Andrzejsr
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| posted on 25/12/20 at 12:25 PM |
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Sierra 7 differential - strange ratio ? 1,7 (???)
Hello! trying to identyfy what internals are in the differential I got with the car (MNR Vortx with Honda CBR1000) , I am confused, because to achieve
1 full turn of the wheel I need to turn the propshaft less than full 2 turns. It is approx 1 and 3 /4 or 4 / 5 turns.
In other diff I have spare , marked 3,92 it is almost 4 turns of the propshaft to achieve one full turn of the driveshaft flange.
I am confused because in all documentation (i.e. http://www.super7thheaven.co.uk/components/sierra_rear_differential/ ) the longest ratios that was
possible are 3,14 or 3,38. But nothing close to 2.
Does anyone know what it could be inside ? maybe there could be internals from some other car that fits sierra diff ?
The propshafts are also not the lobro joints type but the tripod type. Not sure if this is important. (just read that this tripod type joints are not
strong enough, but this is other issue).
https://aswestfield.wordpress.com/
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rusty nuts
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| posted on 25/12/20 at 01:39 PM |
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Take the rear cover off, the diff ratio may be marked on the crow wheel. If not ,count the teeth on the crownwheel and pinion then divide the C/W by
the pinion to get the ratio
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SteveWalker
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| posted on 25/12/20 at 01:43 PM |
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1.7ish turns - presumably a 3.38
Don't forget that normally both wheels turn roughly equally. If one wheel is not turning, the other will turn twice as fast - so 1.7 turns for 1
rev of a single wheel would be 3.4 turns for 1 rev of both wheels.
[Edited on 25/12/20 by SteveWalker]
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Andrzejsr
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| posted on 25/12/20 at 02:53 PM |
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quote:
Originally posted by SteveWalker
1.7ish turns - presumably a 3.38
Don't forget that normally both wheels turn roughly equally. If one wheel is not turning, the other will turn twice as fast - so 1.7 turns for 1
rev of a single wheel would be 3.4 turns for 1 rev of both wheels.
[Edited on 25/12/20 by SteveWalker]
Thank You!!!
If that is how it wokr that is the case probably - i locked one wheel with wood blocks, the other - turning freely in the air and was counting the
revolution of this in the air while turning the propshaft by hand.
And that (3,38) would be like stated in the MNR Vortx specification.
@rusty nuts- trying to avoid to much stripping of the car right now, as there is a lot of other work - engine mainly. But I think someday have to take
the diff out anyway.
https://aswestfield.wordpress.com/
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Ugg10
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| posted on 25/12/20 at 05:59 PM |
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As stated, lock one wheel, other wheel in the air, turn the input flange and count the free wheel revolutions then work out the ratio. If you turn the
shaft ten revolutions and count the wheel this will be more accurate.
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
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Andrzejsr
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| posted on 25/12/20 at 06:32 PM |
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Yes, but what SteveWalker just noticed - in the case of open diff one has to multiply x2 the wheel revolution .
Before I was playing with Westfield which has plate type diff , and when I was turning the propshaft - both wheels in the air was turning. So in this
case - 1 full turn of the propshaft was 3,92 turns of the wheel. (diff ratio was 3,92 for sure, it was rebuilded , teeths counted)
In the MNR I am working now, it seems to be equipped with open diff ( though the seller claimed there is torsen-type LSD, but it seems he was wrong)
, so one wheel was possible to lock easily and the other was turning while I was turning the propshaft.
So it looks like - with open diff- multiply x2 ; with locked diff - the ratio is the exact number of the wheel revolutions.
https://aswestfield.wordpress.com/
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SteveWalker
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| posted on 26/12/20 at 01:08 AM |
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More correctly, the ratio is an average of that for the two wheels, so on the road, in a straight line, you will have two wheels each with a ratio of
3.38:1 or whatever; with one wheel stationary, you have one wheel with a ratio of 3.38:0 and the other with 3.38:2 (averaging to 3.38:1); and when
driving around a curve, you will have two different ratios somewhere between those ranges, but again averaging to 3.38:1). Basically, for a fixed
speed, one wheel slowing, means the other turning faster, but the average remaining the same.
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snapper
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| posted on 26/12/20 at 04:21 AM |
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If you jack both wheels and turn prop non-LSD will have wheels rotating in opposite directions, LSD both wheels rotate the same way. A Torsen or Quife
ATB will need a slight tension on the wheels or it can free rotate the diff cage, the slightest of applied handbrake can allow the ATB to function.
This has been known to happen when one wheel is on ice and the other on tarmac.
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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SteveWalker
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| posted on 26/12/20 at 02:56 PM |
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quote:
Originally posted by snapper
If you jack both wheels and turn prop non-LSD will have wheels rotating in opposite directions
Surely they rotate in the same direction, but not necessarily at the same speed? The carrier is driven around and the differential gears carried round
by it, not turning themselves (or turning only a little), providing drive to both shafts. They rotate in opposite directions when you turn one wheel
and it drives the other wheel the opposite way, because the prop-shaft is not turning, so the carrier is not rotating and the differential gears pass
the reverse drive to the other side, by rotating themselves.
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