not all 'standard' diffs are equal

[aussieneil]

Hi all,

I added some comments and asked some questions in another posting recently, but today's developments I think deserve some treatment on their own. I can't see reference to these issues in other discussions.

To recap, I purchased a dead-original, very low-mileage 1978 short-wheelbase van to use its diff on my 1973 camper. On starting to change the diffs I noted they were totally different in appearance (photos included once again below), with totally different axle shafts, U-bolts, backing plates, brakes and drums (10" on the '78, 9" on the '73). To compound the problems, the '78 diff was also deeper, with the front flange sitting some 35mm further forward than the old diff, which means the tailshaft (2-piece on the camper) will need to be shortened, with a larger flange and uni joint fitted to the rear to match the larger flange on the '78 diff.

All this was organised, so today I went to finally change the diffs over.

However, I've hit another delay, as the shock-absorber mounts are also totally different! On the '78 van, the shock top mounts are mounted INSIDE the chassis rails, with the bottom mounts welded on the diff housing at suitable spacing. However, on the '73, the shocks are mounted on the OUTSIDE of the chassis rails, meaning the bottom mounts are in the wrong position on the '78 diff (far too narrow).

So now the diff will need to have the shock mounts cut off, then re-welded quite a bit further out on the housing to match the spacing on the top mounts. As well as the spacing being different, the bottom mounts face inwards on the '78 diff (the shock bolts to the inside of the mount), while the '73 is the reverse.

So there is a lot more difference between early and later SWB diffs than the size of the brakes! The ONLY commonality is the wheels, and the centre-to-centre distance between the leaf springs. (Even the leaf springs are different between the '78 and 73, and not interchangeable).

And I thought all CF Bedfords would be essentially the same!

[Jeff]

Are the spring platforms on the back axles the same distance apart?
I'm wondering if the SWB cab and chassis has the same Chassis setup as the dual wheel models.
This would explain the different shock mounts and springs.
Can anyone help?

You are sure that your camper is a SWB, aren't you?

[aussieneil]

Yes indeed, Jeff, the spring platforms are the same distance apart (as I mentioned, apart from the wheels it's about the only thing in common, so I should eventually get the damn thing fitted!)

The camper has always been registered as a SWB (although it has a 2-piece tailshaft?) and the original diff has the 9-inch drums that most here seem to attribute to SWB models. Ratio of the older, squarer, diff seems to be about 4.62:1, where the later one I am fitting is a 4.45:1.

One day it may all makes sense to me...

[BusyKiwi]

the bottom diff is a salsbery (sp?), a limited amount of bedfords came out with these.

my diff guy was telling me about these diffs when I was changing ratios on my diff

[Jeff]

I have read that the cab and chassis had the option of heavier rear springs. That may explain why yours are different.
And we may never know about the shock mounts, but those are easy to move and can be welded on without draining the diff I believe.

Welcome to Bedfords! 

[aussieneil]

Thanks both Jeff and BusyKiwi. All helping me understand the Bedford!

I got the shock mounts cut off the '73 diff and mounted on the '78. Initially I was going to use the '78 ones just reversed and put in the right position, but then I realised why the '73 has removable studs, while those on the '78 are fixed. The wider spacing of the shocks on the '73 (which is better for controlling sway) means the shock absorber is on the outside of the chassis rail and on the inside of the leaf spring. There is simply very little room to 'swing' the shock absorber to remove it from a fixed stud on the bottom mount.

So the mounts were cut off the '73 diff, and welded in the same position on the '78 Salisbury, after the original Salisbury shock mounts were removed.

The finished result (before painting) can be seen below.

[jesus_is_alright]

No 2 bedfords are the same. My parts van is a 73ish and my Azzvan is a 79 and i had the exact same problem. 79 with a standard beddy diff, and the 73 had a salisbury diff underneath set up for a 73, so i had to move shock mounts too.
Also noticed, the way the fuel tank is mounted/attached is different, key hole in ignition is different, (although the parts van was in pretty bad shape) and door handles were different. But it justs adds tot he fun of it all