4.56:1 rear axle wanted

[Steve121]

Hi chaps and chapesses

Does anyone have a good second hand, or recon rear axle from an overdrive Amazon?? (mines a '68 so will need an axle with the later suspension mounts)

Steve

[theoldmotorpartsman]

I have available a rear axle from a 66 automatic without brake backplates or drums, but I don't know its ratio.

[Gordon Hunter]

Steve,

I have both 8 & 10 bolt 4.56:1 crown wheel and pinnion sets here.
I could post them to you easily enough.
I'll only be available on mobile though for this next week: 07962 720805.

Cheers,

Gordon

[Steve121]

Hi Gordon, are they new or good used condition, and what sort of price? mines a 10 bolt spicer. Any idea of the complexity of swapping over the cw & pinion?

Steve

[Pigeon]

Exactly which axle is it you're after? 4.56:1 is an estate axle. Overdrive saloons are 4.3:1.

[Derek UK]

The 4.56 axle was fitted to estates, and saloons with factory fitted ODs inc 123GT. fferent axle to the estate though. Non OD cars came with the 4.1. The 4.30 axle is a bit of an odd ball and as far as I know was only fitted to some very late B20s. It's a nice compromise if you do fit an OD though. Although many B20 saloons now have OD I don't think any had it as standard, even the twin carb models.

[Steve121]

like I said, I'm after a 4.56:1 axle
These are for OD cars, I put an OD 'box on mine, so with the standard 4.1:1 axle the speedo underreads a lot.. at a true 80mph it reads under 70mph. So a 4.56:1 will cure this, as well as making the OD more useable

[mike gilbert]

"at a true 80mph it reads under 70mph. So a 4.56:1 will cure this, as well as making the OD more useable"

Doesn't that mean that the car is working as hard at 80mph as it used to doing when 70? That sounds like a worthwhile cruising improvement to me. If I'm right and your old axle will lower engine revs for a given cruising speed, I have a late 4.56 axle, which has nothing wrong with it as far as I'm aware and would do a swap.
Mike

Originally Posted by Steve121

like I said, I'm after a 4.56:1 axle
These are for OD cars, I put an OD 'box on mine, so with the standard 4.1:1 axle the speedo underreads a lot.. at a true 80mph it reads under 70mph. So a 4.56:1 will cure this, as well as making the OD more useable

That's not really true, you'll end up with 5 gears in the space where you previously had 4. Once you swap in the standard overdrive axle it will have very similar gearing in OD/4th to you previously had with in top the 4 speed box, which negates the whole overdrive swap. I would personally either recalibrate the speedo, or figure out how much it is out by and live with it.

[Derek UK]

It's certainly true that having a 4.56 axle makes the OD into a 5th gear that you can use to get a higher top speed than in 4th gear, but only if you have enough power. The 123GT just about makes it if it's in good nick and as you sign your self "Ruddspeed" you might have a little bit more. Nowdays most people want an OD to be just that, A gear that drops the revs and allows quieter and more economical cruising on the motorway. The 4.56 ratio makes all of your gears lower which is why they fit it to the estate so it can work well with heavy loads. With the GT etc it expects you to be using lots of revs to get into the power band for better acceleration.
You should be able to correct your speedo by changing the nylon drive gear. Easier than changing the axle. There are several different ones, which come in different colours. E.g. the P1800 with a D type uses a black gear with fine teeth. Is that right Mike? Perhaps Mike or Andy could post a list if they have them.