DIFF RATIO
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My 74+2s is still a thousand bits. How do you tell what the diff ratio is without stripping it ?

graham  Second Gear
 Posts: 126
 Joined: 18 Jul 2009
 Location: new zealand
Graham,
Fix one of the output shafts to prevent it turning, then rotate the opposite output shaft one full turn and count the rotations of the input shaft/flange. If the input shaft/flange rotates about 3.5 turns then the ratio is 3.54 or 3.55, if it rotates about 3.75 turnes the it is a 3.77 ratio.
To know if it is 3.54 or 3.55 ratio you will need to take the diff apart and count the number of teeth on the CW&P.
Fix one of the output shafts to prevent it turning, then rotate the opposite output shaft one full turn and count the rotations of the input shaft/flange. If the input shaft/flange rotates about 3.5 turns then the ratio is 3.54 or 3.55, if it rotates about 3.75 turnes the it is a 3.77 ratio.
To know if it is 3.54 or 3.55 ratio you will need to take the diff apart and count the number of teeth on the CW&P.
Brian Clarke
(1972 Sprint 5 EFI)
Growing old is mandatory..........Growing up is optional
(1972 Sprint 5 EFI)
Growing old is mandatory..........Growing up is optional

bcmc33  Coveted Fifth Gear
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 Joined: 10 Apr 2006
 Location: Aldridge, West Midlands, UK.
If you hold one of the output shafts steady, won't the input shaft turn twice as many times as the ratio?
Paddy
Paddy
1963 Elan S1

paddy  Coveted Fifth Gear
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 Location: Woking, Surrey
paddy wrote:If you hold one of the output shafts steady, won't the input shaft turn twice as many times as the ratio?
... or half?
1963 Elan S1

paddy  Coveted Fifth Gear
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 Joined: 27 Oct 2008
 Location: Woking, Surrey
To know if it is 3.54 or 3.55 ratio you will need to take the diff apart and count the number of teeth on the CW&P.
Or rotate one output shaft 20 turns (with the other fixed) then the input shaft rotation will be 10 times the ratio and you should be able to distinguish between 3.54 and 3.55.
Roger
S4 DHC
S4 DHC
 oldelanman
 Coveted Fifth Gear
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 Location: Dorset UK
[quote="oldelanman"Or rotate one output shaft 20 turns (with the other fixed) then the input shaft rotation will be 10 times the ratio and you should be able to distinguish between 3.54 and 3.55.[/quote]
Specifically, if you mark the pinion's starting position, then it will line up exactly with that mark after either 18 or 22 turns of one of the output shafts.
After 22 turns means the pinion has 11 teeth so ratio is 3.54 (39/11) or 3.9 (43/11)
After 18 turns means the pinion has 9 teeth so ratio is 3.55 (32/9) or 3.77 (34/9)
Paddy
Specifically, if you mark the pinion's starting position, then it will line up exactly with that mark after either 18 or 22 turns of one of the output shafts.
After 22 turns means the pinion has 11 teeth so ratio is 3.54 (39/11) or 3.9 (43/11)
After 18 turns means the pinion has 9 teeth so ratio is 3.55 (32/9) or 3.77 (34/9)
Paddy
1963 Elan S1

paddy  Coveted Fifth Gear
 Posts: 1197
 Joined: 27 Oct 2008
 Location: Woking, Surrey
Specifically, if you mark the pinion's starting position, then it will line up exactly with that mark after either 18 or 22 turns of one of the output shafts.
After 22 turns means the pinion has 11 teeth so ratio is 3.54 (39/11) or 3.9 (43/11)
After 18 turns means the pinion has 9 teeth so ratio is 3.55 (32/9) or 3.77 (34/9)
Don't forget to count the number of turns of the input (pinion) shaft as well or you still won't know which ratio it is !
Cheers
Roger
S4 DHC
S4 DHC
 oldelanman
 Coveted Fifth Gear
 Posts: 1684
 Joined: 02 Jan 2008
 Location: Dorset UK
Thanks guys for the help was still a little confusing but found we have 3.77 diff. Also found info from this link
http://www.mgparts.co.nz/diff_ratios.html
http://www.mgparts.co.nz/diff_ratios.html

graham  Second Gear
 Posts: 126
 Joined: 18 Jul 2009
 Location: new zealand
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