Newbie - motor positioning for gear mesh

This is a complete newbie question and I don't even know what to search for, so feel free to redirect me to an existing thread that answers the question if there is one.

We have a stock Rustler XL-5. It comes with a 16/90 gear set installed at the factory, and a 28/86 optional gear set in the box.

We wanted to try the 28/86 conversion, but the gear pair is too large to mesh at all. The stock setup includes a plastic bracket (3790 - gear adapter, fixed) which locates the motor in a single "fixed" position. Basically, it fills the slotted motor screw hole on the lower side so that you cannot use the range of the slot.

What is the [B]correct[/B] way to change to a new gear pair? Do we remove the plastic adapter completely? If so, what locks the motor securely in place to maintain the correct gear mesh - is it done only by the clamping force of the two motor mounting screws?

Any tips and advice welcome. Thanks in advance.

Yes, it's done by the clamping force of the screws. You're correct. You can dispense with the plastic retainer.

There are loads of threads/videos on setting gear mesh but what works for me is:

Install the gears. Make sure the pinion and spur are lined up with no overlap in terms of how far along their respective shafts they are. Tighten grub screws and add threadlock.

Have the screws in the fixed position almost tight but free enough to swing the motor. Have the other screw a bit looser. Swing the motor in so the pinion engages fully with the spur then back off very slightly. Tighten the adjusting screw to hold the motor in place. Then turn the gears to see if they rotate smoothly. Look for "high spots" where there's too much friction as they turn. If there are high spots, just slacken the screw and swing the motor away very slightly and try again. Once the gears are meshed tightly with no high spots - you're done. You'll notice a little bit of play if you rock the gears together if you've done it right.

Once you've done it a few times, it'll be easy.

Btw if you run the higher speed gears check your motor temps. If you can't hold your finger on the motor for 5 seconds then it's getting a bit hot.

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