Low Gears, a big block + Turbo 400

[Bosscar9er]

I'm looking for anyone who has experience with a big block 60s or early 70s muscle car with a 3 speed Turbo 400 and either 3:91 or 3:73 gears. I have 3:42s and thought I could lower it just a bit to enhance acceleration. This is a fairly low cost enhancement but I don't know if I will be happy with it. I posted a thread earlier (http://www.automotiveforums.com/vbul...ight=gears)and got a detailed response from a member recommending against changing to lower gears over the 3:42s. What he said made sense so I am leaning against it, however, is there anyone out there who has low gears that can tell me how it performs, and more importantly, are you happy with the gears? My car is a 71 Buick 455 that is not a daily driver, just used for shows and short weekend drives. I don't want anything that is going to cause the engine to wind excessively at 55 mph or cause mechanical problems.

[MagicRat]

I bought my '68 GTO (Pontiac 400, slightly modified, with a THM400) from a friend who had put 3:91 gears in it. He thought it would be a good idea.

It wasn't good. Any cruising over 40 mph was miserable..... noisy, high revving, uncomfortable and inefficient.

Low speed acceleration was not ideal. The car would just spin the tires through first and would actually accelerate harder in second.

One would have to use drag slicks to fully take advantage of such short gears. I swapped in a 3:23 rear end which is a MUCH better all around combo. It provides about the same 0-60 time and is much more liveable on the highway.

[maxwedge]

Seconded, especially with the huge low/mid range torque of the Buick and Pontiac big blocks.

[crazy Jim]

I have a '71 Cutlass (455/TH400). I installed 3.42 w/Posi to keep the engine in the strongest part of its power band. No need to rev it above 5500 for mild street use.