Can you swap 7.5 diff for 7 diff? What would need to be changed. I've got chance to buy a complete 7.5 beam minus diff for my xr4i, as 7" diffs are cheaper can you fit them instead? Thanks

 

Also what ratio would be best for a 2.8 v6 with 150bhp thanks

 

You can put a spacer in between the top mount so that a 7" diff fits a 7.5" beam. For the driveshafts it depends on what kind of diffs they are. There are 7.5" diffs with either 100 or 108 mm flanges. And for the 7" diffs there are diffs with 100 mm flanges and diffs without flanges, where the shaft is stuck inside the diff.

What ratio is best depends on what you want from the car. As standard I think an XR4i had 3.62:1, which is probably what I would choose too. But on my 2.9 24v I have a 3.36:1 as the engine has more power/torque to pull the longer ratio. This gives it a higher top speed and also makes it better on fuel. But if you only care about acceleration a shorter diff is better.

 

Thanks for your info Marc. Forgott about the different flange sizes, thought there was just bolt on and push in. I enjoyed reading your Sierra project thread, you have done well with that car

 

Thanks mate!