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Installation Instructions for Most Straight Shaft Trimmers

These are the standard instructions for straight shaft trimmers.
Not all straight shaft trimmers follow these instructions. You can check the Brands section to see if your particular brand and model follows these instructions or is one of the exceptions. From this point forward we'll use the term "straight shaft" for any trimmer, straight or curved, that follows these instructions.
Straight shaft trimmers with fixed line heads follow the Fixed Line instructions.
Most Echo, Husqvarna, Stihl and Weedeater trimmers follow these instructions even if the models are curved shafts.

All our replacement heads follow the same basic set of instructions. There are a few GrassGator models that require some extra steps. Follow the instructions below regardless of the GrassGator head you are trying to install. If your GrassGator head requires additional steps then you will be prompted to click on a new link once you have reached that stage of the installation process.

DO NOT REMOVE THE DEFLECTOR SHIELD. We removed the deflector shield and / or used different trimmers on the pictures just to show in more detail the parts relevant to the installation. Your trimmer and /or GrassGator head may not look exactly as the ones illustrated.

Straight Shaft trimmers have a short shaft (about 1" long) that is in most cases, male (threaded on the outside, like a bolt) and on a reverse thread (tightens to the left opposite to the "lefty loosey" rule we learned as kids). Straight shaft installations require only a nut. You won't need the spacer cup that comes in the kit.

Remove Original Head

In order to expose the threaded shaft needed to install the GrassGator head, you must remove the original head as a complete unit. Do not take it apart in pieces. If you do that, you'll leave the "spool shaft" on. The "spool shaft" is a long hollow cylinder threaded on the inside that works as an extender to accommodate the original head. If left on, the shaft will be too long and there will be too much play between the top of the shaft and the GrassGator head.

In order to remove the whole head as a complete unit you must lock the shaft before you can unscrew the original head. Most of the trimmers follow one of three styles:

Metal collar with a hole cut on top

Shows where the trimmer head lock hole is.

Right on top of the original head there should be a metal collar with a hole cut on top. Use the tool that came with your trimmer and drop it down the hole. If yours didn't come with one you can use a nail, hex wrench or drill bit. Turn the head a few times until the locking tool aligns with the hole on the plate inside the collar. The tool will sink a little bit deeper and the head will offer some resistance once you try to turn it opposite to how it normally spins. Unscrew the original head as a complete unit. Remember, most straight shaft trimmers are on a reverse thread so try unscrewing the head to the LEFT first.

U shaped slit cut on the side of the plate

Right above the original head there should be a plate or metal collar with a hole or u-shaped slit cut on the side. If your deflector shield covers the plate, look for a hole on the deflector shield. Your trimmer may have come with a tool to lock the shaft (usually a metal rod). If yours didn't come with one then use a nail, screw driver or hex wrench instead. Insert whatever tool you are using into the slit and turn the head a few times. The tool will sink deeper locking the shaft. You'll notice that now the head will offer some resistance once you try to turn it opposite to how it normally spins. Unscrew the original head as a complete unit. Remember, most straight shaft trimmers are on a reverse thread so try unscrewing the head to the LEFT first.

"Nut" above the original head

Finally, some brands like Weedeater have what looks like a pot metal "nut" right on top of the original head that wraps around the handle of the trimmer. If that's the case with yours then hold the "nut" in place, don't let it move and then unscrew the original head off as a complete unit.

If:

The original head of your trimmer is a fixed line then follow the Fixed Line instructions.
If you unscrewed the original head as a complete unit and the shaft is longer than 2" then stop and follow the Curved shaft instructions instead.

Find the correct fastener

The GrassGator kit comes with a pack of 7 nuts and 2 bolts. Most straight shaft trimmers have a shaft that's threaded on the outside (male). Very few have a shaft that is threaded on the inside (female). If the shaft of your trimmer is threaded on the inside then find the bolt from the kit that fits the shaft. If the shaft is threaded on the outside then find the nut that fits the shaft. Most straight shafts require a left hand threaded (reverse thread) fastener but in very rare cases, a right hand thread nut or bolt is needed. Once you find the correct nut or bolt, set it aside.

If:

None of the nuts or bolts fit the shaft of your trimmer try them again but this time screwing them to the right. Make sure you try them ALL, they may look alike but are in fact different sizes.
If they still don't fit then you can go to the Brands Section to check which nut or bolt is needed for your particular model and request one by e-mail or by calling 1-800-210-9949.
If you have a GrassGator 3630 then stop here and follow these instructions.
If you have a GrassGator 7800 then stop here and follow these instructions.
If you have a GrassGator 4750 then stop here and follow these instructions.
If you have a GrassGator 12200 then stop here and follow these instructions.

Otherwise continue with the next step below.

Drop the Nut or Bolt in the GrassGator Head

First locate the bottom of the GrassGator head. The bottom of the GrassGator head is the side with the hex shaped recessed hole. This is the side that should be facing the ground once the GrassGator head is in use. Very important: The hex shaped hole on the GrassGator head will NOT go over the hex on the top of your shaft. The hex hole should be facing the ground.

On bladed units (3600,4600,4680) and models 4700 and 5620, the bottom is the flat round side, not the triangle side.

Shows how to install the nut on a bladed trimmer head.

On Fixed line heads like the 8010 and 5600, the bottom is the flat round side, not the side that sticks up.

Shows how to install the nut on a fixed line trimmer head.

Screw the GrassGator head on

The GrassGator head will work as a wrench. You may have to start the nut or bolt with your fingers but once the head of the bolt or the nut is inside the hex shaped hole on the GrassGator head you can then keep turning the GrassGator head until it's tight. There should be no vertical play at all. The GrassGator head should be tight against the gearbox. Any vertical play may damage the GrassGator head or your trimmer. The GrassGator head is self tightening and it will get a few more threads upon use. If there's play then, you are done and ready to use your new GrassGator!

If:

There are a few inches of play, and the shaft is threaded on the inside go back to step 1 and make sure you removed the original head as a complete unit. Some trimmers come with a shaft extender that needs to be removed.
If there's 1/8” or less worth of play, you can slide a washer between the spacer cup and the GrassGator head.
If you followed all the recommendations above and there's still too much play then you can go to the Brands Section to check if there are any special instructions for your particular model. You can also call 1-800-210-9949 or e-mail us with any questions. Please remember to include the make and model of your trimmer along with your phone number in case we need to ask you some questions. Pictures are always helpful. .