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-   -   Tamiya 801xt Hop up (https://www.rcuniverse.com/forum/rc-truggy-399/11630144-tamiya-801xt-hop-up.html)

DreamOfFlying 06-10-2016 04:52 AM

Tamiya 801xt Hop up
Ok guys hopefully this is not too much of a brain stretcher. I recently aquired a Tamiya 801xt which i dont know a whole lot about. It came with an axial.32 spec 1 that im in the process of rebuilding. The truck runs strong and all seems to be in good condition and fairly upgraded. So what im thinking is that with the bigger engine is it possible to put a 2 or 3 speed transmission in it. If so how do i begin my search for a tranny that will fit with the least amount of structural modification. I hope that wasnt to wordy for what im wanting to do. I will also try to post pics and maybe some videos of the work if it can be done.
Thanks in advance

Maj_Overdrive 06-10-2016 03:55 PM

The easiest way to do this would be with a 1/8 touring car 2speed. 1/8 touring cars are basically 1/8 buggy/truggy with lowered suspension and street tires. These are available in the Kyosho GT and GT2, as well as Ofna GTP, GTP2 and DM1. I'm sure you could find a complete unit on eBay or buy one new. You'll obviously also need the appropriate clutchbell for the donor vehicle you choose. Something like an enclosed monster truck 2spd from a Revo or Savage is simply too large for the chassis. You'd have to move the motor back on the chassis, definitely shorten the center shafts, relocate other components, etc. The 2spd from a 1/8 touring will eliminate the need for all that work.

As as far as mounting goes this could be super easy or more difficult. The holes in the chassis are likely not going to line up with the mounts for the new 2spd. In fact they'll probably be close enough that they'll overlap. You could mark the holes and drill from the top of the chassis easily enough. But when you try to countersink the new hole from the bottom the countersink drill bit will wander into the previous hole if they overlap at all, even with a drill press and the chassis clamped down. Trust me I know from experience. I had to use a dremel tool to manually make a countersink and it's not the cleanest way to do it.

The easy way to do this would be to use the stock Tamiya diff mounts for your new 2spd. There are a couple things you may run into. The bearing sizes may not match up no matter how much mixing and matching you do. But you can order just about any size bearing from Avid, Acer and other bearing suppliers to match the width and inner and outer diameters you need. I doubt you'll run into a height problem as the Tamiya truggy diff supports should be tall enough. But if you do you can space it up with some washers or cut your own spacers easily enough. The biggie is going to be length. If the 2apd is shorter than the Tamiya diff simply add some shims or use wider bearings. If the 2spd is too long you may be able to get away with using a thinner bearing at the front. Maybe use a thinner bearing at the rear too and shave the diff support down until the spur gear clears.

Just some ideas. Let us know how it turns out.

DreamOfFlying 06-16-2016 05:23 AM

So something like this?

And fit it into the mounts already on the buggy?

Maj_Overdrive 06-16-2016 11:37 AM

Yup something like that should work nicely. And yes I'd try to use your current center diff mounts. You'll probably need different size bearings to make it work but I'm sure the size is out there for not too much money. Way better than trying to use new center diff mounts and drilling holes in your chassis.

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