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MG MGA - MGA 4.3:1 gears

Hello everyone,

I am intruding from the 'T' site. I am sure you have probably been asked this many times over but I am pretty new to the rebuild business and have been told it would be best if I convert my ring and pinion to the MGA 4.3:1 ratio. WOuld anyone know where I might purchas such a pumpkin. And again if this is an old and irritating question I apologize.

Rob
Rob Welborne

Rob,

Fair question, as you are asking "where you might purchase.." rather than asking directly!

Not a direct answer, but if you can find an MGB 3.9:1 ratio you would probably find more than one MGA owner willing to swap you their 4.3:1 ratio!

Direct answer is eBay, they come up pretty often.
Neil McGurk

MGA or early MGB differential pumpkin is NOT a direct bolt-n for the TD. The MGA or early MGB ring and pinion gears can be used but require a bit of machining to fit the ring gear to the TD.

The whole MGA rear axle can be used in the TD, but this requires a bit of grind and weld to relocate the spring mounts on the axle, as the TD leaf springs are a bit closer together.

Folks in the TD forum may (hopefully) have the appropriate information for the 4.3 conversion.
Barney Gaylord

You ok up there in Cumbria Neil? I have been pumping water out of the drains here in South Yorkshire all day to prevent my house and Garage flooding again like it did in 2007.
Been pumping for 4 1/2 hours so far and I have worked out that so far I have pumped out 144 cu metres of water (144 metric tonnes!)
Seems to be keeping it at bay for now.
Colyn
Colyn Firth

Unless it is a lightened/competition car I would not convert a TC to 4.3:1. A friend had about a 4:1 conversion in his TC (with 16inch wheels) and it robbed the car of its TC characteristics (eg lively acceleration, spirited road performance, etc). I converted it to 4.75:1 (using a Morris Minor or "A"-series cwp and it is now on 19's) and it is much more like a TC to drive. My car is still on its orginal 5.125:1 and I know it revs its little heart out on the open road (above 50 mph) but does that really matter? I definitely would no go lower than the 4.75:1.
Barry Bahnisch

Hi Colyn,

Sorry to hear about the water, I saw on the weather report you were getting it down there. Ironically we have had nice sunny weather here for the last couple of days!

Still not much chance of a repeat of last year where we had 50cm of rain in three days with over 30cm in 24hrs! all after a long wet spell!

Otherwise we are well used to a good soaking!

Sorry to everyone else for hijacking the thread!
Neil McGurk

You could try looking for the 4.55:1 that was used in the Z Magnettes.

I'm not sure which of the other cars in the BMC range at the time (Morris Oxford, Riley 1.5, Wolsely 15/50 ...) used them as well but it might widen the search a bit.
Dan Smithers

Oops, another senior moment! I meant 4.875:1 (not 4.75:1). Also not sure that they are "A" series, maybe "B" series. These diffs heve a wide range of ratios, from under 4 to 1 to over 6 to 1. They are also hypoid (with tapered-roller pinion bearings), instead of the original spiral bevel, and whilst a small amount of machining is involved, the original axles can be used. They used to be widely available (from breakers/wreckers) but are now rather thin on the ground (especially the sought-after 4.875:1).
Barry Bahnisch

Hello Rob. First question have you seen the book on how to change the gears in the TD/TF diffs'? It involves grinding both the spacer between the pinion head and the inner bearing and the pinion spacer between the two pinion bearings. I have several 4.3 ring and pinions as I use them to do the conversions. I've done close to 100 conversions. Contact me off list for more info.

Butch Taras
TD Y MGBGT
VMG
R Taras

The MGTC rings and pinions are still manufactured to various ratios in the UK. I remember converting my TC in the early 90s. I will check my magazines for the company.

Steve
Steve Gyles

Barry,

Maybe your memory has been effected by the cold temperatures since you moved to Canada.


Mick
M F Anderson

Looking for a MGA 4.3:1 Rear End Pumpkin, Thanks.

Hampphillips@hotmail.com
C.H. Phillips

This thread was discussed between 03/10/2010 and 18/10/2010

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