Zetor 6718 unable to select 4th/5th gear

[djsumcp20oldleawharfcouk]

Hi,
Have removed gearbox cover and find the syncho-mesh coupling will not move along far enough to engage gear either way (4th/5th).
In the manual it talks about synch-mesh gear guide blocks and springs I assume somthing has gone wrong with this.
Can the syncho-mesh coupling be replaced with gearbox in place, do I need acces to the front, back or can it be done through top cover? Manual is not very helpful. Are parts available?

David

 

[Renze]

I never had a failing synchro, but on my brothers 6718 the circlip holding the 5th speed coupler ring was broken. That made it jump out of gear.

The synchro thingies, if you cant fix it with the shafts installed, split between engine and clutch, take input shafts out, take PTO gears out: If you have 540/1000 one gear goes out through the top hatch and one through the bottom.
Then you can take out the top shaft assembly from the top by pulling it forward, then take it upwards.

 

[djsumcp20oldleawharfcouk]

Thanks for the reply.
I have the yellow cover worshop manual but it is not very helpful, the synchro mesh coupling looks different, this is a link to a picture of mine: [/]
The selector will move either way until it touches the cones but will not go any further. The shaft at that end appears to have quite a lot of play, you can move it up and down is this the problem?
If I split engine from gearbox, how do you realign it with such a weight?

David

 

[Renze]

Yours isnt synchronised, just straightforward collarshift.

If you can shake hands with the shaft, you likely lost the needle bearing inside the input shaft. you can reach it from the clutch housing.

 

[djsumcp20oldleawharfcouk]

Where can I find instruction to split engine from gearbox, do I need to remove cab if so instructions to remove cab.

Thanks David.

 

[djsumcp20oldleawharfcouk]

Yours isnt synchronised, just straightforward collarshift.

If you can shake hands with the shaft, you likely lost the needle bearing inside the input shaft. you can reach it from the clutch housing.

Have split engine from gear box and removed clutch thrust bearings and lever shaft, undone nuts on front plate can move plate back a bit but it is blocked by the big tube running [/]through the gearbox. How do I remove this tube, it is fixed either side to the chassis, There is a [url=http://www.oldleawharf.co.uk/imagez/DSC05033_200x150.jpg]plate welded [/]on one side, but none on the other side. There is a theaded rod running through which I have undone and can turn the tube but you cannot get it out because of the chassis each side.

Any help appreciated Thanks,
David

 

[Renze]

Oh yes i forgot about that: We havent had a cabbed tractor open for 10 years or so.

If you jack the cab up, you can undo three bolts on, i think, the right side and pull the tube out. The cab rubbers you can undo with the big bolts.

 

[djsumcp20oldleawharfcouk]

Thanks, i will try that.

David

 

[djsumcp20oldleawharfcouk]

Oh yes i forgot about that: We havent had a cabbed tractor open for 10 years or so.

If you jack the cab up, you can undo three bolts on, i think, the right side and pull the tube out. The cab rubbers you can undo with the big bolts.

Hi Renze,
Thanks for your help , I have got the tube out and removed the gearbox front cover. There is no bearing in the front cover on the Clutch Hollow shaft. The upper lid on the Hollow shaft is floating loose, found one socket head screw in bottom of gearbox.
(Obviously the problem)
I cannot remove the Clutch Hollow shaft as it is blocked by the gears[/] on bottom shaft. The manual just states extract the clutch hollow shaft c/w lid and bearing out of the gearbox housing.
The bottom gears/shaft look different from that shown in the manual, mine has a tube with internal and external splines, which I can pull out and the front gear drops a bit but it does not move the second gear out of the way. (Manual shows just a circlip in front of gear) Should the clutch hollow shaft just come out now or do I need to do somthing else?

 

[Renze]

difficult question from memory. I do remember that on my brothers 6718 in 1997 or 1998 we took one PTO gearwheel through the top hatch and one through the lower hatch, cant remember more unless i see it.

 

[djsumcp20oldleawharfcouk]

Thanks
So do I have to remove the PTO shafts or can I just move them back to get the gears of the front? Manual states to remove PTO shaft 1 you need to disconnect the gearbox from the main transmission. This is going to be very difficult now because I had assumed I could do it all from the front.

