Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Mazda gearbox convertion

If it is the newer generation gearbox you may wish to read through this topic.

https://forum.miata.net/vb/showthread.php?t=610318

I believe the reliability issues (according to the drift and track crowd) relate to the 6spd version of the Mazda gearbox. It is the 5spd version that is being proposed for this conversion.

Peter J - you make valid point about the MX5 gearbox in the Threewheeler application. That V twin will put the transmission under some stress. Also, the subsequent link has been revealing too.

Rory, my memory as jogged by looking back through some old messages.

For what it is worth, I will give you my thoughts but they are out of step with the bulk of advice that others on TM are giving you. Firstly, because I own older generation Morgans rather than new generation ones but also because I have worked extensively on them for 40 years that has included rebuilds and race preparation.

The car is yours and yours to do with as you see fit. However, I feel that the car, particularly given its chassis number, deserves some careful consideration. If it was a Moss gearboxed car, I would definitely suggest not replacing the gearbox as that car's narrow stance and Moss gearbox are part of the car's charm. The 4 speed Rover gearbox has a bit of a reputation for being weak but remember, what gets printed in a classic car magazine ends up being total truth regurgitated by 'enthusiasts' with clean fingernails.

Changing the gearbox will attract associated additional costs including recalibration of the speedometer instrument. These can add up considerably.

Once again Rory, the car is yours to look after and modify as you see fit. Just bear in mind that advice that simply tells you to "change it" should be treated cautiously.

Finally, I have shared recently a full set of sketches for converting a Plus 8 from a Rover 4 speed to an LT77. I am happy to share these with you if you wish. They were given to me by a fellow Norcemog member decades ago (his car was recently sold at the Bright Wells auction) who converted his car. I used these sketches and measurements when I converted my car.

I can only back up what David has wisely advised above.

1 If your car is indeed one of the factory lightweights, then it would be doubly important to consider originality issues if you ever consider selling it.

2 Don't underestimate the amount of time , and money this is going to cost. There will be cuts to the crossmembers and repositioning work to be done. Personally I don't think the Mazda box is the way to go , as outlined by David . Yes I know it is a good box with a rifle bolt action, but is just not designed to take the low down torque the V8 produces in abundance.

3 If you want to keep a strong box go for the Rover R380 box (parts for the LT77 are becoming hard to obtain whereas the R380 has fewer issues in this respect), this will take the torque of a 5.7 litre Holden Monaro which pumps out more torque than any Rover engine is capable of. This will also deal with the handbrake issue outlined by David.

4 If you must go outside of the Rover 5 speeds, try to do a tried and tested route and go for the Ford T5 , I think John Eales does a bell housing to mate this box to the Rover V8 engine. This box is also pretty strong and will take a lot of torque without complaining . It is also one in which different ratios are available , enabling you to tailor your exact needs to the gears on offer, the Rover boxes are rather restricted in this respect.

5 Lastly , if you can learn to double declutch, I am sure your current box would outlast the car, as well as giving you sweet changes.

I have a T-5 in My +8 Bitsa. I like it. It was inexpensive $1,200US sourced from D&D in Michigan. However mine has a rather high 5th gear - .63. Great on the Interstate/Motorway but rather useless otherwise. I also have a 3.73 axle ratio which makes things a bit better. Under My work bench I have a Rover that came with My 3.9 engine. After driving a Friends 2000 +8 I must say I liked the Rover better than My T-5. The T-5 was a bit wider than the Rover so watch out for foot room. My advice would be to get the 4spd Rover repaired. But mind You I am in love with power not a 5 speed. Also My hearing is not good. (grin)

Hope you don't mind me reviving this thread. My '75 Plus 8 has the Rover 4 speed transmission and it is starting to be quite noisy in 3rd gear under load (louder when hot). Early in the New Year I plan to pull the engine/gearbox and investigate. If the gearbox is not repairable I would opt for a 5 speed replacement. I have read plenty on the T5, 380, LT77 as replacements but very little on user experiences with the Vitesse MX5 kit. I am not concerned about durability of the MX5 in my totally original Plus 8 as the 1975 model was actually the lowest powered Plus 8 ever turned out (still more than adequate). I am more concerned about whether the kit is truly a bolt-in or whether mods to cross members/transmission tunnel are needed. I know that the earlier Moss box front cross member and firewall would need extensive changes to accommodate the kit. Does anyone have any direct experience with installing the Vitesse kit in a Rover 4 speed Plus 8? Thanks.

Hi Geoff, I'm not sure how delivery would work, but there's comprehensive info here.
https://www.vitesse-ltd.com/product...-kit-morgan-plus8?variant=21482028138579
Good luck with it
Phil

Thanks Phil. Yes, I had read all the information on the Vitesse site, including the fitting instructions. I only started to feel uneasy when I knew the fitting instructions would not work for a Moss box car (very small opening in bulkhead for the torque tube) and therefore how could I be sure they would be accurate for my Rover 4 speed? Hence trying to find someone who has direct experience with this conversion. Vitesse were not exactly forthcoming when I asked if anyone had actually fitted the kit to a Rover 4 speed Plus 8.

Just I‘ve got a (new 2018) Plus4, but got the Rover Plus8 bug. And I was always in old MINIs.

If you got a old car, keep it, drive it and: love it to use.

So some changes are an option. But they must be easy to do and easy to build back. And if you have a look at the car: it must be done very secret. So far some easy points.

But on the technical side: there are a lot of modern cars around which have problems to handle with torque.
Not the (sometimes massive) power upgrade is the problem. The torque. Have a look at the technical datas of the MAZDAs and
their torque diagram.

As I‘ m in MINIs I always love the 1000. Underrated, but cheap and most with a good gearbox. I‘ve got komplette engines with gearbox
for 20,-EURs or „oh please collect it“ a few years ago… the same gearbox as the 1300. But the 1300gearbox? Most with some problems.


Greets René

I have Mazda box in my supersport engined plus 4, 200bhp, not sure of the torque figure. I wonder what gearbox is used in the Cosworth engined plus 6, probably the Mazda.