Is there any difference between the 3.73s and 3.42s at the track with an auto car? I would like to gear the car down for next year but im not sure witch would be better. o No: Im looking for the best ET I can get.:3gears:
It depends on the engine. The higher numerical ratio will help the car accelerate faster, and the RPM at the end of the track will be higher. The engine RPM will be higher at all speeds, so if you drive the car on the highway, you may want to consider that. BTW, to really answer your question, you need to provide a lot more information about your engine and modifications. I know you have probably listed it in another thread, but it is relevant here, and no one will remember what exactly that is.
What is the RPM range of the engine? If the engine is close to stock in the RPM range then there should be little difference between the 3.42 and 3.73 at the track. If the engine needs to get into the higher RPM to make power than the 3.73 gear will help more. What tire diameter are you using and do you plan on driving on the highway? I went with a 3.42 gear because I want both a good highway RPM and a good quarter mile time. A 373 would put my RPM too high at the track and limit my speeds on the highway. Since I am shooting for a 10 second run @ 135 MPH, and I want to keep the RPM at or under 6000 at the traps the 3.42 gear works perfect for me with a 26.5" diameter tires. On the highway with my 30" tall street tires I get 2600 RPM at 65 MPH which is perfect for me. @ 3100 RPM I could run 80 MPH which is as fast as I plan to run for long trips on the highway. Remember there will be a bit of torque converter slip so factor that in.
I also read that he ran a 14 second quartermile for a baseline... Based on that info sounds like the 3.42 is better for him since the low compression and stock cam will limit the high RPM power.
I had 3.90 in my 67 at 3850lbs with a hemi killer cam, headers, performer, and a 850 holley that ran 12.83 a 103. The heads are stock small valve and I put in a 3.31 to keep the rpms down and ran 12.68 at 106 last weekend. Runs nice on the road now!
I've read threads on this board about a few people who removed their 3:42s and installed 3:73s. The end result at the dragstrip was the same ET and excessive rpm on the highway. It's not really worth it for a mostly street or street / strip car. The torque of a big block Buick seems to do well with a 3:42 or 3:08 gear. That's why they didn't come stock with 4:11s like what some of our Chevy, Ford, and Mopar friends have. Buick engineers knew what they were doing. Stick with the 3:42s and your driving experience with your Buick will be much more appreciative. Especially on the highway. John B.
I changed from a 3:42 to a 3:73 in my 6 cylinder Regal that I bracket race and the car ran the same ET and mph but now turns to many rpm on the high way. Might be different with a V8 car but I bet its not that much different.
As many above have stated, you need a combination that works, not just new rear gears. You need to also have the proper tire choice and torque converter to match your engine's performance. Suspension tuning also comes into play as it all happens at the launch.
I agree on the 60 foot... only way the Muscle cars are going to get better etc is with more stick... Your 60 foot time will cut your ET ALWAYS. If you spin off the line your ET will supper PERIOD. Jim JD
thats right gears are used to optimize your car not to go faster to go faster you have to get more power or less weight just my own opinion scott
It depends on your hp/tq curves. If the rpm drop between gears doesn't drop you out of your power range then the gear doesn't change a whole lot in ET and MPH. Talking to several guys on Drag Week, they've gotten away from running 5.xx or high 4.xx gears because they ran the same ET/MPH with low 4.xx or high 3.xx gears because their engines had broad powerbands or their torque converter kept them in the power band after the shifts. It's all about applying the most average power to the track surface. I found when I ran 3.70's I hit redline as fast as I could lay the pedal down and since I shift slow (5-speed) it was better for me to get a lower gear. I'm pretty happy with the 3.42's right now.
Thanks for the info guys. I Think I will go with the 3.42s. Over the winter I plan on rebuilding my th400, adding a shift kit, 3000 stall. I also want to get a cam and the 3.42s. Someone suggested a TA 288-98 cam. Im going to the track sunday and Im going to try to break into the 13s as is.
Inflate your front tires to the maximum pressure, probably 35psi, to reduce rolling resistance. Take everything out of the car you can, spare tire, clean out the trunk, glove box and back seat. Not necessarily remove the back seat, just don't haul a bunch of junk down the track. These are all free and good for 1 HP on the butt dyno. In the old days, John Osborne used to say you needed at least 1/2 a tank of gas to keep the pickup from getting uncovered under a good launch. So, every pound you can shed is like free HP.
