I think the 3.08 and 3.42 gear are the best high highway use. The 455 torque allows these gears without too much acceleration loss. A 350 needs more gear. most tire shops will help you with fitment, I have seen 245/60R15 on the 66s however I’m not sure if it took any mods to fit them.
Based on him kinda wanting everything at once, I'd suggest 3.08's...he doesnt specify what axle he's using but both 8.2 and 8.5's have the ratio available.
"My bad to get off topic but jw I have a 66’ skylark custom red and white convertible 455 big block with Holley efi sniper and mild cam and headers and intake manifold and air filter and aluminum 3 row radiator and fan and more it had a dual plane intake manifold and dual Holley 850cfm 4 barrel carburetors but insane hassle and unless just use at track and adjust it after every time then it would be worth it but still feels like picked up more power once EFI installed also so I think installing Holley sniper efi system adds more power then dual 4 barrel Holley carbs do and all that but first does anyone know what size is the biggest 15” tires you can put on the car without rubbing or custom modifications like 225/75R15s or 235/75R15s? And second if you can’t get a fan shroud for that big block 455 and it has new 3 row aluminum radiator and aftermarket mechanical fan can you just install a electric pusher fan I front of the radiator too make up for the shroud and would an extra fan on front of radiator and the one on the back pulling and pushing air same way make up some for no shroud? And lastly if anyone’s knows best gear ratio for 455 with th400 auto 3 speed auto non overdrive or my car at around 75mph does 3400 to 3500 rpms with no overdrive 3 speed automatic transmission what would be the best possible gear ratio for it for lowest rpms on the highway without having to install overdrive but at same time not losing too much power for in town or sometimes racing i guess lol maybe like 3.08 or 3.23 or 3.42 or 2.97 or 2.87 maybe? And thanks again and sorry for being off topic here again but any help would be huge help can’t find anything on internet so finally just putting on a forum post lol" That is really hard to read One big run on sentence. Use 3.08 gears and call it done.
I liked my 2.56 gears...could go thru traps in 2nd gear then have the 2.56 for cruising...still ran high 12s with mild 455. Poor man's overdrive. I found 3.08 not good for either cruising (too many rpms) or track (have to go into third gear)
2.93 was stock on 66's, should be easy to find. I've run 275/60-15 on the rear of my blue 66 but wheel backspacing needs to be perfect to center the tire in the wheel well. Here's a handy tire size calculator/comparison tool: https://tiresize.com/calculator/ The 275's I used were 28.2" tall and 10.8"wide. A 225/75-15 is 28.3" tall and only 8.9" wide, it should fit no problem. I would put the taller tires on the car before changing the rear gears. Taller tires will reduce your highway rpm and costs less than a rear gear change.
285/70-15 is what I used when I drove BQUICK to track with 4.10 gears....still alot of rpms...but some help....30.75 tall
I have an 71 8.5 rear end with 3.08 gears in my 66. I'm running 235/60-15 with stock Buick rallyes. It runs down the hwy at about 3000 rpms. Ran a best of 13.03 @ 101 this yr at the Nats. Tires are a bit close to the fender, probably due to the wider 71 8.5 rear and different than factory springs. Check out this thread for more info on rad fan shroud info and other 64-7 Skylark 455 swap info. https://www.v8buick.com/index.php?threads/64-67-455-swap-important-information.368809/
I got 275s inside my 67 convertible, I have to check but I'm pretty sure 6 inch backspace, 8 inches wide
As the speed limits on the highways increase,the numerically lower gear become more desirable. If you do a lot of highway driving with a typical 455 and a 3-speed transmission,I would suggest a 2:73,3:08,or 3:23. Some of the Buick rears have a 2:93. I have a complete 2:73 posi 12-bolt Chevy that I am restoring and will be for sale,if that interests anyone.
Great info thanks guys big time and yea books and school weren’t my strong suit hahah and so I heard great things abt I should put a 9 rear end on mine but yea I I think maybe the 3.08 would work maybe best with taller tires but i will wait once the tires are put on for sure first and test it it should have a 2.78 I believe maybe I’d have to check again but another question I had is it has no fan shroud with a new aluminum 3 row radiator on it now and about to install the high flow water pump also on it and a buddy said he can make a shroud out of a used old shroud he has lying around but if I get a shroud on the radiator would it still help more also to have the mechanical puller fan then shroud and radiator then also in front a 16” pusher fan 2,500 to 3,000cfm I front of radiator just for some extra help or would u not see a change I’m thinking it would help the puller fan pull more air through the radiator but also it is a obstruction still but I would get the thinnest pusher fan for the front for minimum obstruction of air also hat do y’all think?? And also if I get a chance should I do a 4 speed manual I love manual but no overdrive vs a 4 speed automatic with overdrive jw since I seen usually in most case around same price when done or so
And I’d have the electrical fan switch off at like 200 or 210 hooked up to my Holley sniper efi system so wouldn’t stay on always also
I run a 2.56 gear with a 2004R and it turns 2150 RPM at 100 MPH. Works great. My other Buick has 4.56 gears, 33” tall tires and it turns 3100 RPM at 100 MPH. I wouldn’t bother with a 9”, my 71 8.5 handles 600+ Hp with some upgrades and Mosier axles.
oh wow and so u have had 3.08 wat was bad about it jw? And I’m just not wanting to loss too much power but that would be great rpms also
I know this isnt an English forum, but you REALLY need to use periods, and commas, its VERY hard to read and understand
I always loved my 2.56 gears, and was able to run high 12's and drive all day long on the highway (including a few trips from MA to Bowling Green). For people who just have track cars, a 2.56 isn't what you want. But for those of us who like to spend quality time behind the wheel, I can't recommend a 2.56 highly enough. The 455's have PLENTY of torque and don't need numerically high gear ratios to go fast. Just make sure you don't have a high-stall convertor with tall gears, they will slip a lot and create too much heat. -Bob C.
