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Managed to break a losi HD diff cup today

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Old 05-10-2011, 06:44 AM
  #1
millzee
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Default Managed to break a losi HD diff cup today

When I first got my xxl I found the weakest point to be the diff cups. After upgrading to the HD cups, I've ran the truck for almost 10 months with the same cups. Today when I was trying out a new set of wheels I managed to ruin the run by breaking off the entire side of the cup. Kinda sucked as I was just starting to get the feel for the tyres handling, oh well, another excuse to go again tomorrow. My six year old son took some footage of the run today, he did well, take a look http://www.youtube.com/user/1millzee?feature=mhum
Has anyone snapped these, I thought they were bullet proof?
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Old 05-11-2011, 09:24 AM
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Default RE: Managed to break a losi HD diff cup today


Quote:
ORIGINAL: millzee

When I first got my xxl I found the weakest point to be the diff cups. After upgrading to the HD cups, I've ran the truck for almost 10 months with the same cups. Today when I was trying out a new set of wheels I managed to ruin the run by breaking off the entire side of the cup. Kinda sucked as I was just starting to get the feel for the tyres handling, oh well, another excuse to go again tomorrow. My six year old son took some footage of the run today, he did well, take a look http://www.youtube.com/user/1millzee?feature=mhum
Has anyone snapped these, I thought they were bullet proof?
Few obvious points here.

A. Your running brushless. That means ALOT more instant torque.

B. No clutch. Nitro engines have a clutch which helps to ease into the torque band. This means setting the slipper and using the proper diff fluids becomes alot more important. I see alot of thread where people run diff fluids that are just to heavy(20-50k plus). If your running diff fluid in that range or higher may want to think about reducing it. I actually find diff fluid in the 1k-10k range is plenty with 10k being the absolute heaviest to run since it really locks up the diff on hard acceleration. I myself use 5k in the rear, and 1k in the front. Plenty for limited slip. Too heavy and you end up putting alot of stress on the diff gears and outdrive cups. Being your brushless, you may want to think about going a bit lighter than I am in the rear diff specifically.

C. spur gear slipper pad. If your using the stock one, you probably have to set it real tight to keep it from slipping excessively. Try the HD slipper pads if you havent already and set it a bit looser.

D. New tires: I havent seen em but depending on the size and weight, they also will put alot of stress on the outdrive cups. Again may want to check into your spur slipper pad setup and diff fluids used in the diffs themselves.

The HD outdrive cups are very tough, but going brushless means the specifics mentioned above need to be set up more carefully for long term durability of the outdrive cups etc since you have ALOT more low end torque and drivetrain stress taking place.
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Old 05-11-2011, 09:50 AM
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Default RE: Managed to break a losi HD diff cup today

Cool vid..(for brushless.. )

BTW, Big Joes are actually lighter than stock ATX tires... Been a long time since I weighed them, but I seem to remember the stock LST2 tires being a good bit heavier than the Big Joes..
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Old 05-11-2011, 02:34 PM
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Default RE: Managed to break a losi HD diff cup today

I'm running 20k in the front and 30k in the rear, this is the first break I've had since going brushless, I think my weights are fine, landing a poorly driven backflip onto hard pack dirt that is as hard as concreteonto awheel still spinning at app. 25k-30k rpm is what I thought could be the problem. I'll just have to find a softer landing spot of my jumping. Afterspending an hour doing standingbackflips on asphalt and not having any problems makes me thinkmy current drive train/diff set up is ok. http://www.youtube.com/watch?v=ura16...el_video_titlethanks for your thoughts.

I balanced the wheels last night and they weighed 445grams, a tad heavy.
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Old 05-11-2011, 04:49 PM
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Default RE: Managed to break a losi HD diff cup today

I think you can just chalk it up to the fact that no matter what you have or put on it, parts will break at some point or another[8D] Just a simple fix though and if that is all the problem you have, then you are doing pretty good[8D]
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Old 05-11-2011, 05:01 PM
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Default RE: Managed to break a losi HD diff cup today


Quote:
ORIGINAL: millzee

I'm running 20k in the front and 30k in the rear, this is the first break I've had since going brushless, I think my weights are fine, landing a poorly driven backflip onto hard pack dirt that is as hard as concreteonto awheel still spinning at app. 25k-30k rpm is what I thought could be the problem. I'll just have to find a softer landing spot of my jumping. Afterspending an hour doing standingbackflips on asphalt and not having any problems makes me thinkmy current drive train/diff set up is ok. http://www.youtube.com/watch?v=ura16...el_video_titlethanks for your thoughts.

