Steering rack keeps breaking - what am I doing wrong?!

[richhemmings]

Second breakdown in my ownership (of circa 8 months!).

After replacing it the first time, all felt fine and worked for 2 mows. Took it out today and felt a bit chunky in the middle. Stopped and checked after about 200m of mowing as the steering in the middle was not consistently turning the wheels. On review (Pic1) the gears weren't perfectly in mesh -- I'm not sure if they are supposed to be closely meshed or not?
I noticed there was little/ no grease, so I added some after trying to move the steering wheel rod forward to mesh more. I don't think this had a great effect. I also noticed that the main bolt that holds the steering plate on was a bit loose, but not allowing the plate to flap around, so I'm not sure if this is a factor either. Tightened it up in any case, and checked all other bolts for good measure - all tight already.

After some faffing, the steering seemed good again - smooth and turned from 45 to 45... however, I noticed a bump over 45 degrees on both sides - starting on the right, then "developing" to the left. I continued to mow, but tried to not turn to the extremes.

After another 500m or so of mowing I noticed the steering getting worse, and it eventually gave out with the gears falling entirely out of mesh, but I assume by this point the damage to the gears was enough that when pointed straight the gears wouldn't touch. Still turns outside of 10 degrees.

Pic2 - Shows some obvious wear to the central 4 or 5 teeth.
Pic3 - Steering column gear - knackered.
Pic4 - Central teeth - note the shorter one in the middle

[Mick]

Hi Rich, and welcome to TGMForum.

Are you still able to get new steering parts for these? I haven't touched one for a while so I have no idea on availability.

As long as everything is meshed snugly, and there's no movement in the quadrant pivot and pinion bearings I don't see you're doing anything wrong.  I would make sure front tyres are pumped up, and steering arms are greased and free moving so it takes as much stress of those parts. 

[richhemmings]

Thanks for the reply Mick,

I've not found any new parts available.
Preloved - yes -- and this was the replacement I had put on that worked for a while. I've ordered another (used) replacement.

It's odd that it worked fine for a while, then gave up; but I guess such is the way of things breaking down. The grass was thick and a bit wet today so perhaps your theory on stress is the answer.
I used some lithium grease on the control arm joints with a brush before putting it away last time but they look a bit dry now so maybe they need some more when I refit.
I'll pay close attention to the quadrant pivot when I put it back together, I'm sure it was sound, but I cant think what else may have moved. For what it's worth, the steering rod and pinion assembly are mounted to the chassis via a slotted hole, so I think I might be able to 'tune' the mesh a bit.


...and if that doesn't work, perhaps I'll just tie some rope to the control arms