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Adding Overdrive to a vehicle |
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An overdrive will give you an additional gear above the normal high gear in a transmission. Its most common application is to reduce engine RPM on the highway, allowing less wear and tear, noise and improved fuel mileage. Overdrives mostly come one of two two ways: built into the transmission, (usually as a fourth gear in an automatic or a fifth gear in a stick trans) or as an external, additional gear box. The external overdrive can act as a gear splitter as well as an overdrive. In adding an overdrive to an existing vehicle, there are pros and cons to each method. Contents:Automatic Transmission Vehicles(click this link for general auto trans product info)
If you have an auto trans, and want to stay with an auto trans, usually, the easiest and best way to get overdrive into a vehicle with a 3 speed auto trans to swap in an auto trans that has an overdrive in it. (WHY?)
Manual Trans VehiclesConversion to a 5 speed is the general 1st choice. If you have a 4speed Ford or Chevy, and do not mind having a second shift lever sticking out of the floor, in many cases the Ranger Overdrive is a lower cost alternative. If you do heavy towing, a dual range is a good idea. Maybe even WITH a 5 speed.
Convert to an NV4500 5 speed manual transHD trans for Toyota, GM, Ford, Chrysler AMC or Toyota powered pickup trucks/offroad vehicles
Convert to an NV3550 5 speed manual transLight and medium duty GM, Ford, AMC or Chrysler powered 4x4 vehicles
"Dual Range" add-on overdrive/Gear splitter
> 10 speed /NV4500 / Dual Range splitter system"Ranger" Add-on Overdrive/Gear splitterLower cost alternative for GM and Ford powered pickup trucks, Broncos, Blazers, Land Cruisers, etc.
...and for early Jeeps using the Dana 18 transfer case... Saturn OverdriveConversion to an Overdrive Automatic Transmission is also an option
WHY to swap to an Auto-Overdrive auto trasn rather than use a splitter - OD on an auto trans: A splitter-OD WILL add overdrive, however will NOT lock the torque converter. Since you are lowering the gear ratio the engine sees pushing the car, you will turn less rpm, but more torque at the same speed/load. And it will be at a lower RPM, closer to the stall speed of the converter. This means that the converter will slip even more than it did before. So you will save some, but you will lose a bunch of potential savings because the slippage in the converter adds up to wasted fuel and extra heat in the trans. Also, a splitter will have only 20% overdrive. This is excellent for a splitter or a second OD, but for the main OD in most applications the deeper OD of the overdrive automatic is better. (Example: 700R4 is 30%, 4L80e is 25%)
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