Split Differential Cups

[Nutech Racing U.S.A]

I sold a set of center differential cups to a customer for his Firehammer MT, emailed me the next day with some pictures of his drive cups, as you can see below they split right down the center after about 20 minutes of run time with some jumps, I am not real familiar with the Duratrax Firehammer I did some digging around and from what I can see they are a little cheaper entry level 1/5 Scale, I noticed Tower Hobbies has them as discontinued. I have given my Mega MT a good beating tank after tank and my drive cups look great so I am lead to believe he might have something else going on any ideas ?

http://i85.photobucket.com/albums/k55/Sticky_010/IMAG0094.jpg

Thank You,
Scott
Zero Gravity RC

[mooman007uk]

I did one on my MT at the end of last weekend when i was beating on my truck...however it was caused by the turnbuckle pulling out of the upper arm (same arm that took the big rock strike a whiles back...it's been wobbley since then and surprised it lasted as long as it did) and the cvd shaft must have flopped around and caused the breakage...I'll also add it was an old cup and not ae new improved one. I've not busted one in 20 tanks with all the abuse it's had
the cup in the pic is a fr/r cup as it has the slide slot...the centre ones just have a pin hole, if you sent him centre ones then something else is definitely going on.
i take it the guy is also using nutech spider, outdrive gears as the fh uses splines like the fg (though they're slightly different size so don't cross over)

[Nutech Racing U.S.A]

I did one on my MT at the end of last weekend when i was beating on my truck...however it was caused by the turnbuckle pulling out of the upper arm (same arm that took the big rock strike a whiles back...it's been wobbley since then and surprised it lasted as long as it did) and the cvd shaft must have flopped around and caused the breakage...I'll also add it was an old cup and not ae new improved one. I've not busted one in 20 tanks with all the abuse it's had
the cup in the pic is a fr/r cup as it has the slide slot...the centre ones just have a pin hole, if you sent him centre ones then something else is definitely going on.
i take it the guy is also using nutech spider, outdrive gears as the fh uses splines like the fg (though they're slightly different size so don't cross over)

You are right it was for the rear differential, I would hope that my replacement cups are the latest version along with all the ones in my Nutech vehicles so I am wondering now if its something like you are saying with the dog bones or CVD, looks like hes using FG differentials this is all I have to go off at the moment :confused:

http://i85.photobucket.com/albums/k55/Sticky_010/2-27.jpg

http://i85.photobucket.com/albums/k55/Sticky_010/1-29.jpg

Thank You,
Scott
Zero Gravity RC

[Clubin]

Nice bustage. I haven't had that happen to me yet. LOL

[RCKIWI]

I have had a FG one do that but not a Nutech one so far!

[Pipeous]

the firehammer mt arms have a swoop in the middle to allow the truck to have more ground clearance, making the outside lower than the inside. I am betting that at full extension off a jump, on throttle, the dogbone was binding in the dif cup because of the spring and snapped the cup instead of the dogbone pin. maybe center dif parts be better for the fh

[Nutech Racing U.S.A]

the firehammer mt arms have a swoop in the middle to allow the truck to have more ground clearance, making the outside lower than the inside. I am betting that at full extension off a jump, on throttle, the dogbone was binding in the dif cup because of the spring and snapped the cup instead of the dogbone pin. maybe center dif parts be better for the fh

I received some more info from him, he said the truck came with a Nutech differential in it so I am assuming from the pictures he has the GT5R differential in it as that's the only one with straight gears, he said hes running the stock firehammer dog bones, he also stated he installed the old drive cups he has which don't have slots or springs so that means he has center differential cups in it already and tried the f/r differential cups from me with the springs and slots which as you can see didn't last.

I asked him to pull the arms down as far as they would go and spin the wheels by hand to see if there is any binding going on as well as under full compression and he states there is no binding but maybe they are under stress when its jumping, he said hes has the stock screw limiters set but I wonder if he wouldn't be better off with some strap style suspension limiters instead ?

Thank You,
Scott
Zero Gravity RC

[RCKIWI]

Yes seeing the pic's it has a GT5R or alternative diff for FG based cars, they use the center diff drive cups as they dont have the springs in them!

[goneracing_83]

Hello guys, Im the guy that bought the diff drive cup from zerogravityrc. and it did have the diff cups WITHOUT the slot so i thought that they would be better so that way they will move with the suspention. there is a allen bolt (screw) that goes thru the upper rear A arm so that way it dont go down all the way and bind up the drive cup and dogbone. with my truck up off the ground and the rear wheels are just hanging there i can spin them and no binding. i pulled each wheel up all the way and spun them and no binding there either. befor i put the drive cups in i mad sure the bottom of the slot was not to far down and it looks like they were about the same spot. and i figured the spring would take some of the impact of a landing. also the center diff cups ( the one with just the hole in it) i found out that the pin likes to ride on the edge of the gear inside the diff. so i also figured the ones with the spring and slot would make the pin ride closer to the middle of the gear which it is designed for. here is a few pics of the back of my truck. the first one is a pic of the limiter on the suspention. the second one is pic of the dog bone and diff drive cup with the truck off the ground. and the thrid is pic of the diff drive cup and the dogbone with the truck on the ground. hope this helps out. you will have to click on the red X to see the pic.

