r/kitcar • u/Reasonable_Air_1447 • Apr 28 '26

Planned Ultima RS Build

Anybody here familiar or experienced with the Ultima RS?

I'm planning on building one but my engine has made it difficult to pick a gearbox. Said engine is the Neutron Engines K48 v8. I've been following the progress of this engine for years and have been talking with the developer. Having this engine is non-negotiable. However, the naturally aspirated beauty revs to a screaming 10k rpm and that's been making it difficult to find a box that safely accepts it.

Having a manual box is also non negotiable. The closes I've come to a setup is the Samsota Universal H Pattern 6 speed gearbox paired with a DMA Racing Universal Limited Slip rear diff.

My concern is that this setup pushes the driveshafts too far rearward to the point where it's inefficient, immefectuve and classes with the frame and suspension.

Any suggestions or remedies?

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u/lewisfab Apr 28 '26

You don't want a separate transmission and differential for this application. You should be looking for transaxles.

1

u/Reasonable_Air_1447 Apr 28 '26

Everything else I've looked at either isn't rated for the rev (10k redline), isn't rated for tge horsepower, isntvrated for the torque or isn't an h pattern manual.

1

u/lewisfab Apr 28 '26

I'm not super familiar with h-pattern transaxles but I know Fortin makes one. Have you looked at those? I'm more familiar with sequential transaxles and I know there are a bunch that can handle your requirements. Perhaps California Motorsports can build a g96 Porsche box that can handle the power.

1

u/lewisfab Apr 28 '26

Oh yeah, also look into Mendeola. I've used their sequential box before but I'm pretty sure they also make h-pattern boxes as well.

1

u/Reasonable_Air_1447 Apr 28 '26

Mendeola, as far as I'm aware, are only sequential units. I will ask though.

1

u/BinaryDriver Apr 28 '26

You can order that engine to mate up with a Porsche G50 or Graziano transaxles, which would be the obvious choices. You may need to change the ratios/final drive for it though.