Diff for new project

[Alfa Ric]

OK starting a new thread for the search of a Diff for my project.
I allready have the engine (Rover V8) is been rebuild at the moment.
I have also the gearbox ( LT77 5speed ) out of a TR7 with a 2.0 engine but need to get a bell housing to couple it to the engine.
Now looking for rear axel but I want independent suspension all round so I'm searching for a diff with drive shafts.
After a couple of hours in the scapy I have found:
2 complete Mercedes rear axel from a 190D 2.5 (3.07:1)? and 190E (3.46:1)?
2 complete BMW one from a 520i (3.38:1) and 528i (3.07:1)?
1 from a Mazda MX5 (3.63:1 to 4.30:1) depending on engine but don't think it will hold the torque of the V8
1 from a Ford Scorpio V6 don't know what engine (3.36:1)?
2 Vauxhall ones 1 Carlton 2.0i and one Omega 2.0 16V (3.73:1 and 3.90:1)?
Any suggestions ?
The ratio on the diff from the TR7 is 3.90:1 according the internet.
From what I have been reading I should be looking for one with 2.93:1 or 3.07:1
I'm very confused to say the least... 

Ric

['Mendip Wurzel']

With the LT77 and 3.90 diiff it will be too low geared (high revs) in my opinion. I have a 3.14 Sierra diff and that is about right, if anything I would like a bit higher geared (less revs) but having said that I only use my kitcar on the road so something of a cruiser. I suppose it depend to some extent on where you want to use the car. I can easily pull away in 2nd gear.

I like the sound of the 3.07diff. The 3.36 or 3.38 you mentioned would be okay. The rest I would not bother with for what I would want (cruising). 

[Alfa Ric]

Hi Mendip
Yes it's going to be a cruiser.
If I decide to do a track day I can allways change the diff ( I get them cheap).
I would prefer to have the Merc or BMW diff to to reliability.
I forgot to say that I planing on 16" wheels can that be a problem ?

Ric

['Mendip Wurzel']

Ric ... If you send me your email address I will send you a diff/gearbox speed calculator.

Yep... wheel size does make a difference, or at least the circumference of the wheel.

['Mendip Wurzel']

Ric, Just emailed you the calculator

[Alfa Ric]

Thanks

[Richard]

BMW Diff you will be able to find far more than the 2 you've listed. For the ability to take power obviously M3 / 328s etc. have quite an ability and bring with them 3.15 / 3.23 / 3.45 ratio's and LSD.

If you have a gearbox then work backwards to the diff ratio you need. If you aren't after an LSD then BMW Diffs are cheap enough £20-60, LSDs more money of course.

I'm using a 3.38 LSD at the moment.

Depending on what you are aiming to achieve will somewhat determine the ratio you are after, e.g. if you have a track you drive a lot and are after getting the right combination of ratio / power for the various corners then you need quite a lot of data, if you are purely after 0-62 times then be aware of what you can get rpm wise from your engine, then which size wheels / sticky'ish tyres you'll probably use, then gearbox and then diff.