What rear gear ratio is good for highway??? - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

capev86 · 01-14-2010, 10:17 PM

if you want to use your truck on the highway but still want to be able to accellerate, pull loads, etc, there are two words to consider....OVER & DRIVE

i would not want anything less than a 3.42, even in a 1/2 ton. the 3.08 makes for lousy get up and go. a 3.73 with a .7 overdrive comes out to 2.61.....way better than a straight 3.08 in top gear. 3.73 gear isn't bad when you are towing and staying under 60mph. gas mileage is best if you keep the speed low too, regardless of the gear ratio....trucks displace a lot of air and those forces add up when you get moving at modern highway speeds.

my 72 burb 3/4 ton has the 4.57 geared ho52 and i have a 4.10 3rd member to go in with plans to install the factory OD tail shaft on the original 3 speed saginaw (3OT). that will equate to a 2.89 final drive when overdrive is engaged. right now i figure the 307 turns about 3100rpm at 60mph, so i keep it under 50 for long drives and only go higher for short jaunts.

Oldesole7472 · 01-15-2010, 09:06 AM

i hope youre right...

side note...i'm a new owner of mine so this is all fairly new to me...bought it about 5 months ago...have wanted one since this dude had one back in high school (10 years ago) and damn i'm very psyched to finally drive one as my own daily driver...i think it says something about a person who drives a classic car or truck...best way to describe those trucks is simply "American"...plus chicks dig guys in old classic trucks ha ha ok im done...just had to say that

Oldesole7472 · 01-15-2010, 09:31 AM

yeah thats exactly what it needs...it just feels like there should be another gear to go into once i hit 3rd...i just figured replacing the rear would be the easiest. Capev86 did you ever check to see how much that would cost to have done?

Blackbird66 · 01-15-2010, 02:52 PM

My '72 had the original 307 2bl, three on tree and 3.73 gear when I purchased it. I drove an hour one way to work and ran around 70. The motor sounded like it was really turning at that RPM. Now the stock cam and little carb like low RPM,s ,but the motor will not fly apart or anything like that. You can swap out the rear from a truck with a 308, but you will loose any ability to pull from a stop with your current motor/trans setup. In fact if you have tried to pull/haul any real weight yet you have already found that the stock first gear seems a little high for that 307......

If it where my choice, I would swap the cam for a reproduction 350hp 327 cam, and install a 600 holley and intake. This will give you more power, and allow the motor to "feel" more relaxed @ highway speeds.

Remember that we have driven overdrive cars for so long that we forget what it felt like before them............

**Stocker** · 01-15-2010, 02:58 PM

A fixed-blade fan will pull a lot of air and make it sound like the engine is running faster than it actually is. If you still have one, consider a clutch fan. Not only will it cool better (get a recovery tank and sealed-system cap, also) but you won't have the constant roar at highway speeds. If nothing else, it makes for more relaxed highway driving.

Oldesole7472 · 01-15-2010, 03:09 PM

yeah first gear does feel like its a lil high

Blackbird66 · 01-15-2010, 05:04 PM

I blew up the original 3 speed. ( actually had pieces laying on the ground ) After that I went with a tremec 3550 five speed. That gave me a first gear that I only needed to pull a load with, and a super smooth cruise at high speeds. My gas milage did not improve at all, contrary to popular theory. Though I am very happy with my setup, it is not a low cost fix.
I still think that putting a little more cam in your motor would be the lowest cost solution for both high speed cruising, and still being able to pull a load from a stop.

johndawelder · 01-16-2010, 08:29 PM

I have a 67 C-10 custom with a 69 vette 427, 400 turbo trans,3:07 gear in a 72 rear end.I run 32 in. tall tires on the rear.I'm running 2300 rpm's at 75 mph.As you know speedo only reads 100 mph, I've broke speedo cable twice already.As for gas milage,I have no idea.

'72customdeluxe · 01-16-2010, 11:57 PM

My truck did 100+ pretty easily when it actually ran. 3.73 rear and 28" tires. 3.08's are a crap compromise unless you have a torque monster engine that just overpowers the tires anyway. You lose the acceleration and around town mileage of the shorter gears while still getting crap mileage on the open road. I would hold out for overdrive

gonzo6869 · 01-17-2010, 01:53 AM

I can tell you that you have 3.73's. I was in your same situation, I finally got a tach, at 60mph i am at about 2800-2850rpm. I was thinking of changing my rear end as well, but after doing some research and pricing, I felt like my money would be better spent on a new 200R4 Tranny. It will only be a few hundred more, and its pretty much a direct swap unlike a 400 or 700.

'72customdeluxe · 01-17-2010, 02:01 AM

^What he said. Both the 700r4 and 2004r have a deeper first gear ratio than non o/d transmissions, so you get even better performance along with the rpm drop in 4th

wwotr · 01-17-2010, 05:30 AM

Quote:

Originally Posted by Oldesole7472

My 72 c10's top speed is about 55...i wanna swap the rear with one with a higher ratio...any suggestions???

I'm running 3:73 and my Tach reads approx 2300 RPM at 55 MPH.
I like the sound of it, but then again I have a Turbo 350 with no O.D., so theres not much of a "kickdown" after 60 MPH, but then again I don't do a lot of Freeway driving.

