I am wanting to put a 4 speed auto overdrive behind the 403 in my 78 Electra. I am wondering what will bolt in behind it. 200r4, 700r4, 4l60

Tim

 

I'm not an expert with the overdrive trannies so others can chime in and share more details. I'm under the impression the 700R is Chevy bolt pattern only, so unless you use an adapter it won't fit. The 200R4 will bolt up fine but has a reputation for not being strong in stock form. I thought the last one needed a computer to make it work, so I'd lean toward the 200R4 and either drive easy or have a good trannie shop beef it up and have some fun. I've also heard that unless you have low gears to begin with, say 3.42 or lower, you may get worse gas milage with the overdrive because it may cause the engine to run at too low an rpm to be efficient. My 2 cents worth. John

 

You are correct John, the 700 R4 is a Chevy bolt pattern only. The 200 4R is a good transmission; however, it needs to be beefed up to withstand the torque of an Olds motor. I suggest looking into Brian Hofer's work. He builds stout 200 4Rs for the turbo Buick GNs. I have read that he does good work. Check it out.

http://www.turbobuick.com/forums/ven...r-trannys.html

 

You probably have a long tail shaft transmission in your vehicle. The 2004r is the same overall length as the T-350, so you might need a longer driveshaft.