Clutch Brake Adjustment

[gus]

Don,

Well, for certain you have a brake.

It appears that there is more total gap in the bottom photo than in the top but maybe that is just an illusion? As I remember the max gap is 1/2" or a tiny bit less and is best measured with a ball on the end of a shaft or stick.

The clutch brake on my '71 Dodge C900 truck tractor has two metal and two fiber discs as I remember but I haven't fooled with it for a long time. Newer ones may be different. You need to check out the specs or ask a good mechanic to find out if you have any missing discs.

It appears by the small ridge on the ID of the fiber disc that it is quite worn, maybe as much as 1/32" so this could be your problem.

I have instructions for replacing the fiber discs without removing the trans somewhere and will try to find it if you like. It involves cutting out a notch so it will slip over the shaft but not fall off.

[Rick Brown]

Here's what I did for the spinning gears problem:
http://home.att.net/~intermountainac/ClutchCatcher.html
Nothing has improved my 4905 driving experience more than that simple clutch hold-down.
-RickBrown in Reno, NV

[lyndon]

That's interesting, for sure, Rick, and I can see how it would be helpful for extended stops. Do you have concerns about premature release bearing failure, though? I've always assumed it would last longer if you avoid using the clutch for longer than you have to at 0 mph, preferring neutral instead. (Which brings us back to the either having a clutch brake, or grinding, of course.)

Gus, the manual has diagrams showing just a single disk forming the brake, but I wonder if the fiber disks you mention could be slipped in to "fix" the brake until the next clutch replacement? The shaft appears to be 2" in diameter, if I am reading the specs right.

Don

[lloyd]

To check the clutch adjustment you need 1/2" between the brake and the release bearing and 1/8" between the release fork and the release bearing. If there is too much movement between the release bearing and the release fork you will not squeeze the clutch brake. Also make sure you can not spin the clutch brake around the input shaft, if you can then the tabs are broken the brake needs to be replaced.

[gus]

Don,

It would probably be better to remove your worn disc if it is actually worn. It needs to be checked per specs. That may be your whole problem.

Two fiber discs together might not work. My setup has  metal-fiber-metal-fiber-metal.

Then notch a new disc and insert it onto the shaft and you will be back to new specs.

[TrevorH]

so what peice is the clutch brake and what thickness/apperance should it look like?  Also, where is the inspection hole?

[lyndon]

so what peice is the clutch brake and what thickness/apperance should it look like?  Also, where is the inspection hole?

Trevor, sorry I didn't respond earlier, but I've been swamped this week and haven't had time to check this forum. I'll attach a repost of one of my clutch brake shots with an arrow pointing to the brake, as well as a diagram from my manual (a scan of a bad scan, I'm afraid, but look for #17 at the bottom left.)

As for appearance and thickness, I've never inspected one before, which is why I was looking some tips here. I'm guessing mine is well worn just by looking at it. Also, the manual seems to suggest is that it's worn out when you cannot adjust it to start clamping at 1" above the floor without losing the required free play. That would seem to be the case for mine.

The inspection hole is cut into the an access plate right behind the flywheel (well, actually, I guess that would be in front of the flywheel for the rear mounted engine) on the underside of the clutch housing. The hole is large enough to peek inside and reach the clutch bearing zerk for greasing, but it's easy to remove the four 1/2" bolts that hold the plate on for a better look.

Thank you to all who have contributed helpful advice in this thread!

Don

[Sojourner]

After looking at your manual description...it show "Ring, clutch adjustment"...I never work on this type of dual disc with brake. So Goggle search "Ring clutch adjustment" and came this link:
http://www.meritorhvs.com/MeritorHVS_Documents/WC88153.pdf

My MCI-9 Parts Manual don't show what your does....maybe it is a later version?

If your manual is equip with "clutch brake" information...Then read it well or the above link...the step by step is difference than the regular dual disc setup.
Need be sure to:
1) Check Release Bearing Clearance
2) Adjust Release Bearing Clearance by adjusting the "Ring"
3) Adjust Release Fork Clearance via clutch linkage (between pedal to bell-housing clutch shaft).

