On the 140, in North America a non overdrive equipped car would typically come with a 4.1 rear drive ratio. Cars that were originally equipped with OD would typically come with a 4.27 rear drive ratio.
The other consideration in the rear drive ratio is tire size. The original tire size would likely have been 165/78 profile which is not so common these days. If you have fitted more readily available tire sizes such as a 185/65 the effective rear ratio may be closer to the original 4.27. If you retain the original 165/78 profile tires and have a 4.1 rear drive an OD with a 0.76 ratio might be unrealistic for towing in OD. If you have 185/65 tires with a 4.27 rear drive you might be able to tow in OD (no hills allowed!).
When comparing to your 145, keep in mind that a 4.56 rear drive was an option on these cars. I don't know whether it was a dealer installed option or something that was specific to a particular market or particular product (ambulance or delivery vehicle).
|