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hypiod gears

hypiod gears

hypiod gears

so hypoid gears are known for there strength in diffs, just wondering what happens if they are being driven opposite to that, so the crown wheel is driving the pinion? Basically my car is 4wd and the transfer to the rear has this setup and it is one of the weak spots in the gearbox.. I'm wondering whether to make normal bevel gears to take the place of the hypoids.. any thoughts??

Thanks Jason

RE: hypiod gears

Two issues:
Can you stand the noise of bevel gears?
Ar you sure that the shafts are in the same horizontal plane? With hypoid gears that is often not the case.


RE: hypiod gears

Benta- "... often..."? Is it not true by definition? If the two shaft centerlines lie in the same plane, then it's merely a spiral-bevel gearset, right?

Jason- not sure I understand "... transfer to the rear has this setup". For whatever it's worth- a spiral-bevel set would be as quiet as hypoid, but not quite as inefficient.

Historically speaking- I believe that hypoid rear axle drives came into being simply to allow lower floorpans of vehicles, rather than any other particular advantage. Any comments? (wouldn't be the first time I was mistaken!)

RE: hypiod gears

Nope there not on the same plane, but putting them on the same plane is what i've been thinking of doing.

As far as i understand the hypoids in the diffs gives you a lower floorpan, but it also allows the pinion gear to be alot longer..(if the teeth are say 20mm wide on the crown wheel by offsetting it you may be able to have say a 40mm long pinion instead of 20mm if it was kept on the same plane)

I can see how this would be better in a diff situation because the small pinion is driving the large crown wheel, with the inefficiency's not being to noticeable because of the gear ratio, and the extra tooth contact needed due to the increase in torque.. but driving the other way is what i don't understand.. with the large crown wheel driving the small pinion, it seems like it would be half trying to drive the pinion length ways out of the case, similar to trying to turn the wheel on a worm wheel drive..

Problem is that the transfers blow all the time and spare parts are becoming harder to find, and to get hypoids made up are extreamly expensive.. especially when these new gears are not going to be any stronger and will continue to break.

So i don't want strait cut bevel gears just helical bevels so they should be quiet still, but i really need advice from anyone who knows how to work out if there is to much torque to just use bevels, or the fact that its being geared up at this point not geared down would make it ok?

I'm not to keen to make and change all this only to find out it is to weak, so any help would be appreciated..

Thanks Jason

RE: hypiod gears

It might be helpful to reveal what vehicle you wish to improve, and exactly which parts you personally have broken, and under what circumstances.


Mike Halloran
Pembroke Pines, FL, USA

RE: hypiod gears

"Benta- "... often..."? Is it not true by definition?"
You're right, I was mixing up spiral and hypoid.


RE: hypiod gears

Historically speaking- I believe that hypoid rear axle drives came into being simply to allow lower floorpans of vehicles, rather than any other particular advantage. Any comments? (wouldn't be the first time I was mistaken!)'

Basically correct.
The earliest cars sometimes had worm drive back axles but the efficiencies were low as were the speeds.


RE: hypiod gears


The hypoid gearset is used in the final drive of many rear axels because it has good torque capacity, it is quiet, and it packages nicely for use in a rear drive live axle with a center diff. (due to its cantilevered pinion and large hollow ring gear).  The drawback of the hypoid gearset is that it is very sensitive to tolerance variations in its mounting and must be carefully shimmed at assembly, and it has a relatively low efficiency.

If you want a lightweight, high performance 90deg axis gearset for your final drive, I'd recommend using face gears.  Face gears use a standard spur type pinion mated with a face gear ring.  The benefit of face gears are that they are less sensitive to variations in set up, they are very efficient, and they have excellent torque capacity for a given installed weight.  The drawback is that they would be noisy.  You would also need to eliminate the axis offset of your existing hypoid gear geometry with face gears.

Here's an excellent reference on face gear design:

Good luck to you.

RE: hypiod gears

The vehicle depending on which part of the world your on is either Mazda familia gtr, ford laser tx3 4wd turbo, or ford escort in america.
i personally haven't broken anything yet.. but I've been extreamly gentle on it.. supposedly one clutch dump and the transfer gears go bang.. which sucks cause i lose seconds off the start when i race.
I came up with an idea today, and the more i think about it the better it sounds to me, basically if i put a shorter diff ratio in the rear of the car, then (Hopefully my attachment works) i could speed up the ratio in between the front diff and the front transfer.. so the transfer would then run a higher speed and less torque thus becoming stronger..
Any thoughts on whether thats genius or crazy haha?

Thanks Jason  

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