calling every1 who went 1/2 to 3/4 ton axles! - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bigtruck81 · 02-14-2008, 03:12 PM

you'll see no appreciable difference in fuel economy between a 305 and a 350.

with that being said, and knowing you want to keep your trans, you can probably get away with 3.73s and 35s pretty easily. this will likely save you some gas on the highway, but at the cost of some in town milage and get up and go in stop and go traffic. 4.10s seem to be about perfect for 35s with no OD.

theoneandonly · 02-14-2008, 03:37 PM

I found this caculator a while back and it might help.

http://www.4lo.com/calc/gearratio.htm

earl87gta · 02-14-2008, 09:23 PM

here is my favorate one http://www.grimmjeeper.com/gears.html

wibilly · 02-16-2008, 01:05 PM

any body done the math to see how many miles to payoff based on fuel savings alone?

earl87gta · 02-16-2008, 09:02 PM

Im sure you can get alot of fuel for the little bit of milage you would gain.

dinotruck68 · 02-17-2008, 06:25 AM

ive been thinking, my truck already has pretty low gearing in the axles, i dont how low but i can definately tell while driving.. so to run 35's cant i just run my gearing as is.. or get lower gears for the 10 an 12 bolt and sum stronger shafts?????

ND_guy · 02-17-2008, 11:41 AM

Stats:
1967 K20 SM465, 4.56 pumpkins, 35" tires

Old engine:
400sb, Qjet 9mpg hwy.

New engine:
305TBI 14mpg Hwy.

I get 14mpg at 2900rpm at 60mph.

!If I drive 65 at 3200rpm I get 12mpg.!

Overall gearing does play a role in mileage, but
SPEED KILLS MILEAGE slow down

Our aerodynamics kills economy.

earl87gta · 02-17-2008, 02:10 PM

1968 burb 283 with sm465 4:56 gears and 36in tire 10 MPG at 60.
new drive train is 6.2 deisel and nv4500 and 4;56 gears cant wait to beable to tell you the new milage but its not back on the road yet.

dinotruck68 · 02-20-2008, 08:42 AM

i dont know what tbi is but it sounds like its working for ya.. cant wait to hear about that new drive train Earl keep me filled in..

Ive been thinking about converting my 305 to run on propane , my dad had a 72 4x4 with a 350 runnin on propane bak in the 90's an he said it ran real strong, just the big tank was kinda ugly lol! just another thing ive been thinkin about since i plan on bigger tires an axles an such

earl87gta · 02-21-2008, 03:32 AM

TBI throttle body injection its what most GM trucks had threw the 90s looks like a carb with 2 fuel injectors.
A lot of the jeep guys run propane I thought about adding a propane injection system to my d-max .
The 6.2 should be fun Im trying to get some restaurants to donate there used cooking oil to me to burn in it.

68K20 x Drill · 02-21-2008, 05:52 AM

My friend has an 84 4x4 on propane with 700R and super high gears, 32's, I think it gets 18 highway.
Earl you want to be picky about the oil you get. it should be non hydrogenated, and if you can get them to prefilter it for you through a 'shortening strainer' that will be a huge plus for you. I've done a few of these conversions if you have any questions.

dinotruck68 · 02-21-2008, 08:26 AM

my uncle did the propane injection on his 04 3500 4x4.. dont know the specs an such are but it sure is fast... since propane is pretty cheap i thought it would be a good thing to consider for my truck, its also better for the life of your engine, it burns cleaner to

72cheyennesuper20 · 02-21-2008, 11:36 AM

Quote:

Originally Posted by msgross

if you are running 35's with any axles then don't worry about gas mileage... gears, tranny, engine, carb etc.. will all play a big part but don't ever expect over 13 MPG i would guess.

13 MPG, I wish.

earl87gta · 02-22-2008, 04:11 AM

non hydrogenated whats that I guess I have some more reading to do. Im sure when I start the convertion Ill be posting alot to get every thing working.

extd56 · 02-25-2008, 02:39 AM

I will be running a 91 454 TBI with a 4L80E trans and 35" tires with 3.73 gearing. It should be right around 1800 RPM's on the freeway so I will see what kind of mileage I will get. It will be in a 69 3/4 ton crew cab longbed with a 6" lift so I am not expecting too much, hence the 32 gallon fuel tank.

bigtruck81 · 02-25-2008, 12:49 PM

any more pics of your rig? havent seen a 4 door of that vintage before.

earl87gta · 02-25-2008, 02:14 PM

Quote:

Originally Posted by bigtruck81

any more pics of your rig? havent seen a 4 door of that vintage before.

