Quote:
Originally Posted by TomSaintJames
I'm quite enjoying driving the hearse at the monent, after the work done over the last couple of weeks. I eve cleaned the CD players screen to main unit contacts so that the screen didn't keep turning off.
I booked a study today and in a break thought i'd have a quick rekky on which rear diff the hearse has. The internet said it was likely to have a 3.91, so I got some carb cleaner out and managed to unearth the sticker. Took some scrubbing!
So it has the 3.91 ratio at the rear, am I right in thinking that post penta conversion, when there is hopefully a reasonable torque increase, that it may benefit economy to swap the rear diff for a lower ratio? The options seem to be 3.31/3.54/3.73. In the 7 series the 3.31 only came with the B28A and BW55 autobox and the 3.54 only came with the other B28 flavours (B28A/E/F), interestingly the B280 came with the 3.91 ('E') and 3.73 ('F'). Thos early V6's must have been quite the plodders with that high gearing and tiny power! |
My B280E had the 3.91:1 diff Tom, i've now gone
higher to the 3.54:1 diff, it only benefits economy on the open road where i can maintain 50+mph, no difference on the lower speed roads really.
Remember the ratio is input to output, 3.54:1 is 3.54 turns of the propshaft to give one turn of the wheels.
As such, a 3.54:1 is higher than a 3.91:1 as the 3.91:1 takes 3.91 turns of the propshaft to get one turn of the wheel.
To be honest, i'd stick with the 3.91 for now (especially if you have ABS) and see how it goes.