Originally Posted by TwinTurboStroker
Huh....excuse the guy who has no idea what your talking about......but hmmm, what are you talking about guys?
It's the manual tranny. The OBS trucks had the ZF-5 5 spd, and SD's have ZF-6.
I considered this swap my self, but came to the conclusion, that the only reason to do it would be if you had a really good deal on a ZF-6 or got one for free. Even the, I would only swap if the 5 was giving problems. Most people that consider this swap want a higher overdrive ratio and think the 6th gear will help lower the RPM at higher speeds. Both transmissions have almost the same OD ratios. The 6 has a little better spacing of the gears, but I don't think it would be worth swapping just for that reason.