HI, looking for some rear gears help

[pedal2themetal]

HI all,
I have a 75 fury with 318.
Looking to have the heads reworked with bigger valves,
Bigger cam ( I have a .440 IN,EX. in it now) but want to go better or bigger.
Carb is a 450 cfm QFT. Holly, well go bigger if have/need to..
Tires are P225 X 70 14"
I'm thinking it has the 2.73 Rato single leg rear end. 8.25 rear end, Dog off the line. What would be a good Ratio for street and highway. Car is Daily driver and don't want anything crazy. Just more pep off line.. OH and locker or limited slip.

Thanks take care be safe
tim

 

[Aron Gleason]

8 3/4 rear end with 3.55 gears. Either the 742 or 489 case.

 

[Kern Dog]

8 3/4 rear end with 3.55 gears. Either the 742 or 489 case.

There is no 8 3/4" axle made to fit the '75 models.
The car probably has a 2.71 axle ratio. 2.73 is a Chevrolet ratio.
A 3.21 or 3.55 is a good ratio. They can be found in any 8 1/4" axle up to around 1996.
You do not want a locker for the street. Clutch or cone limited slip differentials are great though.
Look at Dakota and Durango models with 4wd.

 

[Krooser]

Forget the larger valves...a waste of $$$.

 

[#41]

Depending on speed and amount of highway time, generally I would suggest a 3.23 or 3.55, but also matched with a larger diameter tire than what you are running to help keep the high revs down.

 

[PurpleBeeper]

There is no 8 3/4" axle made to fit the '75 models.
The car probably has a 2.71 axle ratio. 2.73 is a Chevrolet ratio.
A 3.21 or 3.55 is a good ratio. They can be found in any 8 1/4" axle up to around 1996.
You do not want a locker for the street. Clutch or cone limited slip differentials are great though.
Look at Dakota and Durango models with 4wd.

Really? I had a 77 Cordoba and a shop was able to install and 8-3/4” from some other car when the factory rear ended broke. I wonder what car it came from?

 

[Curiousyellow71]

There are C body 8 3/4s after 70 that should be wide enough for a fury. The perches would need to be moved. The 71-74 b body 8 3/4 are hard to find would also work or even a D100 pickup. But..I would just fix up the 8 1/4.. it is not a bad rearend for a 318.
I suggest getting a custom torque convertor. Several good companies out their but PTC is pretty reasonable on their prices. That alone will transform the car. A good unit will move the car fine cruising and flash more up in the torque curve..I would try for at least 3500. Have it made tight so it moves the car fine at the lower speeds. You don't want a loose convertor unless you stay below a 2500 stall on the street with 3.55.
Going to a salvage yard and finding a sure grip and a 3.21 for the 8 1/4 Is a excellent idea. 3.55 would be ok if you don't do much interstate driving. 3.90 if you want it to go from stop light to stop light.
Bigger valves aren't a good fit on the 318 heads...pick up some later model heads possibly. They flow better..but do some research before you buy. Older 340/360 heads will lower the compression..but will make up for it in performance. They don't help the low end though.

 

[Don Frelier]

14" wheels surprise me?

 

[1967coronet]

I can not tell you about what will or will not fit on 8.25 to 8.75 Rear end swaps.
What I will add is with the smaller dia. tire you are useing the 3:21 / 3:23 gearing is were I would shoot for for hyw. use.

I run a 26.5 dia rear tire with 3:23s that puts my rpms at 2,800 at 65mph.

 

[oldkimmer]

As mentioned in post 7 a custom converter is the best single upgrade u can do to your car. That’s the first thing I would do along dial exhaust. Kim

 

[pedal2themetal]

14" wheels surprise me?

Yeah Door tag calls for F 78 X14" .. F is 7.75...
Thanks everybody for the thoughts to think..
Good luck take care be safe
tim

 

[R413]

Rear end gears are the first thing to change. 2.7 gears are killing the torque. Remember jumping on a 0 speed and it still in 10th gear? Hard to get the thing moving.

3.2 is great for all around driving. Don't go to much with a small engine, like 3.5 and up.