I hope you have some time on your hands one of the coolest build ever.

http://67-72chevytrucks.com/vboard/s...d.php?t=188993

padresag · 02-27-2008, 08:23 AM

Hi; I am am going back to a small block in my 64 4x4 panel. I have had a 453 detroit in it for 17 years. The PO was the one that did the install and threw away the old frame brkts. I am looking for the passenger side eng frame brkt if you are interested in selling it or know where I can find one. I noticed that it was a 283. as long as it isn't a 292 i6 r/s I am ok. 230-250 i6 r/s is fine to
thks
ron
I do run an independent 205 behind it. you can get an independent r/s case from a light duty IHC or dodge trucks and flip in the gears from a ford if need be. the ford is left hand while the others are r/hand. I think that I paid $100.00 for everything that came with the t/c from a 72 scout inc the shifter, mind you that was 15 or 16 years ago. I do also have compltete parts listings for both a t221 and a 205 if you need

02-14-2008, 03:12 PM	#26
bigtruck81 Registered User Join Date: Feb 2004 Location: northern, in Posts: 350	Re: calling every1 who went 1/2 to 3/4 ton axles! you'll see no appreciable difference in fuel economy between a 305 and a 350. with that being said, and knowing you want to keep your trans, you can probably get away with 3.73s and 35s pretty easily. this will likely save you some gas on the highway, but at the cost of some in town milage and get up and go in stop and go traffic. 4.10s seem to be about perfect for 35s with no OD.

02-14-2008, 03:37 PM	#27
theoneandonly Registered User Join Date: Nov 2007 Location: Fayetteville NC Posts: 102	Re: calling every1 who went 1/2 to 3/4 ton axles! I found this caculator a while back and it might help. http://www.4lo.com/calc/gearratio.htm __________________ SSG Jeffery Ahlheim 586th Network Support Company, 525th BfSB US Army, FT Bragg, NC 2009 Chevy Silverado LT ext cab 5.3L If you don't stand behind our troops, please feel free to stand in front of them.

02-14-2008, 09:23 PM	#28
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: calling every1 who went 1/2 to 3/4 ton axles! here is my favorate one http://www.grimmjeeper.com/gears.html __________________ Earl 68 2500 4x4 GMC Burb

02-16-2008, 01:05 PM	#29
wibilly Senior Member Join Date: Nov 2005 Location: northwestern wi Posts: 2,111	Re: calling every1 who went 1/2 to 3/4 ton axles! any body done the math to see how many miles to payoff based on fuel savings alone? __________________ common sense isn't so common anymore

02-16-2008, 09:02 PM	#30
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: calling every1 who went 1/2 to 3/4 ton axles! Im sure you can get alot of fuel for the little bit of milage you would gain. __________________ Earl 68 2500 4x4 GMC Burb

02-17-2008, 06:25 AM	#31
dinotruck68 Registered User Join Date: Jan 2008 Location: Alamo Posts: 104	Re: calling every1 who went 1/2 to 3/4 ton axles! ive been thinking, my truck already has pretty low gearing in the axles, i dont how low but i can definately tell while driving.. so to run 35's cant i just run my gearing as is.. or get lower gears for the 10 an 12 bolt and sum stronger shafts????? __________________

02-17-2008, 11:41 AM	#32
ND_guy Tool Addiction=Money Shortage Join Date: Mar 2006 Location: Grand Forks, ND Posts: 233	Re: calling every1 who went 1/2 to 3/4 ton axles! Stats: 1967 K20 SM465, 4.56 pumpkins, 35" tires Old engine: 400sb, Qjet 9mpg hwy. New engine: 305TBI 14mpg Hwy. I get 14mpg at 2900rpm at 60mph. !If I drive 65 at 3200rpm I get 12mpg.! Overall gearing does play a role in mileage, but SPEED KILLS MILEAGE slow down Our aerodynamics kills economy. __________________ 1967 K20 400TBI SM465/NP205 posi front, Detroit locker 4.56 rear

02-17-2008, 02:10 PM	#33
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: calling every1 who went 1/2 to 3/4 ton axles! 1968 burb 283 with sm465 4:56 gears and 36in tire 10 MPG at 60. new drive train is 6.2 deisel and nv4500 and 4;56 gears cant wait to beable to tell you the new milage but its not back on the road yet. __________________ Earl 68 2500 4x4 GMC Burb

02-20-2008, 08:42 AM	#34
dinotruck68 Registered User Join Date: Jan 2008 Location: Alamo Posts: 104	Re: calling every1 who went 1/2 to 3/4 ton axles! i dont know what tbi is but it sounds like its working for ya.. cant wait to hear about that new drive train Earl keep me filled in.. Ive been thinking about converting my 305 to run on propane , my dad had a 72 4x4 with a 350 runnin on propane bak in the 90's an he said it ran real strong, just the big tank was kinda ugly lol! just another thing ive been thinkin about since i plan on bigger tires an axles an such __________________ Last edited by dinotruck68; 02-20-2008 at 08:45 AM.