I balanced the wheels last night and they weighed 445grams, a tad heavy.
20-30k is really heavy actually for these diffs. You gotta realize if one wheel hits down hard before the other and the fluid is too stiff, it will tend to put undue stress on the wheel that landed first and it will still want to spin since its "locked" to the other wheel. I originally started my diffs off with the "lstforum" recommendation of heavy diff fluid in the 20k range, and i broke a few pairs of the lightened HD shafts along with the stock ones, but after I went down to 1k in the front and 3-5k in the rear the outdrive issues completely went away and I still had excellent and evenly distributed traction to the L and R wheels where I didnt have to worry about the truck trying to pull to one side.

Your HD outdrives lasted a long time, but I bet you will notice improvement in cornering and durability without sacrificing any straight line accelerationby going to a lighter diff fluid.
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Old 05-11-2011, 06:03 PM
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Default RE: Managed to break a losi HD diff cup today

I agree, It was about time for a diff service anyhow. lol
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ORIGINAL: cummins driver

I think you can just chalk it up to the fact that no matter what you have or put on it, parts will break at some point or another[8D] Just a simple fix though and if that is all the problem you have, then you are doing pretty good[8D]
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Old 06-05-2011, 11:35 AM
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Default RE: Managed to break a losi HD diff cup today

Ibusted to stock diff cups the other day jumping.

http://www.youtube.com/watch?v=LQVjq9LU748

I;m going to install the HDcups when I can. I'm running 30k in the front and rear. I'm thinking of going to 10K and see how that works. I've the way my truck handles now and don't want to mess with it but Ithink 30k is awfully thick.
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Old 06-05-2011, 11:57 AM
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Default RE: Managed to break a losi HD diff cup today


Quote:
ORIGINAL: Geofiveo

Ibusted to stock diff cups the other day jumping.

http://www.youtube.com/watch?v=LQVjq9LU748

I;m going to install the HDcups when I can. I'm running 30k in the front and rear. I'm thinking of going to 10K and see how that works. I've the way my truck handles now and don't want to mess with it but Ithink 30k is awfully thick.
Most likely you over compressed your shocks which means your CVD's acted like a big lever and snapped off the cup. Easy cure to make sure this doesnt happen is to put 2 pieces of quarter inch fuel tubing on the shock shafts. One on the outside, and one on the inside under the piston. This will fix the potential issue.
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Old 06-05-2011, 12:17 PM
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Default RE: Managed to break a losi HD diff cup today


Quote:
ORIGINAL: ntrain42


Quote:
ORIGINAL: Geofiveo

Ibusted to stock diff cups the other day jumping.

http://www.youtube.com/watch?v=LQVjq9LU748

I;m going to install the HDcups when I can. I'm running 30k in the front and rear. I'm thinking of going to 10K and see how that works. I've the way my truck handles now and don't want to mess with it but Ithink 30k is awfully thick.
Most likely you over compressed your shocks which means your CVD's acted like a big lever and snapped off the cup. Easy cure to make sure this doesnt happen is to put 2 pieces of quarter inch fuel tubing on the shock shafts. One on the outside, and one on the inside under the piston. This will fix the potential issue.
I'm running 30 wt oil. Thinking of changing that first. The fuel tubing is not a bad idea though.
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Old 06-06-2011, 07:01 AM
  #11
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Default RE: Managed to break a losi HD diff cup today


Quote:
ORIGINAL: Geofiveo


Quote:
ORIGINAL: ntrain42


Quote:
ORIGINAL: Geofiveo

Ibusted to stock diff cups the other day jumping.

