New Brushless Emaxx, not as good a deal as I thought

[Jersey Crewmax]

I picked up a used brushless Emaxx on Friday. I traded my slash 4x4 (not platinum, only upgrades were fans on the esc and motor) which was very clean and well cared for as well as some holes shot tires and $30.

When I saw and drive the car I new it had a few issues such as the body being beaten up and one of the wheels having a tear. It also pulled to one side a bit. Needless to say I didnt turn it down and picked it up.

When I got home I decided that I was going to tear it down. What did I find, both diffs are shot as well as the bearings in the front RPM axle carries being shot. So I'm looking at an additional $100 plus I have to spend. Lesson learned

On top of that the diff in my summit started clicking yesterday too, looks like something else I'll need to tear down.

Being that I have my Emaxx in pieces, any recommendation for cheap while your in there maintenance, upgrades?

Thanks

[M n M]

You may be able to save some money on the RPM carrier. Their stuff is suppose to have a life time warranty, at least the plastic does, I don't know about bearings.

Bearings aren't too expensive, usually a buck or two each. I think a lot of folk like Avid brand. I've got some Boca on my Maxx, their ok, it's the brand my LHS keeps on hand.

Have you completely disassemble the diffs to see what is wrong with them? They are rebuildable unless you just want to get a bigger stronger diff altogether. Seems to me that if the diffs were completely shot you would have noticed it during your test run. It may be as simple as a frozen bearing on one of the output shafts (may be the cause for it pulling to one side).

But you've come to the right place for some help and advise, lots of great folks on here to help you out.

One last thing, to help us help you... What model E-Maxx do you have, is it the 3908 EMBE or is it an older model converted to brushless?

[Jersey Crewmax]

Thanks

Its the 3908, forgot to mention that.

Regarding the diff it's the ring and pinion but I'd rather just replace the whole diff assemblies that way I get all new bearings and I figure the case shouldnt be warped. I can then repair the other ones and keep them as backups.

I checked online and everyone wants $12-15 for the bearings. They are oversized ones. I actually have a complete set of axle carries for my summit, are the emaxx and summit interchangeable in the front? Tried researching with no luck.

[M n M]

Thats right, I forgot the bearings are oversized in the RPM carriers (and I have a set... Duh).

The Summit carrier should fit, the only difference I see on the parts breakdown is that the Summit part # is 5334R which is listed as having larger bearings. The E-Maxx has a part # of 5334 as the carrier.

The newer stock diff for the E-Maxx is pretty strong, the guy who had it before really must have ran the snot out of it in order to have warped the case. For a cheaper option you may want to consider just getting new parts for the stock diff. You would have to order 3 numbers in order to get a complete diff assembly.

(prices are from "buyTraxxas.com)
3979 Diff housing $4
5382X Gear set $14
3978 Diff carrier $4.24

So for about $30 (with oil and shipping) you can have a new diff.

Some folks are doing the Losi 1/8 diff mod. It's a built proof diff but I have no idea what the cost is. Here's a couple of links
http://traxxas.com/forums/showthread...nd-drivesafts)

http://traxxas.com/forums/showthread...my-modded-3906

An other popular option is the FLM diff. I'm holding out and trying to save my money for this upgrade:
http://www.fastlanemachine.net/prodd...LM17750&cat=15

Good luck!!

[HighDollarRustler]

I buy new, complete diffs for $35 for a pair. Just look for lumidave on eBay. He runs a chop shop.

[87 GN]

shim those diffs, helps alot...

good info in both threads..


http://traxxas.com/forums/showthread...-Diff-Shim-Mod

&

http://traxxas.com/forums/showthread...to-shim-a-diff.

[Jersey Crewmax]

shim those diffs, helps alot...

good info in both threads..


http://traxxas.com/forums/showthread...-Diff-Shim-Mod

&

http://traxxas.com/forums/showthread...to-shim-a-diff.

That's my plan when I get the new ones. I'll also pick up a set of just the ring and pinions and fix my broken ones to keep as back up.

Any other suggestions while I have the truck apart? I didnt take apart the teas or the servos because they both appear to be working fine but want to regret it later. I am thinking of going with Rpm bulkheads though.

[M n M]

New diff don't need shimming. It's not until they get old and worn that they could used some tightening up with shims.

RPM doesn't make bulkheads, I think we all wish they would though. FLM is prob the most popular for bulkheads.

While its apart I'd check all the bearings. Replace the bad one; clean the good ones and put some 3 in 1 oil on all of them.

[bentrocker]

New diff don't need shimming. It's not until they get old and worn that they could used some tightening up with shims.

RPM doesn't make bulkheads, I think we all wish they would though. FLM is prob the most popular for bulkheads.

While its apart I'd check all the bearings. Replace the bad one; clean the good ones and put some 3 in 1 oil on all of them.

When running brushless this is not true. I shim my diffs from brand new and they last longer.
If you are going to buy diffs you can do what I do. I buy slayer pro diffs ,they are usually the cheapest. I then take the ring and pinion from them and instal them on the diff cup from the brushlees diff. It has the strong back in it and it is stronger.

[Jersey Crewmax]

When running brushless this is not true. I shim my diffs from brand new and they last longer.
If you are going to buy diffs you can do what I do. I buy slayer pro diffs ,they are usually the cheapest. I then take the ring and pinion from them and instal them on the diff cup from the brushlees diff. It has the strong back in it and it is stronger.

Isn't it cheaper to just buy the ring and pinion gears separately in that case or do you use the internals from the new diff cup or the new bearings?

