FINALLY, I think it's fixed....
 

As many of you know, I finished my e Revo about a month ago. I've been having bs issues after issues getting it right.... mostly the MGM controller.

I thought buying a Neu motor, MGM and a 5S battery, I wouldn't have any issues or problems because I skimped.

Anyway, my main problem lately is the damn truck nose dives at random at any speed and not able to duplicate it at will.

The first time I thought it was because I installed a 3905 ring and pinion in the rear axle and never changed the front. After counting teeth, I realized that they were different. It was like having 4.56 gears in the front and 4.11's in the rear.

So I changed gears in the front to match the rear and it still does it.

Then it was suggested to me to change the programming from low rpm to race mode and install a li-saver. I'm not sure how that helps the nose diving but I'll try anything once.

Now that I've done about everything I can, I noticed it's getting really bad... more and more nose diving. It's gonna trash my truck because it'll come to a sudden stop and end up doing 4-5 somersaults.

Anyway, I took the front diff apart tonight and couldn't find anything wrong. At the last minute, I applied pressure on the front diff pushing the pinion gear into the ring gear. I noticed it basically locked up until the pressure was released.

So simple solution, I placed a small washer in between the pinion gear and driveshaft and voila, no more binding when letting off the gas.

I took it out about midnight and beat the crap out of it on the lawn and never once saw it nosedive. I may be wrong but it seems to finally glide to a stop instead of nosediving.

I'm so happy.

Mark

Nice to here all you needed was a good shim job!

Don't we all???

:yes:

Hmm ... this is interesting. A friend of mine experiences the same problem with his Mugen MBX5T Truggy (MGM 16018, Neu 1515/1Y, 6s2p A123). When playing with throttle (blipping), it basicaly locked the 4 wheels for a split second. We always thought it was due to the ESC programming. We tried different settings, auto tuned it several times. Emailed MGM ... no satisfactory answer received.

I had similiar issues in my truggy with a kontronik Jazz ESC and also had some bad nose diving from time to time when i released the throttle to neutral. After replacing and shiming my diff bevel gears it went away too.

Guess we have to look more carefully into the mugen diff bevel gears shimming.

Thanks for sharing.

8th scales always need special attention to the diffs. Especially when they're new, and the diffs break in. You should check you shims after every run until they break in, then after every bash ideally.

It was suggested to me at one time to increase the throttle trim or open up the deadband percentage. The reason being that as you left off the throttle, it would extend past the dead zone and basically hit "reverse" for a split second.

I tried that and at first it seemed to help but after more driving, nope.

I drove the truck last night for a while with not one instance of nose diving and will mess with it today but I'm pretty sure that will fix the problem because like I said, when you manually pushed the pinion gear into the diff while spinning it by hand, it would literally lock up.

Now with the washer there, it won't allow it to go so far back into the diff.

I'll post more later....

Mark

I'm glad you figured that out and it wasn't the MGM. I feel so bad for people when they spend tons of money and get the stuff to work properly! :lol:

Guess I was wrong....
 

Bashed outside for a few today and the damn truck still nose dives. I honestly give up. I thought the gear thing was definitely the problem.

I guess I'll have to replace the entire diff (s) just to be sure. I don't know what else to do.

When you let off the gas, randomly it will nose dive immediately. No rhyme or reason, and it's not like the brakes all the way around are locking up, it seems to be the front.

It happens for a split sec and disappears.

:grrrrrr:

please, try other tests:
take out the motor from the car and make some throttle brake, reverse etc...
This way you can see if the problem is the tipical bracking issue of the mgm that doesn't do allways.

If your tests with the motor out the car run smoth all the time without reversing, or instant braking.. then try with tne motor on the car and shim diffs perfectly.

let us know about the tests.

I feel for you orangecrush ... this behavior is annoying and could become costly because of the extra stress put on the drivetrain.

Today we drove this mugen Mbx5t i mentioned above (MGM 16018, Neu 1515/1y) and this time we noticed a clear mecanical noise (for a split second) when we went from top speed to neutral. After checking the diff we saw that the pinion gear was completely worn out (back diff) and the front one didn't look much better either. After replacing those parts i will post our findings.

The test proteinas suggested seems the best way to rule the diffs out of the equation.

I think that's the reverse glitch rearing it's ugly head. Have you tried widening the neutral deadband? That has helped others with this problem. Also, make sure free-wheel is enabled.

I have pulled the motor and tried to duplicate the problem or make it do anything out of the ordinary with no success. I can't duplicate it or make the motor do anything wierd.




I'm gonna pull the diffs again, I'm not sure what else to do. We'll see how well I had it shimmed.





I changed the neutral deadband to 15% and even went so far as increasing the neutral deadband on radio to 8% (4% forward and 4% backward)

And yes, freewheel is enabled.

Tell me about the reverse glitch... is this a common problem? Not only is it tough on the drivetrain, sometimes it locks down and god forbid you're on the pavement, the truck is going tumbling....

Well it seems to be the problem with the MGM controllers. It's the only BIG one I've heard of. I have noticed also that even with free-wheel enabled, if you let off the throttle to slowly, it wont free-wheel. That could be happening too. I have that problem with my 16016. I just have to let the trigger "flick" back to neutral and it works fine.

Try replacing all connectors or hardwiring motor. I think some have seen random tap of the brake problems relating to connectors on MM (Glassdoctor?).