Thread: Tractor Repairs

In a recent thread I mentioned that I was mostly involved with repairing my tractor at the moment. Initially I worked on the 3 point linkage, freeing up rusty and seized components. The last 3 days have been spent working on the main problem which is that the diff lock is jammed on. I have just come in for a cuppa after finally getting the cast cover of the gearbox/diff off and slid aside so I can see what the problem was. Easy to see. Nothing there! The operating mechanism is completely missing. I assume that something failed, falling into the gears and was removed as a cost saving measure. I also assume that the diff was not locked at that point in time and that only happened later. I cannot imagine anyone want to leave the diff locked. It makes for a pretty large turning circle. I might be wrong tho.

I saw definite evidence that someone else had been in there before me. Some bolts not matching, a type of silastic sealing the top and dirt on the gearbox forks etc. That was not from me. Most of my time was spent removing the floor and rear wheel guards, just so I could clean the top casting joint. This was not done previously. There is only a few mm gap between the edge of the floor and the joint. Much of this work involved the angle grinder.

Now I have to work out what to do about it. I can probably survive without a diff lock, but it would be a huge advantage to retain it. I would still need to ensure that it did not engage again. It is a lot of work to get at. I don't think it would be that hard to make the required parts.

Tractor gearbox diff cover.jpg

Pedal labled "P" you can just make out the top of the crank arm attached to the pedal, inside the fork at the top of the picture. This is still in place. The components with red arrows are all missing. There is also a vertical shaft near the bottom left corner missing. The blue arrow points to pins attached to a ring which the fork (lower left red arrow) slide left/right to engage diff lock. This is still there.

Dean

I am guessing the diff lock is nothing more then a dog clutch and that some where it is spring loaded and what happened is with all the parts missing the spring loading to disengage is also missing and the dog clutch fell into the on position and stayed on.

Yes. The spring is external, on the pedal. The dog clutch (circle of pins) is free to move. After I returned to the job, I soon realised that preventing consequent engagement will be dead simple. All I need to do is clamp a metal strap around the circle of pins. The gap is about 23mm.

Making it work properly again is a bit of a problem at the moment. I have not worked out how the mechanism operates. I have searched for pivot points or contact points in the case and have not found anything but virgin cast iron. There is the crank arm at the front right corner and 2 bosses vertically positioned at the rear left corner. These are bored 20mm diam. How do you provide the correct movement given the layout? The vertical shaft must be the pivot point for the bar across the bottom of the picture and the fork it moves. I cannot even see any marks at all on the cast surfaces of the 2 bosses. Any shaft fitted into these holes must have something to hold it in position surely. There is a rib cast into the case directly below the holes. My thinking is that there should be some sort of bearing surface on a horizontal face of these bosses. At this stage it is not making much sense.

The manual I have is not actually for the same model, but this part of it is identical. This is the best manual I have been able to find and this took a long time and lots of searches to find. I had to pay for it! The next problem I want to look at may be a bit more difficult. The right brake locking on. May be just adjustment or maybe worn out. It is acting like an over centre lock. The manual is different to my tractor here. The manual shows 3 adjustment bolts each side. My tractor has none. It has a single 36mm bolt head on each side. These may be an acces point for adjustment, but I don't know and I don't have access to a 36mm socket or ring spanner at the moment.

Dean

Having had time to do a quick sketch it may be simpler than I first thought. If the bar at the bottom of the picture is fixed to the fork so they pivot as one, it should give the desired result. It might actually be pretty simple to make the required parts. First I need to make a 20mm shaft. I can use this to make some remaining measurements.

Dean

What make and model is the tractor?

It is a Fiat Model 615. 65 Hp. Made sometime in 60's I think.

The manual I have is for a Fiat 513, but I have a parts list for the 615. Thanks for asking. I just thought to look at the parts list and found this.

Tractor Diff Lock 2.jpg

What I thought was a thread, up near the pedal crank is actually a spring (pn 9023226). It seems that the shaft is held in place vertically by the top plate sitting directly on the casting. There is no machining where it sits. Not really a big wear item I guess.

Dean

Hi Dean
I have a 36mm 3/4 drive socket that is surplus to requirements if you need it.

Roger

Originally Posted by rogerbaker

Hi Dean
I have a 36mm 3/4 drive socket that is surplus to requirements if you need it.

Roger

Thanks for the offer. I will keep it in mind.

The 36mm bolt head mentioned is actually a plug. I don't know what it does, but it does not appear to have anything to do with the brakes.

At this stage it appears that there is no option for adjustment except for on the linkage rod from the pedal. The problem is located internally so it seems it might just be worn out. I guess this tractor was used for a lot of sharp right turn type work. The right brake pedal sits way lower than the left, partially caused by the pedal being loose on the shaft which it pivots on. The left pedal is clamped to this shaft which transfers the left pedal force to the left side. There is a "cup" listed which appears to be a cover for a quite large access hole. I don't recall seeing this, but it faces inwards and I haven't looked underneath much. The ground underneath is wet, even in the shed. I will have a look today.

It is a bit hard to work out how these systems work based on a parts diagram. The parts listing gives names like spring, pin and rod which don't help much. Both of these documents are PDF files. The parts list is a real mess in places. There are large numbers of apparent updates just stuck over the top of existing drawings. Some upside down and some not appearing to be relevant to that page. There are complete pages upside down and the copier must have got distracted part way thru as a large part of the book is repeated. At least the copying is well done.

This book is written for 5 countries. Con, Senza, Veloce, Germania and Australia are listed with designated country codes 01 to 05 respectively. It is interesting to see that there are a lot of pages devoted to just the German model which tend to show quite a bit more complexity. The hand brake control is an example. The German model list 42 parts while all other models has just 14. The German model appears to have an entire system including a seperate brake drum (on another page, more parts listed) while the other models just engage the back of the 2 brake pedals. This extra drum brake confused me for a while. The main brakes utilise disks and I wondered whether there was the option of disk or drum until I noticed the country code.

Never having worked on tractors before, this is quite a learning curve.

Dean

Dean

Have a look here, G.W. Tractors | Tractor Parts Australia and here, http://www.stonyfordtractors.com.au/cms/

Either of them would probably have the parts you're looking for.

Thanks for the links. I can't see my model listed anywhere. There may well be parts that are interchangable, but the problem is working this out.

I am happy to make the parts. This is the reason I have metal working equipment after all.

I have found a 20mm diam stainless steel shaft, probably from a pneumatic cylinder. It fits nice in the top boss, but gets tight in the bottom one. I checked it for straightness. No problem there. I will just polish the end.

I have measured everything and started drawing up the parts.

There is a "cup" listed which appears to be a cover for a quite large access hole. I don't recall seeing this, but it faces inwards and I haven't looked underneath much. The ground underneath is wet, even in the shed. I will have a look today.

Ok I have seen it. Not hard to miss. The drawing is done from the left. I was looking from the right. This cup should be an access hole to adjust the wheel bearings. This will be good because I was levering against the right wheel at one point and was interested to notice the amount of sideways movement of the wheel. The wheel bearings are adjusted from the inside of the axle. The design gives a bit higher clearance, but also moves the rear wheels a fair distance behind the diff axis.

Dean

Hi Dean,
Have found a 640 at McLaren Vale if that's of any help.
Wrights Tractor Sales & Service
60 Chalk Hill Rd
McLaren Vale SA 5171
Phone:08 7007 6847

Regards
Kryn