I'm building up a Rustler for thrashing, and possibly some local racing, and was wondering what most people use for diffs? I was considering getting an adjustable Ball diff, but was also looking at the steel geared planetary diff from the VXL...

Which would be preferred and are there any other options to consider?

Thanks,

For racing, the ball diff would be better since it's tunable. Also having steel gears adds rotating weight, which reduces acceleration.

I just replaced the planetary gear diffs with MIP ball diffs in our (my son and I) two Rustler VXL's. Traxxas support does not recommend the Traxxas Ball Dif Pro for VXL setups. We ran into problems with the MIP assembly on one. The nylock nut is thick and can cause issues. You have to be very careful to make sure that the female outdrive is less than a full thread engaged from the nylock or you will jamb against the small thrust bearing assembly and not be able to fully tighten the dif. If you can get a 4-40 thin nylock nut instead. If it spins for a run or two you'll groove the thrust plates and flat the balls. The thrust plates are not keyed. This is non-standard for all ball diffs and a concern of this design. You will need to back the slipper clutch one full turn from tight or you will spin the diff. There is absolutely no chance of wheelies with this setup but the posi-traction on loose dirt/wet grass is worth the sacrifice. If you're racing, it is far superior to the planetary dif. I've tried thick tacky grease in the planetary dif but it just moves out of the way after a couple of runs and it's right back to spinning out. On pavement, it is fine as long as you ramp up the throttle. We've seen around 12 runs per vehicle and they're holding up good so far. I guess we'll see how long they last. I still have two planetary difs to fall back on. Also, the last line of the instructions say to tighten the dif all the way, then back out 1 full turn. This is way to loose for our Rustler VXLs, even on 7.2V 6 cell packs. I have one 1/4 turn back and the other fully tight (that's the one we had the problem with). We run NiMH 6 and 7 cell packs. Hope this helps.

I wouldnt run a ball differential myself. They are somewhat more tuneable, but they just arent that durable, and are finicky IMO.

Eric

Ball Diff's really don't like brushless power and won't stand up to the abuse very long. Add in the fact that they constantly need adjustment and maintenance and it's just not worth it unless you're racing and looking for the last tenth of a second.

If you're plans are to race and use a mild mod motor then it's something to consider but I personally wouldn't go that route. The stock VXL gear diff will be close to bullet proof for the life of the truck. I've never had diff open in my VXL rusty and it's close to 3 years old....

I'm not quite sure about that john. I agree that ball diffs mean you have to set them properly (whereas gear diffs you just slap them in), so gears are easier. For just bashing and mild racing, I'd just say go gear diffs.

But I do think ball diffs are pretty durable with BL - or have you experienced otherwise? I've been bashing with a Durga (ball diff) and a Novak 8.5 BL setup for a while now, no issues. Same with a vintage Bosscat I was running a MM 5700 in, and a TA05-R with the same electronics - all ball diffs.

Maybe I didn't run them as often as you have? Just trying to understand where the comment comes from regarding durability.

I have had a number of problems over the years with Ball Diffs. It's true that some are much better than others but I don't have any experience with the ball diff in the Durga (car is unbuilt on shelf) so I can't comment on it. Is it by chance the same piece that's in the Dark Impact? I did have a Dark Impact and the rear ball Ball diff worked well. The Front diff was a different story. The rear only required adjustment once in a while but the front would need rebuilds and adjustments often..

On the other side of the coin I did have the Proball in an SRT many years ago and it was a constant headache even with mild power it required a rebuild after almost every weekend of racing. The Ball diff in my B4 has also been a source of frustration sometimes requiring a rebuild after just a couple of runs. In my opinion the B4 is the worst ball diff i've come across. It works well and is nice and smooth for a pack or two but after that you need to be prepared to rebuild it.....I know other will disagree but that's my experience.

The main problem I've had with them is they tend to slip when you apply big power and eventually they get so loose that they burn up or actually melt the diff gear. This happens a lot with the B4.

I really wish Traxxas made a sealed Diff for the slash/rustler/pede as I feel tuning with diff fluid gives you the best of both worlds. I refuse to pay for the FLM piece and I refuse to add that much rotating weight to my gearbox.

Wow, well that stinks. I can understand your opinion based on those experiences for sure. For what it's worth, I've beat my Durga pretty badly, and don't recall adjusting the diffs since after my first few runs (after you 'break it in' or whatever). I'm running a slipper though, so maybe that eases the pain?

You should build yours up and enjoy.

Sorry to be so long posting a followup but things have been down right busy the last two months. Lesson Learned.. I would not recommnend MIP ball diffs for a VXL system. 1) The design is flawed from the get go. No keyed bearing plates. When the balls are locked up the plates do the slipping. Losi has gone to something similar using a bearing material as a "clutch-like" pressure plate rather than balls. I believe it's on the Speed-T. Early reports leave guys scratching their heads. 2) Too delicate for rough backyard racing. We tore both Diffs up in less than two weeks. It was not much longer after my previous post that they both went south. It's a long story with mutple photographs and unanswered calls to MIP. So, I used a 3mm ID x 6mm OD washer in between the sun gears on the planetary diffs to create a LSD, (spin one wheel and the other turns in the same direction. Power down and it's hard to turn) packed them tight with red sticky grease and went back to racing. We've been running Dirt Hawgs in the rear and had been getting the occasional spin outs in damp grass and loose dirt even with the LSD. On a side note, I've personally been very dissapointed with the Dirt Hawgs. It didn't take 5 runs for them to come unglued and start rolling off the rim. I cleaned them up with isopropyl alcohol and glued them back on where the tire seperated from the rim. This happen multple times on all tires. After a while the tire gets out-of-round and out-of-balance. So I ordered Talons. What an amazing difference this tire has made. My son and I have been racing neck and neck with very few spinouts. These tires hookup very well on damp grass. Loose dirt is another story but that's OK, it's navigating that turn in the track that you need to concentrate on good car control and drifting technique. If two months ago I had done the washer diff mod and bought Talons rather than DirtHawgs and MIP diffs, I could have save about 100 bucks, not to metion the skin off my fingers from pulling the ball diffs in and out multiple times. Oh well, we're now having fun like never before, so I have to say with a positive attitude that the lesson I've learned is a good one. I hope that someone else who is new to this hobby reads this before making the same error.

Yes ball diffs are tunable but from my experience I just do not see the ends justifying the means. The maintenance and tuning can become a chore, one mistake and it melts or fails. My new firestorm has the planetary diff and I love the fire and forget maintenance of it and the simplicity. I stay away.

i use both, my srt ive blown like 3 gear diffs and and done about the same using ball diffs, both the trx and mip sets

i have to say though, the gear diffs are much less of a hasle, even if i strip the internals im still only out a few bucks and i dont need to re-find my settings (i never seem remember them)

the ball diff isnt good for thrashing. only good for racing. and as mentioned, it wont work with the power of a brushless motor.
you can put thick grease in the VXL diff to help it not "unload" as easy. but the vxl diff is very strong and holds up well to bashing and brushless power. plus, it only costs about $15 on ebay.