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Old 05-14-2022, 06:11 PM   #1
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Default TRX Based 8x8

Howdy folks. after building a couple TRX-4 and SCX10 II 6x6 conversions (pics below), I wanted to challenge myself and go for an 8x8. So, if ya'll are interested follow along!! Disclaimer: I don't have it all figured out, so I might be leaning on the community for ideas and solutions

Here's my TRX-4 converted rig.



For which I started a thread: TRX-4 to 6x6 Conversion Guide

and the SCX10 II based one.



This build will be based on the TRX-4/6 platform.

Step one is extending TRX-6 chassis rail to accommodate the additional front axle. After staring at the parts I had on hand, I decided to lop off the front section of the TRX-4 rails and use that as the chassis extnsion.

Proof of concept below:

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Old 05-14-2022, 06:18 PM   #2
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Default Re: TRX Based 8x8

The rails have to be hammered flat to remove the curve where the stock rails sway outward to accommodate the skid/tranny mount.



I have brass strips lying around, but for this joint, I really wanted to use steel as there'll be considerable stress (I think) on that joint. Again, scrounging around for something suitable, I decided to use TOOL steel



Step one: fit then drill and tap one side.

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Old 05-14-2022, 06:26 PM   #3
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Default Re: TRX Based 8x8

And joined!!



Here it is with a TRX-6 rail for comparison.



I purposely left the extension long at the front until I figure out what needs grounded/filed off to accomodate a bumper mount. So that's all for now, I'm waiting for delivery of a second hand TRX-4 I bought on FB Marketplace which will be the donor truck for a lot of the parts.
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Old 05-14-2022, 07:42 PM   #4
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Default Re: TRX Based 8x8

Sweet build idea man! Good idea with the chassis as well.

When you hammered the frame straight, did you heat it up at all or just a cold bend?


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Old 05-14-2022, 08:28 PM   #5
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Default Re: TRX Based 8x8

Very cool, looks good so far


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Old 05-14-2022, 10:36 PM   #6
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Default Re: TRX Based 8x8

Quote:
Originally Posted by ScaleLifeNewbie View Post
Sweet build idea man! Good idea with the chassis as well.

When you hammered the frame straight, did you heat it up at all or just a cold bend?
Thanks. The frame straightened out nicely just cold hammering it out on my wooden workbench.
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Old 05-14-2022, 10:37 PM   #7
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Originally Posted by twade984 View Post
Very cool, looks good so far
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Thanks for following along!
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Old 05-15-2022, 08:05 AM   #8
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Default Re: TRX Based 8x8

Sweet... been debating doing this as well, but on an older SCX platform. Curious to see how it comes along!
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Old 05-15-2022, 08:16 PM   #9
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Default Re: TRX Based 8x8

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Originally Posted by OSRC View Post
Sweet... been debating doing this as well, but on an older SCX platform. Curious to see how it comes along!
OSRC, thanks for following along. Parts have started arriving: a rear axle from Ebay where new parts can be found cheaper than from Traxxas. This one has the locker assembly that will be disabled as I plan to run full locked.

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Old 05-18-2022, 09:33 PM   #10
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Default Re: TRX Based 8x8

Mo parts arrived



Was slammed at work this week, but over the weekend I hope to move this along. The deal on FB Marketplace fell thru, so I've ordered a new TRX-4 Sport kit from which to source parts.

Last edited by JimInMiami; 05-21-2022 at 08:10 PM.
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Old 05-19-2022, 12:33 AM   #11
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Default TRX Based 8x8

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Originally Posted by JimInMiami View Post
Mo parts arrived

Was slammed at work this week, but over the weekend I hope to move this along. The deal on FB Marketplace fell thru, so I've ordered a new TRX-4 Sport kit from which to source parts.

The sharp-eyed among you.... might've noticed that I've ordered THREE additional full axle assemblies. Can anyone figure out why?

Three steer axles??


