Back axle Cortina Estate, Issues

[C_Scott]

Hello everyone, Got a Marlin Berlinetta and am starting a thorough rebuild of it after it sitting lonely in my garage for the last 22 years. Back axle diff unit, the rear cover shows signs of leaking oil due to rust. Is there a supplier for old ford parts like this rear diff cover or do i have to work miracles with a welder to repair the teabag metal ??. Any help appreciated greatly. I was also told there are different gear ratios for cortina diffs. All unknown to me. 2000E gearbox and a MK4 estate back diff results in 3500 rpm at 70 mph Is there a type of diff which would de rev the engine slightly. Original 4 speed box from the 2000E

[scott h]

Re: Back axle Cortina Estate, Issues

The first thing is to identify which axle you have got. Here is a link to a pic of the 3 most common Ford axles.

https://images.app.goo.gl/cSNApU6dH5ojqXKq6

There are several diff ratios for each axle but you would have to trawl through classic car ads on ebay etc to find what you want, some are available new but the prices are astronomical.

Have you thought about changing the gearbox for a five speed type nine from a Sierra? This is a very common swap because the fifth gear is an overdrive ratio and will give a bigger drop in revs than a diff change. The problem is that these type nine gearboxes are getting harder to find aswell but not impossible.

[daveghunt]

Re: Back axle Cortina Estate, Issues

If your axle is from an estate it is probably ratio 4.11 (as mine)
Other ratios fitted to Cortinas where 3.89, 3.7 & 3.44
I believe the estate was allso fitted with larger drum brakes.
I found that fitted with the 5 speed box gives around 75 mph at 3500 revs, (unsure of accuracy of speedo reading)
All this is dependent on tyre sizes and pressures of course.
As reply above I would advise changing to the 5 speed box, you do need to modify the gearbox mounting,
As described in some very early pit stop articles.

Hope this helps
DaveH

[C_Scott]

Re: Back axle Cortina Estate, Issues

Thank you for this very useful information. I will follow up on it asap. I had thought about a gearbox change but my neighbour who is into racing newer fords, reckons the sierra gearbox will be rare as hens teeth. And, if available, will cost a packet as they are used extensively for racing. He mentioned a transit van gearbox but I have no background info on these so far. I would think the ratios will not suit the axle for going to lower engine revs.

[C_Scott]

Re: Back axle Cortina Estate, Issues

Thanks for the reply, most helpful. I will need to check the hub diameter on the axle, have not yet bought the replacement shoes so you may have saved me another incorrect purchase. Is there any scribing on the gears etc within the diff units to tell the ratio installed or is it a count the teeth and divide, to get the numbers. Is the pinto engine meant to rev at that high a range normally ?? Maybe I am worrying over nothing. I will still need to find a new(er) cover.

[scott h]

Re: Back axle Cortina Estate, Issues

Type 9 gearbox on ebay. £300 but open to offers and it's at Auchterarder so not far from Glasgow.

https://www.ebay.co.uk/itm/123958682719

[C_Scott]

Re: Back axle Cortina Estate, Issues

Thank you for finding this, I have put in an offer and can collect. Many thanks.

[B_Williams]

Re: Back axle Cortina Estate, Issues

Mt Berli is on a Sierra Type 9, with an estate rear axle and running on 15" wheels
Normal running is fine, but I sometimes find 1st is a but high in slow moving traffic.
If I were to fit a new box, I'd investigate a Type 9 from a Ford P100 pickup, which I think retains ratios for 2-5, but has a lower 1st, but do check up yourself.

[billjackson54]

Re: Back axle Cortina Estate, Issues

Reference changing to type 9 five speed box....I carried out this conversion of a car of mine some years ago....what was required was the replacement of the rear gear box carrier of the 4 speed box....a banana shaped item with that from an automatic car...which was a rectangular item. This moved the gearbox attachment point a few inches back in the underside and everything the propshaft fitted back juts as before.

[boustrophedon]

Re: Back axle Cortina Estate, Issues

Later MT 75 box, found on Sierras are even better, nice gearchange and very strong.

[chris_cussen]

Re: Back axle Cortina Estate, Issues

Transits used the MT75 gearbox as well.
In fact if you use an MT75 from a Sierra you will need to remove the rear flange as it is a horrid rubber job and fit a Transit flange so you can mate it to the propshaft.