Differential Change

Date: July, 2024

The weekend at Snetterton was definitely a realisation that this car is just nowhere near competitive enough. Mainly along the straights but this could be initially rectified by shortening the final gear ratio.

This is done with the differential ratio. The Formula 27 I have is running a Ford atlas axle with a limited slip differential inside it running a 3.1:1 ratio.

This is clearly far too long as I wasn't getting into top gear at the end of the straight at Snetterton so something had to change. I did some calculations and worked out the best ratio would be a 4.1:1 ratio for most of the UK tracks I will be racing on.

A quick stop to that online auction website and I secured exactly what I needed and then watched plenty of videos on how to do this myself.

It seemed simple enough but I took the decision to miss the Cadwell Park race weekend in order to have time and money to fit it.

The hardest part of this was getting the shims in the right place so everything meshed correctly and there was enough but not too much pre-load in the diff. I bought a beam torque wrench for measuring the preload and it was quite a simple process with that.

With the diff replaced I was now more confident of being competitive moving forward even though the car is too heavy and too low on power.

The limit for my class is 280bhp per tonne and I am at 215bhp per tonne so quite a way off the maximum!

This may need to change for next season but we'll cross that bridge in the closed season.