Well, the front diff is repaired successfully and has passed a tough trial run.
Sorry this info took so long but Ive been busy repairing the brakes (new shoes, new wheel cylinders, new rear diff axle oil seals & gaskets, O-rings, shaped seals, axle guide bearings (6009 2z) new handbrake bands & brake lines)
I had not set up a diff before and all I had going for me was a lot of enthusiasm but with the help of some expert advice from BobNZ, I was able to set it up without recourse to the manual ( which was hard to follow anyway).
With Bobs permission, I include exerts below of the relevant bits of advice from Bob that I did not find anywhere on the net despite much information being available on general settings & contact patterns etc. in the hope that it might be useful to anyone wanting to attempt a diff repair. It is not hard, you just need patience.
Have to make 3 posts of this as there is a limit on post size.
I learned that an understanding of crownwheel & pinion gearface contact patterns, how a diff loads up and how the loading affects contact patterns & the dangers of edge loading is the key to setting up a diff successfully.
From Bob:
Setting up diffs is a bit of an art from my experience.
Zetor instructions from memory are pretty straight forward but go into measuring distances and calculating shims. There are other ways. I think zetor also uses some markings of numbers stamped on the casings but that will be clearer when I grab the workshop manual and scan off the pages
I have found that the manuals leave out or gloss over many operations assuming a mechanic would not need detail so sometimes a bit of head scratching is needed.
There is no reference to checking the face contact pattern with blue. The crownwheel and pinion come marked as a pair and set up is made on measurement. I guess it is a low speed tractor so robust contact without any edge loading is their main aim.
It may well be simpler than multiple assembly and testing with blue procedures often needed with unmatched pairs.
The carrier head at least can be set up without the hard work of bolting up and unbolting the diff housing.
I have not done a diff for some years. The blue pattern on the teeth is the final call as to whether it is set up OK.
Do you have a good section in any manual as to what the blue pattern should look like?
Generally it should be broad and mid tooth on the crown wheel.
High or low bearing I have found cracks the hardening on the teeth.
Similarly heavy bearing near the ends of the teeth creates cracking and fracture.
In my experience all end and edges should be clear of bearing.
I am interested as to what the tooth count is on the new crownwheel and pinion. I see Carraro diffs feature on some of the much later Zetors as well but they may be very different models. Perhaps a workshop manual covering one of these later models may have some good info applicable to the Carraro driving head setup.
If your setting up brings contact into an area outside of the old wear pattern then the chances are you will have point loading on the edge of the zone of wear and newly used surface. ( that may be on either the crown wheel or pinion.)
The contact pattern on the drive side which looks to be the more upright face on the Crown wheel, seems to look as though it is bearing toward the inner end of the teeth. If all options have been tried then increasing the backlash may help remedy the contact as the crownwheel moves a way from the pinion.
The used diff would have developed an increase in the back lash and that will be reflected in the wear pattern on that gear set.. A bit of backlash is pretty normal in used diffs and is usually best left alone.
Sorry this info took so long but Ive been busy repairing the brakes (new shoes, new wheel cylinders, new rear diff axle oil seals & gaskets, O-rings, shaped seals, axle guide bearings (6009 2z) new handbrake bands & brake lines)
I had not set up a diff before and all I had going for me was a lot of enthusiasm but with the help of some expert advice from BobNZ, I was able to set it up without recourse to the manual ( which was hard to follow anyway).
With Bobs permission, I include exerts below of the relevant bits of advice from Bob that I did not find anywhere on the net despite much information being available on general settings & contact patterns etc. in the hope that it might be useful to anyone wanting to attempt a diff repair. It is not hard, you just need patience.
Have to make 3 posts of this as there is a limit on post size.
I learned that an understanding of crownwheel & pinion gearface contact patterns, how a diff loads up and how the loading affects contact patterns & the dangers of edge loading is the key to setting up a diff successfully.
From Bob:
Setting up diffs is a bit of an art from my experience.
Zetor instructions from memory are pretty straight forward but go into measuring distances and calculating shims. There are other ways. I think zetor also uses some markings of numbers stamped on the casings but that will be clearer when I grab the workshop manual and scan off the pages
I have found that the manuals leave out or gloss over many operations assuming a mechanic would not need detail so sometimes a bit of head scratching is needed.
There is no reference to checking the face contact pattern with blue. The crownwheel and pinion come marked as a pair and set up is made on measurement. I guess it is a low speed tractor so robust contact without any edge loading is their main aim.
It may well be simpler than multiple assembly and testing with blue procedures often needed with unmatched pairs.
The carrier head at least can be set up without the hard work of bolting up and unbolting the diff housing.
I have not done a diff for some years. The blue pattern on the teeth is the final call as to whether it is set up OK.
Do you have a good section in any manual as to what the blue pattern should look like?
Generally it should be broad and mid tooth on the crown wheel.
High or low bearing I have found cracks the hardening on the teeth.
Similarly heavy bearing near the ends of the teeth creates cracking and fracture.
In my experience all end and edges should be clear of bearing.
I am interested as to what the tooth count is on the new crownwheel and pinion. I see Carraro diffs feature on some of the much later Zetors as well but they may be very different models. Perhaps a workshop manual covering one of these later models may have some good info applicable to the Carraro driving head setup.
If your setting up brings contact into an area outside of the old wear pattern then the chances are you will have point loading on the edge of the zone of wear and newly used surface. ( that may be on either the crown wheel or pinion.)
The contact pattern on the drive side which looks to be the more upright face on the Crown wheel, seems to look as though it is bearing toward the inner end of the teeth. If all options have been tried then increasing the backlash may help remedy the contact as the crownwheel moves a way from the pinion.
The used diff would have developed an increase in the back lash and that will be reflected in the wear pattern on that gear set.. A bit of backlash is pretty normal in used diffs and is usually best left alone.
