Mamba Monster eating front diffs on my X1 CRT

[stallion_explosion]

I've got an X1 CRT brushless conversion with a mamba monster driving the big nitro spur.

It is eatng front diffs. Put a new one in, drove for about 10 mins with my boy and it's gone again today.

I'm thinking about selling it - it is a ridiculusly high powered setup - and getting something that won't be quite such a handful to keep running.

Is there something I could be doing to stop it being so high maintenance? Or should I flog it to someone who will love it for the mental case it is and get something that will be less insane?

Edited October 25, 2015 by stallion_explosion

[capri-boy]

I've got an X1 CRT brushless conversion with a mamba monster driving the big nitro spur.

It is eatng front diffs. Put a new one in, drove for about 10 mins with my boy and it's gone again today.

I'm thinking about selling it - it is a ridiculusly high powered setup - and getting something that won't be quite such a handful to keep running.

Is there something I could be doing to stop it being so high maintenance? Or should I flog it to someone who will love it for the mental case it is and get something that will be less insane?

 

What's could be happening is it's unloading to the front diff only (when the front end comes up the centre diff will send power to place of least resistance) - it likely balloons the front wheels at the same time - does this sound familiar?  If so there's too much power going to the front which will exacerbate front diff wear - strange it's killing them so quick though.  Solution to this is thicker oil in the centre diff - this will semi lock the diff so when the front lifts not all the power will transfer - 60k silicone oil works for me, though Truggies are more prone than buggies in my experience - prob down to the wheel size.  It's a balancing act as too thick and it will lift the front end more, to thin and it'll unload to the front only when the front end naturally lifts under acceleration. 

 

When you replace the diffs are you doing the whole thing or just the internal gears?  You don't say whether 4,5,6S but even on 4s well shimmed diffs are essential for long life - as are diffs filled with oil.  I'm assuming your running the stock 64?68t? (I forget which) spur:

In which case unless you've a custom mount for a huge pinion I'm thinking your not running 4S.  For my X1 CRT conversion I ditched the huge spur for a Hyper ST 52t - I could have stuck with a HN spur (the buggy 48t would have worked) as hyper parts are cheaper, robust and mroe readily available - they are also almost interchangeable in the centre - I had custom mounts built and rather than shim the diff (hyper is marginally smaller length) had the mounts made to offset the difference.  The X1 CRT had that huge spur for two issues - nitro's don't create all that much torque at the lower end, just like a car (in race .21 sizes more so) and HN in there wisdom (stupidity?) used buggy ratio diffs in the X1's - 3.3 ratio, whereas most truggies use a 4.5 - the result being it was much harder to turn those big wheels, hence the big spur to lower the strain on the nitro.  Brushless set ups don't generally suffer from lack of torque so the huge spur wasn't needed for me.  This leads to the other possibility - are you using the correct diffs?  It was common for people (especially when converting) to fit X2 CRT diffs (there a straight swap like most X2 parts) as they ahve the usual 4.5 ratio - It's worth checking your using the same ratio's front and back or else one end is driving faster than the other - which when you've got traction will create issues.

 

C

Edited October 26, 2015 by capri-boy
typo

[-BEZ-]

You shouldn't be destroying a CRT diffs I ran 6-8s through mine and never had one failure on HN diffs.

Firstly make sure they are shimmed correctly, they should not be too tight or too loose, you should be able to feel a tiny amount of play between the gears if shimmed correctly (check the "mesh" at several points, rotating the crown gear a few times to check for tight spots). Also if you are using brushless setups you need heavier oils. 50k front 50-100k centre and 30k rear always worked really well for my bashers and a had quite a few HN's and have built many others for other forum members. Lastly make sure there is a decent amount of grease on the gears before re assembly.

 

edit: If you are referring to the internal gears failing or wearing make sure there are 2 shims behind each planetary gear (the small ones). The manual refers to one but it was later changed to 2 because the internals would slip under power.

Edited October 26, 2015 by -BEZ-

[stallion_explosion]

thanks for the help guys. it's actually the pinion on the front diff that is going. Does this mean anything do you think? i replaced the whole diff in its case last time.

 

 

 

 

 

 

[sputnik]

We have the same issues.

I will try the heavier weights as well.  Have always run about 40% lighter weights than whats been recommended here.  Its always the front ring/pinion gears for me/us.  Never the internal planetary gears [ alum - lol ].  I chalked it up in the past to on power front end landings gone bad.  I also have set my Mamba braking settings waaaay down and that when we here the dreaded "clicking" sounds most often - which is the pinion and crown gears teeth skipping over eachother.  Shimming the pinion and crown together has been tried in all sorts of tight / medium tight arrangements - but still to no avail.

Speaking directly to OFNA - there was discussion about the race team switching away from the spiral cut gears to same tooth counts in the hardened steel straight tooth gear sets.  I cannot seem to find them at this time ... only the Buggy crown gears and pinions in straight cut gearing.

Heres a gearing chart for you that I put together - to help me keep track of all the vehicles and parts needed to run the right ratios

NOTE: [ except for the DM-1 - these are the stock gear rations for "truggies". ]

Im currently in the middle of like 8 different vehicle builds and rebuilds and one of those is the Jammin X2 CRT front diffs on my e-conversion.

Shims behind the pinion gear, and on the proper sides of the diffs bearings in the gearbox to get a rather snug but not too tight mess fit is essential.  Ample grease on the crown gear, and good trigger control on landings and braking settings is key to longer life.  Id actually prefer to try and go back to a mechanical brake vs. the elect motor braking - as I think that is where a lot this issue is stemming from

 

P.S.  Hobao Hyper and Kyosho diffs fit in the Jammin/Hong Nor gearboxen and center diffs ... AMPLE Parts supply if needed.

 

 

 

Edited November 1, 2015 by sputnik

[capri-boy]

thanks for the help guys. it's actually the pinion on the front diff that is going. Does this mean anything do you think? i replaced the whole diff in its case last time.

 

 

 

 

 

 

Can't help any more, but can help with some funds towards the fight if you got any spare diff housings?  I could use four as the some of the mounting holes are a lot loose on both the CR and CRT, though a couple would be great (even one would help!).

 

ta