MG TC Restoration

[Douglas James Taylor]

I have just purchased a 1949 MG TC and I am planning a full restoration when I eventually receive delivery from New York.

I have decided to have the engine rebuilt and have a supercharger fitted along with a ford type 9 gearbox.

The steering will have a VW steering box fitted to help overcome "wondering" at higher speeds.

I was at a classic car show recently and was discussing the restoration of a TD with its owner and he says I should consider fitting a MGA rear axile. Any thoughts?

I will retain ALL the original parts if and when the car is sold and the new owner wants the original bits.

Douglas

[Steve Simmons]

My first recommendation is to get the front end properly rebuilt before doing the VW conversion. There are pros and cons to both stock and aftermarket steering but there are plenty of debates on that in the archives. In my experience the conversions greatly change the character of the car, so consider that before proceeding. With a properly set up front end and new parts where needed, you may find the original steering much better than you thought it could be. If not, then you could always do the conversion at that point.

I don't see any need for an MGA rear axle and the required modifications that go with it. The guy with the TD probably didn't understand that the axle, gearing and brakes are different in a TC. If fitting a supercharger, I would just buy a set of 4.625 rear end gears and install into the stock axle. If you want even higher gearing, you can modify a Midget differential to fit into the TC axle housing. Also consider tapered axles for added strength.

[XPAGnut]

The TC gearbox is a glorious piece of engineering and execution, and can easily handle the added power of a supercharger. The TD & TF gearbox was an ill conceived exercise if cost savings by MG, and TD/TF people are always coming up with schemes like the Ford box to lure another TC box onto Ebay. The original differential can keep up by committing to some rather simple (to do) modifications that are both well known and readily available. The ratio change already mentioned being the only truly essential modification to negate the need for both 5 speed tranny and some other diff.

The VW steering is not a part of a good restoration, today. While it was a way to keep some TC's on the road during the dark ages, when steering replacement parts were either cheaply made or non existent, there is no reason for it today unless your steering column/box is toast, and you lack the resources for a proper restoration. There is nothing cheap nor flimsy about the original steering equipment.

[Tom Lange, MGT Repair]

Your friend has confused TC and TD. The differentials are completely different, and not interchangeable. His point is to change the ring and pinion of the 5.125 differential for a more salubrious 4.3 MGA ratio, to diminish the revs at higher speeds. On a TD, and in America, where highway speeds are a bit greater than the typical UK road speed, that works fine. But a TD has a split rear axle, and must be completely disassembled to remove the gears - which, in any case, are NOT interchangeable with TC gears.

A TC has a removable pumpkin, which lends itself to an easier solution than trying to fit a square peg into a round hole by using a TD rear axle. The Morris Minor pumpkin fits beautifully into the TC differential, with just a bit of welding, drilling and swapping of gears (it sounds harder than it is). That changes the TC ratio to a 4.55, which is better. Morris Minor /Spridget pumpkins are easy to find, and not hard to modify (I've put three in cars). How different is the car after the modification? You will end up swapping low end power for higher top speed with fewer revolutions of the engine, which is a decision you must make. Adding a supercharger is the perfect foil for the reduced acceleration from take-off, and overcomes all disadvantages.

Other than the re-welding of MM holes and drilling of new TC holes in the MM pumpkin, the only other thing you have to do is deal with is the spider gear question. The splines of the spider gears, into which the axle shafts fit, are different between the TC and Morris Minor, so you have two possible solutions. The spider gears can be swapped for the TC spider gears to use the original TC axle shafts (not hard to do at all), or you can get a pair of specially-made axle shafts from Bob Grunau in Canada, which have TC hub splines on the outboard end, and MM splines to fit into the MM spider gears inside the differential.

Here is the most comprehensive article on the swap: http://www.mg-tabc.org/library/diff.htm

Hope this helps.

Tom Lange
MGT Repair

[Douglas James Taylor]

Many thanks guys for all the suggestions and opinions. Much to ponder on.

Hi Tom, you will find that speeds in the UK are greater than in the US, most duel carriageways and motorways are 60/70mph.

Many thanks again.

Douglas

[Steve Simmons]

It's about the same over here. The majority of main highways are 65 MPH, and some large interstate highways through open areas 70 MPH. Smaller highways (and large highways passing through busy city areas) are 55. What we do have over here though, are very long open spaces where you might drive a modern car at 90 MPH (illegal but everyone does it anyway) for hours on end.

[Douglas James Taylor]

Hi Steve, things are the same the world over, when the roads are quite we do the same. On our minor country roads you can legally do 50/60mph and the roads are not straight but with great sweeping bends and curves, ..... real driving roads. These are roads that were about when the TC's were new and they are still great to drive today.

The motorways and duel carriageways are straighter but are patrolled by the police, we can get away with doing 80mph on the speedo, but you need to careful.

We are just back in from having a meal down the Clyde valley, near Lanark, Scotland. The road is very twisty but quite, my good lady was driving her Audi S1 Quattro, at 60/70mph, good fun.

Douglas

[XPAGnut]

Not sure what Tom is going on about, as all there is to do to change the ratio of TC diff is to get a hold of a matched ring gear and pinion to swap out. Abracadabra, new final drive ratio.

No need to swap diff units from some other car or grind metal to fit in a Morris minor pumpkin, unless your TC diff is destroyed.

A number of years ago I got a ticket (radar) for going 140mph in a 35mph zone. It was 3 am and I was driving a farm country frontage road in a souped up Plymouth Fury with a 440 cid V8. Went to pay the ticket expecting to get license yanked and instead ended up being fined 35 dollars. Clerk read it as 40 in a 35, and once I paid it, that was the end of it.

[Douglas James Taylor]

In the UK you can be fined and have points added to your on you licence, 3 points for each affence. When you have 12 points you loose your licence for 12 months or more. Each set of points can stay with you for 3 years.

All of that is not the real punishment, your annual insurance can cost double or more for each car, and we have 9 cars. So being careful is essential.

Douglas

[Steve Simmons]

The Midget diff conversion is for people who want higher than what is available for the stock TC diff. Currently that's 4.625:1, which is enough for most people but there are those who do mostly sedate long distance touring and want lower RPMs at the loss of acceleration.