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Old 05-19-2022, 11:50 AM   #12
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Default Re: TRX Based 8x8

If you need a place to send all those un-needed locking diff parts, you just let me know ;)
I just picked up a used sport that could use selectable diffs 👍
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Old 05-19-2022, 11:58 AM   #13
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Originally Posted by islandlife View Post
If you need a place to send all those un-needed locking diff parts, you just let me know ;)
I just picked up a used sport that could use selectable diffs 👍
The selectable diffs can easily be locked with a washer, but if you send me a couple of spools, I'll trade ya
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Old 05-19-2022, 06:47 PM   #14
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Default Re: TRX Based 8x8

It begins....



The challenge of this build will be figuring a way to mount the frontmost axle's links, so for now I'll concentrate on the front end seeing as the rear setup is pretty much the same as the TRX-6's.
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Old 05-21-2022, 08:04 PM   #15
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Default Re: TRX Based 8x8

I think that for clarity the axles should be referred to from front to back as axle 1, axle 2, axle 3 and axle 4.

I wanted to hang axle 2 today but first had to change it to a "pass thru" axle so that the second pinion will drive axle 1. I used part # 8846 which can be seen in the pic above instead of the stock diff cover. A couple of bearing and a second pinion and it's good to go.



Hung



As I never liked the two-part unit that comes stock, I'm using a Bowhouse RC skid for those wondering.

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Old 05-21-2022, 09:08 PM   #16
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Default Re: TRX Based 8x8

This is very cool, looking forward to seeing how you tackle the “obstacles”


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Old 05-21-2022, 10:14 PM   #17
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Default Re: TRX Based 8x8

Looks good so far!

I’m really interested in seeing how your links will work out on Axle 1.


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Old 05-24-2022, 07:13 PM   #18
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Default Re: TRX Based 8x8

Quote:
Originally Posted by twade984 View Post
This is very cool, looking forward to seeing how you tackle the “obstacles”
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It's coming along!

Quote:
Originally Posted by ScaleLifeNewbie View Post
Looks good so far!
I’m really interested in seeing how your links will work out on Axle 1.
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That's definitely the main challenge of this build. Fingers crossed I think I have it figured out.

Rather than fabricate a custom mount for the links, which given my limited skills would've posed a challenge I decided to try and use the stock rear link mount for the TRX-6. That's part #8830 in the exploded view: https://traxxas.com/explodedviews/TR...assis-Assembly

But.... two problems:

1) There's not enuf room between shock mounts for axles 1 and 2.
2) My front rail extension is not straight, it's "W" shaped.

After staring at this for three days I hit on an idea:

Step 1 reduce the length of the link mount, here is the modified version next to the stock one:



A band saw comes in handy to get an accurate cut here, btw.

Next cut away at the rails to allow the link mount to sit in the channel. I'll clean those cuts and repaint later, I just wanna know if this is gonna work for now.



Trial fit in the chassis rail. With this arrangement the link mount will not interfere with the shock mounts, but I'll really only know if everything also clears the steering mechanism for axel 2 once I reassemble.



Thanks for following along, and stay tuned!

Last edited by JimInMiami; 05-25-2022 at 06:54 AM.
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Old 05-27-2022, 03:45 PM   #19
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Default Re: TRX Based 8x8

I built an 8x8 on Axial frames using HG axles a last year and getting the steering and drive shafts to clear each other took a lot of trial an error. I ended up using fairly short links on the front but the thing still flexes pretty well.

Custom Built 8x8 With Tonka Cab
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Old 05-31-2022, 07:54 PM   #20
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Default Re: TRX Based 8x8

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Originally Posted by 12MPG View Post
I built an 8x8 on Axial frames using HG axles a last year and getting the steering and drive shafts to clear each other took a lot of trial an error. I ended up using fairly short links on the front but the thing still flexes pretty well.

Custom Built 8x8 With Tonka Cab
Impressive build, thanks for sharing!

The cab's arrived



Yes, I know it's premature to be buying the cab seeing as I haven't even sorted out the chassis yet, but even if this build's a fail, I can always use it in something else. Check out the detail!

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