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Are there any taller rear axle ratios available for the B? This might be a cheaper and easier way to get the revs down without buying an overdrive trans. I've noticed that I can almost start in second as it is, so a taller ratio would not hurt, except for drag racing I guess.
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taller diff ratios available?
- Thread starter artmck
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CraigFL
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The MGC came with a 3.07:1 ratio. These are interchangeable and somewhat hard to find. I saw one on Ebay a while ago and it was very expensive-- over $800 I think. A lot of people look for these when they change engines. I thought about it as a possibility befor I bought my O/D.
CraigFL
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If you don't mind it not being original, you could substitue a 5 speed with an overdrive 5th gear like this:
https://www.rivergate5speed.com/mgb_price_list.html
https://www.rivergate5speed.com/mgb_price_list.html
I looked at the ratios on the 280z trans, and 5th is only .864:1, which yields 2888 rpm at 60mph, which is still higher than would be nice. A .80 5th gear would be ideal. Not to say that if a 280z trans can be had cheaply that I would not do it. I will talk it around a bit. There is a guy on ebay selling just the adapter plates for this conversion. You still need to make/buy everything else. Probably the cheapest easiest thing to do is find an OD trans.
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Torque is what causes acceleration. There are three ways to increase torque, a larger engine, higher compression ratio, or more mechanical leverage in the drive train (final drive ratio).
The 280Z & the MGC have considerably larger engines & more torque.
Since the relatively small MGB engine has little torque to start with, the only option is to increase it with gear ratios.
Low numerical axle ratios, overdrives, or 5 speeds will give lower cruising rpm but must be down shifted to get much acceleration. A four speed with numerically low axle ratio will have to be down shifted to third for acceleration & the optimum ratio may be missing (gap too wide between fourth & third). With small engines, the more transmission speeds, the better.
If originality is not of concern, I believe the five speed with a reasonably high numerical axle ratio is the better way to go. Available overdrives are great but costly & not totally reliable.
D
The 280Z & the MGC have considerably larger engines & more torque.
Since the relatively small MGB engine has little torque to start with, the only option is to increase it with gear ratios.
Low numerical axle ratios, overdrives, or 5 speeds will give lower cruising rpm but must be down shifted to get much acceleration. A four speed with numerically low axle ratio will have to be down shifted to third for acceleration & the optimum ratio may be missing (gap too wide between fourth & third). With small engines, the more transmission speeds, the better.
If originality is not of concern, I believe the five speed with a reasonably high numerical axle ratio is the better way to go. Available overdrives are great but costly & not totally reliable.
D
I didn't look at the other ratios on the 280, but for sure the B has all of the ratios shorter than they need to be, that's why I originally though that an axle change could accomplish the goal. The 280 has 15" tires, which implies that the 1,2,3 gears are a bit taller, which would be fine.
Horsepower is what is needed for steady state cruising, and I would think that at 2500-2800 rpm, there is plenty of power for cruising, as long as we are not climbing mountains at 60mph!
Horsepower is what is needed for steady state cruising, and I would think that at 2500-2800 rpm, there is plenty of power for cruising, as long as we are not climbing mountains at 60mph!