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I'm at a loss..............

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MrClean

MrClean

Hardcore RCTalk User
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Location
Kansas City
RC Driving Style
  1. Bashing
I put the center diff and rear brake on my Revo. I took it out to see how it ran, it sorta didn't. Basically I can put my foot in front of the truck and it will hardly push at all. I can see the spur gear and cb spinning and the clutch pads on the slipper clutch are engaged and spinning also. I pulled the tranny back out to double check it. From everything I've read it appears to be assembled correctly and there are no broken or stripped teeth in the tranny or on the cb and spur. I'm beginning to think the mesh isn't correct on the cb and spur.
tranny.gif

Does this appear to be assembled correctly? Any tips for setting the mesh?

Thanks for looking.
 
I've never been inside the trans but it all looks like it is in there correctly. sounds like your slipper is to loose or not installed correctly.. i would check that first.
 
I thought that too, but it seems ok (it's turning with the spur gear), I just went back out and I see the center driveshafts spinning (both front and rear). So to me, it seems the power is getting to that point. I wonder if I'm losing something in the diffs. I've never touched them but maybe my little romp in the mud last weekend did something to them?
 
OK, I'm slowing getting there. If I put just the front wheels on the ground and push it, they turn freely. When I do the same thing on the rear wheels, they spin, then drag, spin, drag. So I'm assuming it's something in the rear diff, at least that's where I'm going to start looking.
 
yeah i would guess if the power is getting to the diffs and then not to the wheels then therein lies the problem.


to test them stop one front wheel and turn the other does the center shaft turn??
repeat with the rears.

also maybe check the wheel hexes and see if they may be stripped??


hope i didnt just tell you a lot of what you already knew.
 
I'm a newbie so throw anything and everything you have at me. LOL
I think the more views/opinions a person gets, the better decision they can make.

I took the whole rear end apart, all the way down to the rear differential, found nothing and the diff seemed to be spinning freely as well. I put everything back together and tried rolling it across the garage floor and it rolled like a skateboard, smooth as could be (well, compared to before). Something wasn't right or was in a bind causing the rear wheels to do what I described earlier.

I troubleshoot stuff for a living, I hate not finding what's wrong, then putting it back together and it works just fine. But I'm glad it's fixed and tomorrow should be a good day. Get the motor tuned since I switched fuels and then have some fun. THANKS for your advice guys!!
 
Glad you got it figured out. I had a similar issue with my GT2 3 days ago. I snapped my rear shock tower so i replaced it. when I went to go for a run it didnt move for some reason. took it back in, removed the rear shock tower and nosed around. Nothing! Yet when i put it back together again, everything ran smooth as a babies bottom. How a shock tower ever created a bind i'll never know, but I apparently had something pinched.
 
MrClean said:
Cool so I'm not losing my mind then...LOL.
Click to expand...

nope, but if your anything like me and keep breaking things, your gonna loose allot of hair! I swear i'm getting a bald patch since i started this hobby. But hey, what can i say...I LOVE IT!
 
No worries there, I sport the shaved head anyway....LOL.


Well I guess I didn't fix it after all. Today it's doing the same thing. The front two wheels roll just fine on the ground. The rear roll...then catch, roll....then catch. I hold the RR wheel and turn the LR, the center drive shaft turns. I hold the LR wheel and turn the RR the center drive shaft 'jerks' and I can feel a sort or grinding that I believe is coming from the rear diff. Does this sound like the place I need to be looking? And what exactly does holding 1 wheel and turning the other tell me? (I'm assuming it's telling me there is a problem in the rear diff) LOL
 
Might be.
The rear brake might be binding. Check the scews that hold the calipers on.
 
I did check to make sure the brake pads were moving correctly and that the caliper screws weren't too tight.

I just realized that this problem showed up the day I was playing in the mud and trying to run the truck up a pile of dirt that I probably shouldn't have been trying to navigate, it was too rough. I thought at the time it was just the mud causing it to drive funny.
 
FINALLY!! I have found the problem. One of the output gears in the rear diff is toast. I also found a torn rubber o-ring.

Question, are the diffs supposed to be completely full of fluid? Mine was about half full when I took it apart. I'm wondering if it was low on fluid, could that have contributed to the failure.
 
The ring and pinion need some grease but the fluid in the diff cup is more for tuning the differential action.It is metal to metal gear mesh so I guess some form of lube is required in there also.A half full diff cup would be plenty of lubrication though I would think but it will allow the diff to unload on the wheel with the least traction quicker.

I am still a rookie so I hope a vetran will chime in if I am giving the wrong advise.
 
Thanks Captian, that does make sense about the level of fluid in the diff.

I trashed the front output gear also...heh. Lesson learned. I'm sure one of the veteren guys will tell us what the correct fill level is on the diffs. I just ordered 2 rebuild kits and some 30k oil, so it'll be later this week before I actually get to put it back together. After this go-around at tearing down the Revo and rebuilding it, I might actually get to run it again.....LOL.
 
the general rule is to fill the diff up to just cover the cross bars. the oil in the diffs will expand upon use and if you fill it all the way up you could blow out a seal.
 
I have another question that has to do with the center diff and rear brake. With these installed, does this affect the ability to control the car off a jump? Can you adjust in mid-air for a landing? I was thinking these add-ons might take away some of that ability.
 
you still have brakes and throttle for jump control, the reason behind the rear brake is 1 with a diff you wouldnt have braking to the rear wheels at all, and 2 you can set brake bias for more tuneability
 

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