Blowing gearboxes like crazy, calling experts!

[mattnin]

Ok guys, I am in a huge predicament. Anyone seen my truck? It has revo shafts throughout, knuckles. But I am blowing gearboxes. I am running a stock unlocked maxx transmission, locked diffs to revo.

I know I am pushing this thing too hard. My truck is a cross between a monster truck/crawler. Please don't bash me because my truck isn't a true crawler, I am here asking because I think these forums are where the real experts are.

Anyway, I am jumping my truck at a local track, not very far. But when I land, I am blowing gearboxes, stripping the gears. Is there anything I can do to avoid this? First I was shredding maxx sliders, now I am rock solid with the revo shafts. Now my gearboxes are stripping. What can I do to stop this? Why is this even happening? :( I have already had to replace gears in my gearboxes twice. It is usually the rear that blows too.

I am running an hv-maxx, 9t pinion, 76t spur. And before you say it, I am not changing out the motor. If I have to I will just not make this thing a crawler any more and go with diffs. Because I enjoy the speed and jumping at the track.

[smokinubyrc]

ide say your problem is the diff when unlocekd has giv in it when jumping but no thats it locked you are putting to much strin on the gears and something has to give i say keep the frunt locked and unlock the rear

[mr.maxx]

Why not get a metal gear set for the trans if you like the truck set up the way it is??

[666]

What part exactly are you breaking?

[RD400]

Okay, are you talking the trans, or the axle gears? If it is the trans and you don't want a full on rock crawler, put the slipper clutch back on. That should take the shock out of the high power landings.

If you are talking about the axles, are the cases being pushed apart from the torque? Might need to go to aluminum ones

Hope that helps

[Cloak]

Watch that you're not landing full throttle. Your tires need to be turning on landing about the same speed as your truck is moving forward.

[mattnin]

It is the axle gears. I would think aluminum would be weaker? There are already steel gears in there.

The gears that I am stripping is the metal gear that attaches to the locking spool, and sometimes the gear that attaches to the driveshaft becomes a little scarred too.

So aluminum wouldn't help me because there is already steel in there. Anyone know what to do? I also noticed that the gear that attaches to the driveshaft (not the spool gear) has a little play, and I believe that could be part of the problem.

Anyone else ever deal with this before?

[peej410]

based on what your saying and the design of the maxx cases, im guessing your landings are putting a great deal of load on the gears in the drive line when you put a high load on gears they naturally push against eachother this expansion in the case is like turning your motor and pinion away from the spur gear, which would change the mesh and strip the gears... , the weak point in the design of the stock maxx cases is that they only have two screws for the case. later model maxx ones use four screws... look them up on ebay and you will see what im talking about. id say upgrade to the later ones. http://cgi.ebay.com/T-Maxx-Aluminum-...QQcmdZViewItem

heres a well used set of cases that you can see has four screws

http://cgi.ebay.com/T-maxx-Aluminum-Diff-cup-Differential-tmaxx-supermaxx_W0QQitemZ6053153625QQcategoryZ44028QQrdZ 1QQcmdZViewItem

heres a set with only two screws in the case

[racerx]

OK, So your stripping the ring and pinioin gears, ( the ones in the front and rear diff housing) 1st you can get hardened steel gears from Robinson Racing, 2nd get aluminum diff cases to prevent the gears from "pushing" away from each other under high power. 3rd shim the ring and pinion for a tighter mesh (not too tight) or you will be in the same boat again. You can find info on shimming diffs on just about every web site about RC. Hope this helps! Good luck.

[mattnin]

Wow thanks peej410 and racerx. I had no idea newer diff housings (thanks peej)were held together with 4 screws, or that there were hardened ring and pinion gears (thanks racerx).

I was also thinking today to open up the slipper just a tad too because I have that locked down pretty tight and hopefully save the transmission because that will be the next thing to blow I think.

Thanks for all the help guys.

[smokinubyrc]

well not all new diff cases have four screws is just stock maxx ones have only two and they arnt in a good spot at the back of the diff my intagy diff cases has three screws and one is up at the frunt as long as you get a case with three to 4 screws and shim the gears and get the harden gears i think you wont blow them anymore

[RCHunter]

Pack your trans with grease. That will help with those gears. I got ultramaxxed alum gears in my trans.
As for diffs definately get aluminum diff cases. Stock gears are fine in the diff if you shim them right. Maybe run thicker diff oil instead of spools?

[RevoRacer]

I think the guy's are on the right track here. Because you are running your truck at high speeds (unlike most of us) and jumping, you are putting MUCH more stress on your drive parts. These forces are the reason why we have slipper clutches and differentials. To help alleviate the stress caused by those forces. So if you are going to have a hybrid seudo crawler/racer you need to compromise and add back in some of those 'stress relieveing' parts.

I would loosen your slipper (to take stress off of you brushless and tranny) and remove you diff spools and experiment with different viscosity diff fluids (to relieve stress caused by the huge rotating mass of the big tires we use on our trucks. they wreak havoc on drive line parts when they hit the ground).

I think if you implament some of the suggestions here your problem will be solved!! ;)

[spookyseven]

you could also look for some kind of 1/8 scale buggy diff conversion
i think trophyclassrc had one, but i cant seem to find any info on them anymore

[mattnin]

Well I ordered the hardened ring and pinion, I am gonna shim, but I have yet to order the aluminum diff case. I am somewhat hesitant because I have to cut a piece off the diff cases to get them to mate to the revo shafts properly. So, if I blow these robinson racing gears then I guess I will just have to get out the hacksaw with some aluminum diff cases.

[peej410]

i just found out yesterday that tmaxx 3.3 shafts bolt right up to tmaxx diffs with no modification, why not just upgrade to the 3.3 yokes...

[mattnin]

Because I am about $80 invested in revo parts, 6 shafts bought from the local shop and about $20 or even more for the knuckles. I think I spent about $30 bucks on the knuckles actually.

[peej410]

no just the yokes meaning the part of the dshaft that mounts to the diff not the entire assembly


look at the yoke ends that mount to the diff, they are turned down to fit inside the maxx bulkheads and stuff. you just need the yoke not the whole shaft

[LowRange]

If you want something that gives you a good amount of lock, but still leaves some slip in the diffs for corners, you can use hot glue. The Maxx diffs just kind of chew it up and it acts kind of like a limited slip: it gives you just enough slip to take some stress off in corners and landings. And as others have said, get the aluminum cases too.

[CustomCrawler]

Use the XXX4 to jump and the maxx to crawl.