C3 Corvette 3 speed man v 4 speed auto

[racer67]

I would like to know from other club members who may have a C3 1969 - 1973 if i would be better to purchase a 3 speed manual or a 4 speed auto. Which one would have the better performance & fuel economy if they where either a 350 or 454 big block. I am currently looking at purchasing a C3 and have looked at dozens which seem to have either one of the 2 motors in them in man & auto

Regards

Craig

[69 DIRTY RAT]

3 speed manuals are very rare! you mean 4 sp manual 3sp auto! Manuals are usually better on fuel. Big Blocks have better performance in a straight line, small blocks are more agile (because of lighter engine unless you have an aluminium BB!) and better on economy. Depends on what sort of fun you want to have? But I reakon Big Blocks are way more fun!!!!

[jdunne]

If you are concerned with performance v fuel economy then the diff ratio will have more effect than the gear box...both manual and auto are 1:1 ratio in top gear......a 3.08 diff will give better cruising and fewer revs at road speed whereas a 4.?? diff will give a fantastic launch(with lots of tyre smoke)and you will be doing 3500 revs at 100 kph....it is a matter of understanding what you want to use the vette for:luv john

[nifty]

my 74 has a 400ci (6.6lt) auto and chews fuel up around town....eg tanks lasts about 200km..and thats cruising with the occ BLURT......but its great on the highway.but then again....mate has a worked 73 with a 350 4 speed,and he gets about the same economy.

[427ozVette]

My 68 427 Tripower 4speed manual with 3.08 diff sucks the gas if you bury your foot down, however as dirtyrat says they are sooo much fun.

On the freeway just cruising, it is actualy very very good. I would easily get 200ks out of the tank. A round trip for me to Sydney is about 200ks and i do this on one tank and still have gas left for the occasional blast here and there.

[jdunne]

My 74 has a hot 383 with 3.08 diff and a 700r4 gearbox,cruising at 100 kph gives about 22/23 mpg,around town about 14/15 mpg,on the track about 5 mpg(it might be less but i'm not game to check):fun:fun:fun:fun

[RHD.68.l89]

IF you have a choice, choose a car with an O/D fitted. Jdunne's 700R4 is a 4 speed O/D auto and I have a 427 tripower with O/D manual 5 sp. I can easily get 400km to a tank, less when playing.
Usually the first gear is lower as well, giving you better "off the line" performance.