Diff balls melting into spur

[NickTheGreek]

On my re re Im running a Dynamite Tazer 4000 kv motor.....
After my first two runs (on a beach parking lot) I noticed my "car" not wanting to move. I noticed the diff balls had melted into the spur gear. I was told I probably had the diff too loose.
I got a new spur, new diff balls ....and I tightened the nut to where if I held the rear tires down and gave a burst of throttle the front end would slowly lift up.

I took it out for a spin at the parking lot and after about 10 minutes of riding, I noticed some black residue forming around the spur gear. I'm thinking that that's the first sign of the diff balls starting to melt into the plastic again. ...They hadn't melted th plastic, but the previous time it happend there was a lot of black residue in the gear cover so Im pretty sure it's the same thing all over. ...just in its first stages now.
What am I doing wrong??? Is it just the motor being too much, or is it something I can fix??

I plan on upgrading to the stealth.....Wth the 4 pole 4000kv motor, will I have problems with the stealth??

The car runs freakin perfect. ...the motor seems perfect(as far as performance goes) ....mega fast, but controllable ....

I raced my friend yesterday who was running a Slash4x4 ultimate vxl on a 3s (I was running on 2s) ..... N was only a couple of feet behind him...basically neck to neck the whole way....probably in the low 40's in mph...
I'm running a 23t pinion and 81t spur ......

......all I know is my "car" is running freakin perfect as far as performance......the perfect combo of speed while maintaining full control.....I just wanna resolve this issue of melting the diff balls into the spur.....
I don't wanna get discouraged ..... It's too much fun....

Is it too much motor?? .... Am I doing something wrong as far as in how I'm tightening the diff nut?? ...... Down the road will I be fine with that motor and a stealth??

HELP!!!

..............

On another note, I had the pin pop out one of my MIP CVDs .....any good way to prevent that??

Thanks
Nick

[DMAT]

its the motor. that 4 pole motor is just too much low end torque.

If you can program your motor/esc, dial back the low end and it might not melt the spurs.

It might be ok when you upgrade to a stealth.

[GoMachV]

I have absolutely no concept of the power that combo makes, but one thing that was typically done to keep from melting gears and allowing the diff to work properly was to pin or glue the drive rings to the hubs. As they are they slip easily and can help create heat unless the diff is run very tight. Just a dab of superglue is all you need.

[NickTheGreek]

Thanks for the quick responses and words af advice, guys!!

.....Being a "novice" and looking for others recommendations, I'm surprised the guys at the hobby shop (whom I like) recommended that motor,being its a 4 pole. A month ago I had no idea as to "2 pole,4pole" ..... If it was me making the choice now, I definitely wouldn't throw a 4 pole motor in a little buggy.
It's too bad if it is the motor because the car runs so good. Even on a burst of throttle it's not like it wheelies n is out of control. It just takes off like a rocket.
I've seen videos of guys completely over powering their cars where they just immediately wheelie or just flip.....I don't have any interest in that.....

Like I said, right now I have that perfect combo of crazy performance yet still having control to where the car isn't just spinning out or doing flips...( but what good is it if the diff balls are gonna keep melting into the spur) ....

I'll be trying the glue, n will go check to see how adjustable my esc is....

Silly question but Im not experinced in these things....would changing the pinions tooth count change?? If I went lower,wouldn't that be fen more torque...and if I went higher, wouldn't that be more friction??

thanks again.

[DMAT]

my only real concept of 2 pole vs 4 pole motor is on the low end torque. As far as i'm concerned, my velineon 3500 still has plenty of torque for a 2 pole motor. I can still make my rustler pop a wheelie at 40 mph if I go full throttle. The car also has a ton of weight too as the entire front end was replaced with aluminum parts.

I recently bought a 4 pole neucastle 3800. i'll be throwing it in a car to test out the stealth once parts are available. If I were to test this on a 6 gear, i'd probably look for some metal spur gears. Not sure if they exist though.

Just a heads up, If you have this problem later on using the stealth transmission. If your using a b4 topshaft conversion like whats on the re-released world's car. Hot Racing make metal spur gears that can be used. I've used them before and one is currently in my all metal car.

[NickTheGreek]

Thanks for threads up....

I just called Horizon Hobby to ask about what the equivilant of that 4000kv motor would be in turns....n was told its probably around a 9t. ....so I'm right around the limit.
Re re manual states " Do not go lower than 8.5" ......
They told me my 23t pinion was too high and was causing too much heat and to drop it down to around 18t which happens to be what the re re manual suggests for that motor.....

Right now, looking at the manual , it looks like I had left the diff too loose the first time I melted the diff balls into the spur, and might've had it too tight yesterday when I starts to melt them again.
Manual basically says turn the nut until the first point where the spur doesn't freely spin when giving throttle while holding down the tires...and not to go tighter for it will cause "tremendous" heat.
I definitely had tremendous heat....lol

Eh.....I might have to give up a few mph n drop my pinion a few teeth and hope for the best.

Definitely ordering the stealth when it becomes available.....Maybe two....The way things are going so far, I might need some back up.