http://www.youtube.com/watch?v=LQVjq9LU748

I;m going to install the HDcups when I can. I'm running 30k in the front and rear. I'm thinking of going to 10K and see how that works. I've the way my truck handles now and don't want to mess with it but Ithink 30k is awfully thick.
Most likely you over compressed your shocks which means your CVD's acted like a big lever and snapped off the cup. Easy cure to make sure this doesnt happen is to put 2 pieces of quarter inch fuel tubing on the shock shafts. One on the outside, and one on the inside under the piston. This will fix the potential issue.
I'm running 30 wt oil. Thinking of changing that first. The fuel tubing is not a bad idea though.
Regardless of the weight you run, the LST shocks have more travel than the actual suspension arms, so when you over compress or over extend the shocks from jumps and landingsthe cvd will put alot of stress on the outside portion of the outdrive cups. By putting a small piece of fuel tubing on the bottom(right above lower spring retainer)and top(inside shock body, underneath piston)of the shock shaft you ensure that your suspension does not over extend the cvd's in relationship to the outdrive cups, and it won't affect your rebound/damping one bit, just gives you an extra "guard" against damage.
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Old 06-09-2011, 08:43 AM
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Default RE: Managed to break a losi HD diff cup today


Quote:
ORIGINAL: ntrain42


Quote:
ORIGINAL: Geofiveo


Quote:
ORIGINAL: ntrain42


Quote:
ORIGINAL: Geofiveo

Ibusted to stock diff cups the other day jumping.

http://www.youtube.com/watch?v=LQVjq9LU748

I;m going to install the HDcups when I can. I'm running 30k in the front and rear. I'm thinking of going to 10K and see how that works. I've the way my truck handles now and don't want to mess with it but Ithink 30k is awfully thick.
Most likely you over compressed your shocks which means your CVD's acted like a big lever and snapped off the cup. Easy cure to make sure this doesnt happen is to put 2 pieces of quarter inch fuel tubing on the shock shafts. One on the outside, and one on the inside under the piston. This will fix the potential issue.
I'm running 30 wt oil. Thinking of changing that first. The fuel tubing is not a bad idea though.
Regardless of the weight you run, the LST shocks have more travel than the actual suspension arms, so when you over compress or over extend the shocks from jumps and landingsthe cvd will put alot of stress on the outside portion of the outdrive cups. By putting a small piece of fuel tubing on the bottom(right above lower spring retainer)and top(inside shock body, underneath piston)of the shock shaft you ensure that your suspension does not over extend the cvd's in relationship to the outdrive cups, and it won't affect your rebound/damping one bit, just gives you an extra "guard" against damage.
I'm going to pick up my HD cups today and rebuild my diff. I'm going to use the trick with the fuel tubing as well. About what length of tubing do you use on your shocks for the outside?
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Old 06-11-2011, 11:07 AM
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Default RE: Managed to break a losi HD diff cup today


Quote:
ORIGINAL: Geofiveo


Quote:
ORIGINAL: ntrain42


Quote:
ORIGINAL: Geofiveo


Quote:
ORIGINAL: ntrain42


Quote:
ORIGINAL: Geofiveo

Ibusted to stock diff cups the other day jumping.

http://www.youtube.com/watch?v=LQVjq9LU748

I;m going to install the HDcups when I can. I'm running 30k in the front and rear. I'm thinking of going to 10K and see how that works. I've the way my truck handles now and don't want to mess with it but Ithink 30k is awfully thick.
Most likely you over compressed your shocks which means your CVD's acted like a big lever and snapped off the cup. Easy cure to make sure this doesnt happen is to put 2 pieces of quarter inch fuel tubing on the shock shafts. One on the outside, and one on the inside under the piston. This will fix the potential issue.
I'm running 30 wt oil. Thinking of changing that first. The fuel tubing is not a bad idea though.
Regardless of the weight you run, the LST shocks have more travel than the actual suspension arms, so when you over compress or over extend the shocks from jumps and landingsthe cvd will put alot of stress on the outside portion of the outdrive cups. By putting a small piece of fuel tubing on the bottom(right above lower spring retainer)and top(inside shock body, underneath piston)of the shock shaft you ensure that your suspension does not over extend the cvd's in relationship to the outdrive cups, and it won't affect your rebound/damping one bit, just gives you an extra "guard" against damage.
I'm going to pick up my HD cups today and rebuild my diff. I'm going to use the trick with the fuel tubing as well. About what length of tubing do you use on your shocks for the outside?
roughly quarter inch, inside under piston and outside shock body.
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