[Suteki]

When running brushless this is not true. I shim my diffs from brand new and they last longer.
If you are going to buy diffs you can do what I do. I buy slayer pro diffs ,they are usually the cheapest. I then take the ring and pinion from them and instal them on the diff cup from the brushlees diff. It has the strong back in it and it is stronger.

Just going to reiterate this. Those diffs definitely need to be shimmed even brand new. They have a lot of play in them and will bust really easy if they aren't shimmed. When I pulled my diffs apart after blowing one, I was amazed at how much play they had, the pinion wasn't even contacting the crown gear until under load; so if you went from no power to on power, the pinion was smacking the crown gear and eventually, something had to give.

[bentrocker]

Isn't it cheaper to just buy the ring and pinion gears separately in that case or do you use the internals from the new diff cup or the new bearings?

Not if you bid on them.

[87 GN]

New E Maxx second run 2/2s, going easy breaking in the truck. Rear diff locked on me, Lucky no damage. Shimmed them up all good. But I do like to put on a few runs, to break in the diff before shimming.

pro slayer.. hummm have to look at that...

[M n M]

When running brushless this is not true. I shim my diffs from brand new and they last longer.
If you are going to buy diffs you can do what I do. I buy slayer pro diffs ,they are usually the cheapest. I then take the ring and pinion from them and instal them on the diff cup from the brushlees diff. It has the strong back in it and it is stronger.

I see... I tried to shim my stock diffs because I heard everyone saying it was the thing to do to prolong the life. It didn't work on mine, maybe I did it wrong but shiming just jammed up the gears. Then I read a post later on that said only the older diffs like in the 3906 model or 3905 diffs that have been worn out need shimming.

Glad it works for you!!

[Redsawacs]

with your axle carriers, yes, RPM will warranty them but you still have to pay for oversized bearings. I found that the new "stock" axle carriers from traxxas have the option to use the larger bearing but it comes with a "cup spacer" that you can still use the less expensive stock bearing. I havent had any issues with my stock set up on RPM A-arms at all....so, your call on the replacement...I think the stock are fine unless you are wanting "BIG AIR", then for sure upgrade.

"Red"

[Suteki]

I see... I tried to shim my stock diffs because I heard everyone saying it was the thing to do to prolong the life. It didn't work on mine, maybe I did it wrong but shiming just jammed up the gears. Then I read a post later on that said only the older diffs like in the 3906 model or 3905 diffs that have been worn out need shimming.

Glad it works for you!!

No, the 3908 (Revo) diffs also need to be shimmed from brand new. If you shimmed the diffs and the gears were jamming, you've put too many shims in there and the gears are binding. You want it so that 1 tooth from the pinion and 1 from the crown gear are always in contact; they shouldn't be so tight that the gears don't move smoothly nor should there ever be a point where the teeth aren't in contact in some way or the pinion is able to 'slide up' the crown gear under power.

If you over shim the gears you'll put extra load on the motor / bind up the drive train, if there is no shimming there then you'll greatly increase your chances of breaking the teeth. Over time the gears will wear down so re-shimming them just makes sure you are back at the point where at least one tooth from the crown gear and pinion are always in contact.

[Wildman4910]

For bearings go to AvidRC, most are $1 each & good quality to boot too.
6x15 & 12x21 are what you need for the RPM carriers.

[bentrocker]

For bearings go to AvidRC, most are $1 each & good quality to boot too.
6x15 & 12x21 are what you need for the RPM carriers.

x2 This is where I buy my bearings, great price and fast shipping.

[Jersey Crewmax]

Just ordered a set

[M n M]

@ Suteki - Yep, tried just one shim at the input gear to mate it up better to the ring gear, jammed it up and wouldn't make a complete turn without forcing it. Don't know, maybe my plastic housing is a little thicker than others.

[Captain_Rusty]

Go HERE and follow the steps. All you need to know is there. Thanks 87GN for the link.

[Jersey Crewmax]

So the car is up an running. It still needs some parts such as shock (the gpm ones that came with it are in need of rebuilding) ad well as wheels for the wheelie bar. Besides that, I have a few questions on the mamba monster 2200 kv combo.

So the truck is setup and it does have a robinson spur gear. What I notice is that the motor is really loud. Loud when first accelerating and it appears to cog a bit. It's especially loud when braking. It also appears to have a slight surge at low speed too. I'm wondering if that is the sign of the motor needing a rebuild. Considering the abuse this truck was put through: Seized front bearing, two heavily damaged diffs and the bearings on the wheelie bar just fell apart today, wouldn't surprise me. Any suggestions?

Thanks

[Jersey Crewmax]

Any suggestions?

[Suteki]

My Mamba Monster is fairly loud. Metal gears like I assume the spur being a robinson racing will definitely be pretty loud and if it's not meshes just perfect it'll be pretty loud. My touring car is the only car I would drive late at night, my Emaxx and shourt course aren't what you would call quiet.

Braking is the same.

The surge I don't know with out seeing it. My car kind of surges, I don't know whether it's the radio or the MMM esc, but it's not what you would call smooth in how it accelerates. Also being sensorless, they do tend to cog or stutter with low throttle input; the esc can't see where the rotor is in relation to the magnets so initially it takes a bit to get it all smoothed out. It never bothered me till I got my other cars which are sensored at lower speeds and sensorless after they get going; they are incredibly smooth on take off. If the sensor cable comes out it's basically the same as the Emaxx.

Checking the bearings never hurts though.