I'm just trying to figure out what size motor will give me optimal performance while running a 2s lipo.....

...................

I've been looking for a metal spur but it doesn't look like they have any out there...

[slapshot1979]

Are you melting diff gear or spur gear?

[Minisforever]

Are you melting diff gear or spur gear?

The spur is the diff on a 6 gear

[knixdad]

If the diff isn't slipping, then I don't know how you are building up enough heat to melt the diff balls into the gear. Excessive diff action can do it but you should notice that driving around.

Any time I have ever melted a diff gear, it has been because it was too loose.

[Jay Dub]

If the drive rings are not pinned on the 6 gear, they can slip on the aluminum drive hub and generate a ton of heat in a short period of time. BITD, the rings were glued on. Unfortunately this is more a band-aid than a real fix. I think the tranny could handle that amount of power, but it would need to be built properly. I race a stealth tranny car, and can attest to its ability to handle the amount of power you are running BTW. -J

[NickTheGreek]

I just called AE to ask them......n first things first, the guy on the line was a super cool guy...a good brother...so kudos to AE for the friendly and patient reps.

Said the 4000 kv is fine but being that the 4 pole is heavy on the torque, to make sure that its on pretty tight......Guess I gotta go even tighter.
Yesterday I had it tightened down till the front end would slowly come up if I gave it a burst of throttle while holding the back wheels down.....I guess I'll have to go to that same point n give it an extra 1/2 to full turn more n see what happens from there....

Thanks for the replies.....
Would dropping the pinion to 18t from 23t make any difference in the issue, or would it be completely non related as far as melting the spur go.

[NickTheGreek]

I actually took the tranny apart a lil while ago and everything seemed to be alright.....Any common mistakes people make when building them??

Good to hear some reassurance about the stealth being able to handle it.....I say that just because being I just got back into rc after not riding one for over 25 years, building this re re bought me a lot of joy....I like invested my emotion into the thing.....I got a lil disheartened melting the diffs on back to back runs right out the gate.
At least knowing if this keeps happening, I could just pop a stealth in there n be good to go in a few weeks puts me it at ease.....
Lol...it's like I'm watching t.v n instead of paying attention to what I'm watching, I'm thinkin about the car. I'll be in bed,having to get up for work in the morning,start thinkin about the car, pop up out of bed n start takin the tranny apart. at 12:30am.

Edit:
The drive rings do have like a lil ring going around the middle of em....probably rigjt where the diff balls touch on them....so it looks like there was friction there.

[Jay Dub]

Yeah, the rings are caused by the balls rolling (and slipping). The 6 gear tranny has a differential, not a slipper. This means that it is not meant to slip, but meant only to offer differential action. The key will be proper build and maintenance. Adjusted and lubed properly I have no doubt that the stock tranny will do ok. You just have to keep an eye on it. When you hold the rear tires and apply throttle, the car should pull the front end off the ground with very little slip in the diff. When you run the car it shouldn't slip at all under acceleration, maybe a bark when landing off a jump . -J

[terry.sc]

Yesterday I had it tightened down till the front end would slowly come up if I gave it a burst of throttle while holding the back wheels down.....I guess I'll have to go to that same point n give it an extra 1/2 to full turn more n see what happens from there....

It's a diff, not a slipper, and it sounds like you are setting it to slip quite a bit. If it doesn't flip right up instantly when you hold the wheels down the diff is certainly slipping. When adjusting it, hold both wheels down and try and push the spur gear by hand, if it moves the diff is too loose and will slip and melt the gear.

[NickTheGreek]

Thanks.....

I just finished adjusting it....Basically I screwed the nut down all the way n eased it up a hair.

......hopefully that does the trick.

The other day when I melted it, I went down to the beach parking lot with two of my friends....One of them says "wanna race" ...so I said "lets go" . (I didnt get the car with the intention to be racing) . My re re is definitely fast, but Im thinking I'm out gunned in this one.
We got 3 cars....On the left, a Losi 5t with a custom pipe....on the right, a Slash 4x4 Ultimate vxl running a 3s lipo....n in the middle (ah yeah babe) ....the lil 6 gear re re running a 2s....
We just went in a straight line.....The Losi, I took it to the brother....n stayed neck in neck with the Slash ...

Basically what I'm trying to say is watching the re re hang with them on my setup which isn't anything crazy, melting the gear was worth it.....Now I'm tempted to throw a 3s lipo in there , gear all the way up ...go for another race....n smoke those brothers like a Marlboro n take the $600+ loss when my "car" either blows up or falls apart....
That's just a temptation though....
I'm actually perfectly content .....I just hope I resolve the issue my next time out.

................

Another question.....When the diff is set too loose, I've witnessed the results first hand. Obviously develops tremendous friction. ...so....when the diff is set too tight, the manual states that can also cause tremendous friction.....
My question is, if it's set too tight...what's that friction affecting?? Would it be burning out the tires??
What ar the affects of having it too tight??

I'm asking this because in order to prevent my diff from slipping with the set up I have on there, it seems I pretty much have to tighten the nut down all the way.

Thanks....