Splitting a tractor

November 2, 2013

My trusty old Bolens G174 stripped a few cogs on its output shaft boss the other day, and sat there sounding like an annoyed pencil sharpener instead of pulling my trailer. A session in the garage revealed that it had stripped a spline boss on the shaft which transfers power from the engine and clutch to the transaxle at the rear of the tractor.

I found the part at Sony’s Bolens on the Internet. Then the problem arose: how do I split the tractor in half to make the repair? The shop has lots of tools and lifting equipment but I was loathe to tie it up for an extended period with a tractor hanging in sections from the hoist.

I asked my neighbour Peter Myers to supervise the first couple of hours of the project. He looked at the situation (the shaft and spline boss are visible from beneath the tractor, but blocked by the front drive shaft) and suggested we might not have to do the 10-hour take-apart prescribed in my service manual for clutch replacement.

He started with the front drive shaft as it was in the way. The manual directed him to the lower end after he removed the pin holding the rear (upper) end and found it would not slide forward enough to come off. The lower end is inside a heavy boot with a strong “O” ring and a bolt which looks like a drain plug. Peter removed these and found another universal joint which was easier to disassemble. As nearly as I can tell, one half of the front universal joint doesn’t take a pin, allowing it to slide on the splined drive shaft just enough to allow the rear universal to come clear of the transaxle.

We decided to split the tractor at the rear end of the drive shaft tunnel, where it joins the transaxle. Peter suggested a wooden block to support the rear half, so I cut two blocks off a 15″ walnut log, one 13″ and one 12″ in length. The 12″ piece worked with two 1 7/8″ pieces of plank on top and a 3/8″ shim to fill the space. A logging chain encircled the bell housing behind the engine and hooked to chain blocks attached to the bar across the top of the car hoist.

Before he left Peter warned me to wedge the engine and front axle together to prevent the engine tipping out of alignment when I split the tractor. (It still tipped a bit, but I corrected it easily by tapping judiciously on the wedges.)

First I had to disconnect the hydraulic lines from the pump and wiggle things around to allow the tractor to separate about 1 5/8″ to allow the spline boss switch. To free the brake rods, the rear pins came out. I also removed a pin on the differential lock. Then I removed four bolts from the front of the foot plates to allow the split.

All of the eight transmission bolts proved to be loose. I guess they had had lots of time to move around since 1980. The two bolts around the foot plates were hard to remove, but a 19 mm stubby wrench did the job.

It turned out that the output shaft will slide forward into the clutch a bit to make the job of removing the spline boss easier.

The old boss which dropped off the shaft (and onto my head) was worn quite smooth on the rear set of splines, so buying the replacement was a good idea. The rear shaft was far from perfect, but Peter suggested that with the new spline boss and pins it would likely run for a long time. A little oil and a few grunts and the shafts lined up for me to tap the spring pins into place.

Then I bolted the split halves of the tractor back together, ending phase 1 of the project.







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