I'm in the proccess of purchasing a gear splitter for my '79 F-350 4x4 supercab p/u.The truck has a NP 435 tranny (truck 4sp manuel w/ granny low 1st gear) and I would like to split the gears and get a overdrive for it. I'm looking at U S Gear and Gear Vendor. Pros and cons with either unit would be apreciated.I understand that with Gear Vendor's you have to be travelling 20 mph and use it in 2wd only. With U S Gear, is it noisey and can the shifting device standup to constant shifting (splitting gears)and is 20% enough reduction? Are there other units available that can stand up to 450-500 lb.of torque and 18,000 GCVW?
Thanks in advance.Mike B.

 

Mike, there is a unit called Ranger Overdrive, I think you can see it at Advance Adapters. Only bad thing is it goes in front of the tranny and moves the tranny and case back about 7 inches if I remember right. The good thing is that it workes in 4 wheel drive as well as 2 wheel drive, it's worth a look anyhoo.
"bowties in the rearview mirror"

 

For the price and hassle, I would just swap in a NV4500 5 speed. It has a .71 OD and retains the granny first gear, (5.61), but the 2-5 gears are closer ratio and it is a smooth shifting transmission (MUCH smoother than the 435). You couldn't split gears, but you would have the OD and with the closer ratios, you might not have to split. I looked at the Gear Vendors/Ranger route but decided against the splitters because of cost, driveline/ crossmember mods, and some reliability concerns. The 4500 5 speed is very heavy duty and is the best choice in my opinion.

If you do an underdrive splitter, the Ranger is the best- but still no Overdrive!

 

TeleMike, would you consider an auxillary 3 speed ? I like the GV unit very much but it doesn't fit my budget at this time. If you don't mind used, how about a brownee ? The brownee is a 3 speed auxillary trans built by Spicer. Ratios are something like 2.54/1.00/0.75, it mounts between your 4 spd and T-case. You would probably need the divorced style case if you didn't have it already. One of our men, Charles F350, put a brownee in his '66 F350. You might ask him about it. DF