[67_C-30]

Originally Posted by mal68ibu

I could kick myself square in the.........well. I personally chopped up that harness in the 93 3500 I pulled my motor from not having any idea what it was. I've now clocked 4000 miles on my "new" truck and have tweaked the fuel mileage up to 14.5 on the highway. I made a bed extender for it out of one of the factory stainless ford units. Huge difference on the HWY. I also stumbled across a Doug Nash (US Gear) under over drive unit for a TH400 at my local pick N pull so that is how I'm getting my overdrive. Tho a 4L80E would be AWSOME.

No doubt about it, an OD would be nice. I did a little number crunching, and found that my set-up is going to be really close to a 4.10 geared truck with a 4L80 in the higher gears, and a little lower in the first 2 gears, so it should work out great. It's amazing that my 3.21's with the NP435 is going nearly identical to a 4L80E truck with 4.10's on the interstate. I'll be able to run 70 at around 2400RPM, and have plenty of gear getting a load moving in the 1st and 2nd gears. I had a '91 C3500 with a service body that had the 4L80E and 4.10's and it worked out well. Here's the comparison between the 2. The top chart is the NP435 with 3.21's and the bottom is the 4L80E with 4.10's.