Hi! I'm having the rear differential on my 68 vert redone at a local shop. I've looked at previous posts discussing gear ratios, etc. I plan on having a standard 400 build with just a little more punch, correct turbo 400 auto, with AC. I'll be doing highway driving and around town on 15" Rally II rims with 235 or 245 60's all around. I know tire height makes a difference. I'm thinking 3:36 or 3:42 gears with a posi carrier. I think 3:55 would be too high. Stock was the 2:56 open. Any huge difference between the 3:36 and 3:42? What manufacturer do you all most recommend? Auburn, Dana, Yukon, Eaton?? Appreciate the feedback!
I had my tranny builder beefup my TH400 with better/stronger stock components and a shifter. You can you the stock shifter for the wholesome look or after market one. Either way your going to bury the guy with the 4sp standard. My 400HIO has A/C as well and thus came with 2:56 gears. The owner replaced the 2:56 with 3:91 and turned of the A/C. I bought the car and played with the 3:91 ripping up the pavement. Lot's of fun for a summer, but not practical for old farts. I have my 3:42 Posi available so I'm going to use it as I sold the 3.91. I think it will be a good combo. Make sure you use the stock Qjet and your ready. IMO, get 3:42, I'd be pissed if the engine booged on 1st jear with 3:36
Engine Test Stand Playlist: https://www.youtube.com/playlist?list=PLwoxyUwptUcdqEb-o2ArqyiUaHW0G_C88 restoring my 1968 Firebird 400 HO convertible (Firedawg) 1965 Pontiac Catalina Safari Wagon 389 TriPower (Catwagon) 1999 JD AWS LX Lawn tractor 17hp (my daily driver) 2006 Sequoia 2017 Murano (wife's car) 202? Electric car 203? 68 Firebird /w electric engine 2007 Bayliner 175 runabout /w 3.0L Mercuiser__________________________________________________________
