Gearbox Experts please

[CornishSilver]

I have a stock box that is crunching a bit on a quick shift in 3rd so am going to be sending it away for a rebuild. I am after some advise really please with what I'm running as to wether I should just have things overhauled or have a 4.57 ring & pinion. I have a 1776 engine with big wheels 215/75/15 the pic shows my max power (not sure but think its around 95bhp). The tyres are not something that can be changed, just thought id best get some advise from you guys in the know before I order a wrong job, lol.

 

[*Sam*]

When buying my gearbox parts I spoke with Mycha. He had a handy calculator that worked out RPM at a desired speed with the desired RnP, 4th gear and rear tyres size.
The result was:
4.57RnP
0.82 4th gear
195/65/15 rear tyres.
Gave 3200 at 70mph using

I got my RnP and gaskets from The engine shop and had my gearbox built by JP Race shop at Silverstone.



Sent from my iPhone using Tapatalk Pro

 

[atafonso]

My suggestion is whatever ratio you choose, make sure you keep the cruising rpm range between 3200-3400 as this is the best engine speed for optimum cooling from the fan. If the cruising rpm is lower, the engine might get too hot. If too high, you will use way more fuel and will accelerate wear.

Abel

 

[CornishSilver]

Well I have had a chat with cog box and bears and they are both saying the same thing. Looks like 1st and 2nd to stay unchanged. 3rd will need to be bespoke to allow for rpm drop for the longer 4th. The 4,57 will be no good for me due to the wheel size. Thanks for all the input