454
 

I have a 454 Suburban with a turbo 400 tranny I want to updat the tranny to one with overDrive can anyone point me to a good one that is realitivly cheap

700R4 or 200R4 are the usual GM overdrives. The 200 has much closer ratios than the 700.

I'd stray away from the 200r4 behind a big block. It takes a good bit of work and cash to make them stand up behind a motor making real torque. For towing, the 700 also has an advantage in that its lower first gear helps get things moving.

IMO, if you're willing to make an investment, look into a Gear Vendors overdrive unit. They work incredibly, you're not going to break it, and it makes towing a dream. It gives you overdrive and splits all of your other gears, basically giving you a 6 speed automatic.

'burbans that had overdrive have the 700r4 i believe. I dont remember if its electronically controlled at all, but if it is there are kits to bypass that. The 700r4 gives you a nice cruising rpm with the stock rear end.

You can find a 700r4 in a junkyard and summit racing makes kits so you will get the functionality of overdrive.

http://streetrodstuff.com/Roundtable...=1&msgId=67637
here is a forum which has a discussion very similar to what you are asking. very knowledgeable here.

thanks guys