what is the overdrive gear i hear about that bolts on to the th400. I have a th400 sitting in my garage and i would rather have that on my car than a 700r4. can someone give me a website?

 

also what ewill i have to do about the driveshaft?

 

It's a device made by a company call Gear Venders. It bolts onto the end of the transmission.

There's nothing wrong with a 700R4 as a street tranny. The very low first gear gets you off the line quickly with highway gears in the diff. The OD gives you good gas mileage with those same gears. Too deep a gear in the diff can easily overpower the tires in first gear because of the torque multiplication.

Using a TH400 or TH350 gives a better gear ratio in the tranny but doesn't give an OD. Using 3.73 gears or deeper will see a drop in fuel mileage on the highway since the engine is running at a higher RPM.

Adding on a Gear Vender OD unit onto the back of the tranny will give that OD gear but also adds more weight and length to the tranny. The extra length of the tranny will need a shorter driveshaft made up.

The ultimate is installing a 4L80E transmission. It has the same gears as a TH400 but has the OD built in. The downside is that it's an expensive computer controlled tranny and is very big and heavy.

A 4L80E with computer is probably cheaper than a built up TH400 with a GV OD on it.

 

what is gear vendors website?

 

http://www.gearvendors.com/