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MX5 bellhousing fit to RX8 gearbox for V6 conversion
KFC - 20/5/14 at 11:58 PM

Hi all,
After chatting to Claire about making a gearbox adapter plate for a KLDE V6, she suggested that the MX5 6 speed gearbox bellhousing apparenty fits to RX8 gearbox?? Does anyone know?
It would save a lot of aggro for Claire.
Splitting both gearboxes and try the swap is the only way to see but I would imagine the alignment of the input shaft bearing and bolt pattern would be different but I would be greatfull if anyone knows it can be done?

KFC - 21/5/14 at 01:13 AM

I've done some searching and the split line looks the same but it's a start.

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scootz - 21/5/14 at 07:44 AM

Afraid I can't help, but it may be interesting for folks who are doing a similar conversion to understand why it would save aggro?

KFC - 21/5/14 at 08:35 AM

The aggro is mocking up a jig or a pattern to make a new design of adapter plate to fit to the RX8 gearbox. Instead the kit could come with a bellhousing from a MX5 6 speed gearbox. The other issue is that the KLDE engine has a 112 tooth ring gear and the RX8 has a 125 tooth ring gear, the diameters are going to be different, the starter gear mesh will be wrong. One thing I've just thought of is the RX8 engine has 2 power options, 231bhp and 190bhp, the higher powered engine has a larger diameter clutch and pressure plate which means the starter position on the RX8 gearbox will be in a position with a larger radius, I have no idea if the flywheel diameters are different. I'll need to find out as it could open options.

scootz - 21/5/14 at 10:23 AM

Cheers. Sorry to be so slow on the uptake... is the RX8 bellhousing a direct fit to the KLDE engine?

PS - I have a 231PS engine / box sat in my garage just now. Let me know if you need any info from it.

rdodger - 21/5/14 at 11:23 AM

I have never done it, but did some research a while ago and was reliably informed that it is the case.

stevebubs - 21/5/14 at 12:19 PM

quote:
Originally posted by scootz
Cheers. Sorry to be so slow on the uptake... is the RX8 bellhousing a direct fit to the KLDE engine?

PS - I have a 231PS engine / box sat in my garage just now. Let me know if you need any info from it.



The way I read it was:

unbolt bell housing from RX-8 gearbox
bolt 6 speed MX-5 bell housing onto RX-8 gearbox

DIY Si - 21/5/14 at 12:38 PM

Whilst this may save some aggro, you do know how much MX-5 6 speed boxes go for right? A single box is likely to cost you £300+, just to get the bellhousing and render the rest of it useless.......

KFC - 21/5/14 at 12:45 PM

quote:
Originally posted by rdodger
I have never done it, but did some research a while ago and was reliably informed that it is the case.


That's good to hear! I just need to find a cheap 6 speed box from a MX5 now.. I'm putting in a 5 speed box in a 231bhp version as it has a 6 speed with the limited slip diff, the 5 speed version RX8 has an open diff with a different final drive ratio. Basically, I don't want to sit on the motorway at 75mph doing 4000rpm, changing the 6 speed to a 5 speed will sit at 3500rpm, the crown wheel in the diff is bigger that makes the difference.

thefreak - 21/5/14 at 01:06 PM

As far as I know the bolt patterns for the 5 speed and 6 speed are the same, as it's an upgrade you can do to the car without much messing around. The only thing different I think is the starter motor has an extra bolt on the 6 speed.

Or are we talking about the narrow end of the bell housing here?
I agree with the post above, the 6 speeds are rare and fetch a premium. A cheap one will still be the best part of £250

scootz - 21/5/14 at 03:29 PM

quote:
Originally posted by stevebubs
quote:
Originally posted by scootz
Cheers. Sorry to be so slow on the uptake... is the RX8 bellhousing a direct fit to the KLDE engine?

PS - I have a 231PS engine / box sat in my garage just now. Let me know if you need any info from it.



The way I read it was:

unbolt bell housing from RX-8 gearbox
bolt 6 speed MX-5 bell housing onto RX-8 gearbox



Ah, penny dropped! I thought the OP was doing a KLDE transplant into an MX5... but then saw the 'building' line under his avatar and realised he was putting a KLDE into an RX8.

KFC - 21/5/14 at 03:49 PM

quote:
Originally posted by scootz
Cheers. Sorry to be so slow on the uptake... is the RX8 bellhousing a direct fit to the KLDE engine?

PS - I have a 231PS engine / box sat in my garage just now. Let me know if you need any info from it.


Thanks for the offer, I dropped a rear iron off the rotary to Claire for the bellhousing bolt pattern in reverse but having the right gearbox to fit will help with the thrust bearing and starter motor alignment.

I've had four 8's now, I buy them with dead engines and put rebuilt ones in, I love driving them so I thought it would be so much better with a V6 on LPG. I spent a bit of time measuring with the engine out and still think its going to be tight. I'll do the minimum amount of cutting.

rdodger - 21/5/14 at 06:55 PM

Try AK Automotive

http://www.akautomotive-mx5.co.uk/

They race and prepare MX5's and may have a knackered 6 speed you could get the bellhousing from

Worth an ask on MX5 Nutz too.