Mardave Ball Diff help

Hi Guys, bought a Marave ball diff today for my V12 circuit car.

It feels pretty aweful out of the packet, quite a tight spot.

What do you guys do to improve things?? Sand diff plates?? Ceramic diff balls??

One other thing when you tighten the wheel (diff side) it all binds up?

Any help much appreciated!

Ceramic balls deffo ..its hard to say on any thing else but make sure its all nice and free and the washer in the diff is V this way round that is point is facing the diff gear

Thanks Gazza, do you know what size the balls are??

try going to chat at the bottom of the main page gazza lurks in the deep blue bttm in the live chatroom lol

Same as the diff holes ...pmsl normaly 1/8th

Head,

I've always been very lucky with the diffs I have had from Mardave. never any tight spots and I have been able to run them for weeks with no added attention needed. They have even been setup the right tension! I gues I might have just been lucky.

However, if you have a tight sopt, strip your diff apart and re-build. Clean all parts (except the intrnal thrust race bearing!) with motor spray to de-grease. Be especially careful to get rid of all grit, dirt etc - extreme care at this point is never too much! Check the moulding of the plastic diff cup - sometimes this has some 'flashing' left and can get in the way. Change balls for cermaic ones and sand plates if that floats your boat. Apply a thin film of quality diff grease to each ball and re-assemble. If you still get tight spots, try new plates.

To get the right tension in the diff nut I find it best to try on the track. In my experience, if I have held the rear wheels still and tried to turn the spur in my hands I find I often strip the non-diff side axel spacer! On the track you should be able to accelerate HARD from standstill with the diff just not slipping. Tighten / loosted by fractons for the right balance. TIP - a nitro glow-plug spanner is a good fit on the adjustment nut.

As for it binding up when you tighten the diff-side wheelnut, that is not unusual! The diff output on this side is a fraction too short really (or the wheel hub is a fraction too deep) and a fully tightened wheel nut will rub on the wheel and 'bind it up'. Back the wheelnut off about half a turn and that should be about it.

Be warned - the diff-side wheelnut is more prone to coming undone in a race than the non-diff-side wheelnut, simply becasue you cannot clamp it up tight. If the nylock bit starts to feel 'loose' when you tighten it, replace the diff-side wheelnut with a brand new one. I think I replace mine about once a month, depending on ho often I race / change wheels...

Hope this helps,

James

Thanks alot for the help and advice James, yes stripped and re-built it today and sanded the plates falt and used some AE diff grease and its alot better.

But as you said still getting the binding when you tighten the wheel up and I too spotted the wheel is slightly proud of the axle shoulder, I may try and find some small shims to take this out so the wheel can be done up tightly.

Does the alloy diff/wheel drive improve things??

No worries, that is what we are here for!

I too use AE diff grease. I used to stick with some old stuff from Corally (this was extremely 'sticky' and seemed to be less prone to being spun out of the diff at high RPMs) but I just can't find it any more.

Shims might be ok in the wheel. However, I have also heard of people drilling a small recess into the outside face of the wheel's axel hole so the wheelnut can be sunk into the wheel rim and rest up against the shoulder on the axel. Of course, you have to be extremely careful to get the right diameter recess and drill it to exactly the right depth....

Another tip is to ream out the axel hole in the rear wheels. I simply run a brand new and very sharp 5.0mm drill bit through mine with a power drill. I always get a tiny bit of swarf coming out so I am assuming it is widening the hole a fraction, but this really is jusy a fraction. I have found this gives a more free diff axtion, but don't go wider than 5.0mm or else the wheel will wobble on the axel shaft...

James

Head wrote:
One other thing when you tighten the wheel (diff side) it all binds up?

Run a drill bit through the centre of the wheel by hand were the axle goes through. May sure it's the same diameter as the axle and no more that 0.1mm bigger. You could also use a straight reamer (not the body shell type we use)

Don't tighted up the wheel nut as it clamps down on the wheel. Drop of super glue, shoo goo, evo stick on the threads helps retain the nut. If you use SG run drive the nut on and off a few times. Leave the nut of until SG has hardend then it should grip without setting.

Thanks again, I'll give the drill bit mod a go on the wheels and see how we get on.

Its a bit annoying but what can you expect for a £17 diff and axle! lol

Nothing like the feel of my old diff on my AE L4!

Yes, the diffs on most 1/12 scale circuit and 1/10 scale pan cars might well feel smoother than the Mardave unit.

Bear in mind though that most of these have extra bearing races in them - usually one to support the spur gear on the axel and a total of two on the diff-side wheel carrier (one of these doubles up as the thrust race). Our Mardave units only have the one... I have played with the idea of machining my spur gear out to accelt a second bearing but have not been brave enough to try it yet!

I have had a prototype alloy wheel carrier on one of my Mardaves for a few months now. I think it might make things run a little more freely - it certainly seems to be machined more concentric than the moulded plastic one. However, just running it side by side in my hands with my second diff it is extremely hard to tell the difference!

One more mod you might want to try - add more cone washers between the diff adjustment nut and the thrust race. But make sure they are the right way around! This can be done, but it will depend on the type of cone washers you are adding (I have no idea where mine came from - they were just odds and sods in my pit box). The theory is that having more washers will allow you to adjust the diff nut more accurately becasue the spring tension from multiple washers is spread over a longer distance. Howver, too many added washers (or the wrong sort) means that the diff nut is too far out along the axel when you get the correct diff tension and this can mess with the diff-side wheel. I used a lower profile diff adjustment nut to get over this.

Just an idea,

James