hi I have a 1980 gmc school bus with a 350 engine and 350 trans well the trans is a little rough it won't go into park and it feels as if it is not engaging fully so i think i am going to get one from a salvage yard my question is about the 400... would it be a wise option to get a 400 trans for it rather than a 350, would this make a difference in the speed of the vehicle, basically i want to be able to drive on highways with it, which means 70 mph which the engine seems to scream at 55 mph how can this be done must the gears in the rear be changed or something????

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(This post was edited by tusseltussel on Feb 15, 2008, 6:49 AM)

They may be interchangable and I don't know. A salvage place should have listings for direct fits. The gear ratio should be the same at the trans and gears in the diff would alter that if wanted and an adaptor to make speedo read right would be needed.

The couple Ive driven or been in sure did scream RPMs at even 55mph which most don't need to do so often or for so long. The 700R would get you an overdrive effect and help with high speed use but would no doubt mean a change in the driveshaft.

You may or may not notice it but wind resistance on this is the worst possible. The resistance at 55 is probably 1/2 of what it would be at 70mph. With a 1,000 hp you'd have trouble busting 100mph with this thing.

Note: Wind resistance is exponential. Doubling speed triples the drag force. Look at what aircraft have to go thru to achieve speeds and lift. Just think of a mega ton 747 - with 300 passengers, cargo and the weight of the thing itself can lift at about 200mph!!
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/

You should have no problem switching to a 400 turbo. We switched back and forth in a Z-28 several times with absolutely no problems.

Thanks johnh61 - I just thought of one possible catch - the Olds trans didn't have a place for the speedo back when as they used the front left wheel. Bus may do that too and the extention housing would need to be swapped??

T
Tom Greenleaf - MetroWest Boston - USA
_________________________________________

http://www.autoacsystems.com/tomgreenleaf/