Topic: Lightest possible RWD differential and a tiny multi-plate clutch pack

I'm on a long-term quest to build something inane, and I'm beginning to source parts. Need suggestions.

One thing I need is an RWD diff. The ones I have on hand don't please me as they're massive cast-iron pumpkins.

It needs to be an IRS diff, preferably with unbolt-able axles, no lsd, and it needs to be (comparatively) featherweight. Naturally, aluminum casing is best. Also needs to be something fairly common, so I can source one at a scrapyard.

The second thing I need is a multi-plate wet or dry clutch pack/basket out of a common bike that's easy to adapt to a shaft coming in and a shaft coming out. Basket will sit on a 1" keyed shaft and the output shaft will be around 1.25" in diameter, most likely.

Those things will probably channel all of 40hp pushing a 1500lb car on 185-wide tires, so sturdiness is not an issue.

K Car Stalker

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

For some reason I remember that the rear diff on the first generation RAV4 is tiny and light, and should be available.  Probably a Honda CRV and other fwd based cute-utes too.

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Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

miata? rear diff from AWD that is based on FWD cars. Ford escape comes to mind, they like bird poo in the city, everywhere as a taxi.
if its 40HP and 1500lb and 185 tires, a spool maybe would be more fun?
clutch thing, I would check harley with divorced transmission. Looks to be an easy thing to adopt, but input and output may not work in your configuration because of the drive method.

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Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

Sonic wrote:

RAV4

... And it comes with axles that mate to a Tercel/corolla/whatever front spindle. I think we have a winner!

K Car Stalker

5 (edited by DirtyDuc 2017-07-13 11:43 AM)

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

With the exception of goldwings, cx500s, BMWs, and guzzis, I think all bike clutches are single splined shaft output, and either gear or belt/chain input.

Guzzis and BMWs are single plate clutches like in a normal rwd car, the Hondas are probably the same... I'm just not sure.

That guy

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

firegremlin wrote:

I'm on a long-term quest to build something inane, and I'm beginning to source parts. Need suggestions.

<snip>

The second thing I need is a multi-plate wet or dry clutch pack/basket out of a common bike that's easy to adapt to a shaft coming in and a shaft coming out. Basket will sit on a 1" keyed shaft and the output shaft will be around 1.25" in diameter, most likely.

Those things will probably channel all of 40hp pushing a 1500lb car on 185-wide tires, so sturdiness is not an issue.


Fabrication might be easier - and you'd get creative misuse points - if the wet-clutch center differential off the same RAV4 was used along with some techno way to modulate it?

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

Subaru WRX (non STI)?

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

I was going to say, the RWD setup on some cheap, tiny AWD thing.  Suzuki has some AWD cars....also wasn't there an AWD Toyota Matrix? 

Yup- Wikipedia sez 2003-2006 Matrix had AWD as an option.  You had to take the 1UZ and slushbox with it, so presumably it was pretty non-beefy.

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9 (edited by nimblemotorsports 2017-07-14 04:32 PM)

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

The MG Midget has about the lightest weight aluminum differential.  It isn't IRS, so you'd have to fabricate that part.

I looked at the CRV and other late models SUV rear diffs, and as I recall they all had clutch-thingies in them which made them heavier
and bulkier than I wanted.

Not sure what you are trying to do, but I took a Taurus fwd trans and hacked out just the differential part for an EV project,
this was very lightweight.

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

The rear diff on a Toyota matrix/Pontiac vibe looks pretty lightweight to me. It holds about a pint of gear oil.

That guy

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

After some searching and a lot of reading...

Two-in-one solution: 1st gen CR-V differential.

It's an all-aluminum, high-ratio (4.562) differential unit... With a built-in clutch. It has two pumps built in, one driven by the input shaft and one driven by the diff pinion, working against each other. If your input shaft spins faster than diff pinion, pressure difference forces clutch pack to apply. Now, if you tap into the oil galley, add a valve, and bleed off pressure generated by diff pinion pump, you can operate it like a conventional clutch - close valve to release, open valve to lock up.

I don't have an easy solution for reverse, but that can be made electric, I think.

K Car Stalker

Re: Lightest possible RWD differential and a tiny multi-plate clutch pack

Before getting to your last post I was going to suggest the clutch off of any Ducati from around the mid-90s to mid 2000s.  Multi-plate and dry with suitable I/O.  They make most excellent rattly noises when run out in the open.  https://www.youtube.com/watch?v=ECg24JWy2vE

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