Diffs.

Post technical questions here.
1970 cortina GT
Posts: 343
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Diffs.

Post by 1970 cortina GT » Thu Feb 28, 2019 12:37 pm

Can anyone tell me what advantages/ disadvantages I would have if I swapped my standard 66 Mk1 GT diff and installed a 69 MK2 GT diff? I am assuming they are interchangeable. Thanks.
Life isn't complete until you have a pair of twin cams in the garage...

peteleo
Posts: 1257
Joined: Sun Aug 24, 2008 11:57 am
Location: San Mateo,California

Post by peteleo » Thu Feb 28, 2019 1:13 pm

They are interchangeable. Just be sure the flange are the same diameter.
Someone may have replaced it with a 105E which is a smaller diameter.

1970 cortina GT
Posts: 343
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Thu Feb 28, 2019 2:06 pm

Thanks Pete. What difference should I see if I switch them?
Life isn't complete until you have a pair of twin cams in the garage...

peteleo
Posts: 1257
Joined: Sun Aug 24, 2008 11:57 am
Location: San Mateo,California

Post by peteleo » Thu Feb 28, 2019 2:56 pm

105E diameter 3" 3/8. GT 3" 5/8. and are interchangeable.

Image

1970 cortina GT
Posts: 343
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Thu Feb 28, 2019 3:16 pm

Ok and performance wise?
Life isn't complete until you have a pair of twin cams in the garage...

peteleo
Posts: 1257
Joined: Sun Aug 24, 2008 11:57 am
Location: San Mateo,California

Post by peteleo » Thu Feb 28, 2019 3:32 pm

Larger the flange the ratio decreases.

JAN
Posts: 169
Joined: Sun Oct 21, 2007 6:57 am
Location: Wigan, UK

Post by JAN » Fri Mar 01, 2019 2:08 am

peteleo wrote:Larger the flange the ratio decreases.
Not with you there: the flange diameter has nothing to do with the ratio maintaining 1 to 1 from the gearbox, whatever its size. The ratio, and this is the important part, is dictated by the number of teeth on the crown wheel and pinion. With Fords it is generally etched into the edge of the crownwheel, e.g. 8/33 = 4.125:1. That's the bit which will alter performance, irrespective of the diff's coming from a MkI or MkII.

peteleo
Posts: 1257
Joined: Sun Aug 24, 2008 11:57 am
Location: San Mateo,California

Post by peteleo » Fri Mar 01, 2019 10:20 am

Driveshaft turning constant speed. Attached to larger flange 1/4 turn movement from point A to X moves a further distance than attached to smaller flange 1/4 movement from B to Y. Thus effecting differential ratio.

Image

peteleo
Posts: 1257
Joined: Sun Aug 24, 2008 11:57 am
Location: San Mateo,California

Post by peteleo » Fri Mar 01, 2019 10:52 am

After doing some re-thinking on this Jim maybe right.
I'm looking at A and B being separate moving points but in reality it doesn't matter what size the outer diameter of the flange is.
I always thought that Ford made two different size flanges to alter the ratio a bit.

Bob_S
Posts: 407
Joined: Fri Nov 27, 2009 8:22 pm
Location: Michigan, USA

Post by Bob_S » Fri Mar 01, 2019 2:13 pm

The larger diameter is to handle more power and torque. A 1/4 turn of the driveshaft = 1/4 turn of the pinion gear no matter the diameter of the flange.
Bob_S
First car 70 Cortina GT

1970 cortina GT
Posts: 343
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Fri Mar 01, 2019 2:54 pm

I guess I've started something here.... so by fitting the MK2 diff on the MK1 it'll give me more speed?
Life isn't complete until you have a pair of twin cams in the garage...

peteleo
Posts: 1257
Joined: Sun Aug 24, 2008 11:57 am
Location: San Mateo,California

Post by peteleo » Fri Mar 01, 2019 3:08 pm

MK1/2 differentials are the same. As Bob mentioned larger diameter flange is to handle more power and torque only. Nothing to do with speed.

1970 cortina GT
Posts: 343
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Fri Mar 01, 2019 3:50 pm

Ok thanks for everyones input.
Life isn't complete until you have a pair of twin cams in the garage...

JAN
Posts: 169
Joined: Sun Oct 21, 2007 6:57 am
Location: Wigan, UK

Post by JAN » Sat Mar 02, 2019 2:05 am

peteleo wrote:After doing some re-thinking on this Jim maybe right.
I'm looking at A and B being separate moving points but in reality it doesn't matter what size the outer diameter of the flange is.
I always thought that Ford made two different size flanges to alter the ratio a bit.
That's it, Pete, you were possibly thinking linear motion rather than circular motion.

peteleo
Posts: 1257
Joined: Sun Aug 24, 2008 11:57 am
Location: San Mateo,California

Post by peteleo » Sat Mar 02, 2019 12:21 pm

I may have been thinking in line with locomotion.

Post Reply