Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
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.
-
Hey Guest!
British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!**Upgrade Now**
(PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
taller diff ratios available?
- Thread starter artmck
- Start date
Share this page
CraigFL
Jedi Trainee
Offline
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
Jedi Trainee
Offline
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.
Offline
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!