Is the Diff Dead?

[YellowPeril1]

So it was my first day out in the SR4 at Blyton last Monday and what a thrill it was! I built the speed steadily over a few runs and really felt at home in the car. Unfortunately, just before lunch the chain let go and the soft link for the spare I had turned out to be damaged so that was the end of play.

The chain had looked correctly adjusted and was well oiled, but I don’t know how old it was. However, looking at the car yesterday there seems to be loads of play in the diff - surely loads of play in the diff can't be right? I assume this will have contributed to the failure.

With the wheels on the ground I took this video. https://youtu.be/XCfXTpj5JkA

Is the diff dead?! Could anyone advise please?

Thanks,
Nick

[minitici]

Looks like you could have problems with the engagement of the dogs on the reverse mechanism.

[GraemeD]

Funny, I just bought an SR1, and on the second lap of the first outing, the chain snapped also. The SR1 has the same diff, and mine seems to have a similar amount of play. For what it is worth.

[Atom Ant]

Wow that really has let go, hope nobody got hit on the head.
We ran a 2013 SR1 on a track day only basis for 18 months with the paddle shift arrangement and the chain never let go. I don't want to be patronising so please don't take it that way but from our experience you have to inspect the tension and apply the dry spray lube at least twice during a track day, someone sprays while the wheels are being rotated so that you get it fully lubed. We also put paint on the adjusters so that they could be seen to be equally adjusted hence keeping the alignment, we found a 1/4 turn every other track day was more than enough to keep it at a good tension. The chain did have a stiffer section and a looser section when rotated but we did keep it quite tight.
I think the backlash in the diff and drives was slightly less than the OP's but we have moved onto an SR3 now so can't check.
It would be good if you could post up more data on the age (running hours) of the chain and sprockets, did it have the paddle shift? The condition of both the sprockets and chain running hours is critical to success.
All the best. Ray.

[BertBert]

chains break all the time, it might or might not be an issue.
Bert

[Gc285]

They all have play. I have just checked and if you turn the wheel back and forth, the inside uj will turn about 10mm before engaging drive to the chain. Mine is 1 year old and has not changed since new. You don't have a chain on so it may be slightly different .

[YellowPeril1]

Thanks for all your comments guys. One of the chaps at Radical has now had a look at my video and has advised that due to the way it’s designed this amount of play in the diff is normal, so that’s good news.

I now have a new chain and a set of new sprockets ready to fit for good measure. I’ve seen loads of posts about the importance of the sprockets being correctly aligned, however, I can’t find anything much about the correct method of actually adjusting the sprockets to get them into line.

I’d be grateful for any advice on this and also the torque to use for the rear sprocket bolts and the front nut.

Many thanks,
Nick

[fast freddie]

I use a hacksaw blade to align the sprockets, its the right length and narrow enough to fit in the confined space.
Using the back of the hacksaw blade [the smooth side] place it on the side of the diff sprocket on the lower side of the sprocket, then you can use this as a straight edge to align it with the gearbox sprocket.
Also when you bolt your new sprocket onto the diff, make sure that the two cuts in the sprocket remain the same width [the width of the hacksaw cut], sometimes when you bolt the sprocket into position, one of these cuts will close up and the other will open up which will of course produce uneven running on the chain. Hope this helps and makes sense!

[YellowPeril1]

Thanks for the tips fast freddie! Nick