US Gear Overdrive Transmission

[v16cat]

2001 6 speed with 3. 55, what experience have members had with US Gear overdrive transmission?

 

[LarryB]

You can use the search function to find lots of posts on this. HERE'S what I found.

 

[pdolan]

v16cat:



I have been considering an overdrive unit for my F450 tractor and found that there were four on the market at one time (USG, GV, Mitchell and Advance Adapters). Mitchell is gone (was a nice remote box with several ratio choices), AA goes between bellhousing and gearbox (only fits separate bellhousing trucks - needs lots of re-location including gear lever), GV is 0. 78 ratio and too many prohibitions at my weight (usually 34k) so only USG was left at 0. 8:1.



Problem is, I want to be able to SPLIT gears on the top end (5, 5over, 6, 6 over) which the 0. 8 doesn't do that well. ZF6 is like your 6 speed inasmuch as ratio between 5th (direct) and 6th OD is 0. 72. For this kind of money, I want no compromise. When I look around, I find that the ZF5, NV4500, 518, E4OD and so on ALL are spaced 0. 7 to 0. 73 to overdrive. The problem is that the available aux trans products were all designed years ago when there were only 4 speeds around, that tended to space 0. 6 or so between the last two gears. For those boxes, 0. 8 was a perfect "split" ratio. For todays multi-gears, it is far too close to the next gear up (in fact, on the ZF6, 4-5 is 1. 25 which is exactly 0. 8 gap).



The NV5600 spaces much more evenly at 0. 7 or so on all of the last three gears (lucky you), but still can't be evenly split. So, the question is, what is it you want the aux box to do? If you just want a higher ratio final drive, either GV or USG will give you that. If you want to add a few gears by dividing the last few evenly, you are out of luck.



With this in mind, I called GV and USG last year. Neither would make a custom gearset. I was on the brink of making my own box, when I decided to give USG one more try (GV doesn't actually cut gears, so they were not an option). Finally, I got someone in engineering who understood exactly what my problem was. They took on the project to do a feasibility study of whether or not there could be a new ratio inside of the old box castings and gear forgings. This month, they finally agreed to run a test batch of 0. 8555s. A friend of mine in Texas will handle distribution to those who want to give it a go. If you are interested, e-mail or PM me and I will fill you in.



Pat

 

[Gary - K7GLD]

Good info above - and I will only add that I used a US Gear OD unit on my '91 Ram 250 with auto transmission for well over 100,000 miles - much towing in the Sierras and similar - with absolutely NO problems - unit was still working perfectly when I sold the truck after buying the new '02...

 

[Utah Willie]

US Gear O/D transmission

I've had a U. S. Gear O/D transmission behind my 5 speed and in front of 3:55s for 60k+ miles running between empty and towing a 13k+ Alfa fifth wheel. I have towed up and down some very steep, long grades throughout the West and Canadian Rockies and have had NO trouble with the unit save the slam one often gets when it shifts and of late, a little reluctance to shift immediately the first time after a long sit. The ratio selection has made the 5 speed a much more user-friendly transmission and when coupled with the Jabobs E-brake, an easily managed combo on the long, steep down hills. I chose the USG unit as I have a 4WD and it is the only one that goes in front of the transfer case allowing its use in the 4WD mode..... Gear Vendors does not. (well... didn't when I bought). I will never own another pickup without such a unit if I do any towing of near GCVWR as I do now. At 80 MPH... I tach 2000 RPM in fifth over. I usually tow in fourth over, however, as it keeps the RPM in a friendlier place.