[TR] high engine rpm

[acs25m at swbell.net]

I own a TR250 that I am having problems with. The car had 185/65r 15 tires
on it when purchased. I knew that these were not the right size tires and it
was causing my Speedo to be off. Well I recently purchased replacement
205/70r 15 tires and with my wife pacing me in another car the Speedo is now
correct. My problem is that the engine is still running at a higher rpm than
I think it should. At 60 mph my tack registers right at 3500 rpm. I
downloaded an excel spread sheet that was talked about on line and the only
way to get that rpm reading would be with 4.55 gears. I don't have an
overdrive and highway driving makes the car overheat. Short of removing and
disassembling the rear end is there any way to tell what rear-end gears are
really in the car.

Any help would be appreciated,

John R Maneke