, 2007, 05:46:07 PM »

I'm working on the clutch on my MC-5. Pedal is way too hard to push. The linkage is free and works well when disconnected from the clutch shaft. I think maybe the cylinder isn't working? I have air at the cylinder and so I figure the next step is to take it off and see what makes it "tick". Do you know, can I just take it off the bus and pull it apart? I don't see any obvious way to take it apart.

I understand how it works, I think, from earlier posts, but now that I'm in there, I'm wondering what I will come across when I try taking it apart.

Fred
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Fred Thomson
Fredward
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« Reply #1 on: October 30, 2007, 08:17:11 PM »

Well I answered my own question. I took it off and just popped it apart. Everything seems fine with it. Tested it with shop air and it works, so I just put it back together and tightened up the linkage where I could. That helped a little. I think maybe it needs an Allison 740 to really make it right.

Anyone know how to check how much clutch lining is remaining?
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Fred Thomson
Tony LEE
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« Reply #2 on: October 31, 2007, 02:29:37 AM »

With the clutch pedal released, is the air cylinder perfectly horizontal.

Other things to check are lubrication of both ends of the clutch cross shaft plus any other grease points on the whole linkage because what may seem free under no load may be locking up under the loads imposed when the pedal is pushed down.
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JimW7
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« Reply #3 on: October 31, 2007, 05:26:05 AM »

Tonylee makes a good point. My 7 was getting hard to work, I adjusted clutch, to no avail. I removed linkage to check, and the bearings on the ends of the cross shaft were oblonged. It would seem to move freely with no load, but when you would step on the pedal with load, it would force the shaft into the slightly oblonged position in the bearings, and would force everything to work slightly crooked. I replaced bearings, now works fine. No harder to push down than my pickup.
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1970 MCI 7 serial # 8425
mikelutestanski
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« Reply #4 on: October 31, 2007, 06:49:11 AM »

Hello;        All good points.   ALSO:   Check the lube schedule (manual section 10 )  and the plate inside the doghouse door. That plate has a row of grease fittings...  In the manual section 10; figure 10-1 illustrates the master lube plate and fittings number 4 & 5 the bottom two are for the clutch cross shaft.. But if you grease then inspect where the fittings go to see if the grease went where it was needed.. If the fitting does not take grease then something is wrong..  (the fitting is blocked or the line is plugged etc etc)  visual inspection is necessary especially if the system is not working properly..
          Certainly a 740 is an option however it its the most expensive..   
     I replaced the manual with a 740 but for different reasons..   An additional 740 feature is the loss of approx. 1.5 mpg.
       Just some thoughts on maintenance.   hope it helps   
          happy busssin     Mike
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Mike Lutestanski   Dunnellon Florida
  1972 MCI 7
  L10 Cummins  B400R  4.625R
Fredward
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« Reply #5 on: October 31, 2007, 08:01:42 PM »

I have more issues as it turns out. The clutch cross shaft bushings which are above the transmission appear to be very worn. So I need to remove the alternator and get in there to remove those bushings to see if they can be rebuilt or replaced. The shaft definitely moves laterally when it should only be twisting.

I also wonder if maybe the clutch lining is pretty worn.
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Fred Thomson
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« Reply #6 on: October 31, 2007, 11:02:52 PM »


 I think maybe it needs an Allison 740 to really make it right.




Sadly, Fred, an HT-740 won't fit in your MC-5A with the 8V71 - it's too long.

OTOH, a 6V92TA bolted to the 740 will work nicely. . . and if you bump the 92 up to 350 hp, wheeeeeeeee!!

All it takes is money. . .   Cheesy

FWIW & HTH. . .

 Wink
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RJ Long
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NCbob
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« Reply #7 on: November 01, 2007, 12:18:34 AM »

Fred, I had a similar discussion with Fred Hobe last winter and Fred told me that the only automatic which would fit in a '5' is the Allison 643. My understanding it that the 643 was used primarily in garbage trucks and many are still available but hunting one up might be a chore depending on where you live. Since I'm not far from ATL my guess is that I might find one there if I were interested.