TJ

http://www.rcuniverse.com/gallery/galleryItem.cfm?itemID=202245&dummy=7701.200608244818&opener=/community/profile.cfm%3Fsection%3Dgallery%26memid%3D319795

http://www.rcuniverse.com/gallery/galleryItem.cfm?itemID=202246&dummy=6837.491635990433&opener=/community/profile.cfm%3Fsection%3Dgallery%26memid%3D319795

http://www.rcuniverse.com/gallery/galleryItem.cfm?itemID=202247&dummy=2648.807500267411&opener=/community/profile.cfm%3Fsection%3Dgallery%26memid%3D319795

[mooman007uk]

looking at the pics i see 2 things 1. the dogbone shaft is way thicker than the nutech ones and 2. you have plastic upper and lower arms...uppers are the issue i believe.
I've had a FH and FG and both suffer the same problem with huge upper arm flex on landings......alloy uppers are pretty essential upgrade for these rc's...looks like on landing you got forward or rear flex, enough to bear the shaft down hard on the edge of the cup and it snapped the one half off as nothing could go anywhere else...post a pic of that end of the bone so we can see if there are any signs of contact there just before the ball

[dc2 man]

imo

i dont know why on earth people use these type dog bones and shafts still,they are crap on any r/c. my fg ones used break the whole time on my on/off road cars.

its balldrive system for me and nothing less.

[bentley marshall]

ive never seen a broken fg dog bone or cups

[goneracing_83]

Mooman, i have is set up so they dont hit but if it flex's then ya i can see it hitting. it dose show some contact on the dogbone but i always thought that was from after the diff cup broke. i just went out and messed around and well broke another one. im about to do away with the diff cups and get FG diff internal gears and get the ball drive set up. everytime i take the darn thing out i have either a diff cup or dogbone problem. i have spent more time fixing the same thing then running it. its getting me upset. i got it to go run it around more then fixin it. at the moment its the other way around... LOL. far as the dogbones being bigger, is there a way i could run a Nutech set. or isnt there a set the same length? if there is then i will have to get the stub drives for the axle side. i have talked to a guy on RCU and he has ran the ball drive set up for a while now and the only thing that he has a problem with is ripping a boot every once in a while. INPUT please

[bentley marshall]

if you put all the fg gears and cups in to the nutech housing if should be fine
i have one on my fg marder and havent had any problems and now its in my fg truck

[goneracing_83]

where can i get the FG gears and ball drive setup. and what am i looking at for damage to the checkbook...LOL

thanks

TJ

[mooman007uk]

I'd try running the dogbones and fg internals (they're spendy but as bentley says work), as i said previously the ball drives are designed for onroads and don't allow alot of up and down suspension travel before they snag the diff cup lip and then gall the ball slides and get notchy...i got thru 2 sets of fg cups, a set of shafts and a set of eclon cups and then i ditched them...if you bash mildly with no sand or gravel you should be OK but tear a boot in gritty stuff and the you'll need a new cup and set of ballbearings. ball drives are not cheap to experiment with

[Pipeous]

you could use the nutech bones if you either swapped to nutech, fg or firehammer buggy arms. they aren't as wide as the firehammer mt arms

[dc2 man]

ive never seen a broken fg dog bone or cups

wow lucky you...

last summer when i was running my fg onroad after an hour-hour& half usage the dogbone would always snap at the end.....

i got so sick of the diff cups wearing that they had to go.....

all adjustments were perfect always,enough play as not to have shafts too tight. still wore neverthe less.....

i do run my cars hard,(not saying the rest of you dont)...the fg monster wore them down in no time at all due to the engine and the weight.

sinse i went elcon balldrive,flawless...........tank after tank zero hassle,no problems.

and i run in all terrain.

i could show you a box full of worn stock fg dogbone & drive cups. and i aint the first one to complain about them.

this here is my 2cents, it was the biggest problem i have had with 1/5th over the years. that and gear mesh,elcon also eliminated this problem permenant for me.

[Clubin]

I split a fg drive cup, inner one. They are easy to change though.

[Pipeous]

if you think fg ones are weak, try firehammer ones LOL.

[mooman007uk]

I split a fg drive cup, inner one. They are easy to change though.

yep, slide old one out and new one back in...gotta love those splines. fg cups wear at the slot though but i think fg make em a bit soft so they wear after a while and need to be replaced with another $35 pair...nothing like designed in life span to sell parts:mad:

[Clubin]

.nothing like designed in life span to sell parts:mad:

LOL Isn't that true.

[Pipeous]

sounds like a zeitgeist thing...

http://www.zeitgeistmovie.com/