What Diff Ratio

[Guest greavesy7]

What's a good diff ratio?

Edited January 5, 2013 by greavesy7

[Guest alfaGTA]

3.62

[Snapperpaul]

3.92

[Snapperpaul]

Diff ratio is dependant on gearbox ratios, wheel size and tyre profile

With Ford gearbox ratios being wide if you get good 1st gear the top end will be unacheivable

Good top end and 1st is useless.

Rule of thumb

MT75 use a 3.6

Type 9 use 3.9

More torque means you can pull a longer diff

More revs means you can extend the lower gears to a more usable range

 

It is well worth having a look at a gear speed calculator to get your head round your speed in gear for a given red line etc

[Guest greavesy7]

Mines 3.62

[Guest greavesy7]

On a type 9

[Guest mower man]

3.62 if you are going to tour with it ,perhaps 3.9 if track days are considered I run a 3,62 now but had a3.31 good for economy but 5th was virtually redundant [tyre size 205x50 x15 equates to std 14"tyre wheel on seirra donor] hth mower man

[richardm6994]

I've got a 3.38 with 17 inch wheels. It was massively over geared when I had the pinto engine but should b okay for the torque of the new v8.

 

3.62 is generally what people go for as a good all-rounder.

[Snapperpaul]

You've got to try the gear ratio program's

The 3.6 may work in the first 3 gears but 4th gives about 140 mph a speed you won't get to

As I stated the big problem is the wide spaced gears your choice is low speed in the lower gears or unobtainable speed in the high gears

I'm currently running the V6 type 9 which is better but still has a short 1st

It's all a matter of personal preference or a big wallet for a custom gear set

[Pete Mar]

I have a 3.6 on 15" wheels and MT75.

[Guest mower man]

I've just checked a few figs , 3.62 diff, 205x50x15 tyres, std type nine ratios at 5000rpm ----1st =25

2nd =45

3 rd 70

4th 95

5th ii5 .

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

mower man

[Guest alfaGTA]

my 3.62 in 4th gear on 13" rims will pull away from higher powered cars.... Can't say anything about the gear ratio calculator thing but judge it by the seat of my pants. How much time do you spend in 1st, 2nd or 5th gear? Making progress in 3rd or 4th is where you drive normally..... Unless you are racing then it makes little difference IMO

[Guest snotfart]

was running 3.62 which was fine with the pinto but with the v8 I found it far to buzzy cruising (3k rpm at 70 mph)

have just built a 3.14 lsd hybrid,not driven it yet but on blocks 3k rpm is now 80 mph which should be much nicer.

[speedtripledan]

Bog standard pinto in an old heavy robin hood then 3.92, when I tuned my 2b 3.92 was as waste of time so went 3.62 which was perfect, in s light weight zero 3.62 if moderate power if you are pushing the 200bhp barrier then 3.38 would work..

[Snapperpaul]

You cruise in 4th or 5th

If your driving you will hit max revs in the lower gears

Or you just not trying hard enough