Just a thought or question about “double” overdrive

[Vitaliykit]

One of my vehicles is 2000 F-250 with 7.3L that is mostly driven with no load on it, but I like it because of the power and reliability. One of the thoughts I have is this: if I drive my truck unloaded with all this power under the hood, why not add an extra speed (double overdrive) to save some fuel while driving on a freeway? Any one has done it? Is it even possible? Is there anything like that on the market? Not my next weekend project, but this thought is not leaving my had.

[milleroutdoors]

Gear Vendor builds an over/under drive unit that works well. Expensive but works very well.

[Vitaliykit]

Good stuff, but $3,000?

[5280]

I have a Gear Vendors OD in my 92' 1T Chevy. Works pretty slick as the truck has low gears in it. Pulls great and I can still run low RPM on the highway. The previous owner installed the unit for towing a very heavy trailer, he wanted to have the ability to split gears. I have been thinking about seeing if I could install the unit in my Ex as I very rarely drive the Chevy. 1600RPM at 75 MPH would be sweet with a PSD!

[piotrsko]

my $.02:

not really sure if the trans input would deal with the torque @ 1600 doing 75 mph.

[Mark Kovalsky]

Originally Posted by piotrsko

not really sure if the trans input would deal with the torque @ 1600 doing 75 mph.

That won't be a problem.

[gasgrunt88]

Why is that not a problem Mark? Could someone explain this in a little more detail. I.E. over/under drive, double overdrive, etc.

[Meeks]

subscribing

[countrycar]

Originally Posted by 5280

I have a Gear Vendors OD in my 92' 1T Chevy. Works pretty slick as the truck has low gears in it. Pulls great and I can still run low RPM on the highway. The previous owner installed the unit for towing a very heavy trailer, he wanted to have the ability to split gears. I have been thinking about seeing if I could install the unit in my Ex as I very rarely drive the Chevy. 1600RPM at 75 MPH would be sweet with a PSD!

Give gear vendors a call and they will sell you any adapters you need, in order to make the change from vehicle to the other.

[Highboosted]

Originally Posted by gasgrunt88

Why is that not a problem Mark? Could someone explain this in a little more detail. I.E. over/under drive, double overdrive, etc.

The overdrive unit attaches behind the transmission, not in front, so nothing changes about the input shaft. The amount of torque at the input shaft at 1600 RPM doesn't change no matter your rear overall geaing, only the engine affects that.

[parkland]

Originally Posted by Mark Kovalsky

That won't be a problem.

What I would like to see, is a unit that attaches between the engine and transmission.

Driving the transmission faster than normal would allow higher axle ratios and less stress on the tranny.

Not to mention, it would be awesome for people who are creating ridiculous amounts of power, or for me if I ever put a 466 in a superduty.

[totin_tools]

I have a US gear setup. Heavier duty rating then on the gear vendors. Can be used in reverse. 72 mph with 4.10's is under 2000 rpm now.

[Mike Allen]

Good info....thanks

[kelwar]

i was also considering doing this to mine but with the price of the overdrive i desided against it unless i can find a used one or a good deal somewhere

[Power_Hungry]

I've installed both Gear Vendors and US Gear overdrives and both have their positive and negative points. I personally like the G/V units as they are smaller and lighter, easy to set up, and function basically as a mini automatic transmission.

The biggest downside on the G/V units is the fact that they don't handle negative torque input (deceleration) very well. If you are heavily loaded and use an exhaust brake, you run a good chance of burning up the friction clutch on the gearset.

If you plan to do some serious hauling and use an exhaust brake, the US Gear set seems to be the better option.

Hope this helps.