How do you like your gear vendors?
Was it worth it?
Well, yes and no...
I do like it. It has made a great difference when towing my toyhauler.
The ZF 6-speed in these trucks has a fairly big jump in ratios between 3rd and 4th (I call "low" 1st, and "OD" 6th). When towing heavy, it's always a b!tch, 'cause you have to wind it up pretty high in 3rd to have enough RPM's in 4th, to stay in the torque band. So being able to split the gears there really makes a world of difference. In actuality, you can split the 2, 3 and 4 shifts, so you end up with 9 (or even 10) forward gears. Also, you can double-overdrive (6th-over) and really drop the R's. Having had my truck in excess of 100mph a time-or-two (not towing, obviously), it was cool to drop the engine speed down to 24-2500 at ~120...
On the downside (which I didn't know 'till I bought it), I can't use my engine brake when the GearVendors is in high (OD). "Normal deceleration" is okay in high (according to the GV manual), but they say NOT to use any engine brake, except in the direct (low/under-drive) gear. It has to do with the way the planetary gearset is designed (helically-cut gears); it wants to "pull" into gear tighter under load, but wants to push out of gear under heavy decell. SOOO, no splitting gears (like 4th under to 3rd over) when descending a grade.
But, I've grown accustomed to it now, and it's not that big-a-deal. Still a GREAT asset for towing.
The other thing is, it can shift a bit harshly, so it takes some finesse, and a feel for working the accel pedal and/or clutch. But it's a short learning curve. Once you learn the feel, it works good.
I should mention: putting a GV in requires MAJOR driveline alteration. The front shaft [of the two-piece rear drive shaft] is lengthened (actually, a new shaft is fabricated) and the rear shaft is shortened, and the carrier bearing is relocated rearward (it comes with all the necessary bracketry required). The driveline shop I used locally, is well-versed in the modifications required for the GV install, so it all worked well. I did have a slight drive-line issue (vibration on takeoff) after it first went in. However, correcting the driveline angles, by lowering the carrier bearing, solved the problem.
I also found (while troubleshooting the vibration) that I had a TON of axle-wrap occurring, particularly when towing (I'm sure this was happening before the GV went in, but I never really thought about it). So I threw on a set of FabTech traction bars, and that eliminated that issue COMPLETELY! The traction "feels" so much better now... like the road is right there; not as "spongy" as before. It's hard to describe until you feel the difference, before and after. I highly recommend traction bars to anyone that tows.
Lastly, I didn't use ANY of the electronics that came with the GV. I designed my own circuits and installed them instead (to prevent operation in 4x4, reverse gear, etc.). My take was that the electronic module that they supply is more suited to an automatic trans., not the manual. I also used an old-school, two-speed red "push-pull" switch on the my stick, instead of the little funky rocker switch they provide.
Sorry for the book-length post. I like to tell the whole story...