question - why reverse cut front diff gears? (1 Viewer)

Bambusiero

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Question to those more sophisticated in drivelines - was reading one of ZUK's narratives about an FZJ80 re-gear to 4.88.
The 9.5" rear diff was conventional, but the 8"front diff gears were "reverse cut" - can someone explain?
Thanks
 

JunkCrzr89

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Reverse cut equals high pinion.
 
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Question to those more sophisticated in drivelines - was reading one of ZUK's narratives about an FZJ80 re-gear to 4.88.
The 9.5" rear diff was conventional, but the 8"front diff gears were "reverse cut" - can someone explain?
Thanks
Reverse cut front axle gears are always driving the strong side when moving forward. Normal gears in a front axle are driving the weaker side (higher angle, which is trying to push the ring away from the pinion) when moving forward. Sounds like a win for reverse cut, yeah? Well, Zuk explained the fallacy of that to me. When you are moving forward, in most challenging situations (like, say, climbing a hill or obstacle) the majority of the weight/strain is on the rear axle. When you are reversing up a hill or obstacle, most of the weight/strain is on the front axle. With reverse-cut gears, that means you are asking the weak side of a smaller diff to do most of the work.

This also applies to pulling someone or something- if you are reversing, most of the strain is on the front diff, on its weak side. Don't pull in reverse. If you are winching someone or something, put it in neutral and hold the truck with the brakes- don't back up under load and don't rely on the parking pawl.
 
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Bambusiero

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Reverse cut equals high pinion.
Reverse cut front axle gears are always driving the strong side when moving forward.
Oh - OK - so using the term "reverse cut" for the landcruiser front high pinion diff is only relative / compared to the "normal" of the low pinion rear diff, but that is completely normal for the front, and nothing special or reversed from normal at all.
Because when you look at the front and rear ring gears side-by-side, the teeth curve in opposite directions, do I have that right?
Thanks guys. Just learning the diff lingo.
 
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Oh - OK - so using the term "reverse cut" for the landcruiser front high pinion diff is only relative / compared to the "normal" of the low pinion rear diff, but that is completely normal for the front, and nothing special or reversed from normal at all.
Because when you look at the front and rear ring gears side-by-side, the teeth curve in opposite directions, do I have that right?
Thanks guys. Just learning the diff lingo.
Normal for the 80 series, yes.
 

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