For Bashers, By Bashers!

Everybody’s Scalin’ For the Weekend – Locking a Yeti Differential the Old Fashioned (Cheap) Way

axial-yeti-diff-lockThe Axial Yeti is a capable “do it all” type of truck, what-with a plush suspension, 4wd and a solid locked rear / open independent front setup. This works great for someone looking to do a bit of crawling but still maintain a vehicle that performs reasonably well at high speeds and/or in the air.

I didn’t buy this thing to use as a “do all” type of rig, though. My Yeti is being built as dedicated trail machine, and as such that open diff just isn’t going to cut it. I need full time 4WD at all times. It was time to lock it.

Before locking the front, lets talk limited slip. Some people use very heavy 1/8 buggy silicone diff oil which lets it spin only under heavy duress. This (in theory) gives the best of both worlds. You keep the front locked but if it gets really nasty it’ll have some give. You’ll also have a bit of easier handling given that the front will open up under hard cornering. I’ve never really seen this work out well. When crawling you almost always wind up just spinning the tires on the rocks. I saw that a lot with the Vaterra Twin Hammers last year.

So yeah, if you are wanting to really do any crawling with it you will have to lock the diff. There are several lockers available on the market but due to the fact that I have no need to ever unlock the front I figured I’d go with a very cheap and reliable method – JB Weld.

JB Weld is a two part bonding epoxy that can be had on the cheap (about $6) at most auto supply stores. I started using it in differentials around 15 years ago (I’m getting old, yikes) when I took my first foray into the world of r/c pulling and it’s never let me down. It’s still really popular with hobbyists as when allowed to cure properly it’s basically like welding your gears together.

Before I show you how to do it, remember that the big downside with the stuff is that it is permanent. If you ever want to unlock the diff you’ll need a brand new set of parts. It can also be messy if you aren’t careful. Another thing to be aware of is that if you roast the ring and pinion you can’t open up the front to salvage the internals…again, you’ll need all new parts for a new one.┬áSo yeah, in general a dedicated, removable locker is a more elegant solution. Ok, without further adieu hit the “Read More” and let’s get to it.

This is the Yeti's front differential assembly. You need to remove the 4 screws to access the internals.

This is the Yeti’s front differential assembly. You need to remove the 4 screws to access the internals.

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Here are the internal spider gears. You’ll want to take them out of the cup and drain the oil before continuing. It’s a good idea to wipe the inside out with a cloth before putting the gears back in.

Ok, one quick note before adding the JB. In most cases you want to use a disposable surface (like an index card or junk mail) and mix a 50/50 solution from each tube

Ok, one quick note before adding the JB. In most cases you want to use a disposable surface (like an index card or junk mail) and mix a 50/50 solution from each tube and then apply it to where it’s needed. Dealing with differential cups I’ve found it’s easier to apply it directly from the tube to the housing and mix in place because it’s quicker and less messy. It’s just a personal preference of mine to do it this way.

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Now it’s time to add the JB Weld. You will use the black “steel” tube first. Once you’ve got a good amount added it’s time for the silver “hardener”. You want around a 50/50 mix. Make sure you don’t overfill the diff because if it overflows it is very goopy and it can be a pain to cleanup. It can also ruin bearings if it makes contact with them and you don’t clean them off quickly.

Here's the solution with compounds added. You want to blend them together as best you can with a toothpick or other similar small makeshift mixing device. The better you mix it, the better it will setup.

Here’s the solution with both compounds added (I hadn’t mixed it up a ton yet in this pic). You want to blend them together as best you can with a toothpick or other similar small makeshift mixing instrument. The better you mix it, the better it will setup.

Carefully assemble your diff just like you took it apart, with the gear on top. This will keep the JB Weld from running. I'd recommend you leave it out overnight for it to harden. After an evening or

Carefully assemble your diff just like you took it apart, with the gear on top. This will keep the JB Weld from running. You need to give it around a day to fully cure. After it’s set, you can put it back in the truck. Pretty simple, right?

Go crawling with your newly locked front diff!

Enjoy your newly locked front diff!

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Posted by in Axial, RC Rock Crawling, scale rc on Friday, November 14th, 2014 at 4:15 pm

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