i came across a disc brake rear from under an 85 iroc. the owner said the rear was rebuilt with 4.10 gears as a posi unit. its a ten bolt.

when i get on it both rear tires spin. when its up in the air, and i turn the driver side wheel forward the passenger tires spins backward. thats not a posi but an open rear right?
i also used a piece of string and taped it to the drive shaft. (aluminum factory) one full turn of the wheel (17 inch) is two times around the shaft. whats the math on that and make the rear ratio?

i have a 5 speed and think the gearing is too much. am i wrong? its a driver not a track car.

 

Check the 10-bolt FAQ for info.

JamesC

 

Did you have the car in neutral? If it spun both rear tires it is a limited slip, if however you had it in gear or park when you made your test rotating one wheel forward will make the other reverse.

 

it was in nuetral. so its limited slip. now i need to figure out the gear ratio.

 

2 drive shaft turn for one wheel turn is a 2:1 ratio, that can't be right. Bock one of the wheels from turning and check it again.

Do a burnout, 2 solid black lines equals either a limited slip or locking rear. Not sure which one of the 2 'posi' refers to.

 

after reading the 10 bolt faq, it appears i have a limited slip. with two turns of the wheel for this rear it seems its a 4.10 rear.

as a weekend driver and not a track car, what would be the best rear end ratio for a 305 tpi 5 speed.? i think this 4.10 rear is too much.

 

The L69 cars had 3.73's. I like 3.23's as an all around gearing.

JamesC

 

well, if anyone has a disc rear with 3.23s and want to trade out let me kow. im in the savannah ga. area.

 

No thanks bro, I love my 4-wheel discs and 3.23 posi 4.10s are for like a drag car, the only time I ever see myself buying a set of 4.10s is on my 2nd gen firebird Drag car I want build for show and drag use

 

my point exactly. this rear belongs under a drag car, not mine. ill come across one or just switch the gears out.

 

With a long-tube-runner TPI set up you don't need 4.10 gears. Those gears would work well with a high-rpm engine with a mini-ram style intake. 4.10 gears will quickly get you up out and away from the low-midrange rpm band that TPI works best for.

With TPI the deepest I would go is 3.42, just like GM did with these cars. 3.23 gears are a good all around ratio as well.

 

Your tpi is better off running with 3.27"s or 3.45"s, running 3.73"s or 4.10"s will make u lose a lot of torque cuz rember 305"s are torque monsters

 

So, when you popped the cover off to verify the PO's runny-mouth, what did you see? What was the ratio? Was it a posi?

Nothing else matters besides THE PARTS. Only way to be absolutely positively 100% ironclad CERTAIN what those are, is TO LOOK. All the spin-the-bottle and posting on the Internet and all the rest, is a total waste of time. Go turn 10 little screws and GET RIGHT STRAIGHT TO THE UNVARNISHED TRUTH. Why do people INSIST on wasting their time, everybody else's, and all that valuable bandwidth, on a bunch of spanking off about a bunch of "maybe it's this, maybe it's that" BS instead of FINDING OUT WHAT THEY WANT TO KNOW?

 

Dayum Sofa!
tonys91rs: dude, if that was a 9 bolt I'd trade you straight up. Mine's a 3.27 but I'm afraid I'd kill that 10 bolt in short order.
I do have another 9 bolt that needs a gear set, a posi rebuild and a set of wheel bearings due to some moron storing it with the cover off.

 

The only way you can be sure of what you have is to remove the cover and look inside. A good posi (limited slip differential) will turn both wheels in the same direction when you have it off the ground. A worn posi will allow one wheel to spin in the opposite direction, so you can't be sure of what you have unless you look inside. The Governor Lock will allow the wheels to spin in opposite directions until they reach a certain speed, and then it will lock up and both will go in the same direction. A standard differential will almost always make them turn in opposite directions, but a standard differential that has been damaged from doing too many one wheel burnouts will make them both turn in the same direction. So you see, there is NO WAY to tell what you have until you remove the cover and look at it.