Bizarre differential problem
 

Even since changing to the new outdrives (not the problem as far as I know) I have had a problem.

One of the differential loosens itself. It is becoming a major pain now. Simon Moss rebuilt it all at the Petit RC race except for the thrust bearing (thanks for the help) but the very next round it came loose. I then rebuilt the thrust assembly and it was fine for the rest of the meeting.

Today at Newbury however it would only last about 3 or 4 laps before slipping. I completely stripped, cleaned and rebuilt (AE Black grease on thrust bearing, AE White on diff components) the thing twice with no luck.

I have used ball diffs for 14 years, and often leave them when dirty and mucky without issue. (Simon said the black in mine was not good at Petit Race, glad he hasn't seen my Mi2EC...) Yet this is a mystery. No-one seems to be able to figure it out. The grub screw is proper locked in place, and it seems fine.

My personal feeling is, it's the stupid "disc springs". The thing is, no-one else has had a problem as far as I am aware. So, opening to the general public... has anyone got any suggestions please?

Thanks :)

we had a simalar problemwith a friends car the cure was to replace the springg washers circlip and rebuild the diff to the manual very slowly paying attention to the washer layout it cured it no problem since

Okay thank you.

I have a feeling maybe my weird washer disc springs have compressed somewhat and not as good as they used to be. I will order some spares and give it a go.

Thanks again for your help.

hope it helps mate;)

Can never count anything out - but, i have never seen the disk springs compress to the point that they can't be used. As long as everything is locked up correctly, should all be fine.

Well I thought that would have been the case too Matt. But something is causing this issue, been driving my bananas. Still getting into the B final at Newbury with a 2wd CAT has got to be an achievement of some kind :D

I'll make sure I'll report back here if changing disc springs work, just in case anyone else has same problem and searches.

Those spring washers ought to last donkeys. I know with the Losi diff, the best one I had was one built with the similar spring washers and was a diff bought 2nd hand - and id been using it 4 years on and off.

If something is gripping on the last thrust washer, or it is a little oversize, then that could turn the screw and loosen it.

Try rebuilding it - but when refitting, put it in the opposite direction, as if the forward motion is a factor that it current drives, then that direction becomes the braking force which is far less.

Had exactly the same issue earlier on in my CAT SX life. We had to keep re-building the front diff as it was 'slipping'. It all happened after I had broke an outdrive at Worksop (not sure if this is a coincidence Glypo), it wasn't a design fault before anyone says, I drove off a jump slighlty sideways shall we say......

We just re-built it slowly and put it in opposite way to what is shown in the 'blown-up' diagram (I know the diagram is only a guide anyway but we were down to desperation tactics to solve the issue!!) and all has worked ever since.

I think we've put it down to lack of concentration while re-building it previously.

All is ok now (touch wood)

Hiya, i did have a similar problem with one of my diffs when i was rebuilding then with the new outdrives before the petit and found in the end that it was down to the clip holding in the thrust race. What had happened was that when i'd taken the clip out it had cent slightly so that when it got put back together, although all looked good once i put it back in the car and tested it it came out of the locating groove and caused the diff to loosen off. I stretched the clip back out a bit and get presto it was find.

i also had similar problem and i found that i hadnt put the grub screw back in the male out drive doh simple but easy to forget

The circlip has a rounded and square edge to it if put in backwards the (rounded edge to inside) clip can push past the groove when under tension.

Did you fix this in the end Jason ?

Not sure yet.

I have got some new springs and bits, and rebuilt them all perfectly. As soon as the weather is good enough I will give it a test. Failing that I will find out at Newbury at the weekend.

A very odd problem, if it is fixed I won't know why, as it seemed fine to start with.

Did you solve this? I'm getting the same. Undoing itself in 3 minutes of running.

I found I got the bearings on the male diff component swapped with each other thick vs thin but not convinced fixing this will solve my problem.

I'm having the same problem. Re-built the dif, but still slipping by 3rd race. I am running 13.5 about to put a 8.5 in, so really concerned that the dif will loosen during the first race after rebuild.

Anyone found any cure? Is it worth putting thread lock on the screw?

off the subject but what are you gearing the 13.5? are you running the stock internal ratio and spur as well?

Yes I am running stock internal. I have changed to the 80 spur and running 27 pinion. It's the most I can squeeze in there. I need to change the internal because the car is under-geared. Though I am winning most of my races, and keeping up with some cars (but not most) on the straight. Motor is a Speed passion.

I rebuilt the dif again and tried the trick Losi_110 advised of stretching the cir-clip. It seems to have worked. Just went a whole race meet without issue. This kind of makes sense. I have a lot of trouble getting that clip out. I am going to purchase the right tool from Schumacher.

Cat was smoking hit at the meeting. It looked like a missile was coming up behind other cars when lapping or catching up. Sick.

Not fixed mine yet but only takes 5 mins for mine to undo itself. Has been suggested I got the diff stack in the wrong order so going to rebuild it when the parts arrive. The circlip certainly isn't popping out. Was yours?

Schumacher sell a complete assembled diff assembly U3338. You guys are spending ages over this issue which sounds very frustrating, why don't you just cut your losses and drop in a fresh diff.

You can then completely strip the diff which is slipping, bag up the components and use those parts as spares when you come to rebuild one again.

Im sorry I can't suggest much for fixing the slippy one, but without it infront of me and myself repairing it I find it impossible to diagnose it. :blush: Id be very willing to give it a complete rebuild for you if we were ever at the same meeting though.

