How do I know if a Cutlass came with a factory 4 speed

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Oct 26, 2018
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I ran across a 1978 2 door t/top cutlass Supreme, it now has an automatic, but still has the 4 speed linkage. Will the serial # tell me if it came from the factory with a Saginaw. It doesn't run the engine has been changed with what he says is a high output 305. I would want to put it back to a 4 speed , but it needs a lot of work
D. White
 

TURNA

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Where is the hole cut out in the floor It may have come with a 5 speed
 
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TURNA

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Red78Calais4speed

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The VIN # won't tell you if the car originally had a 4-speed but it may help to narrow it down a bit. The 4-speed in 1978 was only available behind the Chevy 305 V8 2bbl motor. The 5th digit in the VIN would be a U. For a 78 Supreme the VIN would start with 3R47U as the first 5 digits. California and high altitude cars also got the 305 V8 2bbl motor but only as automatics. Those cars would also have a U in the VIN. The 3-speed, 4-speed, and 5-speed manuals weren't available in California or high altitude locations. The presence of a U would help narrow it down a bit. Check the steering column for a key release lever just below the ignition switch. Only manual transmission cars got them. Otherwise, look for the build sheet (most likely under the rear seat). All 4 of the manual trans cars I've owned have been found there.
 
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DoubleV

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Turna, that's an interior pick of my actual car! Pretty funny you probably dug it up on the interwebz somewhere!

Another tell tale sign would be if the radiator was swapped, there's a chance it could had a manual trans radiator.
 
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GP403

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That's a 5-speed car anyway :p

If you can dig up the build sheet, it would show MM4 (I think) on there.

Why would they leave the shifter on the floor.... Seems a bit odd. I mean, is the linkage just flapping around under the floor or something? Does it still have the pedals and manual steering column w/ the key release switch? If so, all you'd need can be gotten aftermarket IIRC.
 
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pagrunt

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Sep 14, 2014
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Besides the MM4 RPO for merchidising there will be the M20 RPO for wide ratio 4 speed, the Saginaw.
 
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Steveshow

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Apr 13, 2015
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I ran across a 1978 2 door t/top cutlass Supreme, it now has an automatic, but still has the 4 speed linkage. Will the serial # tell me if it came from the factory with a Saginaw. It doesn't run the engine has been changed with what he says is a high output 305. I would want to put it back to a 4 speed , but it needs a lot of work
D. White

I assume that by "but still has the 4 speed linkage", you mean that it still has the clutch pedal and related linkage (?)
 
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TURNA

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OP .....and just like that "poof" he was gone............
 
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