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MG MGB GT V8 Factory Originals Technical - MGC Rear axle mod

Hi everyone,
I've found a MGC rear axle. It is a wire wheel axle.
Is it just a matter of changing out axle half shafts from a MGB axle to make it work with disk wheels?
(I havn't seen it yet)

And, are there any numbers stamped on them so I can make sure its a 3.07:1 before I buy it? I'll have to have it shipped in, so I want to make sure before I spend the cash.

Thanks,
Kelly
Kelly Combes

Most axels will have numbers stamped on them, but the numbers will be the gear tooth count of each gear with a slash between them. If you divide the larger number by the smaller number you will get the axle ratio.
George Champion

Kelly,

If your new C axle has a 14 tooth pinion gear it is a 3.07. That's the only C diff w/14 tooth pinion.

I converted my C years ago from wires to bolt on by removing the rear hubs (not difficult), having the splined portion machined off, getting longer bolts to replace the ones already in the hub, then either getting 5 bolt wheels (5x4 3/4 bolt pattern) with the correct offset or having an adapter made to go from 5 bolt to MGB 4 bolt pattern. If you don't use an adapter, you will need wheels with different offsets front & rear, since the wire wheel axle is shorter than the disc wheel axle.

I'm doing the exact same thing right now on my B V8. E-mail me with your progress or questions.

Allan
Allan

Great find; MGC 3.07 rears are not exactly something you trip over these days and my humble, humble opinion is that they may still your best bet if you want a minimum of re-rigging. Boy are you gonna be psyched, because on a V8 unless you flare the fenders you'll WANT the narrower wire wheel rear end so that you can get some more rubber on there (I got 195/60R15 tires under there with nary a flare). Keep the wire wheel assembly and just swap out the hubs. It's really, really easy to do but you're gonna need to procure a 1-5/16" thinwall socket to get the big nuts, which hold the hub to the end of the axle, off. When you ask for one at Pep Boys they look at you like you're from Mars but when you persist the future high school graduate behind the counter will see that he can indeed order one for you. Other than that it's absolutely trivial -- just take off the brake drums and you'll instantly see what to do.
Ted

There are several possible ratios for MGC rears: 3.07, 3.307, 3.70. All can be good in a conversion. The 3.07 & 3.307 are excellent with 14" wheels, I am using the 3.70 with 15" wheels.

Remove the wire wheel hubs & replace with steel wheel hubs from a MGB rear axle & use the complete rear brake setup from the MGB axle. It is a direct bolt up with no mods. You may have to change the emergency brake cable to match the wire wheel rear due to possibly different mounting points. Use the MGC wire wheel rods & linkage, as this is easier than swaping & modifying the MGB parts.

It may be necessary to use up to 3/8" spacers depending upon the wheels you use. Do not be suprised if one side needs 1/8", the other 1/4" spacer.

Because it is likely that the MGC rear will have over 100,000 miles on it, it is a good idea to replace the copper & fiber spacers & the cross shaft. This is easy to do before the axle is installed in the car, only requiring partial removal of the axles. This should prevent any axle "clunk".
Jim Stuart

Jim,
What gearbox are you using and what is the OD ratio? I am just about to install a 3.7 MGC axle in my car which uses a Rover SD1 5-speed and 15" wheels and am very uncertain if I will be happy with the result on the highway, but it is what I have right now. I did the math so I know the numbers but I have no seat-of the pants experience. I also have a 3.3 gear set and carrier that I was traded a few years back by a fellow who I will not name, but it has a chunk of one ring gear tooth missing.
David

David, the gearing produced with the 3.7's probably gonna be a little low (to clarify, the gearing's low when the diff ratio is high). Assuming you use something like 195/50R15 tires, you'll be making turns for roughly 3,000 rpm at 70mph in 5th. That's kinda high; of course, there's no real downside other than that it'll seem a bit loud and your 1st gear won't be terribly useful. Going up to a taller 3.07 gearset will reduce this to about 2,500 which is still well within the motor's torque band but perhaps more pleasantly lopey.
Ted

Well, it sounds like shipping the axle is the killer.
That adds $300 to the cost. Ted and Jim, its up in your area in NY and I'm is south FL. I think I'm going to have to pass it up and have a Ford 8" built here. It will be about half the cost.
Like I said, I havn't seen it so I'm leary of spending a lot to get it here.
David, I'm using a Rover 5spd from a TR7. I'm not sure what the ratio for fifth is.

If anyone else is interested in the MGC rear, drop me a note and I'll forward the name of the owner.
Thanks for all your help. Too bad it didn't work out.

Kelly
Kelly Combes

David-

I have a T-5 with .63 5th gear & run 195/65/15 Yokohama Avids. This is a slightly taller tire than Ted calculated. 3000 rpm in 5th gives about 75 mph on an speedo that is close, but not 100% accurate. 1st gear is very usable, & makes the car much quicker off the line than my GT with a 3.55 rear & the same tranny ratios.

There are so many variables involved in determining the "right" choice, so no one is right or wrong. Much depends upon how you are going to use the car & the size/state of tune of your engine. I used the 3.70 C rear because it was $50.00.

The roadster with the 3.70 C rear has a very stock 215 with only a cam upgrade & is very good around town, on the beltway, but only OK on a long trip. My GT with a 4.2 Rover & the 3.55 Ford 8" is a better highway car, good on the track, but not a world beater in the 1/4 mile. Both very dfifferent cars, both very much fun.

Now the GT under construction has a hopped up, over bored, big (very big) valved 300 CI Buick with a 3.55 rear & tire size unknown at the moment. Come Spring, we will see what that is like.
Jim Stuart

Yes, that's much better. 8" Ford Torino 3.00 rear end for $100. Local machine shop will put on my MGB axle tubes and axles for $200. And if it ever breaks, or I don't like the ratio, there are parts to fix it.
Kelly Combes

Jim, $50 for a 3.7 C rear end? That's a pretty good deal! I paid a lot more for mine, which I'll be using in my 2 liter. Do you know of any more such deals? :)
Wade Keene

Wade-

Sorry, no good deals at the moment. The 3.70 C axle was cheap because everyone wants the 3.07 or 3.307. The 3.70 is pretty close to the stock B 3.90, & does not yield a big advantage over the 3.90, but with 15" wheels it is enough of a change to be worthwhile, & it is a bit stronger than the B & has larger U-joints.

Kelly-

Don't see how you are going to use your B axles with the B/ Ford assembly. Length will be wrong, splines different, Ford axle was much larger in diameter which is important as you try to mate with the center section.

Mosler makes a B/Ford axle for this setup which is Ford size at one end, MG at the other, but they are not cheap. Be sure when the work is done that the PINION is centered. It is offset in the pumpkin, so don't center the pumpkin.
Jim Stuart

This thread was discussed between 08/01/2003 and 12/01/2003

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