I'm not frustrated just don't have much time to spend on RC cars with a new baby. Pretty sure I got the stack in the wrong order though so will try that next. Is there a recommended way of spotting the 0.2mm difference in them? I bought a magnifying glass but haven't tried that yet. Maybe some VERY accurate callipers?

Even a pair of cheap hing hong digital calipers will show you the difference, and are a worthy purchase :)

G

Bought some genuine hing hongs with an ABS button on your advice. Dunno what the ABS button is for, but its more buttons that most of the others had :thumbsup:

Schumacher would do everyone a favour if they were more upfront in the required tools listing! I'm sure there are lots of us who couldn't visually see the size difference of those spacers and who frigged in the e-clip with some pliers possibly bending it in the process. No wonder there are so many with diff probs!

Diff Problem
 

I've had the same trouble with my front diff, coming loose since i fitted the new out drives?
I fitted all new diff internals one at a time to try and get to the bottom of it.
The only part of the diff i hadn't changed was the female outdrive, which i swapped with the old type.
This cured it! Dont know how or why? but it did!
Very frustrating though.
Hope this helps:D

Did you try stretching out the C-clip? Might be even worth picking up a new c-clip.

Seems to me, that if you have put the old female outdrive on, it will only be a matter of time before it breaks. Probably in the A final when you are leading. It is worth having the new outdrives on, if you can get the dif to stop slipping.

Diff problem
 

I put a new e-clip in that comes with the new thrust race, but your right about the old outdrive, its only a matter of time before it breaks,
Not be an A final though! LOL!:woot:

Ok think I've fixed my problem and for me at least it was a bit non obvious what I'd done wrong.

I had assumed I'd got those to small disks in the thrust bearing the wrong way round, but using a magnifying glass (callipers not arrived yet :( ) I could see they were right. What appears to have been wrong is that the actual bearing was upside down between them. It isn't terribly clear from the diagram and there are no notes on it in the instructions, but it seems that the side of the bearing which has the balls sticking out most proud, should be facing into the diff assembly where I had it facing out. Before I stripped and changed this, the diff was undoing itself in about 5 minutes.

So if anyone else is having trouble, worth looking at this as I think it's solved my problem. Need to run it a bit longer though as only had a small bit of charge left in the pack.

That doesn't make a difference!!

As long as your problem has gone away though, it's all good.

Mine came loose yesterday after rebuilding it, but turns out the grub screw had come out, so make sure this is very tight, and with threadlock!

Paul

Oh well lol. I also stretched out the eclip, but that hadn't been popping out so can't see how that would help?

maybe I didn't ahve enough battery yesterday to make it undo :(

me too
 

I ran my cat for the first time friday and my front diff kept loosening:mad:. I rebuilt it, retightened it, threadlocked it but it kept coming loose. It happened about 8 times. I finally discovered that the oring seal was grabbing the adjusting screw and gradually loosening it. I removed the seal and the problem was resolved.:thumbsup: It sounds crazy but I noticed this occuring when turning the diff by hand. It doesn't matter how hard you tighted the set screw because the seal would loosen the screw. Weird, but I ran it the rest of the day and the following sunday and no problems.:confused:

I popped one of theses in the rear ...3 heats and a final later the inevitable happens.... :thumbdown:... only running a 17.5 ty :cry:
(i doubt they come with grubs screws loctited... so) tightened it and applied loctite...seems ok after 1 more final...so far !...smells of design weakness IMO

No design weaknes, if they are built correctly the diffs don't come loose, and to be perfectly honest some of the nicest diffs I have built.
I admit, I had a couple of diffs when built came loose, but that was due to the c clip not seated properley. I discovered this by spinning the diff a couple of times, so didn't have to run the car. Just took the diffs out and double checked the c clip. Even, no need to put the loctite on the grub screw as long as it is very tight. As with all my RC Cars I carry a spare diff, mainly to save having to build one when I am racing.

I disagree, too many loose diffs to say the design is not weak...

If the reliability depends on which side the e-clip is facing then its inherently prone to user error.

Another area of design fault is the rubber o-ring grabbing the screw head.

...(no disrespect but) don't stick your head in the sand about the issue....

It's such a week design that i don't believe any of us suffered at prototype stage, and the touring car has been using the design for at least 6 years without any major issues. So personally i think it's a great design.

Agree with Matt, no design fault. Aslong as the Diff is built correctly, as per the instructions, there isnt an issue. Surely you can say the same about any car if you dont follow the instructions?

So true
 

Guess all contributors here are lousy diff builders or just unlucky with FT diffs... bunch of winging pikes we are ! :p

That rubber washer is a late amendment (an insert to the build instructions with mine) to the design though so maybe thats why it hasn't come up before. I stripped and rebuilt mine twice and nothing was wrong with how it was assembled. Still not sure if its fixed as not run car since.

There has got to be a difference in application from touring car to off road. Maybe that is why there are issues. Saying that, the issue only arrises with the new out-drives.

In defense of the monkey, he actually put in a new Schumacher built dif. So does that mean that the factory are not assembling them correctly?

I built up my second dif using the new out-drives. Had no problems. My rear dif has only just started to slip again, but that is with over 3 hours of driving on 8.5 motor. So it's all good once it's right. Right?

It does seem a little odd, i will say that. Is there differences between touring and off rd? don't know. Off rd maybe has more "shock" loading, but touring probably has more torque loading from 3.5 motors etc.

The circlip has been used in off rd diffs since the late 90's. Sure less power then, but same shock loadings.

Both Si and myself have posted to say we've had no problems - and we've had Cat SC longer than anyone else - over 1 year now for us.