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Deer Rockshaft Repair Tool Saves Thousands
Mechanic and inventor Bruce Gamble of La Feria, Texas, designed and built a tool to repair the cast rockshaft housing on Deere 8400T tractors.
  "It saves a lot of money on repairs," says Gamble.
  The problem is that the rockshaft has no grease zerks on the fiber bushings, which are only 1/16-in. thick. The shaft wears through those bushings and into the casting, thus "egg-shaping" the hole. If you try to put a new bushing in the hole, it won't hold.
  Gamble's tool makes it possible to drill out the old hole to a larger diameter, and then install a new steel bushing that returns the casting to its original size so the factory bushing can be used. You can make the repair right on the tractor.
  The tool consists of a 1 1/2-in. dia. boring bar that attaches to a 1/2-in. electric drill, a guide assembly, and a drill press-type feeding mechanism. Gamble bolts a steel plate onto the rockshaft housing to hold the guide assembly in place. The guide, with the boring bar inserted into it, bolts to the plate. He drills the egg-shaped casting out until it's round, cranking the handles on the tool as necessary to slowly feed the boring bar into the casting. Then he drives a steel bushing into the hole to bring it back to its original size and reinserts the fiber bushing.
  "It takes only about two hours to install the tool and bore out the casting," says Gamble. "Otherwise, replacing the casting is a labor-intensive job which can tie up your tractor for days. You have to remove a lot of parts including the transmission and differential. When this problem happened on my Deere 8400T (tracked) tractor, the local Deere dealer said it would cost $20,000 to $25,000 to repair. A new casting alone would've cost $6,000. The problem isn't quite as bad with Deere's 8400 wheeled tractor because the casting is smaller and bolts onto the back part of the tractor. However, the casting alone costs about $3,500."
  Gamble says he also uses the tool to repair front castings on Deere MFWD tractors, using a longer boring bar and a different mounting plate.
  He sells the tool for about $2,000 plus S&H. Custom made bushings - depending on the size of the hole you have to drill - sell for $200 apiece plus S&H.
  Contact: FARM SHOW Followup, Bruce Gamble, Rt. 1, Box 173, La Feria, Texas 78559 (ph 956 797-2169).

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2002 - Volume #26, Issue #3