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differences in RWD A series gearboxes

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Paul1976

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differences in RWD A series gearboxes

Post10 May 2018 21:55

Hi All

I've bought a 1300 marina motor and box ( Early drum braked van ) to put in the Farina, but a local told me Id need to panel beat the tunnel near the starter motor to make it fit. Id rather make new engine mounts and lower the engine a bit, if this is whats needed.

How do I identify different generation or type of gearbox from the A series? And what are the benefits/ weaknesses of each type

Thanks,

Paul
Christchurch, New Zealand
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Keith Bennett

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Re: differences in RWD A series gearboxes

Post11 May 2018 13:20

Hello Paul, and a warm welcome to our forums. I myself aren't an expert on such mechanical matters but I know there are several inmates on here who will soon be helping you. A40 owners are not thick on the ground in New Zealand although we do have a Club member down in Invercargill. Thanks for taking on an A40 - is it a saloon or Countryman model, and what year?
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dave the rave

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Re: differences in RWD A series gearboxes

Post12 May 2018 15:04

Being a Marina that'll have the Triumph gearbox. That's why you've been told such. Probably a better box as it has synchro on all gears. Not au fait with them myself, but it sounds like they're a bit bulkier. Be a LOT easier if you can get a Midget rib case box. With a Midget 1275 backplate its a direct fit. No mods required.
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johnsearby

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Re: differences in RWD A series gearboxes

Post17 May 2018 15:33

Marinas have Triumph box, so you will need to get a propshaft made and modify the gearbox tunnel. 948 engined cars have a smooth case box and 1098 cars have a ribbed case box. Both have brass bushes on the mainshaft gears. 1275 Spridgets have a ribbed case box, but they have roller bearings on the mainshaft so are much stronger. They are however quite rare now. If you fit any of the Austin/ Morris/ Spridget boxes you will need the backplate and flywheel to match. As far as I rmember the Marina has a 6 bolt crank like the Spridget so a Spridget flywheel will fit but the smaller engines have a 4 bolt crank. You therefore need a Spridget flywheel and backplate whichever box you use. Don`t forget to have the crank, flywheel and clutch balanced as a unit. It might be simlpler to spend the money on tuning your existing engine; you can make a 1098 go quite well.
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dave the rave

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Re: differences in RWD A series gearboxes

Post18 May 2018 11:02

Ah John......"Midget flywheel will fit"......NO it won't, the Midget crank has two diameters on the end, the larger one, ( same as Marina ), tapering down to a smaller diameter. Ergo, the Midget flywheel has a smaller hole that fits the crank. The Marina crank is a uniform size.

Marina diameter is 3.131"
Midget " " is 3.131 initially, then the tapered part, and finally 3.031"
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johnsearby

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Re: differences in RWD A series gearboxes

Post19 May 2018 08:11

Had forgotten that, thanks for pointing it out.
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dave the rave

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Re: differences in RWD A series gearboxes

Post20 May 2018 12:19

If deciding against the Triumph box, ( which i would ), there's two ways round it. Fit a Midget crank, ergo then you have Midget flywheel and clutch and box all matching. THOUGH will need Midget conrods, as crankpin on Midget crank is smaller, 1.625" as opposed to Marinas 1.750". Plus pistons are press-fit on the rods, so if they're damaged being taken off, new pistons needed. Cranks are not too difficult to locate, conrods perhaps a bit more so.
The other way is to have the back of the Marina crank turned down to suit the Midget flywheel. Of course, could use the Marina clutch & flywheel, but i think the flywheel is a bit too big for the bell-housing. And, the clutch plate will undoubtedly NOT fit the Midget gearbox input shaft.
So, yer pays yer coin and takes yer choice. Either way, looks like an engine strip.
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Paul1976

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Re: differences in RWD A series gearboxes

Post21 May 2018 01:17

Thanks all for the replies.

My A40 did come with a ribbed gearbox but no motor, so Ill have a rummage round and see if I can fit that as I don't fancy too much panel beating to the tunnel. I've got the marina 2 piece drive shaft and the rear end with the bigger drums and hub PCD, so was going to fit hose as well, and match with a Minor Front disc set up. End result is a road registered classis racer; here in NZ unfortunately they don't scrutinize cars too closely, so the wrong gearbox and rear end isn't going to be picked on.

Paul
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Paul1976

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Re: differences in RWD A series gearboxes

Post01 Jun 2018 00:41

Keith Bennett wrote:Hello Paul, and a warm welcome to our forums. I myself aren't an expert on such mechanical matters but I know there are several inmates on here who will soon be helping you. A40 owners are not thick on the ground in New Zealand although we do have a Club member down in Invercargill. Thanks for taking on an A40 - is it a saloon or Countryman model, and what year?


Hi Keith, sorry for late reply, Think my car is a 64 Countryman, bought it in a box of bits, good solid body ( we dont use salt on the roads here in winter, just grit )

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