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We once made a little video of the diff-lock pedal mechanism, so thought it was worth putting it in here so you could understand how it works.  This may help you to understand what is going on if you have a stuck pedal.

The video was shot using a mobile phone (so apologies for the quality), but it shows the mechanism quite nicely…



Now for the discussion…


  1. baldeagle60

    Hi, today, I noticed that the tractor was not stearing as easy as in the past. The front tires which are already quite bald, appear to be scrubbing and even on tarmac it is difficult to stear the tractor. In a muddy field, it is almost imposable.
    I do have quite a heavy rear loader on, and no front weights.
    in investigating, I noticed that the differential lock pedal is rigid, where there used to be some play in it.
    It feels like both rear tires are moving forward at the same time, and not allowing the front tires to turn the tractor…. Any suggestions as to how I can investigate this? and free up the differentiallock pedal?

    Thanks Dennis

  2. Ian@vte

    Hi Dennis,
    You can easily check if the diff-lock is engaged by simply jacking up one side and trying to turn the lifted wheel (while out of gear) if it turns the diff lock is disengaged but if it won’t turn it is locked to the oposite wheel by the diff-lock mechanism.Sounds like the pedal may have seized where the spindle passes through the housing.try penetrating oil.Heavy impements do reduce stearing effort quite alot,can you add weight at the front to improve balance ?Also try increasing rear tyre pressure a bit (not too much)(be careful)as flatter tyres prefer to go in straight lines

  3. Thanks Ian
    Thanks for your reply, I will soak it a bit more next time I am up at the fishery
    It sounds like this is a common problem. The Differential lock does not get used much, so I guess it could seize up. the pedal is solid and there is no play at all. I will also try putting up on blocks or a jack and try to rotate one of the rear wheels as well… dennis

  4. We managaed to free up the differential lock with heat, but when it cooled down, it was again so tight you could not move the pedal. I will have to keep putting on penetrating oil, and trying to get the pedal to work… I think it is freed now, I am working on some weight on the front end, and we are looking for some new front tyres, as not having any front tread does not imporve steering. any suggestions as to what type of tyre we should have for a working tractor in grassland? (really, a muddy mess at the moment rather than grassland)

  5. Meridian

    What tyre does the tractor have on at present? Are they 3 rib 400 x 19?

  6. I am not sure of the size, the tyres are well scrubbed, and unreadable especially the front ones. I would imagine they are regulaur size tyres for the mf 35. but very bald…

    the differential is still being difficult, but there is some play in the pedal now, will just have to keep working it, and hopefully it will sort itself out. The local engineer is going to stop bye and have a look at it for us… Another tractor enthusiast had a look this past weekend, and said not to worry about it…

    I realise that the rear loader is very heavy, but it would be nice if the tractor would turn around cornors without having to do a three point turn.

  7. Meridian

    I swapped my 400 x 19 3 rib front tyres for 600 x 16 trailer tyres with muti-rib pattern as I was experiencing ‘cutting up’ when turning on our pastures. (Obviously you have to change the wheel rims too – but they fit perfectly).Just make sure the bolt holes distance (pcd)is correct.I believe you can use landrover tyres too.
    I was also told that you can go up to 750 x 16 tyres but because of the extra width you would have to move the steering chassis over one hole (so that they run in line with the rear tyres) – not an easy job on an old tractor if the bolts haven’t been undone for some time as they rust in their holes.
    D & S factors of Donnington, nr Spalding, Lincs were very helpful with this.Their phone number is 01775 820309 and email is info@dsfactors.co.uk.
    web site www.dsfactors.co.uk.
    Hope this helps

  8. Hi, thanks for the advise, actually the tyres that are on the tractor are 600X16, and we have ordered two new ones and will have them put on in the next day or so….

    regards Dennis

  9. Just an update on the differential lock problem…..
    I have recently taken the tractor back into the shop to have the brakes looked at. They were not holding me or the tractor on a slope… worked well on the level, but needed to know that if I were heading down hill backwards that It would stop me..
    Anyhow, while stripping the tractor down to renew brake pads, the shop pulled the axel shaft and put it back in… They said that the dif lock was engaged,and well rusted, and that was the only way to solve it…The dif has been well greased, and this should not be a repeat job if it is used on a regular basis… The mechanic thought it was through lack of use…that it siezed up. I also needed a new oil seal on the left shaft, so it too had to be pulled… The tractor garage made the whole operation seem so simple… Am so glad that it is finally fixed… the mechanic said they were probley the origional brake pads, as the tractor was mainly used on the level, and the brakes would not have been used much… Thought you all would like to have the end results…. baldeagle60

  10. admin

    Glad you’ve finally got sorted out with the diff lock. Obviously there was no quick fix for this problem, but at least you got the brakes, diff lock and oil seal done together while it was all in bits.