65 Rear end gear ratio change - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hb32 · 03-31-2010, 01:54 AM

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 · 03-31-2010, 02:52 AM

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 · 03-31-2010, 03:31 AM

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* · 04-01-2010, 06:23 AM

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 · 04-01-2010, 10:48 PM

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* · 04-03-2010, 08:33 AM

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

03-31-2010, 01:54 AM	#1
hb32 Registered User Join Date: Feb 2009 Location: Surrey B.C. Canada Posts: 255	65 Rear end gear ratio change 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. __________________ Life is too short to drive a boring vehicle.

03-31-2010, 02:52 AM	#2
andyh1956 Registered User Join Date: Mar 2010 Location: thomastown mississippi Posts: 1,261	Re: 65 Rear end gear ratio change 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

03-31-2010, 03:31 AM	#3
collins10672 Registered User Join Date: Jan 2009 Location: bean station tennessee Posts: 398	Re: 65 Rear end gear ratio change 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.

04-01-2010, 06:23 AM	#4
blackedoutharley Account Suspended Join Date: Jul 2007 Location: Plumas Lake, Ca. Posts: 1,009	Re: 65 Rear end gear ratio change 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.

04-01-2010, 10:48 PM	#5
jewing3886 Registered User Join Date: Nov 2008 Location: Hoschton Ga Posts: 15	Re: 65 Rear end gear ratio change 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 Last edited by jewing3886; 04-01-2010 at 10:49 PM.

04-03-2010, 08:33 AM	#6
lakeroadster Account Suspended Join Date: Sep 2009 Location: High Plains of Colorado Posts: 2,485	Re: 65 Rear end gear ratio change Check out this link... very helpful: http://www.sierrabronco.com/TireGearRatio.htm



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.