Following Andrew's job on his JCB leaky front axle, I needed to do a similar job to replace the steering knuckle/trunnion bearings on my tractor which were making for some interesting steering choices (occasional inability to turn left at all!!).
Started on the tractor trunnions on 14th Sep There are three jobs needed:
1 Replace right track rod end.
2 Replace bottom & top trunnion bearings on left front hub.
3 Replace at least one of the U/J’s on the left driveshaft (double U/J type).
So – find a reasonably flat spot of grass within electric & airline range of the garage, leaving room for cars to get out to the lane, jack up front left side & insert axle stand, remove wheel & have at it. Always surprises me just how heavy tractor wheels are &, of course, anno domini increases their mass exponentially.
Job 1
Easy peasy? Not! This is a drag link that joins the two front wheels with a long threaded tube across the front. One side taper broke easily, the other (of course with the wheel still on, did not. Neither of my ball joint separators would fit despite my hopeful modifications – I had to borrow one from a friend just down the lane. OK track rod off & into garage. I should have realised from the welded up left T/rod end that there would be problems. It took a 4ft scaffold tube on the 24” stilsons plus heat (I only have propane) to shift the knackered rod end &, of course, marred the thread on the tube so the new end would not thread in. The thread is 27M x2 & I didn’t have a tap, plus the tube is too big to fit the mandrel of my M250, so no good there. Close inspection revealed that only the end couple of threads were ruined, so I just cut ¼” off the end of the tube & spaced the new rod end accordingly. Locknut was similarly damaged so not refitted. There is no chance of the track altering in use, since the other side is welded to its rod end. So Job 1 complete & only took a day!
Job 2
I knew this would be difficult & I wasn’t wrong! The trunnion arms have jack-off threaded holes that line up with the locating dowels, so once you remove 4 M16 bolts on each, you just insert bolts & jack off the housings – yeah! Top jacking holes were full with 40+ years of rust & sh1t, but eventually proved to be M14X2. Fortunately I had the tap, so cleaned the threads , filled with Duck oil & on to the bottom ones. These, naturally were a different size (why?why?why) & were 12mm – no problem there though the threads were only about 3/8” long & not in the best shape. Found some M14 & M12 bolts & turned the ends down so the threads didn’t mar when jacking happened. Inserted the M12s & carefully made a start – no chance! Even with hand pressure on a 9” length spanner (prob. less than 60 lb ft – I’m old) the threads in the holes stripped (I’ll rethread to M14x2 once I get the blighter off). So after just about 7 hours over two days I finally have the bottom trunnion off. The welch plug that seals the top of the bottom bearing had rotted away, so I was able finally to get a punch onto the top of the peg & drive the housing down sufficient to get chisels in each side to remove the thing. There was only one position of wheel rotation & angle that allowed the punch to pass the double U/J (what are they called?BTW) & I knew it would mar the end of the peg, but needs must etc. Would have been easier if I had someone to hold the punch in position, so I could use both hands on the small sledge, but some wire & a scrap of shaped steel to prevent the bottom of the punch slipping (not 90 deg, more like 75 to vertical is the best I could achieve).
Right on to the top one, jacking bolts are secure but I really don’t think they’ll work – time for more propane & a large copper hammer on the steering lever to see if sideways impact will do it. No sign of a gap appearing to date.
Update at close of play 16Sep: Got the top trunnion housing off – the jacking bolts worked with the addition of more heat & a succession of chisels. However the top peg is separate from the housing (it’s all one on the lower item) & that is beating me at the minute. There is a central hole tapped M12X1.5 to be used with a bespoke puller, but I’ve cobbled up a puller using a standard (but small) puller beam & using 2 of the M16 securing bolts to jack up the beam against the central M12 bolt. So far I’ve got it to move out about ¼” so I think about another ¾” to go, but it’s tight as hell all the way. I’ve quit for today & left it under tension for tonight soaking in duck oil. Two days on this so far… ho hum.
Will try heat in the morning, then I just have the outer races of the top & bottom bearings to remove ( may need to weld a bead on them, but access will be OK once huge heavy wheel centre, hub & epicyclic reduction gears are safely lifted away with my pickup crane. Then it’s out with the driveshaft to do the U/Js, but that should be easy bench work once I’ve found the circlip to release the shaft which is hidden behind a couple of inches of grease/cowshit/chaff/earth etc.
