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Old 09-12-2013, 03:50 PM   #1
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Angry savage flux xl diff bevel gear problem

Hey guys I have a savage flux xl 1717 on 6s and I keep on stripping the bullet proof bevel gear. Yes I know its 6s and a 1717 but I just replaced the gear like 1 day ago and when I ran it today it stripped and I was only going back and forth on my street then guned it a little too much on its back and thats when I heard the cracklin noise. Im seriously getting sick and tired of it!!, for me its always a problem after another never had good luck with any of my rc's not even my e revo ither only my rc8.2e which I like but cant go over to many things like a savage can. Any suggestions are welcome or else its probably going to be off for sale Thanks
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Old 09-12-2013, 04:48 PM   #2
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Have you been shimming the gears for proper mesh (smooth with no play) or just dropping them in? HPI's instructions don't tell you how to actually shim them for proper mesh. There are lots of guides out there for shimming for proper mesh if you need them. You should also carefully check the bulkheads the diffs sit in for cracks or any deformation as this can cause improper mesh. Don't forget to the bearings, check them for any play as well.

If all this stuff is good there is one other thing that could be happening. The Savage bulkheads are plastic and can deform with big power allowing the mesh to go out of wack and chew up the gears. Replacing them with aluminum units from GH or another source will eliminate the deformation.
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Old 09-12-2013, 05:20 PM   #3
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I havent been shimming because the one befor lasted me a long while and I thought dropping them in would be the same. Also it didnt feel the same like I had it befor. Also im going to check all the bearings and bulk head for anything wrong. I guess for now im going to have to run my Actual only bullet proof rc which is the rc8.2e
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Old 09-12-2013, 05:57 PM   #4
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The last one might not of had as much play therefore lasting longer..If you shim the diff it will last...Also check make sure the case isnt cracked or no wear damage...

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Old 09-12-2013, 06:50 PM   #5
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Unfortunately the gears in our stuff arent built to the most exacting standards. Plus any wear that's occurred on the bulks, bearing faces, even the shims wear and that can throw the mesh out of whack. The high power of brushless also makes proper gear mesh even more important. Pick up a pack of shims for both the ring and the pinion gear and if you can, get two different thicknesses.

Edit: Pay attention to the diff cup too. Make sure the bearing doesn't fit too loose to the diff cup. If the part of the diff cup the bearing rides on is plastic it could be worn or deformed and mess up the mesh.
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Old 09-12-2013, 07:47 PM   #6
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you need a center differential.
center diff protects the drivetrain way better than transmission with a slipper clutch. The main advantage is that it allows wheels to spin at different speed, which means that if you happen to land on throttle or brake or accelerate hard, you will not damage the diffs.
The main advantage of a center diff in comparison to a gearbox is that the diff distributes the power according to the load on the wheels. If one end of the truck has more traction, the diff will send more power to those wheels that have less traction, to those that are unloaded. This might become an issue if you put a very thin oil into the center diff, but a thick oil is an easy fix. On the other hand it protects the drivetrain. I am yet to break a single front or rear diff or a diff pinion. If one diff gets stuck, the center diff will send more power to another diff , instead of damaging it. The gearbox can not send more power to one end and less to another, it transfers the power evenly to both diffs all the time, so if one diff gets stuck or blocked etc, it will spin it and destroy easily if your slipper is set too tight.

there are 2 ways how to mount a CD into a savage ( except for custom mods): alza racing CD conversion or super 5sc flux gearbox, that comes with a center diff

I would go with the alza kit. less gears than in a 5sc flux gearbox and easier maintenance
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Old 09-12-2013, 08:27 PM   #7
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you dont need a center diff as long as the cases are good bearings are good and diff is shiimmed properly it will last a long time...
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Old 09-12-2013, 09:05 PM   #8
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I ran a 1717 on 6s for awhile. I went through one set of bevels, than dropped in the lightning bevel gears and never had another problem
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Old 09-12-2013, 09:53 PM   #9
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Quote:
Originally Posted by johny723 View Post
you need a center differential.
center diff protects the drivetrain way better than transmission with a slipper clutch.
A center diff is not going to help the diff gears live if they aren't setup with the proper mesh. The OP has admitted to making the mistake of just dropping in the last set of gears without shimming as well.

As far as a center diff (cd) protecting the diffs better than a trans, that is debatable. The thing that kills diffs, especially in brushless applications, is shock loads. The shock of starting from a stop, the shock of applying the brakes, even coasting and then cracking the throttle wide open shocks the drivetrain. Land a jump on throttle or other shenanigans and the diff is the first to see a shock load regardless of trans or cd. Any slop in the diffs, the cvd's or dog bones just amplifies the shock loads. This is why shimming out any play in the diffs (including the spiders) is so important. It's also why Traxxas sliders should be replaced when they start to "oval" the holes for the universal joints.

