Refurbing my 8N's shift gate

This is going to be a project thread, documenting my progress refurbishing the shift gate and shift lever of my 51 8N.

The beginning;

Was heading out to mow some acres and upon shifting into second the tractor would not move. There was no grinding or thunking, the wheels just would not spin. The shifter was loose and would just flop around without engaging any gears.

I removed the top plate and found that the forks and plates would move through all gears and I could turn the them by hand untill they fully engaged. The clutch freeplay was adjusted and I was able to stomp the clutch while in gear and could then turn them by hand once more. So, no damage to the gears, plates, forks, clutch, or wheel hubs; just an out of spec shifter.

Upon examining the shift gate whilst still installed on the top cover I noticed chipping, pitting, and grit trapped in the spring and fingers that helped cause the wear to the shift gate. I drilled out the four rivets holding the gate and found that there was a large amount of grit trapped in old, hardened oil that was acting like sandpaper. I suspect sitting in the rain and a bad shift boot to be the root cause of the problem. This tractor was obviously ill used for years and had been sitting for quite a while before I purchased it.

http://imgur.com/a/sgzc0 shows the rounded fingers on the gate as well as the pitting on the shifter. I did a quick clean up with de-greaser and a wire wheel. I think the shifter is not so much a problem as the shift gate is. I'll be adding weld material to the fingers and then filing them back into proper shape which shouldn't take more than a couple hours. I'll hit the shifter itself with a bit of material as well to fill in the small worn area just as a safety measure so I don't have to pull it out again.

Continued once I've gotten to the welding.

Be very careful welding if you have used brake cleaner to degrease the steel parts. The residue
from brake cleaner turns to poison gas when heated. I have gotten a whiff of this a few times, and
it is real bad!

Do a final wash with paint reducer or solvent before welding, and let it dry completely. Do the
welding in a well ventilated area.

This is serious, so take extreme care.

The one on my 8N looked a lot like that too. I took the
quick/lazy way out and swapped it with one from another
tractor. I still have the bad one so if something comes
up where you need a part for it, holler. They'd be free.

Do a final wash with paint reducer or solvent before welding, and let it dry completely. Do the
welding in a well ventilated area.

This is serious, so take extreme care.

Click to expand...

I do a final wash with easy-off, then I scrub the metal with a wire brush and dish soap(which cuts grease unlike laundry soap). Plus I always do a pre-heat with a torch to burn off impurities and to help the weld puddle more effectively. I don't have a shop so I [i:9e24b150be]have[/i:9e24b150be] to pre-heat or my welds would look like crap.

Current progress;

Went out this morning with the welder, shift gate, and gear shift. Despite the heat there was quite a bit of fog so I pre-heated the metal to drive off any ambient moisture that might contaminate adhesion and set to. It took me about fourty five minutes of work start to finish. I was going slow, building up layer upon layer of weld material and attempting to not create too much clean up work for later.

http://imgur.com/a/XecQ7

The steel in the shift gate took the weld without any problem at all. As the pictures show I did what I would call a fair job. Because I don't have an enclosed shop(yet) all work has to be done open-air and the mist in my area comes in thick and heavy most mornings. I'm very happy with the quality of most of the welds, with one exception, so filing will be pretty easy and shouldn't take more than a couple hours.

Nearing completion;

Spent some time this morning in the cool air, some metal, and a host of files.

I began with the shifter itself, filing down the weld material and shaping carefully. This took no more than ten minutes from start to finish and I only had to use two grades of file to complete the shaping. Moving on to the shift gate itself I began with a rough cut "fatherless son" file and cut down the metal to about 30% of finished and then moved to finer and finer grades of file so that the finished product has very few cut marks and is very nearly polished.

Gallery here; http://imgur.com/a/W5W4U

The most difficult part of this was realising that the gate walls were a bit erroded so I had to compensate for that in my cuts. You can see in a couple pictures where the new material isn't perfectly in line with the gate walls but I feel that the action of shifting will ride smoothly enough that this won't be a problem.

Test fitting of the gear shift shows that there will be a nice, positive, engagement and no slop. There is just enough space for shifting to be solid but without any un-due over travel of the shifter and also without any hint of binding or tightness between gears.

At this point the project is nearly done with re-assembly happening after I get some food in me and I can find my box of rivets. I should have a final report this evening when the top plate is back on the tractor and I have a chance to give it a true functionality test.

Project completion. Results and notes;

I had to grab some larger diameter rivets so I was unable to finish the project last night. I was out at dawn this morning and reconstructed the top plate in short order. I did spend the next two hours pounding rivets. The key is to use four small C-clamps to hold the shift gate in place while you tap on the rivets. This helps hold the gate close to the plate and insures no shifting issues. It was fiddly work since I had to balance the plate on my thighs while the rivet head was on the edge of my vise's anvil.

Shifting assembly complete I took it out to the tractor for fitting and testing. I cleaned off the mating surfaces of old gasket and gasket sealant then checked the transmission to make certain everything moved freely. I then put on the new gasket and assembly. Two bolts were snugged but not tightened and I climbed aboard for some engine-off tests.

There is a huge difference in lock-up now. Shifting isn't mushy as it was previously; when you are moving into gear you know it as opposed to wandering around the shift gate fingers trying to find a gear. I'm very happy with my repair at this point.

I then re-attached the started switch, ground cable, and steering wheel for a test under power. Tractor started up and purred while I let it warm for a moment and then I shifted into reverse, let out the clutch, and didn't move a milimeter. Looks like I get to split the tractor despite the work on the shifter. I need to replace a bearing or two in there anyhow so I'll get to see if my clutch needs it as well.

Notes;

If I ever have to do this repair again I [b:2701f93dcb]won't[/b:2701f93dcb] use rivets. I'll square off the holes and use carriage bolts, lock nuts, and peen the bolt bottom.
I found out there's a channel where the shift boot goes. Previous owners had let grease and dirt build up in it and then [i:2701f93dcb]painted over it[/i:2701f93dcb]. I got to clean it out so the new boot would fit snug in the channel.
I'll weld and file twice on future repairs. There was one weld that chipped a corner under hard shifting so I had to do a quick touch-up with everything already installed. A twice-over repair may avoid this.

Conclusion;

I would have no problem doing another repair of this nature. The difference in shifting is worth the time and puts the tractor closer to factory performance with just a few hours work. I'd say that no more than 4 total work hours were spent on the project, and those were well spent.

That looks like a great fix. Mine is getting a bit sloppy, not bad enough to worry about yet, but nice to see an example for when I get ambitious!