I have a '76 929, which I would like to make a bit more practical on the highway.
I have recently had the engine rebuilt and and put a set of 14'' rims and larger tires on her. I put a 5 speed on a few years back.
The problem been that the speedo is 10% out and that it is doing 4000 rpm at 110km/h which seems a little hight for cruising in 5th gear.
Was thinking of changing the diff ration.
Any help or info on whether this is normal or what my options might be would be great.