Have you put a guage on the air pressure line to the clutch cylinder? It would be interesting to know if you're getting full system pressure to it or just 65#'s. I believe there's a  small regulator on the forward bulkhead in the drivers' side doghouse which might be adjusted for more pressure but that's a guess on my part. I won't fool with mine until we get to FL in another week or so.

We just missed a couple of those cylinders on the Eplace last week.

Bob
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Tony LEE
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« Reply #8 on: November 01, 2007, 03:26:01 AM »

"The clutch cross shaft bushings which are above the transmission appear to be very worn."

Yes, mine is on one end as well but just a little.  If you have the hatches in your floor still accessible, I would have thought you could do the job without removing the alternator.

The other cross shaft I was talking about is the one inside the clutch housing itself. That also has greasing points on each end.

Have you pulled the assist cylinder apart. It works much better with a clean bore and a bit of lubrication. Need to check whether the seals are leaking badly - get someone to push the clutch pedal with air up and see if there are significant leaks once the cyliner rod moves.
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Fredward
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« Reply #9 on: November 02, 2007, 07:04:08 PM »

Tony,
I found the grease zerks you mention and gave them a couple of shots. No my access hole is covered over and I could cut an opening but it might not be any harder than removing the alternator; its a belt drive one. But very valid points. The assist cylinder is horizontal when the clutch in engaged. I took in apart and cleaned it and lubed it. The connection to the operating rod from the front of the bus was loose so I replaced the bolt and tightened that up. The cylinder seems fine and does not leak.

Back together, the clutch seems easier to operate; I'll test drive it Saturday. Still planning to replace the shaft bushings.
Fred
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Fred Thomson
Fredward
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« Reply #10 on: November 02, 2007, 07:05:20 PM »

Bob,
Thats an interesting point. I don't know how much pressure I have back there. Definitely worth checking because it takes a lot of force to move that clutch arm.
Fred
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Fred Thomson
Fredward
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« Reply #11 on: November 02, 2007, 07:08:32 PM »

Russ,
You should have never told me that. My neighbor has an Eagle 05 with a silver 6V92/740. The bus is just a shell and she is planning to just dump the bus maybe I should grab that engine tranny combo. Brian Diehl lives nearby; he knows all about engine upgrades! Are you sure it would fit? Isn't a 92 series taller than a 71? Its a tight fit back there in an MC5.
Fred
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Fred Thomson
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« Reply #12 on: November 02, 2007, 07:52:34 PM »

Fred, egads...I'd be the last one to try and bust your bubble...but if you'd compare the clearance differences between the 5's blowers and the later models you'd see that our fans are much lower...hence not enough clearance for the larger engines.

Let's face it m'friend, we wanted a 5, we're stuck with the shortcomings of a 5, they won't grow into a 6, 7, 8 or a 102...so ehhh? Let's enjoys them and live with 'em.  I love mine and wouldn't trade it for another bus.

And, for the record (Cliff) I wouldn't take a GM as a gift!  (inside joke guys...no offense meant.  Cliff and I
have this private war going..)

"I have found the perfect woman...who could ask for more?  She's deaf and dumb and oversexed and owns a liquor store"

Be happy with what you have...life could be worse!

Bob

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Brian Diehl
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« Reply #13 on: November 02, 2007, 08:10:47 PM »

Russ,
You should have never told me that. My neighbor has an Eagle 05 with a silver 6V92/740. The bus is just a shell and she is planning to just dump the bus maybe I should grab that engine tranny combo. Brian Diehl lives nearby; he knows all about engine upgrades! Are you sure it would fit? Isn't a 92 series taller than a 71? Its a tight fit back there in an MC5.
Fred

Sure, volunteering me for more engine work, eh!  Sure, just let me know when and I'll be there! :-)
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Tony LEE
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« Reply #14 on: November 03, 2007, 06:51:42 AM »

"might not be any harder than removing the alternator; its a belt drive one"

Possibly. I have removed the alternator on mine to replace a shorted stator - after removing the big air cleaner first - and the air cleaner brackets - and its a bit wearing on the arm and shoulder muscles that's for sure.

I left both hatches accessible and have been glad I did a couple of times, but not all layouts make it possible.

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