Help with the dreaded 2.56 ratio differential
November 7th, 2009, 02:53 PM
#1
'71 Convertible
Thread Starter
Join Date: Mar 2009
Location: Tuscumbia, AL
Posts: 14
Help with the dreaded 2.56 ratio differential
I'm about to go through the differential out of my '71 Supreme Convertible. As expected, it's the dreaded 2.56 ratio. It is my understanding that the carrier won't accept a gear swap without a spacer and longer bolts. I really want to put a limited slip unit in anyway, so I'm I correct that the housing (stamped R6 if I remember correctly) will be fine and if I'm going to change carriers then the whole 2.56 stock carrier problem doesn't matter? What I'm hoping is that my housing will work fine with a limited slip (Eaton or other) and 3.42 gears. Thanks for any advice!
November 8th, 2009, 12:38 PM
#4
Registered User
Join Date: Jul 2006
Location: Richfield, Oh
Posts: 1,735
10 bolt 8.5
You are lucky to have the 10 bolt 8.5 as the parts are pretty readily available.
eaton
dura grip eaton
true trac
auburn
factory reconditioned units are all available
3.08 3.23 3.42 3.73 3.90 4.10 4.56 4.88 and on are gears out there new and used.
If you need a quote on parts PM and will give you something to start with your search.
Jim
eaton
dura grip eaton
true trac
auburn
factory reconditioned units are all available
3.08 3.23 3.42 3.73 3.90 4.10 4.56 4.88 and on are gears out there new and used.
If you need a quote on parts PM and will give you something to start with your search.
Jim
November 8th, 2009, 01:25 PM
#5
Registered User
Join Date: Nov 2009
Posts: 3
People really want those 2.56's? I've been sitting on a set for a bunch of years now. I figured that it'd be fun to swap out the 5.00's in my W-31 and see what she'd do for top end. The 5.00's only let her get up to 105. I don't know if I'd want to be putting all the extra strain on that aluminum carrier though. : )
November 8th, 2009, 06:30 PM
#7
'71 Convertible
Thread Starter
Join Date: Mar 2009
Location: Tuscumbia, AL
Posts: 14
Oh, I understand Larry! I actually bought my car in Tampa and drove it home to north of Birmingham, AL ... over 700 miles. Not only did it drive beautifully on the Interstate, but it got fantastic economy as well. That said, it's undergoing a body-off restoration and the days of roadtrips are over. A little around town and that'll be about it. I've done an extensive rebuild of the 350, which appears stock other than the intake, but it isn't stock . That, mixed with the 3.42 gear should wake it up a little!
. That, mixed with the 3.42 gear should wake it up a little!
November 17th, 2009, 05:57 PM
#10
Registered User
Join Date: Jul 2006
Location: Richfield, Oh
Posts: 1,735
gears
The freeway gears do better smoking on the burnouts because the tires are actually spinning at a higher rate of speed. NOT rpm SPEED. Look at your speedo and you will see what I mean. lol. The motor will not even be working up a sweat and the tires will be smoking like crazy... Jim
Jim
November 17th, 2009, 08:36 PM
#11
Registered User
Join Date: Sep 2009
Location: KY
Posts: 1,489
Oh, I understand Larry! I actually bought my car in Tampa and drove it home to north of Birmingham, AL ... over 700 miles. Not only did it drive beautifully on the Interstate, but it got fantastic economy as well. That said, it's undergoing a body-off restoration and the days of roadtrips are over. A little around town and that'll be about it. I've done an extensive rebuild of the 350, which appears stock other than the intake, but it isn't stock . That, mixed with the 3.42 gear should wake it up a little!
. That, mixed with the 3.42 gear should wake it up a little!You go from 2.56 to 3.42 you won't be waking it up a little. It will be like hitting Big Foot with a stick when he's a sleep. You better run.
November 18th, 2009, 05:16 PM
#13
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Join Date: Feb 2008
Location: Plano, TX
Posts: 11,798
Just obtain another diff assembly and upgrade that to the ratio of choice.
Then put the 2.56 one back in the closet in case you ever want to continue your road trips!
However, posi is almost a must with these cars, even with the 350s.
Don't some of the stock GM truck gears / carriers fit into these units?? I heard rumors...
Then put the 2.56 one back in the closet in case you ever want to continue your road trips!
However, posi is almost a must with these cars, even with the 350s.
Don't some of the stock GM truck gears / carriers fit into these units?? I heard rumors...
November 25th, 2009, 09:43 AM
#14
Registered User
Join Date: Oct 2009
Location: Erie,PA
Posts: 3,814
Most of the trucks with 8.5's have the gov-lock posi unit,which is equivalent to a grenade with a loose pin.
You will be very happy with a 3:42 in your car.You might even get better mileage than you do now.Your gear is a torque multilier.Having a 2:56 is like having it chained to a brick wall.Not as easy to get going,but runs at a lower rpm when cruising.It just takes a little more squirt to get it moving.The 3:42 will be better all around.
If you need help finding parts,I have plenty,new & used/rebuilt.
You will be very happy with a 3:42 in your car.You might even get better mileage than you do now.Your gear is a torque multilier.Having a 2:56 is like having it chained to a brick wall.Not as easy to get going,but runs at a lower rpm when cruising.It just takes a little more squirt to get it moving.The 3:42 will be better all around.
If you need help finding parts,I have plenty,new & used/rebuilt.
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