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 Post subject: awd and mid engine
PostPosted: August 16, 2016, 12:06 am 
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anyone ever turn an ls from transverse to longitudinal and use the its fwd lsd as the center diff in an AWD system? would it even handle that kind of load? you could have a VERY fast awd car like that. Id think you need a custom front diff or custom front and rear ones to keep your drive ratio sane.


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 Post subject: Re: awd and mid engine
PostPosted: August 16, 2016, 12:19 am 
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That last bit is what stops everyone.

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 Post subject: Re: awd and mid engine
PostPosted: August 16, 2016, 12:50 pm 
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Even with 2.26 final drives (the lowest 8.8 ratio Ford makes) you'd probably need a tire taller than this;
Quote:
Lexani Tires LX-Thirty 255/30R30 XL 103W
http://www.discountedwheelwarehouse.com/Discount_Tires.cfm?pn=LX-LXST303030010&pID=89196
It's only a 36" diameter......

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 Post subject: Re: awd and mid engine
PostPosted: August 16, 2016, 1:20 pm 
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They do that for some small rock crawlers but the gears in the differential basically give you a very ''low'' low range transfer case, works grate for crawling not so good for sports cars. The only one I saw that would work for a sports car was in a land rover magazine about 10yrs ago where they took a Freelander engine and trans mounted like you were saying in a series 3 used for high speed off road racing. In there case they had a custom set of 1.5-1 gears made to allow for the speed. Thought it was interesting and filed it away in my brain, have no clue how much it would cost to do but probably the only way to make it work.


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 Post subject: Re: awd and mid engine
PostPosted: August 18, 2016, 4:20 pm 
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I have had this exact thought many times as a way to do a mid engine, awd car. As the others have said, the ratio's are all wrong. Find a way to get a 1.0 output or close to it and it would be an option. As you can imagine a typical 4.1 final drive coming out of the transmission then going to another 4.1 differential in the front and rear will gear that thing down 8x's. So if typically first gear would go to let's say 32 mph, like in my honda, it will go to 15-16 mph. UGGGGGG. Can you even imagine. Rock crawler guys are all over this, but unless making custom gears gets a lot cheaper this would never work for a street car.

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 Post subject: Re: awd and mid engine
PostPosted: August 18, 2016, 4:55 pm 
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junior wrote:
...Find a way to get a 1.0 output or close to it and it would be an option. As you can imagine a typical 4.1 final drive coming out of the transmission then going to another 4.1 differential in the front and rear will gear that thing down 8x's. So if typically first gear would go to let's say 32 mph, like in my honda, it will go to 15-16 mph...

It's even worse than that. If the top of first gear is ~30mph, add a second 4:1 differential into the mix and the new top speed in first gear is 30/4, or 7.5mph. Just as bad is overall top speed. Have a 150 mph car? now it's 150/4 = ~38mph top speed.

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 Post subject: Re: awd and mid engine
PostPosted: August 24, 2016, 3:31 pm 
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KB58 wrote:
junior wrote:
...Find a way to get a 1.0 output or close to it and it would be an option. As you can imagine a typical 4.1 final drive coming out of the transmission then going to another 4.1 differential in the front and rear will gear that thing down 8x's. So if typically first gear would go to let's say 32 mph, like in my honda, it will go to 15-16 mph...

It's even worse than that. If the top of first gear is ~30mph, add a second 4:1 differential into the mix and the new top speed in first gear is 30/4, or 7.5mph. Just as bad is overall top speed. Have a 150 mph car? now it's 150/4 = ~38mph top speed.


True. My example was using the lowest diffs you can find, which was the 2.58:1 diffs in a ford the guy talked about above.

BUT. Would it be so hard to have a final drive gear made that was 1:1 coming out of the transmission? You see a company like this:

http://franavehicles.com/finaldrivegears.html

that says they will make a set of 3 for $1200 bucks and I think to myself that's not too bad, and this could actually be possible. What am I not thinking about though?

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 Post subject: Re: awd and mid engine
PostPosted: August 24, 2016, 6:09 pm 
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Getting down to 1:1 will probably require a different gearcase, so it is not only gears that require replacement .... doesn't mean it can't be done.

If you didn't mind front and rear locked together a simple chain drive from gearbox to driveshaft would allow 1:1. I can't remember the link, but a member here built a bike-powered AWD ice racer that way.

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 Post subject: Re: awd and mid engine
PostPosted: September 30, 2016, 1:10 pm 
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I believe the old Honda AWD Wagovans had a 1.05:1 rear diff ratio or something similar. But I also don't think that drivetrain is built to handle a lot of power, so it's anyone's guess how far one could push a setup like that.


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 Post subject: Re: awd and mid engine
PostPosted: October 17, 2016, 10:06 am 
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Honda Wagonvan diff is 2.529 so nope.

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 Post subject: Re: awd and mid engine
PostPosted: October 17, 2016, 12:41 pm 
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What am I not thinking about though?


Those prices look like they are for gears they have already designed and they look to be straight cut. Mind you, I like the sound of straight cut gears, nothing sounds better than a high powered track car going down a straight.

You could use a quick change rear axle diff as a center diff and see how big of a gear overdrive you could put in the quick change part. That's not so great an idea though. Maybe if you converted to all quick change diffs?

Gears used in really high power outboards might be suitable? What do they use for final drives in really high powered snow mobiles?

I think this stuff gets really expensive. Industrial parts from catalogs with high prices. Maybe hydraulic stuff?

I think Subaru is the only viable option. Set it up like a Porsche or, for lack of a better description, a Subaru!. You can buy a billet block for these now, so power output is well beyond silly for us. Like you can run your airtools off the boost... :rofl:

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 Post subject: Re: awd and mid engine
PostPosted: October 17, 2016, 8:43 pm 
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The 7.5 inch gm 10 bolt was available with a 2.14 ratio and the mopar 8 1/4 with a 2.26 those are a little better still not ideal but I think they are the lowest ones you'll find


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 Post subject: Re: awd and mid engine
PostPosted: December 20, 2016, 10:53 am 
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Heh, pretty sure I started a thread with the exact same idea something like 10 years ago... :lol:
V drive boats run gears in the neighborhood of 1:1, might be worth looking into that and see if anything can be adapted somehow.

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 Post subject: Re: awd and mid engine
PostPosted: March 2, 2017, 4:33 pm 
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Now that Subaru's transaxle can have a flipped ring and pinion installed for VW's 5 speed conversions is it posible to have awd with engine in back? Or leave alone midmount and V drive to front?


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 Post subject: Re: awd and mid engine
PostPosted: March 3, 2017, 10:11 pm 
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You could have rear engine awd before the subaru ring gear flip. There's the vw syncro vanagon and the porsche carrera 4. That you could use transaxles from.


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