Mgb rear axle ratio

[bluetr3]

Just for interest. Has any one tried a 3.3:1 rear axle in a standard 1800 mgb. I have had one in mine for about 4 years, and I love it.
Tried a 3.7 for a few years it was ok. I think a 3.5 would but ideal, can’t get one. The 3.3 is good, and my car a 1970 gt is an every day driver summer, and winter. Fuel consumption is around 35 mpg. 70mph is 2600 rpm. With 14x175/70 tyres.
Basically it’s like driving a standard car with permanent overdrive engaged - then on top of that, I can engage my overdrive and gain an extra increase in gearing. If that makes sense. Just wondered if anyone else has tried experimenting with axle ratios.

[Not_Anumber]

That should be very good for motorway driving in particular. How does it feel driving around town. Do you generally need to be a gear lower in urban traffic ?

[bluetr3]

Hi, thanks for the question. It is actually better for rural driving, just think of driving around in permanent overdrive, but on all four gears.it also makes 2nd and third gear far more usable, as we know 2nd gear on an mgb is virtually useless (compared with my tr3 which will do 65 mph in o/d 2nd). This means I tend not to use the overdrive as much with rural driving, less wear and tear on the o/d system.
Of course there is a bit of a downside in that top speed maybe limited, due to lack of engine power but 70 mph cruise is absolutely no problem. If so, just click out the o/d and you are back in a standard mgb in o/d.
Regards John

[bluetr3]

Come on Ian, what do you think of it then?

[Not_Anumber]

Longer legged gears sound a good idea and presumably will also help with economy. With the ratio you are running does non OD 3rd gear equate to non OD 4th on a standard 3.9 ratio ?

Where did you go about trying to source a 3:31 diff and will it fit into a standard late axle casing using the same halfshafts and prop flange ?

[bluetr3]

Hi Chris
The axle was from an MGC, it came in wire wheel casing which I removed and fitted in a steel wheel (rostyle) casing.
I’m not too sure about the 3rd gear question, I would have to do some tests to answer that.what I would need to know is the speed / rpm that you are achieving in a standard car in non o/d third.
All I can say is that with my setup, when I drive in non o/d top it is identical to driving a standard 3.9 car in o/d top gear. One problem though is Speedo calibration, I have not had the Speedo calibrated, but at the moment, I am using a 1000 tpm speedo, and it is indicating about 8 mph low, confirmed with my gps Speedo. I think probably a 950 tpm would be a little better.
Regards John