When I use this calculator, I get that your RPM's should be 2864, using .86 as your T5 overdrive ratio. I wonder where the discrepancy is?
http://www.novak-adapt.com/knowledge/gearing
Speedo gear not matched properly? But you said you checked that? Hmm
I also get a discrepancy using this calculator, but it's been used a million times by others so I doubt it's wrong. The people at Novak usually know what they're doing.
the 258 has torque and can do well at lower RPM's.
In my experience, the T5's used behind the 6 cylinders have the .76 overdrive ratio. The 4 cylinder models have the .86 ratio.
Easy enough to figure out:
Hold engine at 3,000 RPM in 4th gear, shift to 5th, RPM will drop to around 2,280 with the ,76 5th gear ratio.
Hold engine at 3,000 RPM in 4th gear, shift to 5th, RPM will drop to around 2,580 with the ,86 5th gear ratio.
The three T5's I blew up all had the .76 5th gear ratio, which is steep if you are borderline on power band/tire size/gear ratio.
I'll check my green Scrambler and see what the ratio is.