Have a 2.56 rear currently in my 71 Skylark 350 with a 4bbl, headers, Magnaflow exhaust and Petronix ignition. Is there any benefit going to a 3.08 or higher ratio other than the obvious? I know I'll sacrifice some MPG changing things but it doesn't mean as much to me as getting more out the the car. Looking to get the most out of the car without ripping the motor apart.
Steve, It all depends how much you want out of your car. I have a 72GS with a Buick 350/ Turbo 350 and a 3:08 rear ratio. If you want want some serious performance I would go with a Bucik 3:42 posi and kill two birds with one stone. Your off the line performance will be great but highway will will suffer. Gary
Thanks Gary, Guess what I'm looking for is some sort of compromise as my motor is not built up and I want to make the most out of what I have. Still need to use the highways!
3.08 is the all around compromise gear without an Overdrive trans. 3.42 revs a bit on the hiways. 3.23 splits the difference. especially considering the stock motor Id say 3.08s will be just what youre looking for. my $.02
I am in the process of doing the same with my 71 GSX clone. I decided on a 3.23 since I run a taller (28") tire. Play around at the site below and decide what RPM you can live with on the highway. http://cyclone.he.net/~idea1/gearhead/
Thanks for the info guys. I should have mentioned I'm still using 14" rims and tires as I like the look!
Watch the 3.23 gears on the 8.5...They one of the most expensive gears...Just something to think about. If you find a used set for less than 100.00 grab them. Jim
It will be noticeable. Both in the get-up-and-go department and the hiway cruising rpm department. 3.08s are strong all around cruising gears IMO. You will be going from a fuel economy minded gearset to a compromise gearset. Remember you'll need to change your transmission speedometer gearing to match your new ratio. Easily done.
Going a 1/2 a ratio is bigger than you think. You will notice a difference. 3.08 are very plentiful and 3.42 are plentiful in the aftermarket and 4x4 trucks and full size Vans with over drive.
Since my gas mileage isn't that great as it is I'm not too concerned. However, as I like to cruise on the higway as much as I like off the line pull I want to try to make the best choice overall. Only posi I ever had was 3.73 and she wined on the highway.
clutch style limited slip. common for the 8.5, rebuildable, best of both worlds traction wise. 3 series units on ebay go maybe $180-$225 (#410408 Chevy, #725 BOP) 2 series units go maybe $135-$150 (#410409 Chevy, #726 BOP) Theres also lots of aftermarket support. Nice new diffs.
3 series carrier can be used with 2.73 and higher (numerically) ratios, without a ring gear spacer. 2 series carrier will need a ring gear spacer (Mr Gasket 908A) to use those gears.
You currently have a 2.56 rear. That means you have a 2 series carrier. If you are just going to change gears, you need a spacer. If you're going to do gears and go to a posi, you need to buy a 3 series posi carrier. You can find a used GM unit, or buy a new unit. Doing this will eliminate the need for a spacer.
Just to let you all know the clutches are getting harder to get through the dealer and aftermarket prices are high. Spider gears are not available I found only 3 sets in the country and they were 350.00 a set...??? Geez. So I am sure there are plenty of used unit still in the yards BUT do not count on too much more NEW NOS parts . Just some added info for you to chew on. Spacer is not all that bad as long as you are reasonable and are not going to race everyweekend with more that 500 HP etc. Street you will be fine. If you find a 2 series at a decent price you may want to get it and a spacer. Sometime 8.5 3 series used are beat on a bit more ... Some more thoughts...
Re: Last gear question. Any opinions which is the best overall gear for street and highway. Will eventually work the motor but for now its all bolt ons, trans kit etc.
