Rear Axle: Sky Hawk Rear End Ratio?

[345 DeSoto]

Am I reading the Shop Manual right, or am I missing something? It says that the standard rear end ratio for the Sky Hawk with an overdrive transmission is 3.92 to 1. Is this right?...

[Stunt]

Sounds like a good ratio if you have an overdrive. 3.92 would give you lots of pep off the line, and the BW overdrive, dropping your final drive ratio 70%, would effectively drop it to 2.74 when you kick the OD in - a great highway ratio, right?

[345 DeSoto]

That's what "I" was thinking...but is what I Posted correct?

[64studeavanti]

The 56J I just bought with t85 overdrive has 3.92.

[SN-60]

Yes, I think that 3.92 ratio was standard only on the 56J....with stick O/D..........A 56H with stick O/D would have probably been shipped with a 4.27 rear end.

[JoeHall]

Looking at Shop and Parts manuals, the 3.92 was standard in Sky Hawks, with 3.54 and 4.09 as optional. I have driven a couple of 56Js with the 3.92 and OD, and they seemed geared too low (high, numerically). At 2500 RPM in OD, the 3.92 runs around 70 MPH, but that is with a T85 tranny. With a Sky Hawk's T86, it probably would be around 71 MPH, due to the .7 OD ratio, versus the .72 in the T85. For those who like to play with numbers.

[345 DeSoto]

Thanks, all, for the help. In MY day, a 3.90 was a pretty nice rear end for the street. I'm hoping it will give my Hawk a little "snap"...if that's what it has...which is most likely...

[64studeavanti]

my 64 Avanti R1 4spd has 3.54. It is very drivable on the street and seems to have plenty of snap.

[StudeRich]

my 64 Avanti R1 4spd has 3.54. It is very drivable on the street and seems to have plenty of snap.

That is a good Medium Performance Ratio but, it does not apply to an Overdrive Car like Tony's in the least.

[JoeHall]

That is a good Medium Performance Ratio but, it does not apply to an Overdrive Car like Tony's in the least.

Since the OP's car was available with 3.54 as an option, driving the Avanti would give an idea how he'd like a 3.54 in his 56 Sky. Alternately, the Avanti owner could give him a driver's report, from behind the wheel, to include RPM at selected speeds, etc. A 3.54 would perform basically the same in both cars, except, the Avanti has no OD cable to push in, when tired of the higher RPM.