Diff Lock Test

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PeaCue

PeaCue

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Arrma RC's
  1. Nero
I'm not seeing my Nero act as it should with the center diff locked. With the center locked, I expect front and rear power to be fixed, but instead I see massive ballooning of the front tires while the rears spin just a little.

I tested out the Nero on a bench with the various diffs locked, and it is obvious when the front or rears are locked - both L/R wheels are locked and rotate together.

But when I test the center diff in locked position, I can still rotate the front and rear wheels independently. There is a bit of a resistance but it is very easily overcome with a small 'thump' feel.

Should locking the center diff force front and rear to rotate together, or is there something else at work here too, like the slipper clutch?
 
yes...locking the center should get front and rear moving together. ..but power is still allowed to transfer differently left to right...until you lock all diffs...


hmmmm...since the fronts are still balooning...like with all diffs open...then I would say the center is not locking...slipper will have no influence this case...

as you change to each setting...can you hear the servos actuating?...if so maybe an issue with the linkage...lock pins..etc...

check all connections etc...hate to say it but after that you will need to open it up and see what the problem is. ...

check youtube vids posted by the Undisputed Nero Master. .TP-PARTS RC EXTREME...https://www.youtube.com/user/ThomasP74?app=desktop


he has detailed vids on dissassembly of the differentials.. etc...go to vids page...you will see it...wealth of info there...and he is also a forum member...

center locked is an instant wheelie..so that should happen all the time unless the slipper is too lose.
 
There is only a small amount of grease in the diffs... i have put 50k in center 100k in rear and a mix of 3/4 50k and 1/4 100k in front. I have yet to run it... my nero did same thing as you decribe with yours. When i opened center diff case the servo arm was not in the groove on the locker causing it to not work properly... i am waiting on some push rod ends to show up and then i will be running again and see if the difflube made a diffeence and i replaced center servo with a new one because it was not working i think it burned up or something happened to the gears. I installed lockers myself so i blame myself for the malfunction and did not call arrma to get a new servo i actuly bought it because it was my mistake. I cant wait to get it going again its been on my workbench for almost 3 weeks now...
 
I can hear the locking servos clearly, including the center one. I definitely don't get instant wheelies, in any mode. But most importantly crawling is hopeless right now. Could be an issue with the locking pins I suppose, but that would be a pretty dramatic failure I would think. You're right in that I'll need to open this up to see.

This was a RTR Nero w/Diff Brain and I didn't check anything after unboxing before I ran it. Later I found seriously loose front pillow balls and very sloppy steering rods - but only after a wheel came off from a loose lug nut! At this point, who knows, maybe the slipper clutch is super loose too. Should I expect new RC's to be truly "ready to run" out of the box, or is tuning always step #1?
 
goes either way I suppose on whether or not RTR is "ready to run"...just depends on the size of hangover the assembler is nursing on monday morning...and luck of the draw...

I ran mine first day out no problems...about a week later ...servo link rod screw came out...

yeah...those red pillow ball nuts...you have to keep an eye on them...in a previous thread...can't remember who to give credit to...but one member suggested using Teflon tape on them...that sounds like a good idea ....I have yet to do it ...because I am always running the truck...

mine has been trouble free ..I did replace the sticky tape beneath the speed control...since it came loose...that tape gets dirty...and eventually the esc gets liberated...

have fun...fix as needed...
 
Every rc i buy i check all screws that are easily accessible and make sure everything is tight... wheel nuts being #1... it is assembled in an assembly line not piece by piece... iafter every run i chexk everything over to be sure i have not broken anything. The rod ends pull out easily sometimes a dab of super glue on the threasd will help stop that. Rtr means it has everythig included you need exxcept batteries. Itas always a good idea to check things over before you run it.
 
Thanks for all your quick replies! Before I rip things apart, can you test how your Nero behaves on the bench with all diffs locked? When elevated, if you rotate the rear wheels by hand, are the front wheels forced to turn too or can you easily hold them steady? Also up for consideration - is this even the right test for this issue? Thanks guys!
 
front wheels are forced to rotate...if not...then I would suspect something deeper going on...

it's as valid a test as any at this point...

tear it open dude...take pics or video for the forum...share results and experience. ..
 
Well I'll be! I found the defect, and it was immediately fixable. I tore down the center diff and found that a burr in the housing was preventing the lock collar from sliding into the diff.

If you look at the picture you can see it somewhat. The locking collar was caught behind the burr preventing it from sliding inward. I took some pliers and easily broke the burr off. There were two burrs actually on opposite sides.The burrs came off so cleanly that I am thinking it was not a result of internal rubbing or failure. There is a grease grove along this edge and I believe the manufacturing of this grove left the burr behind. Also, the locking collar was in fine shape which also leads me to believe that the burr was present from the factory.

Reassembled with darned burr removed and voila, all diffs locking as designed. Charging batteries now, can't wait to bash it around.
 

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Thanks for starting this thread. I was trying out climb mode today and failing miserably I knew something wasn't right when the fronts were turning but not the rears. Off to the workshop I go. Changed gearing the other week and now wondering did I reconnect the centre diff servo either way it's coming apart to see. Thanks again

Good news in that the problem was obvious as soon as I undid the bottom plastic guard. I went to undo the drive shafts only to find screw/pin had come out of the rear drive shaft...Odd thing was it was still feeding enough power to the rear shaft to wheelie a small amount... Bad news is I have no spare pin
 
To revive this thread...

The servos died in my big rock. They were replaced under warranty but now it seems like my center diff does not lock. I have tried playing with the end points on the brain.

I would have to have to pull it apart again!

How do you test the center diff?

When I rotate one of the rear wheels, I know that the other rear wheel will spin in the opposite direction of the diff is open, and in the same direction if locked. Same for the front.

How do I test the center though? For example, when setting endpoints, when it comes to the center end point adjustment then the front will be locked and the rear still open by the diff brain. If I rotate one rear wheel and then later one front, what should the rest of the wheels do if the diff is either open or closed?

Thanks!
 
Put the truck up on a stand all 4 tires must be up in the air for these tests.
  • With all the diffs unlocked, by hand rotate both rear tires at the same time forwards and the front wheels should rotate backwards. This means the center diff is unlocked. If the front tires rotate forwards the center diff is locked.
  • With only the center diff locked, by hand rotate both rear tires at the same time forwards and the front wheels should rotate forwards. This means that the center diff is locked. If the front tires don't rotate forward the center diff is not locked.
  • With all the diffs locked, by hand rotate one back tire forwards and all 4 tires should rotate forwards. This means all diffs are locked. If the front tires don't rotate forward the center diff is not locked.
 
chevyrumble said:
Put the truck up on a stand all 4 tires must be up in the air for these tests.
  • With all the diffs unlocked, by hand rotate both rear tires at the same time forwards and the front wheels should rotate backwards. This means the center diff is unlocked. If the front tires rotate forwards the center diff is locked.
  • With only the center diff locked, by hand rotate both rear tires at the same time forwards and the front wheels should rotate forwards. This means that the center diff is locked. If the front tires don't rotate forward the center diff is not locked.
  • With all the diffs locked, by hand rotate one back tire forwards and all 4 tires should rotate forwards. This means all diffs are locked. If the front tires don't rotate forward the center diff is not locked.
Click to expand...
Perfect! Thank you. It was rotating BOTH wheels that was the key for me to test.
 

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