E Revo Center Diff questions and Opinions

[sikeston34m]

Hi Guys,

Well I've trashed my second diff in my E Revo so far.

The first was the stock rear diff. It sheared a tooth off the pinion, then began chewing it up.

I upgraded with RCM V2 diffs using 13/43 gears. Everything shimmed perfectly. For output shafts, Ofna Mutilator cups were used. These took the place of the inner cups for the Traxxas CVD's. Also installed.

The front diff pinion bearing on the RCM diff is gone this time.

I also see the rear center drive shaft is about to shear off the Rear U-joint.

My current setup is:

MMM ESC
Medusa 36-70-2000kv geared 22/40 (46mph with the 13/43 diffs)
4S Lipo.

I do like to run a tight slipper. It is usually screwed all the way in, then backed off about 1 turn.

I know the Traxxas center diff will lessen the shocks to the drivetrain, but it will also change how the truck drives. Front Tire ballooning on acceleration, difference in braking, and other things I'm sure.

Should I get the center diff? Please tell me about your opinions and experiences.

I'm really tired off rebuilding/replacing diffs, but I want my truck to haul butt.

I'm putting together a parts list. Should the Traxxas Center Diff be part of this rebuild?

Thanks

[Bondonutz]

If you mostly bash, don't even consider the Traxxas CD. They leak and are weak.
If you ultimitely decide you want a CD either look for a premade 1/8 scale used one or build your own.
Check out "Mistercrash" erevo build thread,he's posted pics and details on a CD build.

[Kevlar]

I like my center diff, if you tape your tires you won't have as much ballooning, almost not noticeable at all. I don't know how it affects braking, but it's nice keeping the front tires down, but with a loose slipper, you may not have that issue anyways.

I have ran a CD from the start and never had an issue with a diff, since March anyways.

I say get one, try it out! For the price, it's worth a shot!!!

[simplechamp]

I'm currently debating if I'm going to make one of those hybrid center diffs. The hardest part is grinding all the teeth from the Thunder Tiger spur and drilling/tapping the hardened steel. After that it's basic assembly.

I'm wondering what is the reason you need to use the TT spur and modify it? Seems like it might be easier to make your own out of alum. since the hardened steel is so much tougher to work with. All you need is a circle of alum with the correct diameter, then drill/tap the four mounting holes and drill a hole through the center for the shaft to go through.

[mistercrash]

Originally Posted by simplechamp

I'm wondering what is the reason you need to use the TT spur and modify it? Seems like it might be easier to make your own out of alum. since the hardened steel is so much tougher to work with. All you need is a circle of alum with the correct diameter, then drill/tap the four mounting holes and drill a hole through the center for the shaft to go through.

I would say it's a bit more complicated than that. You need a small round groove on the inside of the cap for the O ring to fit in nice and snug so the lube won't leak around the output shaft. A lip around the edge of the cap that fits over the diff case to center it. The hole for the output shaft has to protrude by 6 or 7 mm so the shaft turn straight and true and doesn't wobble all over. The aluminum cap you speak of would have to be quite a bit thick if you want to screw into it to hold the output gear in place. The modified spur gear or ring gear is not that thick but it is so hard that even though there's only 4 or 5 threads to screw in, you can torque those screws very hard and the threads won't strip, the threads on the screws will strip first even if you're using 12-9 screws. CowbyRay made his cap out of aluminum but they were done right and there was some extensive machining involved. It was more than just a flat piece of round stock.

[simplechamp]

Well, so much for that idea. I have a drill press, but don't know how I'd grind down all the teeth on the TT spur since it's so hard, but I'll have to figure something out.

mistercrash: Do you have to use the TT center diff or will most common center diffs work? Is there any reason the TT diff was chosen in particular?

[mistercrash]

I went to the store and got a long 6 mm bolt with a lock nut and a couple washers. I put the bolt in the 6 mm hole of the gear for the output shaft and secured the whole thing with the washers and nut. Then I chucked the assembly in the drill press and made it turn fast. I put an angle grinder to the gear and started grinding away at the teeth. A lot of sparks and a lot of noise but it worked.

[simplechamp]

The reason I ask if you have to use the TT diff is because I'm going to be putting the RCM Slipperential in my Caster truggy so I'll have the stock Caster center diff already that I'd like to use instead of buying the TT one.

EDIT: I decided I wanted to make things easier on myself so I ordered the Thunder Tiger parts. Maybe the Caster diff will work, but I'm going to have a hard enough time following the directions with all the correct parts, let alone trying to modify it for different parts. I might be PM'ing with some questions once I start the build if that's alright with you mistercrash.

For anyone else interested in building the hybrid center diff: Total cost shipped for all parts came to about $50 (I ordered two of the plastic Revo gears in case I mess one up or shred it while driving). You'd expect to pay close to that for any other decent buggy/truggy diff so it's not too expensive IMO.

[shaunjohnson]

traxxas CD sucks balls

[mistercrash]

Originally Posted by shaunjohnson

traxxas CD sucks balls

Other kinds of diffs work to make a CD out of them. I used a Thunder Tiger diff, I used an Ofna Hyper 7 diff following scjrss instructions and I am presently running a CD made of a Losi LST2 diff.

[Bondonutz]

Originally Posted by shaunjohnson

traxxas CD sucks balls

Isn't that a good thing ?

[sjcrss]

I used a bench grinder to cut the teeth off of the hyper 7 diff's ring gear, I just cooled it with water after it started to get hot, also the revo plasic gears won't work, the teeth count is incorrect, you need the gear from the traxxas CD or mod the original lower gear like Mc did. Don't forget the (1) 8X12 bearing for the one end also.

[simplechamp]

Originally Posted by sjcrss

you need the gear from the traxxas CD or mod the original lower gear like Mc did. Don't forget the (1) 8X12 bearing for the one end also.

I ordered 2 of the plastic Traxxas gears that mistercrash listed (Traxxas Output Gear 33T: TRA3984X) I believe they are from the Traxxas CD. Going to get the bearing also.

EDIT: Where did you guys find the 8x12x5 bearing? I can only find 8x12x3.5, which probably would work? mistercrash are you sure it's 8x12x5?

[sjcrss]

The gear you ordered is for use in a 3.3 revo tranny, you need the gear from the traxxas CD or use the original one and mod it for use with the Erevo trans. Also look on avid rc, and the bearing you find is the 8x12x3.5, and it will work just fine. Thats what I used and it works great.

[sikeston34m]

So Can the Traxxas Center Diff hold up to the power of the Castle 2200kv Motor on 6S?