In my case it's a kit car with big wheels that makes needs a lower ratio than I seem to be able to get in 7".
I now have a 4.27 which presumably is from a Granada.

I also now have a 7.5" beam to fit it to.

Is this a reasonably straight swap otherwise?


Main issue I can see for now is drive shafts to suit drum brakes? Any advice on that would also be useful

 

The process I hope to use is to swap out the beam, fit the current susp arms to it but with Lobro/bolt-on style hubs so as to allow Lobro/bolt-on driveshafts to fit at both ends.
I have drum brakes and they are fine but I have read somewhere that you can use drum back plates on disc style hubs by cutting off the caliper lugs.
The only other concern is whether the 7.5" diff is also longer so that the rear hanger has to be moved backward, which will be difficult in my car. If it's longer in the forwards direction that may be ok as I have plenty of slack in the prop shaft

 

The diff mount is in the exact same location for the 7 and 7.5" diff.

 

Thanks for that. A bit of a relief.....

 

A bit of an issue has come up. The diff doent quite fit the beam becuase there is a bit of webbing in the way. The diff width is ok and it almost fits but not quite.
Looks like I could cut away some of the webbing on either the diff itself or the beam, but which would be best?

I'm guessing this has come up becuase the diff is from a 4wd car (or possibly a Granada?). It has 100mm drive flanges. Howeever although these shafts may be weaker I'm not bothered as Im only running a 2 litre Zetec. The beam on the other hand may be from a cosworth. Should all be fine as long as I can fit the diff to the beam

Any help out there?
Thanks

 

I'm not sure what kind of diff and beam you have. Are trying to fit a 7.5" Sierra/Granada mk3 diff into a beam for a 7" diff? Or are you trying to fit a 7.5" Scorpio diff (which is slightly different) into a 7.5" Sierra beam?

 

Thanks Marc.
Actually I am not sure where either of them came from really (ebay)
But it is a 7.5 diff and it also seems to be a 7.5 beam. The width between the top bolt seems fine. It's a bit lower down where the problem is, right in the middle of the webbed area in this pic. It could esily be cut away I think, but the question is whether to cut the diff or the beam. I'd guess the beam since that can be welded back together easily. - just seeking advice though.....

 

Looking from the pic it must be a Scorpio (bug eye) diff. I have no experience with fitting that one.

 

If the webbing needs cutting the it is a post 1994 Scorpio diff.

it will fit as I know someone who has done it, but the webbing needs “adjusting” carefully.

it will be an open diff as well as the Scorpio had traction control.

 

Thanks for all that, I got the diff fitted to the beam now



Might have cut a bit too much out really. Still this is not a high power setup

Next problem is how to fit drum brakes to hubs that were meant for discs. I heard that you have to cut the caliper lugs off

 

After having got the 7.5" diff/beam into the car, my next problem is how to assemble the hubs. I thought that would be the easy part.....

So being a bit cheap, I thought I'd stay with drum brakes at the back as they are fine. I've managed to fit the drum back plates to the hubs by cutting off the caliper mounting lugs and by enlarging the centre hole slightly. So no that is not the problem!

The problem is that the drive shafts will not quite go into the trailing arms. They very nearly do, but not quite so far. It seems that the bolt flange is scraping on the top side of the arm. This surprises me since although clearly it's a non standard setup the standard one for disc brakes was I thought 108mm whereas my ones are 100mm.

Are the Trailing arms on a Cosworth etc any different to the drum brake models?

It's so close I wonder if a large hammer would fix the problem
Here is a drum brake back plate fitted with an ex-disc brake hub. It was all looking so promising until I tried to fit the 100mm drive shaft!

 

So I guess this is not really a Diff issue at all. Nor is it necessarily to do with drum brakes with disc hubs. It's more likely to do with using 100mm drive shafts on a setup that previously had Lobro shafts. Same as a Drum to disc conversion really.

Perhaps I should move this across to another topic?

 

Yes, rear disc braked cars use different arms than cars with rear drum brakes due to the bigger cv joints on cars with disc brakes.

 

Thanks Marc. But also.... Argh!

 

Well I managed to get it all togther using the original trailing arms.
I was using the slightly smaller 100mm diameter CV which probably helped. However providing clearance was basically achieved by the use of a large hammer to dent the top of the arm just under the CV itself. There was a decent amount of clearance in the end.

So there we have it, a (so I am told) a bug eye Granada Scorpio diff (4.27) fitted to a Sierra rear beam and equipped with drum brakes. Why? I was mainly after the higher diff ratio since it's all fitted to an Eagle RV Jeep Renegade replica with very large wheels 205/80R15 and a granada diff seemed the best way to get a higher ratio than the 3.7 that was there before. Being a 7.5" diff the beam needed to be changed and It came with bolt on drive shafts so the hubs also had to be changed to suit - but I felt no need for a rear disc conversion so just cut off the caliper mounting lugs and the drum back plate bolted straight on







7.5" diff, bolt on drive shafts and drum brakes