So mid April I started what turned into an 8-week conversion. Out came the H55F with the T-case and the Mark's bellhousing adapter (sorry guys, already has a new home) and the Toyota rear axle. In place of all that went an NV4500 with an NP241 behind that, and a 14-bolt semi floater rear axle with disk brakes so I could have a centerd rear diff. The price was right, $30.00 for the axle. First off, I already had a 350 under the hood, that's the only reason any of this makes sense. I went to Moab last weekend, a bit nervous since I built the T-case myself, (that was ridiculously simple) and I also set up my own gears in the rear axle, something I have never done before. Anyway, love the trans! Excellent ratios, shifts beautifully, makes almost no noise at all and has a 27% overdrive as opposed to the 17% of the H55F. I highly reccomend this gear box if you're doing the Chevy thing. The new crawl ratio is right about 70:1. That is a whole new world! No more clutching in low range, the rig almost stops without throttle input. Climbing and descending rough stuff is so much fun when you can slow down to almost nothing. Mileage on the trip down was 17MPG, 16MPG on the trip home. That's up about 3 MPG and that's due entirely to the gear box changes; more overdrive, less power loss through the T-case. Anyway, I loved my H55F. But If you're going V8 power, you might as well get the NV4500, it's an awesome beast, and you won't be disappointed!
