Blown Bearing in RCM Hybrid Revo Diff - RC-Monster Forums

jpoprock · **Blown Bearing in RCM Hybrid Revo Diff -** 08.27.2009, 01:38 PM

Blew a bearing in my RCM Hybrid Diff for my Revo last night. Very strange too. I hadn't really been doing much with it either. Nothing fancy anyway. At first I thought it was the tranny, but upon further inspection, I found that the output cup leading from the rear diff to the tranny was loose and could wiggle around. Pulled the diff, and discovered that the bearing was literally blown to bits!

My question is... the outer ring of the bearing is stuck inside the diff case. Should I bake it to get it fall out?

Also, what kind of bearing goes back in there??? This bearing looks sorta "deep", but it's hard to tell because there is nothing left! I can't tell from the product description what size goes back in it.
http://www.rc-monster.com/proddetail...=rcmrevohybrid

Thanks!

J

08.27.2009, 03:20 PM

The V3's use 8x14x4mm bearings for the pinion, I believe.

jpoprock · 08.27.2009, 04:21 PM

Well, it's hard to say. I mean.. if you say so! I'm going to the LHS tonight, and if I don't get them tonight, I'l have to order them. I live an hour away from the LHS, and hopping in the car and just going is not usually an option for me. I try and maximize my trip. There is no way for me to measure the bearings because there are two of them, and they are blown to bits!

jpoprock · 09.02.2009, 05:25 PM

Well, so far I've heard nothing from Mike, nor can I do anything until I do. I've discovered a "hole" in the diff case, which looks more like a defect in the thin case more than a crack or hole. Plus, I can't get what's left of the bearings out to save my life. My ERBE is just sitting in a heap of parts until it gets resolved. That's awesome!

Plus, I've learned that the diff cases are made special for these diff's. So that means that I can't just put the gears , etc inside of another diff case and be done with it. I need the RCM case. And really, I only need one half of it. My gears are just fine. So, I'm in a holding pattern until Mike gets ahold of me and tells me what he wants me to do.

Here are some pix:

The outer rings of the bearings are stuck inside, and I can't get them out for nothin!

That hole had to have been caused by the bearings going bad I'm guessing. The truck was running fine, then stopped moving like the pinion moved off the spur. That was the first thing I checked and it was fine. Then it seemed like a tranny gear was bad cuz it was locked up. But that checked out fine. Then I noticed the rear ctr CVD was really loose feeling, so when I pulled the diff, the bearings were gonzo. I didn't notice the "Hole" until I got the diff apart and cleaned it up. So, there ya have it!

j

simplechamp · 07:49 PM

Wow I can't believe how thin the aluminum is in the spot where the hole formed.

Do you have any guess at all as to how long you were running the truck after the bearing failed?

Bondonutz · 09.02.2009, 07:47 PM

Unfortunately it was grinding away at the case for a little bit, In the second pic you can see how the edge of the material around the hole is flaired out.
Wouldn't take long for hardend steel to grind away at aluminum.

simplechamp · 09.02.2009, 11:20 PM

Yeah that's what I figured. No way it would have been designed with such a thin spot. Too bad though, that case is beat.

jpoprock · 09.04.2009, 09:58 AM

Hey guys! Looks like my first email to Mike got caught in his spam filter, despite my getting the "thanks for the email, we'll get back to you soon!" reply.

I'm thrilled to know that they do sell the cases and bearings, but they are out. Which is why I didn't see them in the store. I think I'm going to purchase the RCM output cups to use with 1/8 scale diff's, then pick up an couple more XXL diff's to have as backup. I've heard that RCM's diff cases run $40! which is super salty. Especially if they are likely to be toast if you lose a bearing. I've never really lost a bearing in a diff before. So I'd have to guess that it's not common. But I'm gathering that the bearings RCM used for theirs were not all that great. Maybe the key is to invest in better bearings from Nova or wherever?

But here is what he said about my diff. Looks like there was nothing I could do or did, to prevent it from happening.