David

 

[Renze]

You can do it by taking the PTO shaft out from behind, on both the 540rpm and the 540/1000rpm versions, if my memory serves me well. You can drop the pump plate on reassembly to guide it by hand when putting it back in place. I'm not sure if its required, because we removed the cab and 3pt lift cover during that operation: Though i expect you need a hand in there to get the shafts inside each other.

===edit: You need to pull back the PTO stub from the rear, by undoing the bearing collar with four bolts on the back of the tractor. Put on a PTO cardan shaft to have something to pull the bearing out with. The slip tube that engages the oil pump and ground speed PTO will then drop to the bottom. Then you can pull back the 2nd inner shaft back, which releases the PTO gear shown in your picture, so you can drop down the hollow tube that holds the gears. Then you can push back the front part of the inner shaft and get the gears in front to fall off.

Thats what i can do from memory. Exact details i dont remember, but you do NOT need to split the main gearbox from the diff housing.

 

[djsumcp20oldleawharfcouk]

Have made some more progress, removed PTO II shaft,Hydraulic cover and moved PTO I shaft, back to drop gears at front. Have removed Clutch hollow shaft and clutch shaft. There is NO roller bearing in the end of the clutch shaft. The problem now is the coupling for 4th/5th is damage [/]on the end, burred over, I can tap it back onto the spline but it is very tight. I was trying to file the burrs off but it is very difficult to get at. I need to remove it, to file it or replace it but cannot get it of due to the gear on the lower shaft.
Is it possible to remove the [url=http://www.oldleawharf.co.uk/imagez/DSC04959_200x150.jpg]top shaft [/]this is on, without separating the gearbox from transmission housing? The manual is not very clear on this and does not show all the gears as I have.

Thanks for your help, David

 

[Renze]

Its very difficult to do this from memory with your very small pictures. But you can get the 4th.5th gear shifting collar off without separating the tranny from the main transmission housing.

I find it really hard to advise from here on, because i dont know where you're getting stuck.

From which end did you take this picture ? http://www.oldleawharf.co.uk/imagez/DSC05126_200x150.jpg

 

[djsumcp20oldleawharfcouk]

Hi Renze,
Thank you very much for your help .
The photo you refer to was taken looking through the clutch bell housing, the direction shown in this larger photo,[/] the bulkhead you can see is the first one in the gearbox at the point where the clutch shaft joined with shaft holding the 4th/5th coupler.
The coupler will almost come off but is stopped by hitting the gear on the lower shaft as shown in red on photo.

Not sure whether the shaft the coupler is on needs to be removed or how to remove it, there appears to be a split with roller bearing as shown on the larger photo.

Thanks David.

 

[Renze]

Yes, now i'm right with you again. Indeed the top shaft can be removed from the top end: Check if there is a large circlip holding the bearing, and if the shifter sleeve can slide further onto the shaft.

I had the 3011 top shaft out from above by sliding all gears to the back, then sticking the shaft through the front bulkhead, then pulling the bearing end up and away.

By the way, where are the sliding slots on the back of your gearshift mechanism ? is it just the angle of the photo or are two of them broken off ?

 

[djsumcp20oldleawharfcouk]

Hi Renze,
Thanks, the large circlip holding the bearing in is on the transmission housing side, the bearing will only go out towards the transmission housing. The gear behind the bearing is part of the shaft and it would appear only come out through transmission housing.
Yes there two sliding slots broken. I have had this tractor for tweleve years and can't believe it has run all that time without the bearing in the gearbox front cover and the needle bearing in the clutch shaft missing.

David.

 

[Renze]

I would weld a spacer on the gearshift sliders. Welding on the transmission itself is hard because its cast iron, but the sliders should be weldable. It would at least do something.

Anyways, you have your way in.

 

[hve]

At this point i would be going to the wreckers to get a good used transmission.
Did you find where the broken bolt came from?
Sounds like someone had it apart before!

 

[djsumcp20oldleawharfcouk]

At this point i would be going to the wreckers to get a good used transmission.
Did you find where the broken bolt came from?
Sounds like someone had it apart before!

The bolt came from the lid[/] on the clutch hollow shaft, there was only one, should have been three. This part was loose on the shaft and has been damaged by hitting the gear as you can see.

It looks then the only way to extract the top shaft with the coupler on it, is by removing tranny as it ha to be extracted out the back after removing bevel [url=http://www.oldleawharf.co.uk/imagez/DSC05108.jpg]gear[/].

David.