Rx8 5/6 speed gearbox conversion to ford engine (zetec,I4,pinto and x flow)
I just thought i would make a basic guide to fitting an rx8 gearbox to a ford engine in a classic ford. This guide is to fit an 6 speed rx8 box in my mk2 escort rally car that has a mk5 rs2k 16v engine along with a group 4 tunnel. Engines cars and x members may make fitting slightly different but the principals are the same.
To fit the gearbox you will need
rx8 gearbox 5 or 6 speed box
rx8 slave cylinder, clutch arm and release bearing
an adaptor plate (that i can supply)
2l of ford fully synthetic motorcraft 75/90w oil (recommended as the best oil to use)
X2 counter sunk m10 bolts
X10 cap head m10 bolts
Your original prop shortened and an rx8 end fitted (i use BAR Props, Neath South Wales)
an old or new set of anti tramp bars and bushes
3mm steel plate
Some fabrication skills to make a gearbox mount
If you already have a type 9 fitted in you car the conversion will be pretty straight forward as you use all the same clutch, flywheel and starter motor. You original prop normally needs shortening by around 2" though.
Which gearbox? 5 or 6 speed?
This is up to the individual really but i would recommend the 6 speed for an n/a engine as they have better/closer ratios to make the most of the power. Like wise for the 5 speed to use with a big v8 or a turbo engine as the ratios are longer and more suited to big torque engines. It is also rumoured that the 5 speed box is stronger.
Is it the same fitting a 5 and 6 speed?
In a quick answer yes. They have the same bellhousing pattern the gearsticks come up in the same places. They are also the same overall length too.
Clutch. Hydraulic or cable?
I would recommend going hydraulic really despite the extra cost of the pedal box there are no draw backs really. The clutch is lighter, self adjusting and makes the car much easier to live with. People have converted the clutches to cable but i haven't got any photos of this. It doesn't sound too hard but a lot of effort when there is an easier option though.
Pros and cons of the rx8 box
The pros to the box are they are stronger than the type 9 gearbox, easier to find and cheaper to buy. There will still be more ending up in the breakers for years to come too. That is before you mention the slick gear shift. It has a shorter and slicker throw standard than the type 9 with a rose jointed quick shift. Along with a hydraulic clutch it make the car that much easier to drive. From 2nd to 5th gear the ratios are almost spot on the same as a tran x type 9's 1st to 4th gear which is a £1500 kit plus bearings and a donor box it is nearly 2k. All this as standard for £50-£200. The gears and syncros are also a lot bigger than the type 9 ones. Right now the cons. First gear on the 6 speed is pretty short depending on what final drive you have you might not even need to use it, unless you need it for hill starts or very tight corners. Ect ect. It is also a tight fit in an escort auto box. I haven't heard off anyone who has fitted it in a standard tunnel yet either.
Fitting the gearbox
First up you will need to offer up your adaptor plate to the engine and the starter motor.
You will then need to bolt the box to the adaptor plate and use the dowels in the adaptor plate kit to center up the input shaft with the spigot bearing
The next step is to make a rear gearbox mount. I welded in two threaded 5 mm plates into the reinforcement brace in the escort tunnel as i had painted the inside of the car and didn't want to burn the paint off. It is also in the perfect place to weld a mount to a bolt on plte on the gearbox.
Here you can see the captive bar tacked into the brace.
Here is my gearbox mount used making 3mm plate and a pair of cut up anti tramp bars along with the bushes. Depending on how solidly you mount the gearbox will affect how much gearbox noise you will get in the cabin.
The position of the gear stick comes right up where the type 9 stick does.
This one is to show the size difference between type 9 and the rx8 box
This photo shows that even though the splines are the same on the rx8 and the type 9 box the outside diameter is bigger on the rx8 prop end. This is why you need to change to the rx8 end. There was a 'mod'/bodge going round that you would just change the oil seal and use the type 9 smaller diameter prop end but this is seriously wrong. If you use this bodge the prop end will not be supported by the sleeve in the tail housing and will cause the bearings or gearbox casing to fail.
This photo shows how much too long the original rx8 prop is. Which is a shame as the carbon prop is nice and light.
These photos shows my rx8/ atlas axle prop fitted
Here is a link to my build thread of my rally car if you want to check how the box is holding up or need any more information on fitting an rx8 gearbox.
http://www.turbosport.co.uk/showthre...276802&page=28
This is also a handy thread for information on the conversion too
http://www.turbosport.co.uk/showthread.php?t=500016
Reference photos
Type 9 clutch and spigot bearing fitted on rx8 box
6 speed rx8 box
5 speed rx8 box
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