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Old 04-21-2005, 11:03 AM
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350 vs 700r4

Well I have been looking into uprading my trans, I really want a 4th gear with some better top end. Im now running a 350th with a good shift kit and hardened gears. I just want to know how the 350 and 700 compare, What exactly is the lock up converter about, and any experiences you might have had with the swap. I also looked in to a over drive unite but I realized a new 700r4 set up to race will cost me 1000 less then gettin the over drive unite in. so any comments, critisims, or great thoughts let me know. my set up is below
350, bored .030 over, performer rpm intake, 2.02 heads, comp cam .490 lift, 286 int/236ex @ .050", 650 edelbrock thunderseries carb, msd 6al ignition with a 55k volt coil. 3.73 rear end.

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Old 04-21-2005, 05:49 PM
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7004Rs are great units and would make a great swap. They can be built for 400hp fairly reasonably. 200R4s are every bit as good and have a better ratio spread, for heavier cars anyway, and since they came on Olds and Buick wagons and aren't as sexy as 7004Rs that came on Corvettes, price is often a lot lower too. I can't think of a good reason not to switch.

The lock-up converter does pretty much what the name implies. A normal torque converter when the car is up-to-speed is operating as simple fluid coupling - power is transferred from the drive torus to the driven torus by high quantity of circulating oil. For there to be a transfer of torque there must be a slight difference in rotating speed of the two tori so there is a built in 1% or so loss in efficiency. To get rid of this loss, engineers designed in an electrically actuated friction clutch that locks the two tori together solidly so there is zero efficiency loss. This lock up happens at pre-determined time such as in OD at steady cruising speed. You can add a manual over-ride switch to lock it up whenever you want too.

It's a great feature and should be activated on any tranny that has it.
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Old 04-21-2005, 09:19 PM
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I'm building a 41 caddy street rod on a budget (aren't we all? ) Anyway, I'm using a 350/th350 combo that I already had. I want overdrive later when I can afford it. Thing is, I'll have to have a drive shaft custom made, then have to redo it to install a 700r4. A 200r4 is the same length as a th350, so I'm gonna use one of them.

To answer your question about the lock up..... All Torque converters slip once they get up to cruising speed. Its the nature of the beast. By locking all the internal parts together, you eliminate that slip. That will lower engine rpm, lower trans temps and increase mpg a little bit.
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