"Jason,

This is the 1st email I have seen from you – perhaps you sent the other email to an incorrect address or it got caught in a spam filter? When the diff pinion bearings fail, it usually takes the case with it(when the bearing fails, the pinion gear chews through the side of the diff case). The bearings are 8x14. I can likely find a new case for you, but I am out of these diffs right now(can likely scrounge one up). I am searching for a stronger bearing option for the next batch – I have seen about 4 or 5 failures of the bearings, and they all lead to the chewed up diff case.
Often, the bearing failures are a result of improper installation – there is a coiled steel insert that fits between the bearings in addition to the sleeve that also must be between these bearings. These two items are crucial to the strength of the bearings, as they allow the bearings to share the thrust load caused by the diff pinion. If the sleeve or steel coil is not installed, each bearing will fail separately(most likely consecutively). Did you assemble the diffs, or were they assembled before you received them?

Mike
RC-Monster
www.rc-monster.com"

sikeston34m · 09.04.2009, 10:20 AM

Quote:

Originally Posted by jpoprock

Hey guys! Looks like my first email to Mike got caught in his spam filter, despite my getting the "thanks for the email, we'll get back to you soon!" reply.

I'm thrilled to know that they do sell the cases and bearings, but they are out. Which is why I didn't see them in the store. I think I'm going to purchase the RCM output cups to use with 1/8 scale diff's, then pick up an couple more XXL diff's to have as backup. I've heard that RCM's diff cases run $40! which is super salty. Especially if they are likely to be toast if you lose a bearing. I've never really lost a bearing in a diff before. So I'd have to guess that it's not common. But I'm gathering that the bearings RCM used for theirs were not all that great. Maybe the key is to invest in better bearings from Nova or wherever?

But here is what he said about my diff. Looks like there was nothing I could do or did, to prevent it from happening.

"Jason,

This is the 1st email I have seen from you – perhaps you sent the other email to an incorrect address or it got caught in a spam filter? When the diff pinion bearings fail, it usually takes the case with it(when the bearing fails, the pinion gear chews through the side of the diff case). The bearings are 8x14. I can likely find a new case for you, but I am out of these diffs right now(can likely scrounge one up). I am searching for a stronger bearing option for the next batch – I have seen about 4 or 5 failures of the bearings, and they all lead to the chewed up diff case.
Often, the bearing failures are a result of improper installation – there is a coiled steel insert that fits between the bearings in addition to the sleeve that also must be between these bearings. These two items are crucial to the strength of the bearings, as they allow the bearings to share the thrust load caused by the diff pinion. If the sleeve or steel coil is not installed, each bearing will fail separately(most likely consecutively). Did you assemble the diffs, or were they assembled before you received them?

Mike
RC-Monster
www.rc-monster.com"

I installed a set of RCM V2 diffs in my E Revo after the stock diffs failed.

The stock diffs gave me about 50 packs worth of HARD running. They took alot of abuse.

Now after about 5 packs, the bearings in the front V2 RCM diff are gone. I haven't torn it down yet, but I HOPE it didn't chew through the case.

The V2 did NOT come with the sleeve or the steel coil.

My Question is:

Obviously, this was part of the revision from the V2 to the V3. Is there any way that I get those two things seperately?

Pinion Bearings on the V2 is definately their weakness.

jpoprock · 09.04.2009, 09:59 AM

BTW Appetite... you were correct about the bearing size. But you said, "I think", and I was looking for a "For sure". HA! Mike didn't say that they were x4 though, but I'm positivie you are correct about that.

jpoprock · 09.24.2009, 11:39 AM

Sorry for the delay in replying. I've been on a bit of an RC break to work on other things.

You know, I'm not sure about where to get the sleeve or coil. I think you can get that stuff from RCM, but I think that Mike is out at the moment. That's why you can't find it in the store.

I lucked out and was able to get a new case with bearings and guts, but mine is like the "display model". I don't care though. I should have it soon. I'll be anxious to see what Mike comes up with as far as finding a new vendor for bearings.

I'm going to have some bulkheads sent off to be modded by a friend of a friend. $5 each end... so $10 a truck. He's got modding these down to a science, to allow for the use of the Losi XXL diff's. I'm going to then order some cups from RCM to have on hand as a back up plan in case I run into more RCM Hybrid diff problems.

I'm REALLY bummed about all this down time my ERBE has experienced. Soon it'll be winter, and I don't drive my trucks in the winter. It gets pretty cold here, and cold air + plastic = easily broken parts. I'll probably be doing the Mini-T thing on carpet w/ my 8 yr old son! That'll be fun.