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I bought a 1990 Brought with a 307 with a 200r4 transmission in it. But the motor was bad. So I had Olds 350 rebuild and put in it and kept the factory transmission. I changed the factory carb and distributor to aftermarket. The issue I'm having now is the gas mileage sucks. And the power isnt there like i was hoping for. So I done some research. And I've been told when I changed everything. The tranny won't lock up. That i need to put the factory parts back on it. Is this true? Or is it another way to make it lockup. And will that help on gas mileage?

Thanks!!
 

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1991 Cadillac Brougham D'Elegance 5.7 Litre, 1994 DeVille
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6,796 Posts
lockup shouldn't affect performance. but it will improve gas mileage maybe a little bit. Those transmissions are in a lot of cars that have had engine swaps, carb changes, and anything else you can think of. It shouldn't be too hard to make it work with your combination.
Those 350s were never known for good gas mileage.
 

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87 Brougham
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Hey I have an87 brougham. 2ND gear is slipping and grinding and I have fluid so I guess I'm gonna have to buy a trans. But what trans should I got. I'm thinking when I have the $ I wanna put a 403 olds motor so what trans should I buy now and still use if I upgrade the motor?
 

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70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
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3,310 Posts
If you put a non-overdrive trans in it like a th400, you will miss that overdrive very soon. I did it and that thing revved pretty high just to go 55 mph . I would try getting the stock trans rebuilt and hope that it lasts a while. They can be rebuilt stronger than stock.
 
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