With the 3.31 diffs you can get more speed than the 4.3 models.
Would need a fairly large pinion though.

so i basically have to decide if i want speed or if i want to race there is no way to get both is there maby having a car do like 50 and changing the pinion to make it race worthy (slow it down) or something like that.

what is the higest pinion i can get to fit the 7XL without killing the esc (i am getting heatsink and 1 fan with esc)

pretty much ...yes

so i guess there is no way for me to have both speed in the mid 40s and then just be able to change the pinion and make it race ready is there. Maby stick with the slipperential get maximized diffs. and then get a high pinion to get me into the mid 40s and a low pinion for recing in the low thirties. does this sound possable with my setup.

brian it seems that when i make the balooning go up/more my speed goes up so does this mean if i dont tape my tires on the inside that they will baloon more giving me more speed.

what is the highest pinion i can get to fit the 7XL

Alright i think i have the solution to my problem tell me if it sounds good I will go with the maximizer diff cups(standard gear ratio 2.84), slipperential, feigao 540c 7XL, quark 125B, heatsink and, (2) 2 cell orion 4800(7.4v) batteries, a 20t carbon steel 5mm bore pinion, a revo 36t slipper. With this i can speeds of the mid to upper 40s for bashing and by the swap of a pinion get speeds in the lower to mid thirties for racing. and in the end i get the lower cg of the slipperential, the improvement of racing ability form the slipperential, but yet by changing the pinion i can get the speed i want for bashing. I also can get maximizer diffs which should hold up to anything. Is all of this true and should it work if so it sounds like a solution dont you think.

I guess I'll start with your first unanswered question:

There is no set max pinion size for any motor. The spur/pinion is just part of the gear ratio. If you ONLY had the spur/pinion as the means to reduce the motor speed, you'd need a really small pinion to gear it down enough. To get the total reduction, you simply multiply the diff ratio by the tranny (or slipperential in this case) ratio by the spur/pinion ratio. So, if the reduction ratio is high enough, you can use a large pinion.

Yes, ballooning will make a large difference in speed! And no, you really don't want ballooning because it's hard on the tires and traction suffers. Sure, it's cool to watch, but not healthy. :dft012:

The highest pinion will be whatever you can find that's a 5mm bore Mod1 pitch. The highest Mike has listed in his store is 20T. The problem is if the pinion is too big, the motor physically won't be able to be bolted to the mount because of the diameters of the spur and pinion together.

If you use a standard maxx diff ratio of 2.84:1, the slipperential, 36T spur, 4s lipo, and 7XL, you'll be right at 47mph with a 20T pinion.

Personally, I still think a direct pinion to differential drive would be easier, especially since you're looking for a speedy truck. I know there's no slipper, so that's a downside. However, you'd have lots more gearing options without having to use such a large pinion. And it would allow you to use a slower motor, which will have more torque resulting in more gearing options. For instance, an 8XL, HB Pro diff (3.31:1 version), 4s lipo, and 46T spur on the center diff would give you right around 49mph using a much more manageable 16T pinion. And it would still leave a little room to go up/down a tooth or two on the pinion for fine-tuning.

I don't know, maybe someone else will chime in with another suggestion. I know a slipper would be ideal, and the slipperential is a very nice product, but it may not be the ideal part for this application.

so you dont think the slipper should not be recommended even though i am racing. but anyway wat is this way to get a direct pinion to gear or is there some modification to be done can you show me and explain what you mean. this way you explained seems more logical. but if for some reason if i dont do this and i go with what i told you earlier with the maximizers acording to you calculations i can go down to 14t to get speeds as low as 34 mph for racing and 47 mph for bashing which is plenty enough speed for me. But i like this new idea could you explain with elaboration and or pictures. thanks

What I would do is e-mail Mike. I know for a fact he can get you a 24T pinion. I think a 22T as well....He should know if it will work with the slipperential or not as well.

when you say hb pro diff do mean for the direct middle diff or for the use of the diffs that go to the wheels.

The one at the wheels. For the center diff, you can use whatever one you want that'll fit the 46T Kyosho spur.

Before you take my recommendation and buy stuff, I'd wait to see what others say on the subject in case I overlooked something...

EDIT Sorry Squee, I didn't see your response.

gorillamax;

did you ever ran a model at 50 mph?

Not bashing you, but 50 mph for bashing? that's plain redicilous.. for bashing you can do with a slower truck than for racing.

If you run the 7XL on 4S at 50mph it will heat up very quick. (not good)

im not saying anything but have u driven a truck with a center diff?????? because i personally hate them lol i like to drift in the corners with the back end all out but thats just me, so i think figure out how u like to drive and then figure out gearing because the slipperential isnt cheap....