hot bodies diffs - RC-Monster Forums

**hot bodies diffs -** 12.01.2009, 12:21 PM

hi all...more possibly stupid questions

. now that i have the gearbox sorted on my max (3906) im looking at hybrid front and rear to handle the mm combo alloy g/box case and alloy hubs all round. so whats the difference between the normal diff and the pro diff please ? ta...

wallot · 12.01.2009, 01:03 PM

pro diff is hardened. I would not bother with the old non hardened version. never had any issues with the hardened diffs in my maxx.

suicideneil · 12.01.2009, 01:07 PM

Pro diff has a lower gear ratio meaning you need to gear much higher at the spur/pinion to get the desired speed. The Pro also have spiral cut gears that load the bearings more, causing them to fail more often; the standard buggy diffs ( non-pro) are the ones everyone uses including myself- they last forever, though there are actually better ones out there that have metal inserts inside the diff cup, to reinforce the spider gear shafts. I forget the exact model they come from though at present...

wallot · 12.01.2009, 01:46 PM

if i remember correctly there used to be non hardened buggy (43/13) and truggy (43/10) diffs and the hardened that were called pro also buggy (43/13) and truggy (43/10)
I had in my maxx pro buggy diffs - hardened 43/13 :)

suicideneil · 12.01.2009, 02:41 PM

I'll take your word for that- I know there were hardend versions and non-hardend, I think the ones Mike has are the hardend versions (they felt had when I last checked them, lol, no signs of wear), so the normal buggy ratio 43/13 ones are the ticket

**spiral cut -** 12.02.2009, 08:56 AM

hi all...thanks guys, spiral cut gears eh? sounds interesting, spiral cut should be stronger, more than one tooth engaged at any time- it should take more power, if cut correctly that is

. i know it would deflect at a different angle but cant see why the bearings would go quicker? same power same wear factor?? oh well now i cant decide between the two, spiral should be better thats why they were designed,
same power down a smaller lighter diff

suicideneil · 12.02.2009, 04:23 PM

Stronger yeah, through larger contact area, bu the ormal straight cut gears are uber tough- rare you ever seen a damaged or blown one. Aparently the spiral cut gears place a sideways load on the inner pinion gear bearing, causing to to fail quicker- the solution is a thrust bearing perhaps, but making that fit correctly + shimming woudl be a pain. PLus theres the gear reduction issue- I havent ran the numbers for a while, but you need something like an extra 4 or 5 teeth on the motor pinion to gether the same reduction ratio vs straightcut diffs, so it obviously causes issues if you have a limited gearing range to start with (due to motor hitting the tranny or lack of adjustment space/ spur gear options etc). I really would stick with the normal 1/8 buggy diffs- they havent let me down with my ~13lb rig pushing 5s lipo on a 2000kv motor, not a sniff of wear on them

redshift · 10:42 PM

^Yep overwhelming consensus on the helicals is bad. The races are too shallow on these little bearings for anything more than moderate side loading. Like Neil said they'd have to incorporate a thrust bearing, which would require preload to work in the radial axis. Scaled up just a little the helicals would be superior to straight cut, but size is the limitation. In that vain I don't think I'd wanna drive a 1:1 with straight cut gears...

Some info on compatibility here- http://www.rc-monster.com/forum/showthread.php?t=23255

George16 · 12.02.2009, 11:14 PM

Just buy the Ofna Hyper 7/8/8.5 buggy diffs and you're set. They are a lot cheaper and lasts just as long. I have them in my gmaxx running on 6S and no problems whatsoever.

07:01 PM

thanks all...spiral cut bevel gears have to be mounted on tapered bearings...straight cut it is then.

george, do them hyper diffs have same size shaft for drive cup as std e maxx ones??

suicideneil · 12.04.2009, 01:12 PM

Yep, standard 5mm shafts to take pretty much all drive cups. The input shaft is 8mm though so you need to use a different cup- HotBodies #C8068 for example (one for each diff, also requires a 4mm grub screw) clicky

12.04.2009, 03:15 PM

thanks neil.

George16 · 12.04.2009, 05:41 PM

Yup, what Neil said.

**plastic casing? -** 12.15.2009, 03:18 PM

hi all...neil those diffs come with plastic diff housing? makes me think so by what you said about metal inserts...i want ally ones if possible but i can make them..(there just such a pain to machine innards out). just would be nice to be able to put some thick lube in front diff and for it to stay in there longer than 5 mins...hmmm maybe sum oil seals.
hey is that an oil seal gap i see cut into the shafts on mike's webpage?? those shafts are to use original shafts or mip's for e maxx, does it work???
does the thick lube stay????
thanks all...

suicideneil · 12.16.2009, 01:04 PM

They do come with a plastic diff cup yes- its a strong cup though, not the mushy plastic like traxxas uses.
Some brands/ versions do use the metal inserts, though it is still rare that the plastic cup fails as such.
I do believe that most if not all these 1/8 diffs have o-ring seals around the output shafts- yep, the ones Mike sells have little grooves cut into them for said o-rings; never had any oil leak out of my diffs (7k front & 5k rear).
The shafts Mike sells are designed primarily so that you can use traxxas drive cups or the stock sliders with drive yolks, but pretty much any 5mm bore drive cup/ yolk will fit just fine.