diffs

[Brian (up north) Morris]

hello can anyone reccomend a good sight where i can read up on ford difs ....i keep hearing this one is better for this and this one for that.....to be honest i dont know anything about them. and how do you id your diff.

thank`s chaps 

[Brian (up north) Morris]

thanks steve. can you explain the difference in stud size on the wheels....? its puzzeling me

[Brian (up north) Morris]

best pic i have of axle for now......

[Steve Kerswell]

no, cant help with that one, yet :-)  Do you have ford front hubs? e.g. are the space of the bolts the same as the back?

[Brian (up north) Morris]

yes steve.

[Steve Kerswell]

Not forgetting that Fiesta had crossflow albeit in fwd mode, I had a cracking xr2 crossflow engine in my son's first car, which was a Mk1 Escort campervan. AX blocks were African and a mystery, never seen one, but may have and not realised !!

[Steve Kerswell]

Brian says 7/16 and 1/2, that's not metric. 7/16 are Mk1 Escort, in fact old Ford's. So I presume the back is metric ??

[Adrian Southgate]

Are group 4 studs the same as standard M12/1.5TPMM, Some ally front hubs are available with holes drilled for 'group 4' studs. I assume that rear half shafts and brake drums would have been adapted also? 

[Brian (up north) Morris]

me too. so is it a cortina axle...? 

[Brian (up north) Morris]

CONFUSED. folks. dont worry tune in next week for more confusing information. ......thanks anyway.

[Adrian Southgate]

Simple facts then Brian.When built the diff would have had al ally tag under one of the bolts holding it into the axle with a ratio and part number on it..

Unless you have an LSD (unlikely) then you will have a timken differential in a english axle. The origin of the axle however is what determines the width of the casing and also the length of the half shafts. 

A 3.77:1 diff is slightly lower than the 'normal' 3.89:1 and will improve top end but reduce acceleration. If you want to go faster you need lower numbers like a 3.54:1 (rocking horse poo) if you want to go quicker then you need higher numbers (also rocking horse poo) like a 4.41:1 or a 4.44:1.

[Brian (up north) Morris]

best explantion goes to adrian. i thank you.

[James Doulton]

At the risk of causing confusion, the lower the number the higher (or taller) the gearing!

With a 4 speed you wouldn't really want to go for a lower gearing than you've got because 4th gear is already fairly frantic at cruising speed. A 3.54:1 would be better and wouldn't make much difference to the acceleration but would reduce the revs when cruising. In a 5 second race from a standing start, the 3.54 would cost you about 2 metres (half a car's length) compared to the 3.77.

If you have a 5 speed then I'd cash in the 3.77 and go for a 4.125 (which is pretty common). That'd make a reasonable difference off the line but still keep 5th good for cruising.