Bryan Lepley wrote:
> My top speed was 69 mph at 5,000 rpm.
> I know the speedo isn't off . . .
> The car doesn't have overdrive or a 5th gear . . .
> BTW it has a rebuilt TRF tranny in it from the previous owner.
I have a pretty reliable spreadsheet that shows speed vs. RPM, the variables
being tire size, rear end ratio and the gear you're in (It also calculates
the results for the two available OD ratios, but they're apparently not a
factor here).
Since all TR gearboxes have a 1:1 ratio in fourth gear, that's not a factor
either.
If you're in fourth gear at 5000rpm, and if Bob Lang is right about the
stock tire diameter being around 26.5 inches, the spreadsheet shows that
your speed should be 81 mph with the lowest available rear end gear (4.875).
And that rear end gear is pretty rare and hard to find AFAIK.
With the more common 3.70 or 3.45 rear end gears, your road speed at 5000
rpm should be 106 or 114 mph, respectively.
If you're doing 69mph in top gear at 5000rpm, there's something seriously
wrong somewhere - either with the car or with the assumptions we're making.
Whether the transmission has been rebuilt shouldn't be a factor, unless
someone has found a way--and a reason--to build a TR gearbox with a third
gear in place of fourth.
A seriously slipping clutch perhaps :-)
Jim Hill
Madison WI
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