Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Axle ratio

I have an 1971 +8 car - at the moment with 5 speed LT77 gearbox od a 3,58 axle ratio.
I consider to change the axle ratio to 3.07 from JB-engineering.
Has anyone experience with this ratio - how high is 1-gear, usable ???
The change would be good if I go back to the Moss-box to keep it original !

Joergen

First a few questions:

1 Most importantly why do you want to change the axle ratio , is this just to decrease the revs while touring? The 5th gear does this for you anyway, so dropping 2 ratios down to 3.07 will certainly affect this. Agreed if you revert to a Moss Box (for originality?) then a lower axle ratio might help , but dropping two ratios from 3.58 through 3.23 to 3.07 is quite drastic.

2 The gearbox has been modified in your car , have their been any engine mods ? Is the axle a Salisbury , or has it been replaced with a later Dana Spicer? What tyre sizes are you running?

3 With a higher power engine you would be able to get away with this , with a standard 3.5 on carbs it might struggle. I have a 3.9 which develops about 250bhp and my 3.23 axle is pretty good for touring , giving 25 mph per 1000 rpm on 205/60 x 15 tyres. I would not want to go much lower than this as I would lose acceleration.

I would need to look at some graphs of revs/mile but would need tyre sizes etc to be able to do the calculations accurately.

Hi Andy
Thank You for the answer.
I want to change to drop revs and to have the possibility to go back to the Moss box.
Its the orininal Salisbury 7HA axle and the engine is around 200Bhp and running on 185/80x15.
Is 3.23 a possibility for the 7HA ??

BR
Joergen

Now running a 3.08 Salisbury with a good 3.5 engine pushing 205/60 15 tyres.

Lovely cruising gait of 2,500 rpm at 70 mph (true speed) in fifth.

Plenty of torque, no problem.

Spiny.

Hi Spiny

No problem when starting on a slope ??

No problems. (Can no longer start in 5th gear!)