G40R close ratio Mazda gearbox by Raceline

G40R close ratio Mazda gearbox by Raceline

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jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
Following on from the 2.5 litre engine upgrade, recently Raceline had their close ratio gear kits for the Mazda 5 speed gearbox ready. Besides Ginetta, this box is used in Caterhams, Morgans etc, so I hope Raceline will find a good market for this kit. The gears are helical cut, so no crude noisy straight cut stuff.

Here is the gearbox emerging from my garage pit.



It is possible to drop the gearbox out with the engine in situ, but clearance in the tunnel is very tight.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
With access to the tunnel, I was able to run a pipe and cable rearwards to the boot and relocate the windscreen washer bottle away from the air filter.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
Lovely new close ratio gear kit parts:



New 1st, 2nd, 3rd gears with matching layshaft and new input shaft. For 5th gear, the existing Mazda gear is retained, but the overall ratio is closer due to different input pair on the new shafts.

Vitesse Global are the UK Mazda motorsports agent who supply and rebuild these gearboxes as part of their everyday business. They also supply conversion kits to fit this Mazda box to popular classics – Triumph, MG etc. Luckily for me, they are less than an hour away up the A5 in Hinckley, so off I went with the gearbox and the new gears.

jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
A week or so later, I have a rebuilt gearbox with the Raceline close ratio kit fitted and a nice new concentric clutch slave cylinder to replace the archaic external cylinder and arm which came from Ginetta. Vitesse did a great job – recommended.



All the old clutch actuation bits about to be fossilised.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
This lug sticking out was snagging badly inside the tunnel when trying to remove the box.



It serves no function in the G40, so I cut it off.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
Powder coating on various brackets was very flaky, so needed to blast clean and re-paint with epoxy. The larger bracket is from the front of the differential. Removing this bracket gives clearance to pull the propshaft out before dropping out the gearbox.



I reinforced the lugs of the diff bracket with brazed on washers, as the original thin steel was distorting under pressure from the M12 bolts.


Brackets restored to good condition.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
Easing the gearbox into place on blocks of wood from under my garage pit.





Holding up the tail of the box with a ratchet strap from inside the car through the gear stick opening.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
With the gearbox in, I decided to change the differential oil while I was at it. There is no drain plug, so I had to drop the diff out to up-end it and drain through the filling port. Then I found the main top bracket also going rusty. More blasting and painting – great!! Also a lot of flaky powder coating and rust on the chassis needed to be dealt with. It was too sad to take pictures of all that!!



Diff ready to go back in, finally. It’s a Sierra 7”, 3.9:1 ratio with Quaife ATB. The factory have written “Junior/road car” on it. Presumably this ATB has the alternative less aggressive helix angle than used on the race only cars.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
To get better access to the nuts for the diff top mount, you can remove the fuel tank access panel from inside the boot.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
The hydraulic connector for the concentric clutch slave emerges out the top of the bell housing. You can just about get access to this at the right rear of the engine. It has the hose connection and bleed nipple all on the same fitting. I made up a new hydraulic hose from -3 Earls fittings I had lying around from old bike racing days. The clutch hose is the one with white spiral wrap covering, going on to the black plastic connector.


jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
It’s not ideal weather right now, but I’ve driven the car for a few miles. The new gears all work very nice and smooth. The clutch action is miles better with the concentric cylinder. The new gears are as quiet and good change quality as the originals.

1st gear is now a useful gear and fine for slowly moving along through residential areas. I’m sure it will be good on track for tight hairpins too, like Mallory Park etc. The old 1st gear wasn’t much use above walking pace.

The gaps between all the gears are closed up, especially the huge gap going from 2nd to 3rd. With the standard box you are screaming the hell out of it in 2nd, only to bog down when changing up to 3rd. That’s all fixed now and it’s easy to stay in the power band.

The close ratio kit is a Raceline product, so talk to them if you want one.

I would say that if you don’t want to spend a load of money on a bigger engine like I did, just the close ratio gearbox upgrade will allow you to make much better use of the power from the standard engine. That would go for the G40, or a Caterham, or Morgan, or even an MX5!

jwoffshore

Original Poster:

448 posts

221 months

Friday 8th January
quotequote all
Maybe I should put the bonnet back on...



Beep, beep!