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Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 10:31 am
by ironcorn
As part of the initial build I decided to do the Traxxas Revo axle swap, for durability and weight reduction. I searched online for a DIY and found tons of data, but nothing that had good pics or complete information.

Here's the axle you need. These are on eBay for about $20 for a set of 4.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 10:35 am
by ironcorn
The Traxxas and Tamiya shafts are almost the same size.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 10:53 am
by ironcorn
It's pretty easy to adapt the Traxxas axles.

You need to tap the stub axle yokes for 4mm x .7 on one side, shorten the halfshaft housing by 30mm and machine the flat on the drive shaft .7mm deeper. You need to trim a small area on the underside of the yokes on the transmission side so they will fit.

One key difference I did from what I saw others do is I used the stub axle yokes on both sides, whereas all the other DIY's I saw used the Traxxas transmission yoke, part 5458, on the TXT axle side. The 5458 yoke does fit on the TXT axle without any modification, but the fit is sloppy with more runout than I can tolerate. There is enough play that you have to hold it while tightening the screw and guesstimate if it's on center with the axle. Ultimately, it's an RC car so it will work, but the stub yoke provides a much better fit with perfect alignment. Also, removing 30mm from the halfshaft housing is a baseline and works with a stock wheel base, but I would measure for each installation.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 11:09 am
by ironcorn
I used a 1/8 bit to prep the hole and once tapped, the Traxxas screw pin (which is used on the Traxxas transmission yoke) fits right in, but it's a little long on both sides. That's where HPI part 86094 comes in. Fits perfect, like it was made for this mod.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 11:19 am
by ironcorn
The stub yoke has a deep pocket and the pin hole is set further down, which is good for a solid fit and alignment, but bad because the Tamiya shaft needs .7mm more length on the flat of the shaft to fit so that the pin hole lines up. In the picture you can see the holes aren't lining up.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 11:28 am
by ironcorn
I used a vertical mill and added .7mm to the flats, keeping everything square, and the yokes snap on with a perfect fit, tight and solid.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 11:39 am
by ironcorn
You need to remove a little from the underside of the yoke on the transmission side. One side requires a little more than the other. I put the yoke on an axle and spun it in a drill while shaping it with a dremel. I didn't need to trim the trans housing, but a little trimming there would have allowed less trimming on the yoke. I also needed to trim the heat sink just a touch. No trimming needed on the axle side.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 11:45 am
by ironcorn
That's about it. You save a little weight as well, which is almost always a good thing.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 8:36 pm
by soze
Excellent work so far. Really making me want to build this truck sometime this year.

Re: ironcorn's TXT-2

Posted: Tue Jan 02, 2018 11:14 pm
by andymac0035
That looks really good. I do believe you are supposed to re-use the blue dust boot though, as dirt makes those telescoping shafts bind up quite easily.

Re: ironcorn's TXT-2

Posted: Wed Jan 03, 2018 2:38 am
by ironcorn
I thought about this as well, and am going to keep an eye on it. Some of the examples I looked at online used the boot, some didn't. The boots are glued on pretty good and we're destroyed when I removed them.

I did put the open halfshaft housing on the transmission side, which angles it up, with the idea that dust with have to fight gravity to get in there. In mud or submerged, it could be an issue. Also, the halfshaft only telescopes in 2mm at most during full suspension compression, not nearly as much movement as I would have suspected. With a stock wheel base, you could really cut only 26 or 27mm off the housing and have very little shaft exposed.

Most of the examples I saw that used the transmission yoke kept the open halfshaft on the axle side, being lower dirt would get in pretty easy.

Interestingly, Traxxas uses the same halfshaft for the center drive shaft and uses no boot and no plug on the open halfshaft end (very small rubber plug). Without the plug, the telescoping action is super smooth, but there is no real movement on the center shaft. With the plug in, the fit is tight enough to create positive pressure in the housing, maybe helping to keep dirt out?

Either way, once I start running it I'll keep an eye on it. Worse case I'll boot it up or include shaft cleaning in the maintenance schedule.

Re: ironcorn's TXT-2

Posted: Wed Jan 03, 2018 3:50 am
by 87lc2
Andy knows his stuff so I wouldn't doubt him, but I've been running these shafts on my TXT-2 for a few years without boots and they're good as new. I run the truck through mud/water/snow quite often and never had an issue with them. I'm sure the boots would help protect them, but I experienced the same thing you did, they tore pretty bad when removed no matter how careful I was.

Re: ironcorn's TXT-2

Posted: Wed Jan 03, 2018 8:54 am
by ironcorn
87lc2 wrote:
Wed Jan 03, 2018 3:50 am
I run the truck through mud/water/snow quite often and never had an issue with them.
Awesome, that's good to hear.