02-21-2008, 03:32 AM	#35
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: calling every1 who went 1/2 to 3/4 ton axles! TBI throttle body injection its what most GM trucks had threw the 90s looks like a carb with 2 fuel injectors. A lot of the jeep guys run propane I thought about adding a propane injection system to my d-max . The 6.2 should be fun Im trying to get some restaurants to donate there used cooking oil to me to burn in it. __________________ Earl 68 2500 4x4 GMC Burb

02-21-2008, 05:52 AM	#36
68K20 x Drill Registered User Join Date: Apr 2007 Location: Freedom CA Posts: 488	Re: calling every1 who went 1/2 to 3/4 ton axles! My friend has an 84 4x4 on propane with 700R and super high gears, 32's, I think it gets 18 highway. Earl you want to be picky about the oil you get. it should be non hydrogenated, and if you can get them to prefilter it for you through a 'shortening strainer' that will be a huge plus for you. I've done a few of these conversions if you have any questions. __________________ 68 Chevrolet k20 Longbed 350 SM465/205, Dana 44, 14bolt, Power steering, Power Disk Brakes, 35" BFGs. 84 Chevrolet Suburban K20 6.2 Banks turbo TH400/NP208 Now with G80 68 GMC C20 Parts? Truck And a few cars

02-21-2008, 08:26 AM	#37
dinotruck68 Registered User Join Date: Jan 2008 Location: Alamo Posts: 104	Re: calling every1 who went 1/2 to 3/4 ton axles! my uncle did the propane injection on his 04 3500 4x4.. dont know the specs an such are but it sure is fast... since propane is pretty cheap i thought it would be a good thing to consider for my truck, its also better for the life of your engine, it burns cleaner to __________________ Last edited by dinotruck68; 02-21-2008 at 08:26 AM.

02-22-2008, 04:11 AM	#39
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: calling every1 who went 1/2 to 3/4 ton axles! non hydrogenated whats that I guess I have some more reading to do. Im sure when I start the convertion Ill be posting alot to get every thing working. __________________ Earl 68 2500 4x4 GMC Burb Last edited by earl87gta; 02-22-2008 at 04:12 AM.

02-25-2008, 02:39 AM	#40
extd56 Senior Member Join Date: Nov 2004 Location: Vacaville, CA Posts: 2,272	Re: calling every1 who went 1/2 to 3/4 ton axles! I will be running a 91 454 TBI with a 4L80E trans and 35" tires with 3.73 gearing. It should be right around 1800 RPM's on the freeway so I will see what kind of mileage I will get. It will be in a 69 3/4 ton crew cab longbed with a 6" lift so I am not expecting too much, hence the 32 gallon fuel tank. Attached Images

02-25-2008, 12:49 PM	#41
bigtruck81 Registered User Join Date: Feb 2004 Location: northern, in Posts: 350	Re: calling every1 who went 1/2 to 3/4 ton axles! any more pics of your rig? havent seen a 4 door of that vintage before.



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02-27-2008, 08:23 AM	#43
padresag Registered User Join Date: Feb 2008 Location: Sidney,b.c. Posts: 4,425	Re: calling every1 who went 1/2 to 3/4 ton axles! Hi; I am am going back to a small block in my 64 4x4 panel. I have had a 453 detroit in it for 17 years. The PO was the one that did the install and threw away the old frame brkts. I am looking for the passenger side eng frame brkt if you are interested in selling it or know where I can find one. I noticed that it was a 283. as long as it isn't a 292 i6 r/s I am ok. 230-250 i6 r/s is fine to thks ron I do run an independent 205 behind it. you can get an independent r/s case from a light duty IHC or dodge trucks and flip in the gears from a ford if need be. the ford is left hand while the others are r/hand. I think that I paid $100.00 for everything that came with the t/c from a 72 scout inc the shifter, mind you that was 15 or 16 years ago. I do also have compltete parts listings for both a t221 and a 205 if you need

Register or Log In To remove these advertisements.