FWIW

Sojourn for Christ, Jerry

[TommyT]

A picture of the clutch brake with the clutch pedal pushed to the floor would help us alot If your linkage is worn or has alot of slack you may not be getting enough stroke to compress the clutch brake.Grease on the clutch BRAKE is actually a good thing(per eaton/spicer/dana) spicer clutch installation instructions (that little piece of paper in the box that your new clutch comes in that nobody reads )will tell you to grease the clutch Brake before you install it.(I have had to dig the instructions out of the box for the new clutch one of my buddys had just installed, just to prove I was'nt crazy!!) A clutch brake works more on compression than friction,and friction will wear it out.(as properly stated in earlier post about coasting with clutch pedal to the floor while in gear!!!!) You may only need to adjust your linkage and then re-adjust your clutch? Whoever installed the clutch may not have inspected/adjusted the linkage properly,and just adjusted the clutch to make up the difference??? You can also go to any HD truck dealerships parts dept. and ask to look at a new one to get an ideal of what condition yours is in by looking at/measuring thickness etc.(I would measure one for you,But I just used the only one I had in stock this week.)As for the fiber+metal washer+fiber clutch brakes they have been replaced with the single piece like you have.  I hope this helps some,I don't post much,just lurk in the shadows(I guess if I could type with more than two fingers@5 WPM I would post more???) I probally could have adjusted your clutch and linkage quicker than I typed this!!!!!! But I'm trying             P/S I don't own a bus yet(don't have the time).But I do own a 85 Newell 8V92TA/HT740.         Boy I hope that last remark does'nt get me kicked off this board!!!!!!!!!!!!!

[Sojourner]

As per Tommy posted about grease & linkage adjustment.........it does show it hasn't been grease in along time or never. Good chassis grease is use.

However before any linkage adjustment being made....you must have 2 of 3 clearances corrected first...then the linkage is the final adjustment. You may have to disconnect linkage to get the first 2 steps adjusted.

Use this link to follow the procedure using your MCI's spec requirement:
http://www.meritorhvs.com/MeritorHVS_Documents/WC88153.pdf

FWIW

Sojourn for Christ, Jerry

[lyndon]

Tommy, a picture with the clutch on the floor will show contact (we checked), but at 1 inch above the floor, none. The result is no squeeze. You mentioned the grease thing, and I recall seeing somewhere else on the web that more is better for the release bearing and not to worry about grease on the brake.

Something in your comments that jumped out was the having a worn linkage and a lot of slack; sure enough, that is the case. I checked the pedal height and it's about an inch higher than the recommended 8.5" from the manual, so there's lots of travel. Maybe the linkage adjustment has been pushed to compensate for all of the slack. This deserves a closer look and I appreciate the guidance.

Jerry, both coach ('88) and manual ('89) are "newer" versions; I don't think MCI made many MC-9s after mine. I don't have a matching parts manual. but the basic specs from the service manual are posted earlier in the thread. AFAIK, the Dana brand has been assimilated by Fuller. Thank you for the link, as it supplements the manual description (which could be a lot clearer).

Don

[NJT 5573]

lyndon, all the double disk clutches I have seen have an internal adjustment to release more spring to compensate for wear. To give you an idea what this does lets go back to your 1.5in freeplay. If the clutch does not start grabbing at about 2.5 in from the top then you can turn in some adjustment and gain some compression on your clutch brake. There are 2 style locks and adjustors I am familiar with. They both do the same thing. The first is a simple lock bolt with a Y lock that sets in the internal clutch ring. Take the lock out have someone hold the clutch to the floor, (or it won't turn) and use a pry bar to turn the ring 3 or 4 teeth. (Rarely do they need more). Put the lock back on and reset the free play if necessary and you will be close. The second style adjustor uses a lock bolt that sort of ratchets the ring by turning the bolt after you remove the lock. Try about 1 full turn with a rachet with this style and reset free play. You want to turn both adjustment styles clockwise to adjust for clutch wear and gain a little more clutch brake. Both methods of internal clutch adjustment require the clutch pedal be held down or the guts just won't move. It is possible to have a very small distance between clutch disengagement and clutch brake if you turn in to much adjustment.

[buswarrior]

Hello Lyndon and other clutch brake fans.

I'm here to eat crow.

Upon securing a couple of binders of Eaton Transmission books, and talking with the real deal, it appears that once again, it is best to not repeat what you hear from "reputable sources" unless you can back it up with print.

The clutch brake may be given a squeeze while moving IF the transmission lever is in neutral, as Lyndon described, to assist in one of those steep take-offs to get the gear sets to slow quickly enough to grab the next gear.

You must NOT squeeze the clutch brake while the lever is in a gear position and moving, otherwise, popularly, as noted, the tangs snap off and then the clutch brake spins around the shaft it was attached to, not accomplishing its task.

Damn driver trainers, NEVER believe a thing they SAY... no matter what battle scars they may have, and what reasonable sounding long winded explanations they give, unless you can verify every word.
I got caught with my pants down on this one.

My apologies to anyone who was lead astray or provoked by my erroneous typing.

happy coaching!
buswarrior

[NJT 5573]

Buswarrior, thats how we used to shift 2 sticks with a 220 Cummins on a hard pull!