Sorry guys I am putting in a 919 blade engine I've got a 3.77 in the car and I was given another diff Which has 39 teeth on the crown wheel and only 10 on the pinion from what I can see it that a 3.54 has 39 and 11, I've recounted again and again and still come up with 10? And it's in a locost. Cheers

[Edited on 24/5/13 by Nurburg2006]

[Edited on 24/5/13 by Nurburg2006]

what engine you using?
what is the car used for?
what car do you have?
What gearbox?

Why?

Ill look at my crystal ball !!!!!!!!

3.54 would be better

Shouldn't the diff pinion for a 3.54 have 11 teeth?? Mine has 10?

It's not teeth but diameter that affects the ratio so it's hard to tell what you have, did they arrive as a matched pair? The ratio should be scribed on both items along with matching numbers.

FYI 3.65 diff on 919 blade with 185/60/13 wheels gave max speed ~125mph at ~12,750 rpm which for short tracks is bang on as the standard engine will not pull anything much higher in a locost, very buzzy for the road. At Lydden hill or brands Indy circuits this is perfect.

If you can get a lower ratio it would be better for the road, 3.77 will be annoying.

Regards Mark

The one you've been given then is a 3.9.

Mark, think about it... crown wheel/pinion=ratio

Yes your right it's a 3.9 now looking for a 3.54 or maybe exchange my 3.77 for one and cash