65 Rear end gear ratio change

[hb32]

Slowly swapping out parts to make my 65 step a little more fuel efficient. Ordered a Pertronix ignitor and coil this morning and looking for a good Holley 390 cfm carb for the Offy manifold I got from geezer#99. Now thinking about swapping out the ring and pinion or rear end to 3.08 or 3.42 from what I suspect are 3.73. I don`t really need the stump pulling power and not wanting to swap out the tranny. Thoughts? What gear set or rear end will swap in without any mods? I am sure this has been answered several times on here but not having any luck finding anything.

[andyh1956]

iv'e swapped lots of 3.08s in- don't slack up for a 3.42 unless you have o.d. the 2.73 won't fit cause the pinion gear is too large for the housing. 3.08s make a big difference. go to local gear shops & you can pick up used gears cheap where they put in 4.56 & stuff for the rock crawler guys.
andy

[collins10672]

definetly 3.08,some people called them 3.07 back in the day.it is the highest factory gear you could get in these trucks.by the way i like your super solid truck.

[blackedoutharley]

Depending on the engine trans combo and tire size you're running either the 3.08 or 3.42's will be good.

I have 3.42's in my '65 behind a small block/SM420 with a 30.7" O.D. Tire. I previously had 3.73's and it rocked but frankly it sucked on the freeway. Switched to 3.08's and that was great on the freeway but you could tell a difference in town or when accelerating. When I blew that rearend up I installed new 3.42's (along with every other piece including axles) and I think that it is probably the best all around choice for both low end as well as freeway.

[jewing3886]

I just went from 373 to 308 love it. The cheap way find a 12 bolt at junk yard. The guts are the same on all truck 12 bolt rear ends. 63 to 80

[lakeroadster]

Check out this link... very helpful: http://www.sierrabronco.com/TireGearRatio.htm