Look at page 35.8 of the latest version of the Bentley. DK trannys have
4.57, tallest of the r+p combos sold in North America.

Your tach, speedo, and/or memory must be off. Plugging in the numbers
for an air-cooled DK tranny in 4th gear shows rpms much higher than you
recall at 70/75 mph. You need to know the 'tire actual revs per mile' of
your tires to precisely solve the equation but a sample of some values
will give a range way outside of your 3100/70mph and 3300/75mph.

engine rpm x 60min divided by (.85 x 4.57) = axle revs per hour ....( in
.85 4th gear for DK with 4.57 r+p)

Assume 810 revs/mile of 185R14 tires.
3300 x 60 divided by 3.88 = 51032 axle revs/hour, divided by 810
rev/mile = 63.0 mph at 3300 rpm
3100 x 60 divided by 3.88 = 47398 axle revs/hour, divided by 810
rev/mile = 59.2 mph at 3100 rpm

Larger 27x8.5x14 tires are about 780 revs/mile (BFG specs), so these
give 65.4 mph at 3300 rpm, 61.5 mph  at 3100 rpm.

Mark

Stan Wilder wrote:
>
> I was trying to look throug the Bentleys to discover te gear ratios and
> although I've found mineTranny type 91. at .85 final drive, that is 4the
> gear and not the ring gear ratio.
> 806 revs per mile on the spedo, 185x14 Agilis Tries.
> Tranny type 91.
> I haven't sat down to calculate an rpm at 70 MPH, not knowing the actual
> diameter of the tire.
>
> Final drive on a ACW code type 091/1 is 4.83
> Final drive on a DX (diesel 5 Speed) is 5.428, also see 5.43
> Final drive on a DU Type 091/1 is 4.86
> Final drive on a ABD Type 091/1 is 4.83
> Fourth gear on a DK is type 91 is .85 but I don't find a final drive
> number.
>
> My Bentleys door stop has let me down again.
>
> Stan Wilder
>