Knowing this lets take a cd equipped savage and put it on pavement. Let's say the cd oil is light enough to unload the front tires and not wheely much if at all. There are still the same shock loads when you apply throttle because the front tires are gripping at first and the cd has yet to unload, still the same shock loads when you apply the brakes. Light oil will diminish those shock loads somewhat but I'd have to say its about the same amount as a loose slipper. Thicken the oil up until the truck will wheely and it's the same thing as cranking down the slipper until the truck will wheely. Either way the cd has to unload before it starts protecting anything, that doesn't happen instantly. Hell I had a 1/8 e buggy that came with grease in the cd and it would still wheely off the line. Only popped the wheels up for a second or two and wouldn't wheely from a roll but it proves my point that the diffs dont unload instantly and were definitely getting hit with shockloads.

A cd will make a difference if one end of the truck gets stuck. Jam a wheel and yeah the cd will send power the other way. But that's only helpful when you get a rock, stick or something in a wheel that stops it from moving. Even then the front or rear diff will unload not necessarily the cd. If the actual front or rear diff gets stuck its because it's already toast and nothing is going to save it.
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Last edited by Overdriven; 09-12-2013 at 10:05 PM.
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Old 09-13-2013, 09:28 AM   #10
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Well, a looser center differential will actually stop those gears from tearing up, because it won't let any power jerk them around too much.

A properly shimmed differential IS needed for regular use, without center diff, however.
Shim it, and if you're not into going for a center differential, the Robinson Racing Gen 3 slipper will let you have a give point for the transmission, whereas the stock slipper doesn't work and you HAVE to lock it out.

Also, the whole thing about the CD not doing anything, I have to vouch for that not being true versus the slipper.
Yes, you MUST still be careful, somewhat, about landing jumps on 100% full power, but it does a WHOLE lot more than a slipper can.
Yes, there is still load on the front differential on a dead stop, on pavement. However, static friction from a stop =/= shock load from the truck slamming into the ground at full power.

After running this truck silly with a center diff, and inspecting the diffs, I can definitely vouch, with proof, that the center differential does a lot more to save the drivetrain than a slipper can. If you're going to be slamming into landing jumps @ full throttle, then yes a slipper is going to be a better option in ANY case. Mechanically, it's got a better design for that type of use. A CD can't compare with that. If you're using it for just bombing around, track driving, or general driving, I can vouch and say, without a doubt, that specifically for this truck, the CD is far better an option than a slipper. It costs more, but it is worth much more than it's own weight on the whole.


Regarding the munched bevel gears, that will happen running a 1717 motor with this truck on 6s, at least on a stock tranny. The Robinson Racing Gen 3 slipper will help you by giving you a functional slipper clutch, and that'll RIDICULOUSLY increase your spider/bevel gears life span. It's a lot cheaper as well. (well, about 1/2 the cost of the whole CD option(s) )
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Old 09-13-2013, 02:36 PM   #11
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IMO a center diff is a must in the savage flux, the truck just weighs to much and even with the HD tranny, you will always break pinions in the diff, shimmed or not. Heres a video of me purposely trying to break my truck on 6s. I thought I broke the servo but what happened was the arm to the horn locked it in place. Nothing broke! Ive tried many times to break this particular truck just because and couldnt. Something that plays a major role in diff carnage and tranny failure is not neccesarily the power but the wheel choice. A big heavy wheel will defiently break things that a lighter wheel wont. The alza setup is affordable and will pay for itself after a few runs. I must agree that shimming the diff is a must! I put 2 shims on the ring gear side and 1 shim on the cup side. You should also shim the pinion, i put 1 to 2 shims behind the gear.

As far as CD vs Tranny, CD all the way, if you want the truck to move the same as it would with the tranny drop some 500k oil into the CD. Thats what I run. Some guys run 300k but imo thats to light and unloads to much power.

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Old 09-14-2013, 06:55 PM   #12
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I think we're all missing the obvious... A savage on 6S is a little much on the drivetrain. Why not keep it to 4S? A savage on 4S is a blast to drive! 6S on these heavy, big-tire monster trucks is basically an invite to drivetrain destruction.
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Old 09-14-2013, 09:00 PM   #13
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Quote:
Originally Posted by Dadic 78 View Post
I think we're all missing the obvious... A savage on 6S is a little much on the drivetrain. Why not keep it to 4S? A savage on 4S is a blast to drive! 6S on these heavy, big-tire monster trucks is basically an invite to drivetrain destruction.
He's running the 1717....Its a snail on 4s...
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Old 09-15-2013, 12:54 AM   #14
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Well thanks alot guys im going to check everything u guys have mentioned and actually take my time doing it so I can really make everything last longer and be bullet proof.
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