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Discussion Starter #1
Evening all. My first post to the forum so bear with me.

I have a 1974 406 with front and rear PTO and 6 speed cascade transmission.

My first mog so I'm learning as I go.

The issue I'm having is engaging the PTO's.

Depress the clutch fully yet the pto will not engage without grinding the gears.

I have made the adjustments today through the small inspection hole on the bellousing and re-bled the clutch with no success.

It seems there is excessive travel on the pedal and am wondering wether the clutch arm is actually being pushed right down by the slave cylinder.

So, any ideas? Is there any adjustment in the cab to remove free play from the pedal?

Many thanks

Chris
 

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1973 416 Doka, 1978 416 Doka, 1980 416 Doka..... Help me, I can't stop buying them!!!
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If the hydraulics of the MC and slave cyl. are all good, than I would say the PTO clutch disc is rusted to the flywheel. You can try to un-stick it by stalling out the motor with the PTO. Like if you have a bushhog on it and just drop it down in some thick stumps, while your foot is on the clutch petal. You would have to start the tractor with the PTO already engaged, so do be careful.
 

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Discussion Starter #3
I believe they're both ok. How would you tell if the MC wasn't right?

Is there any adjustment in the cab for the pedal?

Watching the slave cylinder move, in my opinion it doesn't seem like the clutch lever actually moves far enough down but I am unsure of how far the lever will travel and cannot manually push it down to check this.
 

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1976 406
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CJ,

Welcome to the forum.

When trying to engage the PTO's on my 406 I get the same results. This started on my truck after I had a new double clutch installed and had the gearbox (20 speed) rebuilt. The work was done by an excellent Unimog factory trained mechanic. He was perplexed as I was so he pulled the engine and transmission a second time and found that the slight texture on the clutch plate was enough to cause a very slight drag. He rechecked all his clearances and told me that after the clutch gets used a bit I won't have this problem.

The drag on the clutch is so slight that when the transmission is cold and the gears are mired in the thicker oil the pto can be shifted into gear without grinding. As soon as the gearbox warms up, the gears spin a bit more freely and the grinding begins. After the truck warms up I have to kill the engine before engaging the ptos. Thankfully this isn't very often as once I engage the pto for use it stays engaged for hours.

There is adjustment in the cab for the pedal. Look at the top of the pedal arm for a cam bolt. Adjust that so it gives you maximum throw.

What is the history of your truck? Did the previous owner use the pto's much? If so, what did they use them for?

BWSwede
 

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Discussion Starter #5
Thanks for your reply swede.

My issue sounds slightly different to yours. Regardless of being hot or cold the pto does not want to engage.

This evening I tried engaging it before firing the engine and even then it didn't want to 'go in'. I had to get out and rotate the pto shaft by hand in order for it to allow me to engage the stick in the cab.

It's almost as if the clutch isn't actuating fully...

How could you tell wether the master cylinder is functioning correctly? I have my suspicions that the master cylinder may not be quite working properly...

CJ
 

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1976 406
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Often times mine won't slip in when the engine is off either. This is because the gears are not aligned. I sometimes have to push the starter one or twice for a brief moment to get the gears to align before the pto lever will move.

Have you reduced or removed the prescribed clearance at the slave cylinder to see if it makes a difference?

BWSwede
 

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Discussion Starter #7
When you say removed the clearance at the slave I take it you mean the 3mm free play between the slave rod and the clutch arm?
 

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1976 406
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Yes. Just to see if it makes a difference.

BWSwede
 

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Discussion Starter #9
No I haven't. That was my initial instinct, to lengthen the slave cylinder rod. But after reading my manual and people saying how important it was to have the free play in the clutch I didn't try it.
 

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1976 406
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It is important to keep the free play at the clutch slave cylinder. I am just suggesting you try it temporarily to see if your situation improves.

BWSwede
 

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1976 406 w/ backhoe and dozer blade, a small collection of implements too
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The PTO transmission and main transmission have straight gears where they both meet, so everything has to align just right to get them to go in. I know on my single clutch six speed and my double clutch 20spd behave exactly the same. I can't just jam the PTO lever into place like I would with a drive gear in the main transmission, I have to gently move it into position, and I always feel a little drag as the spinning gears slow down enough to allow me to engage the PTO (I of course have the clutch disengaged when doing this). If done too quickly, I get some light grinding, but when done slowly and gently, I can feel the resistance and a little clicking as the gears slow down. I know that even with the clutch fully disengaged, some spinning goes on, due to fluid viscosity but there is little or no force there. When it's cold out and I have nothing attached to the PTO, and the PTO is out of gear, the shaft will ever so slowly rotate until the tranny fluid warms up.
I use my PTO all the time and have had it out and found zero wear where the gears meet so I don't have any concerns with my methodology. Perhaps give my technique a go and see if it works for you. There may be no clutch problem at all.
 

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Discussion Starter #12
Britbike thanks for your reply.

Sadly even if I try to ease the pto into gear as you do it doesn't slow down and engage.

I'm beginning to think that as others have said the clutch plate may be rusted stuck.

Hopefully I'll be able to put a flail on it at the weeekend and try and free it up.
 

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1976 406 w/ backhoe and dozer blade, a small collection of implements too
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Nuts. I should have known the easy solution had no chance.

Good luck. Please report back so we can all learn some more.
 

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Discussion Starter #14
Yeah I've been hoping for easy solutions, Sunday I adjusted all the fingers on the clutch plate thinking 'yeah I'll adjust them up and it'll work just fine'....nope!

I certainly will. Thanks for your input
 

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1985 416 DOKA mid-mounted Rotzler winch, 1984 U1200AG
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Fingers are crossed for you!

Hope the fail frees it up...otherwise I think you may be tipping the cab and pulling the motor to free/change the clutch. So fingers are really crossed for you!!
 

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'78 Mog 416.141 DoKa
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The deal with clutch plates being frozen is well known on some John Deere tractors. A lot of guys actually store their units with the clutch pedal blocked down.
 

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1976 406
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Britbike's description of engaging the PTO matches mine, when the transmission is cold. When my tranny is warmed up there is no slowing down the spinning gears regardless of how much pressure I put on the PTO lever. When the tranny is warm you would think that my clutch plate is rusted stuck but it isn't because as soon as the mower, winch, or snowblower is hooked up, the PTO shaft stops or spins depending on the position of the clutch pedal just like it is suppose to.

I have often wished the PTO had a manual brake on it to aid in engagement like our old Cat dozers do.

BWSwede
 

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1976 416.141
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Hello,
If you go to post 5 on this PTO thread one of the members has installed (made) a steel shim to adjust the engagement of PTO to transmission gears. I may have to do the same as my PTO was removed and reinstalled and now it is almost impossible to get it into gear (it was fine before). Hope this helps, thanks Hammogger!
Rick Montez
416.141


http://www.benzworld.org/forums/unimog/1395232-pto-box-noise.html
 
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