MGC rear axle ratios

Can anybody tell me what rear axle ratios were available in the MGC?
thanks!
John

'68 model used 3.07 non-overdrive/3.307 overdrive. '69 model changed to 3.307 non-overdrive and 3.7 overdrive. MGB was 3.9 all years and configurations.

And the MGC auto used the 3.307.

Ron

The 3.7 is fairly worthless in my opinion.

The 3.07 and the 3.31 are the most desirable of the three diffs, with the 3.31 being "top dog".

I am in the market for several 3.70 FWIW

auto mgb has 3.7 also fitted ..robert

Don't care where it comes from as long as its a 3.7 for the tube axle or banjo for that matter...

Thanks Steveio...get my package yet?

I also like a 3.7 in a MGC with od. Makes a great car better. I will have to admit with a V8 and a 3.07 it is even a more relaxed cruiser but if I want to really cruise I break out the SV which gets 30 mph per 1000 rpm. Rpm limited to about 6500 since it is not a 3 or 4 valve engine.

Ron

That's my point.

You need an o/d in order to make the 3.7 an appropriate gearset.

My 1968 MGC does NOT have o/d.

The MGBs with BW35's are as rare as hen's teeth in the North American market.

I've seen two examples since 1974.

I have one hens teeth but it is a RHD GT.

You guys with multiple models hopefully I will see some of you in Dillard (now that I have a MGBGT). First tank of gas (premium) mostly city driving and mpg was 25. Second tank is mid grade and not empty yet but no problems so far. Begenning to like this car.

Ron

Wouldn't that be, "I have one hen's tooth"....

Its OK Ron, I know a dentist who can get you a full set of mammalian teeth...:devil:

i was aware that 3.7 did only come with overdrive!! my later mgcs without od have 3.307.. or have i misread ricks post

Robert
When I think of one tooth I think of the front row of a Willie Nelson concert, so I just forgot about the singular/plural thing. If a chicken truly has no teeth then would it matter if you used the plural term for tooth?

As far as mammalian teeth some are herbivors, some carnivors and some omniverous. All require a different set of chompers.

Ron

the 3.7 diff also ran the best gear set in the box closer ratio between 2nd and 3rd not that i can tell the difference when driving

So it appears:
1968 no OD 3071 (14/43 stamped) P/N BTB900 also MG V8
1968 with OD and 1969 no OD and auto 3307 (13/43 stamped) P/N BTB841 aka BTB842
1969 with OD 370 (10/37 stamped) P/N BTB1244 also used in the most rare MGB auto

MGB tube axle w/wo OD 3909 (11/43 stamped) P/N BTB856


Is that the consensus gentlemen?

Edited as per SteveioRomereo....:)-D

Re-edit per other xpertz(tu)

couple of digits have slipped robert on you keyboard 14/43was the first one and if you look on btb841 its always stamped as btb842!! wonders of mowog

Dont forget a 68 with od used a 3.3

Ron

Rick

Can you give a wider view of the axle showing where the Differential Case Gearset Markings are located. I want to verify what my spare axle is and haven't been able to find the markings. Couldn't find them on my spare B axle either so am probably looking at the wrong spot.

Thanks

I understood they never stamped the B axle like the C because they were all 3.9's. I am sure there may be an exception to that rule somewhere.

Ron

Ron N
Earlier in the thread I believe it was determined no 1968 got an OD.

I stand corrected....the memory is a terrible thing to lose.

Did the rear housing have different stampings on the outside for the different gear ratios used on the inside? I'm getting an MGC rear end but have no idea what year car it came out of or what the gears inside might be. Any help in determining where the markings might be and what they mean (if they even exist) would be huge ! !

Thanks,

TC

What do the 13 and 43 signify?

Divide the larger number by the lower number. This is the ratio of the gearset.

Thanks ! ! I guess that the lower the number, the more desirable the gear set/rear end.

One last question, hopefully. If the rear end that I'm picking up is a 3.7, would it be that much better than the MGB 3.9? Is the difference in highway driving noticeable enough to warrant the effort and money to buy and swap in the MGC rear?

Thanks so much for the clear and quickly posted info, this place is just terrific ! ! !

TC

I suspect but do not know the stamped numbers are the tooth count of each geared item. The lower the number the more potential the highway speed at lowest RPM. The higher the number the more rubber you can leave by dumping the clutch at 5000rpm....that according to John "Powerman" Powers :devil:

The ideal ratio actually rests on your specific goals for driving and the ability to produce the HP to justify the lower ratio set. That is why the advanced 1800 engine is mostly limited with or without an OD to the 390 ration gear set. Add just 50% more engine (HP) and you could pull the 307 gear set.

Oh . . . sorry, good question.

It's for my 1958 MGA and will have a 1989 Mustang automatic mated to it.

TC

Were I you, I'd strongly consider the Mustang 9 inch rear end. A little more info on your hotted A engine would be more helpful. I think the stock 390 is the best route for you...
Unless you have a carrier and even so, getting all to fit into the B tube axle is no walk in the park...about a $200 trick by my machinist...no problem if you have the C rear, carrier and gear set.

Dont know, automatics usually use a different ratio than a manual and am not familiar with Mustangs. What motor are you using?
Agree with Robert and would probably modify a Ford unit even though it is said the MGB/C rear axle is pretty robust and can handle a lot more hp then was ever used by the factory.

Ron

Ron
The unedited version was more to the salient point imho. The mod in question is more about will the motor have enough HP to drive the rear end from a standing start. Final drive ratios are very dependent on engine output. The MGA gear set is ideal in a TD for instance for flat land driving. Add a moutain or tall hill along the Iowa banks, and the gain is no gain at all and you may never be able to reach 4th gear. MoPars never had an issue with the R&P gears but LBC 4s certainly did and do. As you suggested Ron, the ever present 390 in all MGBs would indicate a very good reason at Abindon to leave it they way 1962-1980

Robert

After I read that Thomas was using a Mustang transmission and I am going to assume a Ford V8 up front it seemed that my original comments did not apply to his car. Agree that the MGB with a 3.9 passed the test of time, over and over.

Since there are no hills here in the low country a lot of TD's have the 4.3 conversion but find fewer done up state in the hilly country for the points you mentioned.

Dont mean to digress form the orig post.

Ron

Right Ron...it seems like its all about his engine. I'd think a V block in an A would be a hard squeeze...

The engine and trans package that I finally found for the car (from a buddy in Maine) is just a stock 1984 Mustang 5.0 and a strong 1989 Mustang automatic. The injuries/surgery to my knees demands an automatic for now rather than a more desirable T-5 standard trans. The Mustangs came stock with a 3.9 rear end in most instances, I was going to use a stock 3.9 MGB rear end and, with the softer transfer of power from the automatic, just go with it.

Then several folks mentioned that the MGC rear end not only has better gearing for the highway, but might also be just a smidge stouter as it was built to handle the extra power of the sic cylinder engine. The same person who sold me the car(s) and fiberglass hardtop also has an MGC rear end (complete from wheel to wheel) for me at a very good price.

The cost of a narrowed Ford is well beyond my budget, especially for this little experiment. I'm hoping that the MGC rear end will work well and the gearing will provide that that little extra that I'd like for the highway. The info on the gear set and where to find the markings is a terrific help. I will probably get the rear end anyway, regardless, but it's great to know the gearing too.

Hope that this helps explain a bit.

TC