1994 L4200 Spiral Bevel Pinion Shaft Replacement in Front Differential

[PNW Ariel]

Hi I'm a brand new tractor owner with my first major repair. I just bought used 1994 L4200DT with FST with 1800 hours from a local used equipment dealer without a warranty. I thought I tested it pretty good at the lot but when I hauled it home it was apparent that the front wheels did not pull in 4 wheel drive. After getting it unstuck I opened up the front drive shaft cover tube and noticed that the coupler between the prop shaft and the shaft coming back out of the front differential was not connected, the coupler was slid all the way back on the prop shaft, the roll pin was missing and the splines on that shaft (which I believe is called the spiral bevel pinion shaft) are toast.

I called the dealer I bought it from and if I haul it back (100 miles, and I need to rent a truck and trailer) they will weld the coupler on to the spiral bevel pinion shaft so that it functions.

Is welding an acceptable fix? Or rather than several hundred dollars in transportation costs and two days to move it, leave it, and pick it back up a waste and I should just fix it myself?

I called two other dealers (new Kubota dealers with a service shop) and they both advised against welding because that shaft needs the slight degree of freedom the coupler has to prevent wear on the transmission or front differential/shaft bearings. They said fix it right and it would be about $500 in parts and 8-20 hours in labor (something around $2000).

It seems like all the transport effort and cost is a waste and maybe I should just buy the parts and fix it myself. I bought a service manual and I am relatively mechanically inclined. Is this a task I can tackle as my first tractor repair? It seems like the labor suck is trial and error in setting the backlash between the pinion gear and the shaft I'm replacing. Anyone know of other major pitfalls.

Here is a photo of the parts and some exerpts from the service manual to help:

 

[North Idaho Wolfman]

Yea the dealer is just trying to cheap out and do you some serious harm down the line.

Before you jump in too far get a new coupling and see if it will bite on the pinion splines, I've seen several that looked too worn but actually were fine and worked well.

And yes just do the repairs yourself, that's a pretty easy one to work on.

 

[hagrid]

Welding anything on to an input shaft risks scorching the oil seal. Then, what happens if you need to dismantle it down the road?

Bad idea.

 

[PNW Ariel]

Thank you for the info. My first step will to be just replacing the coupler. Assuming I have to proceed with the full repair I have at least one more question:

In the service manual on page 6-S12 (one of the pages I coppied above) it seems to indicate that the first step is to pull both the left hand and right hand yoke shafts to replace or to work on this differential and spiral bevel pinion shaft. Looking at the pictures it appears that I can probably get away with just removing the right hand yoke shaft because that is the only actual obstruction before I can insert a punch through the plug hole on the front of the axle tube (part #10) and knock out the spiral bevel pinion shaft.

Any oppinion on whether I actually have to remove both sides of yoke shaft?

 

[North Idaho Wolfman]

Most likely the reason you need to pull both is because you cant put the the differential back in without the axles being out because of alignment of the shafts.