![]() |
![]() |
#1 |
Registered User
![]() Join Date: May 2011
Location: Long Island NY
Posts: 787
|
Gear Ratio Swaps?
My 69 is finally done and I notice this thing is revving on the highway. To the point where I feel uncomfortable at 65 mph. I generally toot along at 55-60 but everyone is passing me up.
I have the 250 3OTT with a posi rear. Im gonna chack my ratio tonight but I suspect it to be 4:11. I was looking at swaping in a lower ratio like 3:42 or even 3:08. Its strictly for show and I wont be trailering or hauling anything, but would like to be able to go down the highway and maybe even pick up some mpgs. I notice the aftermarket gears reference two different carriers. Gears to fit a 3:73 and up and those to fit a 3:42 and down. Do I need a different carrier to swap in some 3:42 or 3:08's? Any other pros/ cons? Thanks! |
![]() |
![]() |
![]() |
#2 |
Registered User
![]() Join Date: May 2011
Location: Long Island NY
Posts: 787
|
Re: Gear Ratio Swaps?
Okay. So turns out it has 3:73. Thinking 3:08 would be the better swap to make a noticable difference
|
![]() |
![]() |
![]() |
#3 | |
Active Member
![]() Join Date: Jul 2007
Location: Centrally located between Houston, Austin and Waco. BCS area.
Posts: 7,947
|
Re: Gear Ratio Swaps?
Quote:
Personally, I would stay with the 3.42. |
|
![]() |
![]() |
![]() |
#4 |
Moderator
![]() Join Date: May 2007
Location: Southern Cal
Posts: 20,006
|
Re: Gear Ratio Swaps?
Even if you go to a 3.42 you will need a series 3 carrier. 3.73 and numerically higher gears use a series 4 carrier.
__________________
1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
![]() |
![]() |
![]() |
#5 |
Registered User
Join Date: Jun 2009
Location: Forest City IA
Posts: 56
|
Re: Gear Ratio Swaps?
I think you are being misled by fan noise. The cooling fan tends to mask the motor sound at high rpm. My wife's truck has a 250 with 5.13 gear and tall 16 inch tires. The tach reads 4200 at 72 and it will run there all day if you can buy the gas .http://67-72chevytrucks.com/vboard/i...ilies/wink.gif
I think you could easily run 80 at about 3600 rpm without any harm assuming you are running regular 15 inch tires. |
![]() |
![]() |
![]() |
#6 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,940
|
Re: Gear Ratio Swaps?
The lower gears that came stock in that truck are to get the thing moving with the I-6 when hauling stuff. So as stated before... the engine will labor more with higher gears in there.
The '67 C10 I had originally came with a 292 and a granny low 4 speed. It also had a posi-traction rear with 4.11's. It was great when I tossed a street/strip 355 and a TH400 in it. It barked rubber in every gear... but sucked on the highway. ![]() Gary
__________________
'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
Quote:
|
||
![]() |
![]() |
![]() |
Bookmarks |
Thread Tools | |
Display Modes | |
|
|