I hesitated for years after I built a 4.1 axle for my Spider. I reasoned that as my motor made good power to 7000 rpm I would never max it in 5th. In reality it went to 7000 easily in 4th but did not pull hard above 100 mph when I shifted into 5th. I finally installed the 4.1 last year at the same time that I got my 45DCOE's sorted out. Now it still pulls hard to 7000 in 4th but now I am doing 110 mph. In my case the 4.1 is better suited to my motor.
85 GTV6 3L
76 Suzuki GT500
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