I´m running the S6 650 in my truck, a 78 K20... I think it is a great shifting tranny. Better than any other truck manual I´ve drivven before. But Larry is right, you need to pretty much cut out the whole transmision tunnel and fab a new one because this tranny is about 2 to 3" higher than the stock 4 speed...
Was it a lot of work to put it in: YES, youbet. Was it worth it? I would say so as I don´t know many 78 K20s with a 6 speed manual!
I´m happy with the swap.
And to the shift pattern: there is a reason for that. rev. and 1st are in line, so if you back up a trailer and need to go between 1st and reverse a lot you don´t have to switch the gate -> faster shifting. And mine also has a huge resistance to go into the rev./1st gate. you almost have to slam the leaver over to even get into that gate. so going into 2nd to start out is as if there was no gate to the left of it. Seems like you must have a realy early version. Mine is from an 06, so the last year they were offered.
I absolutely love mine behind the 6.2l L92.
Quote:
Originally Posted by DirtyLarry
Muckmorris,
I am not running any kind of speed sensor. Just the stock speedo cable from the NP205 tcase to the speedo head.
Critter,
Nah, I never considered a ZF S6-650. I have one of those behind an 8.1L in my 2500HD and not real fond of it. It is one awkward shifting transmission. Have you ever driven one? The NV4500 is so much nicer shifting. Aside from that, I don’t think it would fit without a body lift or significant firewall and trans tunnel work. The ZF is HUGE but is probably a much stronger trans than a NV4500. I haven't heard of any ZF's with OD gear set issues or anything else that the NV4500 are famious for 
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