904-based overdrives that don't suck as much power as the 727-based Turds.
Nice sentiment for the racing forums but hardly germane for a hauling truck.
I will try to answer this in not such a negative way but I agree with Grizzly.
I did the 518 swap from a 904, for the overdrive. This was on a 14 sec 5.9L Magnum in a 4000lbs 87 Ram.
The original 904 with it's deep 1st and good efficiency seemed run good w 2.76's. No official numbers with this combo since the trans failed in a few weeks.
Swapped to a fresh hydraulic 518 with lockup and 3.55's. Truck had a taller 1st so a swap to 3.55 was absolutely necessary. Mileage seemed the same, high teens and the power was 15.0 @ 90.
The 518 eventually lost overdrive but I continued to drive it for a year. Without the overdrive my highway cruising speed changed from 120km/hr to 100km/hr which even without the OD, the lower speed made my mileage calculations spit out the same high teen numbers.
Up to this point, I still liked the 518 but a switch to a NV3500 5 speed manual transmission made me realize Grizzly is correct.
The 3500 does not have good ratios for racing but the truck went 14.7 at 93mph. To me this is HUGE. The mileage also increased to low 20's, again huge.
Those are solid numbers for you guys to soak in but some things can not be put in numbers like a bridge near my house. I had to switch the lock up OFF and 4rth gear OFF to comfortably climb it with the 518. Even though the NV3500 had a similar 5th gear, I could easily climb it in 5th. Same for towing a car. I would try to tow in 4rth with the 518 but it struggled so often I'd let her rev out and just tow in 3rd but the NV3500 had no problems towing in 5th gear.
