AWD front IFS Diff suggestions: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Aug. 30, 2010 5:47 p.m. jakeb New Reader

I am working on researching for my fiat 500 project for 2011 and am thinking I am going to going with a bike engine mated to a front diff out of a AWD car. I jsut about have a deal worked out on a yamaha XS1100 shaft drive engine, trans, etc etc.

If possible I would like to keep the suspension fully independent but if I have to go to a solid axle I could do that. The engine will be behind the axle and spun around. So with a regular axle the car would go backwards all the time.

Does anyone have any suggestions as to what diff I could/should use?

TIA
Aug. 30, 2010 6:22 p.m. mith612 Reader

Couldn't using the rear diff from any Subaru or Miata turned upside-down do the trick?
Aug. 30, 2010 6:42 p.m. turboswede SuperDork

Chrysler used an AMC Eagle front diff in the rear of the Daytona 4WD prototypes.

Perhaps a CR-V/Escape/Lightweight-Stupid-Useless-Vehicle rear subframe would work well for you? I've noticed more than a few have nice long control arms along with the requisite diff, etc.

Not sure how hard they would be to add steering to, but some of the yard hounds might find you the proper mix of cheap parts needed to make it all work together.
Aug. 30, 2010 6:56 p.m. jakeb New Reader

I actually don't need any steering components because it is going in the back of a fiat 500.

mith: I was thinking of just using a rear diff and flipping it over. How would that work for lubeing everything? any issues?
Aug. 30, 2010 7:04 p.m. mith612 Reader

Can't imagine flipping the rear diff from a Subaru could do it any harm. The R160 has the outputs pretty much centered up/down so the gears would likely get the same oil bath. Filling it may be tricky unless you were to prefill it before putting it in place. The cover looks like it MAY be able to be flipped as well, leaving you with an wrongsideup diff with rightsideup fill and drain holes. I've never tried though so YMMV.
Aug. 30, 2010 7:27 p.m. ansonivan HalfDork

Another good diff option would be the small case 4.10 lsd from an e30 318is.

The only issue I can see with flipping a diff (aside from the venting and filling workarounds) - the gears will now be stressed on the opposite face from which they were designed, this could cause problems. Diffs do see load on the back sides of the teeth during engine braking but it's not prolonged.
Aug. 30, 2010 7:29 p.m. mith612 Reader

ansonivan wrote: The only issue I can see with flipping a diff (aside from the venting and filling workarounds) - the gears will now be stressed on the opposite face from which they were designed, this could cause problems. Diffs do see load on the back sides of the teeth during engine braking but it's not prolonged.

Granted that is true, but how much will it really matter for a challenge car?

I mean, do the ACVW guys run into issues with maintenance/longevity flipping those transaxles?
Aug. 30, 2010 9:11 p.m. oldopelguy Dork

The ACVW guys don't flip the transaxle, the swap the ring gear to the opposite of the case, and since the pinion gear comes into the center of the gear it doesn't matter.

With a chain-drive bike engine I would suggest just pulling out the input pinion and mounting a sprocket to the dif that would drive through a new cover with a couple of holes in it. Pack the spiders with grease and maybe slide a piece of silicone tubing over the dif to hold the grease in.

With a shaft drive I've got nothing.
Aug. 31, 2010 7:19 a.m. RossD Dork

Randy's Ring and Pinion

Ford 8.8 came in the front of IFS Expeditions and F150s. That would allow you to get just about any gear ratio and traction device since the rear and the front diff internals can be swapped, IIRC. (IRS 8.8s are in the T-birds for cheap pickings)
Aug. 31, 2010 9:04 a.m. jakeb New Reader

After a little research it looks like the stock bike has a 3.3:1 final drive. I need to check a bit more into all the gear ratios to keep the engine in it's powerband but not be wound all the way out at 70mph.

The 8.8 isn't a bad idea. It might be a kittle bit big/heavy for what I am doing.

I was thinking about the Suzuki sidekick but it looks like the ratios are around 5;1 so that might be a bit high.

It would be nice to get the axles and hubs along with the matching diff.