Question about Troy Bilt Tb70ss Gas Trimmer

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Fix the flexible drive shaft has a problem

Troy-Bilt 791-182833 flexible drive shaft has a little medal clamp at the end where the cutter is and it has come loose. Everytime I go to start up the machine it works for a second and then the cutter stops spinning. Then when tilt the cutter toward the sky it slips back into gear. So how far up the drive shaft should I put that little clamp and how do I tighten it correctly so the drive shaft does not slip out of place? Thanks

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The Metal Clamp referenced clamps directly on the end of the '2-Piece Gear Box Assembly'. The gear box assembly is an aluminum casting held together by 3 machine screws. The Metal Clamp does not actually lock the drive shaft housing into the gearbox assembly. The flexible drive shaft cable engages the engine output shaft, and the gear box assembly. This is a fixed length (non-adjustable) assembly.

First ensure that the drive shaft assembly is fully engaged at the quick connect fitting and that the "snap" is engaged. Then make sure the knob is fully tightened. The quick connect allows you to quickly switch between various attachments offered on this unit.

Now, based on your description, it sounds like the 'anti-rotation screw' 791-182519 has backed out or is gone. This will allow the entire cutting assembly (gearbox forward) to slip off of the drive shaft housing and disengage the flexible drive shaft. If your cutting assembly is attempting to rotate while in operation, or the drive is not engaged as you described.
Do not continue to operate the unit until you get this fixed as you could strip out the drive shaft end or cause other serious damage to the equipment or yourself.

If it is the anti-rotation screw, then make sure to push the drive shaft housing firmly into the gear box and ensure to align the holes in the drive shaft housing and the gear box. If the screw is lost, then find one similar sized, but be CERTAIN that it is not too long as it will actually engage the flexible drive shaft and prevent rotation, or cut the drive shaft.

Back to the clamp: If it is still wanting to move, then remove the lock nut and place slightly oversized washers on the bolt head and the lock nut. This will force more pressure (does not take much) on the clamp and will lock it down.

I just fixed mine today (071809) in fact and had to drill a new hole in the drive shaft housing as the original was completely wallowed out.

I hope this helps.


Posted on Jul 19, 2009

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