Any options for the Super/King Blackfoot Differential Bevel Gears?

[jimbo858]

hello all!  I'm hoping someone can help point me in the right

direction.  I just got ANOTHER Super Blackfoot off of ebay. 

At first it looked like it was RTR.  But, then when I took apart

the gearbox to add ball bearings to it (instead of the plastic

bushings) I found that the bevel gears in it had grinded away their

supports that hold them in place. So, does anyone know of a better

solution to the stock differential gear?  will the ball bearing

gear for the M03 work?

http://www2.towerhobbies.com/cgi-bin/wti00...=LXGE35&P=M

thank you for your help in advance!

[OCD]

Hmmm... that's good question!

I have a Manta/TA ball diff here, so I might tear down my KBF to see if

it's a fit.  Unless someone else has already tried and

failed?  I know that it uses the standard cups, but the diff gear

might be a different size or 'offset'.  Would love to know if it

works: A Blackfoot with a ball diff is a good thing!

(If I don't see a definative answer here soon, I'll get that KBF on my bench and let you know!)

[jimbo858]

Hmmm... that's good question!

I have a Manta/TA ball diff here, so I might tear down my KBF to see if

it's a fit.  Unless someone else has already tried and

failed?  I know that it uses the standard cups, but the diff gear

might be a different size or 'offset'.  Would love to know if it

works: A Blackfoot with a ball diff is a good thing!

(If I don't see a definative answer here soon, I'll get that KBF on my bench and let you know!)

OCD... thank you, thank you, thank you!!!

I've already ordered a set of bevel gears from Tamiya. But, looking at

the design with the metal bevel gears spinning on the stationary tiny

metal shaft. To me it's just a matter of time before it grinds through

the new replacements as well...

[OCD]

So I did a complete tear down on my King Blackfoot this evening. 

I'm not sure if the Super BF is anything like the KBF, but a Manta ball

diff will NOT fit in place of the stock gear.  The stock gear

(much as I expected) is about 10 teeth taller than the ball diff

gear.  On the bright side, all the internals are standard fare, so

they are quite easy to obtain. When I rebuilt mine, I replaced the diff

cups with TA03 pieces I had in my toolbox.  I also replaced the

dogbones with TGX pieces that are identical in size/shape!  Like I

said, this is for the KBF, so I don't know if this applies to your

Super Blackfoot.

[jimbo858]

OCD thank you for trying. I really appreciate it.  The King

Blackfoot and the Super Blackfoot have identical gearboxes from what I

can tell.  So, I'm sure that it still won't fit in my gearbox

either. So, I guess I'll be rebuilding my differential with some stock

bevel gears. Unfortunately, everyone seems to be out of them at the

moment.  Any suggestions on how to best protect the bevel

gears?  I'm thinking that I put a buttload of grease all over the

metal pieces and then screw the differential closed...

[OCD]

No problem Jimbo.

I'm not sure what the problem is that you're having...  My outer

diff plates had some wear, but nothing that would effect

performance.  As far as I can tell, the diff uses standard tamiya

internals, so any of the bevel gears/plates/etc. should fit inside the

gear. 

(If I'm wrong about this, somebody step in and let me know.)

As far as protecting the gears:  No use in loading up the grease;

most of it will be flung out the first time you hit the throttle. 

What you'll end up with is a messy gearbox full of grease.  Just

use the kit supplied ceramic stuff in moderation and you should be

fine.  When I had a closer look, my diff was worn where the outer

plate contacted the outer bearing. Not bad enought to cause any

problems, but eventually I may add a shim on both sides to take up the

slack. These gearboxes really are one of Tamiya's better

designs.. dare I say nearly bullletproof?

[jimbo858]

Hello OCD, below is a picture of the bevel gears that I'm talking

about. it's the small support metal support that holds the bevel gear

that wore away on my Super Blackfoot. I know that eventually the gear

will wear away at the support.  But, I'm hoping that if I add some

extra grease in the differential case and then screw the differential

cover back on (the cover that covers the differential gears that it'll

keep enough of the grease in the differential to help prevent the

metals parts from wearing away at each other...

[OCD]

This might be one of those 'if it's not broken' type scenarios..Since

the bevel gears are nearly stationary most of the time? 

Are the outer ring gears rubbing the bevel gear shafts?  If so, you might be

able to shim it from the inside.  I can't recommend it though, as

I think that the added friction my be no good here.  Have you

thought about using extra heavy grease to slow the diff down?  I

use this in all of my geared diffs. 

[jimbo858]

actually that's the problem. it IS broken.  I got this truck off

of ebay a few weeks ago and it looked okay. but, when I was taking it

apart to put ball bearings in it I noticed that the previous owner ran

the thing til it almost fell apart. Some of the plastic bushings were

almost worn through. never seen that before.  then when I opened

up the differential to see if it was okay I noticed that two of the

bevel gears just popped out.  then I noticed a couple of "extra"

metal pieces.

As for thicker grease, that's what my plan was all along. BUT, what

grease do you recommend?  I've been using all-purpose lithium

grease that I got from a local automotive parts store.  Seems to

work pretty good on some other gears...

[OCD]

Ouch !

Now I get it- Those stupid bushings probably allowed enough play in the

axle cups to cause this kind of failure.  My guess is that once

you've replaced the bushings with bearings, that'll be the end of

that! 

For grease I've been using a bottle of 10,000 weight I got from Tower

Hobbies.  It came with no lable on it, and looked completely

different than the picture on the website, so I have no idea what it

actually is[:$] 

I've heard some people use friction damper grease that comes with some

of the Tamiya kits, but I'm not sure about this.  My TGR came with

a small pot of "AW Grease" for the diffs and it worked perfectly. 

Unfortunately it was a very small pot, as I used every bit of it for

the two!

[jimbo858]

YES!  That's IT! 

Well... I'm hoping that's the problem and that when I get the new gears

and rebuild the gearbox with metal bearings that it will fix this

problem. BUT, it would have been nice to have a ball bearing

differential in there! 

I'll probably just stick with regular all purpose lithium automotive

grease for now.  It seems to have worked really well in my other

Blackfoots AND I can get a BIG can of it for cheap.

again thanks so much for the help!