Ball diff.

[lykan]

Ok, I have a stadium truck, the XTM X-cellerator. I have a question about ball diffs.

Now I understand the slipper, and the clutch in the clutch bell are for letting the motor rev up before you go.

This ball diff thing...All my rc's have had open diffs. I used to run a lot of the old 7.2 Electrics.

This thing I have is a nitro, the ball diff, they say needs to be tightened as much as possible for some reason... what is that reason?

Seeing as how I play on and off road, I want an open diff at times, and at times not. It's hard as hell to turn on pavement when you hit the brakes with a locked up diff. Hit the brakes, the front comes down, go to turn, and the front just plows.

Is it ok to loosen the ball diff? If so how much? I dont want a wide open diff, but some turning ability would be nice..

As for traction.. hell I don't need a locked up diff on a nitro stadium truck. LOL the damned thing winds so tight the tires baloon and I'm going to get some grip anyways.

I'm heading to go bash with the boys tomorrow and I am doing some maintenance.. would be cool to get an answer tonight so I dont have to tear the tires off before we head out..

Thanks a lot as always..If this forum hadn't been around I'd still be either
a) getting more blisters from the pullstart or,
b) returned it for a electric.

This car has been a blast, and the good folks here are the #1 reason it worked out that way. I hope in the future I have some new stuff to contribute to pay you all back..

BTW if anyone needs the 411 on the X-C let me know..love it so far..

 

[lykan]

Shameless bump any help out there?

TTT To The Top

 

[Error401]

A ball diff is just that, instead of having a gear setup, it uses a set of carbide balls between two steel plates. The balls allow for smoother diff action, but the tension (or compression) between the plates needs to be real tight or the diff will slip. You can adjust the nut a bit to get a small ammount of slip (like a slipper clutch), but not much. Ball diffs are nice, I run one in my Micro RS4 and it made the world of difference in handling. Remember, the diff is there to provide a differential movement between the inside and outside wheels in a turn, not slipper clutch like action.

Hope that explained things,

 

[lykan]

I was told oto tighten the heck out of it. When I do that, it seems as if the rear is kinda of locked lock a posi, is this how it is supposed to be?

Or should I tear it down and have a look inside? I had no idea they actually slipped.. as in power to the tranny, but none to the wheels.. hrmmm

 

[Error401]

If I'm understanding right, it is the main differential between the wheels. If this is correct, then yes, it should be as tight as possible. On pavement, both rear tires would have about the same ammount of traction, and whatever diff you had (ball or gear), it would react the same as you described (understeer). Same goes for being on the gas, same power going to the tires. It is 2wd, right. It's late here, and I'm making alot of assumptions. I have the same problem with my Savage and Lightning and both are 4wd. How much brake action do you have at full brakes on the Tx? if they lock up, then you have too much brakes dialed in. Generally, set your brakes so that at full Tx brakes, on the surface you run on most, the wheels that get the brakes nearly lock up. This will reduce understeer on braking. All 1/8th buggys have 3 diffs and 2 brakes. one for the rear and one for the fron, so you can dial in different ammounts of brakes for the front and rear. This allow for more brake action in the rear, less in the front. But the setting principle is the same, never set then to lock up completely.

I digress. If the differential "feel" is smooth, and there is very little (or no) slippage in the diff, it's set right and is working properly. I would tend to think that the understeer is due to over braking.

 

[lykan]

I gotcha on the braking, its a ST so only one brake, 2WD.

The diff doesn't really feel all that smooth.

I have motor to Clutchbell to slipper clutch to rear diff.

I understand the concept of wanting equal traction for both tires. But with 2 Wheel drive you need some give in the rear so one tire is allowed to spin faster than the other while cornering..

As it is now it seems their is no give on a corner making it "push" the front rather than turn. It is possible my camber and alightment abilites suck as well
I guess I should have been more clear, what guess I am asking is..

Is it ok to loosen the ball diff so one wheel is able to turn faster than the other realitively easy? I dont want any slippage as far as the motor is concerned, just enough for turning.

With a geared diff it was easy there was no slip one wheel or the other turned. Maybe only one, but it was direct drive.

 

[Error401]

Originally posted by lykan
The diff doesn't really feel all that smooth.

This may be the problem. It should feel silky smooth when locking the input from the slipper and turning one wheel. If there's some dirt or whatnot in the diff, it'll make it act funny. I hate to say it, but I'd take it apart, clean the balls and plates, relube it and see how it feels. The plates should be mirror smooth, and there's no real way to look at the balls to see what kind of condition they're in (round and dent free). The ball diff needs to be lubed with a thick grease, silicon preferably, and the kit might have had some spare lube included with it (hopefully some balls too). I hope this works out for ya, the ball diffs require a bit more care than the gear ones, but they are nicer when they're tuned up.

 

[lykan]

Well, I thank you for your help. I pulled the dogbone out, and the nylon cover.. I found it wasn't as tight as I remembered or as it should be.. the tigher I got it, the smoother it became, but still not smooth..

Now that you mentioned about the inside of the diff and I thought about it, it kind of feels like a couple of the balls may have flat spots. Possibly because it wasn't tight in the first place?

Anyhow I defentaly need to do a tear down now.. not looking forward to it though ;( Wonder if I can get by running a tank or two tomorrow until I have the time (and my hands work) to tear it down.

 

[lykan]

I changed the Camber today of the front wheels, also lowered the rear end a bit. I nosed the tiresin in the front as well. I

Think I kinda over did it. It does really well under normal conditions.

But if I get hard on it, it'll whip right out. it is kinda nice for bashing to be able to hit the brakes, spin a 180 and head the other direction FAST to keep from hitting a curb tho... Just not for the track (like I'll ever race anywas).

Thankls for your help much appreciated.. As for the ball diff.. it's either about shot with flat spots., or just not run/broke in yet.

 

[Error401]

Playin with the alignment will make it handle different. Just tweak it a bit at a time and you'll find the sweet spot. You might want to start a thread on alignment in the ST section, some other guys would be alot more help than me in that area.

I'd keep an eye on the diff too. It might not be run in yet, but then again it might be shot. Only time will tell.

 

[StaticSag]

I'm kinda new at this stadium truck thing myself and was thinking in the same lines as lykan. The best teacher is to try it and record the results. I lossened (once tight as I could get it without breaking it) the ball diff in 1/8 turn increments and it started to help when turning but it soon (after 3/8 turn out from bottom) it began to vear towards the right on the long straights, especially under hard acceleration. I tightened it back up and it went away. So I read more forums on ball diff setup and ended up a 1/8 turn out from bottom. But the biggest key I myself learned was with the slipper. With your ball diff adjusted, hold the pinion and passenger side rear wheel and rotate your left rear towards the rear and as it tightens up the slipper will barely begin to slip. This is where ya want to start. Another bit of advice I got from the forums is if ya spin out on turn exits you can loosen the spur for some added traction due to slippage and less power actually getting to the ground....again 1/8 turn increments. Also ...my RTR came with some cheap diff balls and after the first diff tightening they were cashed....replaced with carbide balls. The rough feeling diff went away and hasnt returned.

Anyways just passing on what I recently went thru myself and the advice I got from several forums. thanks goes to the writers of those posts. I would have sold it if it weren't for them.

-Sag