What Diff Ratio

[Guest merc190provan]

I am running 225bhp, 3.62 slipper diff with MT75 on 15" rims and i have to say that i am more than pleased with the gearing, acceleration is strong with plenty of length in the gears and when cruising it is just right.

[Snapperpaul]

That's Cosworth power and well suited to the 3.62 & MT75

If you look at the Cosworth T5 ratios you'll see that 1st is 2.93 much more like it.

I have a spare Type 9 V6, have found the BHH casing modifications and the gear set oil way mods, if I can get the 2.7 1st gear and modified lay gears I may have a crack at doing it all myself as a project

[brumster]

I recently swapped to a 3.9 from a 3.6 as it suits the car use and engine more. The 3.62 was a nice setup but with a revvy motor and only occassional fun use, it really didn't warrant it. So I got the BGH uprated HD gearkit with tall 1st and short 5th, and dropped a 3.92 in. Much nicer; suits the car more and with only 110-odd bhp in a heavy old Exmo it punts along just a little nicer. With a grunty 2-litre lump you would be fine with a 3.6... mind you I've never seen RH's as long tourers so would always plump for the shorter, sportier gearing I think!

[Bob Tucker]

how many of us [not bike engines]actually run at much more than 4k for long? honest replies please

 

me...

 

 

GearCalc v2.0.0.3 Copyright ©2001, Peter Ogden

Gear Ratio, Speed and RPM Calculator

 

Gear set: Ford Sierra Type 9/N BGH 2.8 Sporting Close 5 Speed

Gear 1 2 3 4 5 Final

Ratios: 2.800 1.810 1.260 1.000 0.850 3.920

 

RPM Limit: 7750

RPM @Peak Power: 6800

Tyre Size: 185/60 x 14

Tyre Diameter: 22.74 in

Tyre Circumference: 71.44 in

 

 

Gear Mph per

1000 RPM 6800 RPM 7750 RPM

--------------------------------------------------------

1 6.16 42 48

2 9.53 65 74

3 13.70 93 106

4 17.26 117 134

5 20.30 138 157

[Snapperpaul]

Well 2 opinions based around the 2 most popular diffs and its down to personal preference, not surprising realy.

I confess to having several diffs, in 3.6 and 3.9, open and LSD

My engines have various peak bhp/revs all of which are above 4k

[Guest mower man]

To be honest the real plan should be a BGH gear set and a 3.6 it would be all things for all men with the exception of screaming bike engines or lazy old V8's ,but at £600 it's not cheap .mower man

[Bob Tucker]

The 3.6 was best for the tuned pinto with a standard box, i tried the 3.9 but 1st was useless.

I then fitted the redtop & a BGH box (I wish it was £600!) but the 3.6 killed it..it did almost 60 in first & wouldnt pull 5th.

The 3.9 transformed it. The biggest benefit from the BGH box was a tall 1st gear...may be worth asking them if they can fit just that to a standard box.

Bob

[Al Milton]

I would say the best diff ratio is the one that suits your driving style/needs when matched to your engine output (& budget!).

But the most popular are 3.62 & 3.92