Rear differential for a 5 speed box

[jaguar68]

Hi guys,

Can anyone tell me what would be the best differential ratio for running with a 5 speed gearbox?

What is anyone running with this set up?

Regards

John

[MarkyB]

I'd suggest you go with what you have now then change it if you feel the need.

[bmcecosse]

Sounds like a good plan to me - unless you have the 5.33 ratio at the moment..... It also all depends on what power you have to lug the car along. With a diesel engine for example - a 3.7 would be required!

[IslipMinor]

John,

What engine spec, gearbox and diff ratio do you have now?

I have a 3.9 diff with a Toyota 5-spd box that gives 20.6 mph/1000 rpm in 5th. With a well modified 1380 this gives a very easy motorway gearing and little need to change down for hills or overtaking.

[mike.perry]

It depends on what engine you have but as 5th gear will be an overdrive then you will probably not need to change the diff.

[jaguar68]

The engine would be a +20thou overbored 1098 cc, with a 1 1/2" carb, either a HS4 or HIF 38, and either a Mini exhaust manifold or an LCB (haven't decided quite yet). I believe the diff would be a standard 4.22 1098 one, unless someone in the past has swopped it over for a lower ratio one at an earlier time in the cars history. I have a 3.9 diff, but was hopefully going to use this on a 1275cc Hot Rod project.

Regards

John

[chrisryder]

we seem to have identical vehicles.

i too have a 1098 + 20 thou with a standard cam and a 1 1/2 inch HS4 carb.

recently fitted a five speed myself, (before that i had a 4 speed and 3.9 diff) so when i fitted the 5 speed i kept the 3.9 in. i didnt really get along with it, much too 'long' geared especially in fifth, so i changed back to the 4.2 it had originally. very happy with the performance.

i too have a 1275 project which that 3.9 will be saved for!

[jaguar68]

The 5 speed box was going to be fitted to a '56 Series II, but after some negative comments, it looks as though the '56 will be fitted with a midget box, converted to fit the Series II floorpan. Well, it will be after sorting out the 'box and engine on the 4 door and funds allow.