High ratio diff......

topcatcustom · Post by **topcatcustom** » Wed Mar 30, 2011 7:29 am

Hi, anyone know of a diff that has a ratio of about 6:1 from any car/van etc ever made?! (Yes I know its the CW&P not diff but I need a whole thing!)

kiwicar · Post by **kiwicar** » Wed Mar 30, 2011 9:57 am

Hi Tom,
Ford 9.5", 9" or 8.8" Dana 60 and chevy 12 bolt will do ratios in that region
8.8" has a 5.71 and 6.14
http://www.summitracing.com/search/Depa ... Rank%7cAsc
9" will do from 2.86 to 7.33
http://www.summitracing.com/search/Depa ... Rank%7cAsc
9.5" certainly does up to 5.56 and I think beyond
chevy 12 bolt go up to 6.14
Dana 60 goes up to 7.17
As you get beyond about 5.56 the pinions get a bit small for ultimate strength, so you end up going to a bigger set up, for a given engine output but you can certainly run very low rear ratios if you want. Mind if I ask what you are thinking about now??
Best regards
Mike

topcatcustom · Post by **topcatcustom** » Wed Mar 30, 2011 10:20 am

I'm after much smaller, cheaper English stuff mike! Only got to take about 100bhp and very little weight so even a moggie size one would do!!

Be rude to reveal my latest secret so soon!!!

kiwicar · Post by **kiwicar** » Wed Mar 30, 2011 11:05 am

Hi Tom,
landrover 101fc diff is 5.57, and tough as old boots, milk float? stupidly low from what I remember, bedford RL 2 ton truck, not sure of the actual ratio, but 55 mph flat out in high range top at 5250 rpm has to be pretty low
some of the transits have ratios in the low 5s and nisan patrols are about 4.88.
Best regards
Mike

kiwicar · Post by **kiwicar** » Wed Mar 30, 2011 11:26 am

Hi Tom
as another thought, using your extensive engineering and fabrication skills, you could make up a case to hold an autobox sun and planet gear set on the front of the diff driving the diff pinion straight out the case and use a more normal ratio diff. The low ratio out of a power glide comes in 1.76 or 1.82 and is pretty light ( you would probably want to reduce the low gear hub quite a bit but that is just a quick job in a lathe. As it happens I've got a 1.82 powerglide low ratio carrier and hub you can have for £50

.
Best regards
Mike

SuperV8 · Post by **SuperV8** » Wed Mar 30, 2011 11:56 am

How about using a low range transfer box? or is that too low?

What overall drive ratio are you after?

Tom.

ChrisJC · Post by **ChrisJC** » Wed Mar 30, 2011 1:09 pm

Seriesl Land Rovers are 4.7:1

Some Sherpa stuff is similar, LDV 200 that is.

Chris.

topcatcustom · Post by **topcatcustom** » Wed Mar 30, 2011 1:18 pm

Cheers guys some useful info and ideas there, using a transfer box or similar could be an idea! Will elaborate soon

DaveEFI · Post by **DaveEFI** » Wed Mar 30, 2011 4:03 pm

topcatproduction wrote:I'm after much smaller, cheaper English stuff mike! Only got to take about 100bhp and very little weight so even a moggie size one would do!!

Be rude to reveal my latest secret so soon!!!

You'd be looking at one from a low powered vehicle with large wheels.
Perhaps the original Austin A40? The 803cc Minor had very low gearing and 14" wheels - but I doubt that axle would stand much torque.

The B series axle - MG etc was 4.55:1 on early Magnettes with 15" wheels. There may have been a version for vans etc with a larger ratio. But probably hens teeth these days.

ChrisJC · Post by **ChrisJC** » Wed Mar 30, 2011 5:05 pm

I think it must be bike engine based.........

Chris.

DEVONMAN · Post by **DEVONMAN** » Wed Mar 30, 2011 5:26 pm

Tom,
The Austin A40 Devon and A40 Somerset had live axles with 5.28 ratio for the saloons and 6.14 ratio for the pickup and vans. There are plenty of guys out there doing hotrods of these cars and ditching the original axles.

The diffs are strong but the half shafts were butter material.
Broke 3 shafts in my time. (Former boy racer)

Good luck with the high reving project????

Regards Denis