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I suppose this might be kicking the horse while he's still down, but I'm pretty sure I remember a BEC build on here that used an inverted diff with good sucess. And here's another completely unrelated vehicle using an inverted Dana 60 with a rear mounted, blown Hemi. He runs over 100 mph in the 1/4, wheels up all the way.

Kristian

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V6 in a book frame build. Now registered.
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Another possible AWD answer.

Use a Audi quartto 4000 transmission, mount it in the rear (mid engined rear transaxle) and using a lay shaft and either a gear set of chain off of the rear output of the transaxle, run the jack shaft to the front differential (along the side of the engine and through the normal driveshaft tunnel).
The engineering answers would probably be easier to answer using this method. You can pick your connection from the transaxle output depending on the front differential requirements. (Chain drive to jack shaft vs gear drive to jack shaft would change direction of rotation of jack shaft)
You would already have a rear differential built into the transaxle (less weight then a seperate transmission and rear differential).
There are limited slips (the quaife is one) available for those transaxles and the ability to find drive axles would be easy (read cheap).

On the subject of a BEC using a differential in reverse rotation, No torque.
On the thought of the wheel standing blown big block. Chances are he is running the differential in the correct direction (note the engine looks like it is behind the center line of the axle) and he doesn't need a lot of power to run through the 1/4 at 100 mph. My 200 hp (through a stock 02A transaxle) Jetta runs 14.5 to 14.7 at 98 to 101 mph depending on how much I want to beat on it.

I was talking to the guy that built it, he was the one that told me it was a flipped diff. He's been running it for something like 5 years with no problems. You're right about the power though, he's only making about 700 hp, miniscule compared to most drag cars. I would imagine the shock load is up there though.
Kristian

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The question is which way is it flipped? Both diffs in my drawing are flipped, the front is rotated around the axis of the axles and the rear is rotated around the pinion axis. The rear is also being driven in reverse, which is why it had to be flipped. I would venture to guess that his is rotated around the axles and is being driven in the normal direction.

I think I said that previously.

Oh wait, I did.



Thanks firestorm, I figured that I would let someone else point that out.

The wheelstander uses a normal diff that is flipped upside down to get it to drive the car forward. I see what you're getting at now, I'm pretty sure his is flipped around the pinion axis. His setup uses a 4wd transfer case with the driveshaft that would normally go to the front axle, connected to his rear diff. Not sure how well I explained that, but it would be like flipping the front axle in a 4wd to make it have 5 speeds reverse and one forward.
Kristian

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by what you're saying it's flipped around the axles (as I'm describing it) and being run in the normal direction. This means that the gears are not being loaded backwards and thus the only problem that could arise is with lubrication due to it being upside down. Here's another one of my MS Paint masterpieces to illustrate my descriptions:

firestrom, you have it exactly correct, and seeing as differentials are splash lubed, they really don't care which direction that they are sitting is as long as their loading against the teeth are correct and there is enough lube in them.

Gears may be splash lubricated, but the bearings probably aren't. A wheelstander may not be getting very much lube to the pinion bearings, but since it is only driving 1/4 mile at a time, I don't think the bearings would necessarily wear out on it. On a road car on a long highway drive, I could see inadequately lubricated bearings failing over time if the axle was flipped.

Keep in mind that most diffs have the pinion low in the case, meaning they are pretty much partially submerged in the diff fluid. Flipping them over puts them well above the fill level and would only be lubricated by any sling off the gears that happens to land behind the pinion and is not slinged off more by the rotating pinion shaft.


Now that I think about it, A wheelstander may get plenty of gear oil to the pinion bearings when it is actually standing on end

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+442E, SR20det, Thunderbird/Markviii IRS with clutch lsd, R1 suspension all around, Mustang II 2" drop spindles, Woodward steering rack

Interestingly enough, this is how reverse cut axles are lubricated too. They aren't just a differently cut gearset in the same style housing as a standard axle. Rather they actually use a unique housing that places the pinion above the axle, due to the way the gears are cut.

And much the way standard cut axles were used in the front of 4x4's for many years, some off-roaders actually use reverse cut "front" axles in the rear of their rigs (reverse loading). They do this because the high mounted pinion noticably improves driveshaft angles on lifted trucks. Yes they have to use a somewhat heavier duty axle to achieve equivalent strength to a standard cut rear axle, but they most certainly are doing it.

I know it's not the same exact loading situations being discussed for this method of creating a VW diesel AWD system, but it is probably the most readily available real world information on the subject. In fact one of the best places to learn more about the general strength and longevity of both standard and reverse cut R&P's under both normal and reversed loading, might be searching around the "Pirate4x4" forums as they probably know more about it than anybody here...Just some more food for thought.

http://www.pirate4x4.com/forum/

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Rock crawlers and off roaders also wouldn't have the problem of bearings wearing out too bad since the pinion bearings wouldn't be under load at high speeds for long periods of time without lubrication. If a crawler is rolling around and its pinion bearings aren't fully lubricated, it is not likely the bearings will see much wear since the speed is still low.

Also, 4x4 guys tend to maintain differentials and axles much better than any of us will. They are fine with big heavy duty axles and refurbishing them constantly. If I had to take the diff out of my car and replace the bearings or gearset every 20k miles, I wouldn't be a happy camper.

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+442E, SR20det, Thunderbird/Markviii IRS with clutch lsd, R1 suspension all around, Mustang II 2" drop spindles, Woodward steering rack

Not all 4x4 offroad rigs are slow, some are capable of very similar top speeds as a locost, offroad.

I grabbed this pic really quick, without reading up much about the instance. But I believe this is a low pinion 9" flipped to drive on the coast side. It's from a rear engine(rear facing engine) Class 1 desert car built by Shannon Campbell.


Build thread: http://www.pirate4x4.com/forum/showthread.php?t=848268

On the high pinion front differentials I have worked on (d30, d44 and d60) there is an 'oil slinger' between the pinion and inner pinion bearing. I don't believe it's function is so much to 'sling' oil, as to slow down the departure of already slung oil from both pinion bearings. I imagine it would be worthwhile to install a similar slinger/baffle in any LP diff run upside down.

Again, how many miles would be put on that racetruck before the diff is torn apart and serviced? How many times will the gearing be changed? Was it specially prepped to be flipped upside down? Is there anything different about it since it is a racing part and not a normal street part?

Apples and oranges here.

If you took a normal low pinion differential from a car and flipped it over and used it on a street car, there are a number of problems that could possibly occur.

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+442E, SR20det, Thunderbird/Markviii IRS with clutch lsd, R1 suspension all around, Mustang II 2" drop spindles, Woodward steering rack

As to the AWD build, being an offroader I would do away with the CVs on the transaxle and run ujointed drive lines to the front and rear differentials.

There is a good longitudinal Honda build on Pirate as well. He welded the center diff in the transaxle, I'm not sure if that would be appropriate for your application or not.
http://www.pirate4x4.com/forum/showthread.php?t=562853&page=21

How many miles will a locost see in it's life? How long is this piece of string?