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Replacing Ammco 4000 Lead Screw Bushings

by Goodson Tools & Supplies For Engine Builders

You're going to have to replace the lead screws on your brake lathe from time to time or maybe it's time to upgrade it to a larger size. That's what we're going to explain in this article.

First, let's identify the types of Rotor Lead Screw Bushings – Early, Late and Extended. 

Early Model Rotor Feed Bushing
Late Model Rotor Feed Bushing
 LSB-78529 Lead Screw Bushing from Goodson
Early Model Rotor Feed Bushing
Order No. GT-10868 		Late Model Rotor Feed Bushing
Order No. GT-10868X 		Extended Lead Screw Bushing
Order No. LSB-78529

We are showing this procedure on the Ammco 4000 Lathe for two reasons.

  1. It's what we have in our shop and 
  2. It's the most popular brake lathe out there.

Before we get into the nitty-gritty of removing the existing lead screw bushing, let's cover a few basic safety issues.

  • Disconnect your brake lathe from its power source. You don't want someone bumping a switch and turning it on while your hand is inside the works.
  • Safety glasses or goggles. It might seem like overkill, but it's better to be safe than sorry. After all, dressing as a pirate for Halloween every year is not all it's cracked up to be.
  • Gather your tools and place them in an easily accessible place so you're not fumbling around looking for the correct tool for the brake lathe. 
Step 1: Remove the factory silencer pad assembly

Step One

Remove the factory Silencer Pad Assembly by removing the square head set screw. Put the assembly aside.
Step 2: Rotate the Rotor Feed Assembly all the way out

 Step Two

Rotor feed assembly fully extendedRotate the Rotor Feed Assembly all the way out by turning it counter clockwise. 

 
Remove the bolts holding the gearbox assembly

Step 3

Use a thin wall socket to remove lower boltsRemove the four (4) bolts holding the gearbox assembly in place. You may need to use a thin wall socket on the bottom bolts as a wrench will not fit (see right).
Push rotor feed assembly forward to give access to the feed nut

Step Four

Now it's time to push the rotor feed assembly forward. Be sure to support the gearbox assembly. This will give you access to the brass feed nut.

NOTE: Your feed bushing may look different than pictured in step five. The one shown there is the extended version.
Remove the allen bolts holding the feed nut to the housing

Step Five

Remove the two (2) Allen bolts holding the feed bushing to the housing.
Pull the Feed nut free of the gearbox assembly

Step Six

Pull the feed bushing free of the gearbox housing and push it forward against the feed screw threads. You will now have access to the roll pin in the shaft.
Drive the roll pin out of the shaft

Step Seven

Gently drive the roll pin out of the shaft. Be sure to support the shaft on the underside so you don't damage the feed screw.
The gearbox assembly will come off in your hand

Step Eight

The gearbox assembly will now come off in your hands.
Remove the rotor feed bushing

Step Nine

You can now remove the rotor feed bushing. Before installing the new feed bushing, inspect the rotor feed screw and threads for any damage. Replace as necessary.

To install a new feed bushing, simply reverse steps one through nine.

 As always, if you have a question about this or any other technical issue, contact the Goodson Techxperts by phone (1-800-533-8010) or email.

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