Blackbird66 · 01-17-2010, 04:49 PM

200r4 is NOT a direct bolt in for any manual transmission truck. You will need an auto column, or aftermarket floor shifter ( witch may not clear your bench seat), and you will need to ditch the rear motor mounts in favor for a cross member and trans mount, as your three speed does not use a trans mount. And you may still need to modify the drive shaft. I'm not sure the trans yoke is the same on three speeds, as that for th350 or 200r4.......
Did I miss anything else? Oh yea, you will need the kickdown/tv cable brackets....

wwotr · 01-17-2010, 05:49 PM

Quote:

Originally Posted by Blackbird66

200r4 is NOT a direct bolt in for any manual transmission truck. You will need an auto column, or aftermarket floor shifter ( witch may not clear your bench seat), and you will need to ditch the rear motor mounts in favor for a cross member and trans mount, as your three speed does not use a trans mount. And you may still need to modify the drive shaft. I'm not sure the trans yoke is the same on three speeds, as that for th350 or 200r4.......
Did I miss anything else? Oh yea, you will need the kickdown/tv cable brackets....

Didn't know if you were directing that at me or not.

gonzo6869 · 01-18-2010, 12:14 AM

What I said was that it is almost a direct swap, I believe he has a TH350, as I do too. So for us with auto's the 200R4 is a good choice, it is the same size as the TH 350, but like you said, it is not a direct bolt in, it needs minor adjustments in order for it to work.

wwotr · 01-18-2010, 12:24 AM

Quote:

Originally Posted by gonzo6869

What I said was that it is almost a direct swap, I believe he has a TH350, as I do too. So for us with auto's the 200R4 is a good choice, it is the same size as the TH 350, but like you said, it is not a direct bolt in, it needs minor adjustments in order for it to work.

For ME, I just found out we have this "Tranny Guru", within 10 miles of me.
You tell him what kind of Engine (HP Rating) and he can recommend a Tranny based on that HP, your Driving habits and what type of performance your looking for. When the time comes I'll let him know what I have, what I want and throw the cash at him and say "Make it happen".

hippie-46 · 01-21-2010, 06:44 AM

i agree with longhorn man i think you got other problems . maybe clutch or pressure plate slipping .

Longhorn Man · 01-21-2010, 10:39 AM

Quote:

Originally Posted by gonzo6869

What I said was that it is almost a direct swap, I believe he has a TH350...

Quote:

Originally Posted by Oldesole7472

I have 307 CI, 3 on the tree...no OD.

Nope... 3 speed manual.

Oldesole7472 · 01-21-2010, 10:56 AM

i highly doubt anything is slipping...but it could be...i am going to replace the clutch, throwout bearing, etc.

Oldesole7472 · 01-21-2010, 11:00 AM

i love the nostalgia of the column shift...im going throw a tach in her, and see what its pullin...and if its high im going to put an OD in the trans...are all of the original 3sp trans Saginaw trans? I heard Saginaws are crap trans...is this true? my gut tells me that they are fine...mines lasted 40 years...thats gotta mean something...right?

gonzo6869 · 01-21-2010, 11:49 AM

I stand corrected, did not remember seeing that post. Are the gear ratios different for the auto and manual trannys?

tjsblazer · 01-21-2010, 12:21 PM

Don't know if this will help you or not but it is an awesome calculator. check out the link.

http://www.grimmjeeper.com/gears.html

Oldesole7472 · 01-22-2010, 11:25 AM

ok...just got off the phone with the transmission place...apparently they cant put an overdrive in my original 3sp...i have to find one that had one in it from factory...

Oldesole7472 · 01-22-2010, 11:43 AM

are there any direct swaps for my manual trans that would allow me to keep the shifter on the column???????????????????

Blackbird66 · 01-22-2010, 05:22 PM

no
your column shift will only work a three speed manual.
the column shift also makes for a more roomy cab.

I still say that, for the money, put in a slightly hotter cam and 4bl carb. This will make your motor "feel" more comfortable at speed, and the added power will help you pull from a stop better as well.

01-14-2010, 10:17 PM	#26
capev86 Registered User Join Date: May 2009 Location: Eliot, Maine Posts: 1,314	Re: What rear gear ratio is good for highway??? if you want to use your truck on the highway but still want to be able to accellerate, pull loads, etc, there are two words to consider....OVER & DRIVE i would not want anything less than a 3.42, even in a 1/2 ton. the 3.08 makes for lousy get up and go. a 3.73 with a .7 overdrive comes out to 2.61.....way better than a straight 3.08 in top gear. 3.73 gear isn't bad when you are towing and staying under 60mph. gas mileage is best if you keep the speed low too, regardless of the gear ratio....trucks displace a lot of air and those forces add up when you get moving at modern highway speeds. my 72 burb 3/4 ton has the 4.57 geared ho52 and i have a 4.10 3rd member to go in with plans to install the factory OD tail shaft on the original 3 speed saginaw (3OT). that will equate to a 2.89 final drive when overdrive is engaged. right now i figure the 307 turns about 3100rpm at 60mph, so i keep it under 50 for long drives and only go higher for short jaunts.

01-15-2010, 09:06 AM	#27
Oldesole7472 Registered User Join Date: Jan 2010 Location: Hanover, PA Posts: 18	Re: What rear gear ratio is good for highway??? i hope youre right... side note...i'm a new owner of mine so this is all fairly new to me...bought it about 5 months ago...have wanted one since this dude had one back in high school (10 years ago) and damn i'm very psyched to finally drive one as my own daily driver...i think it says something about a person who drives a classic car or truck...best way to describe those trucks is simply "American"...plus chicks dig guys in old classic trucks ha ha ok im done...just had to say that

01-15-2010, 09:31 AM	#28
Oldesole7472 Registered User Join Date: Jan 2010 Location: Hanover, PA Posts: 18	Re: What rear gear ratio is good for highway??? yeah thats exactly what it needs...it just feels like there should be another gear to go into once i hit 3rd...i just figured replacing the rear would be the easiest. Capev86 did you ever check to see how much that would cost to have done?

01-15-2010, 02:52 PM	#29
Blackbird66 Registered User Join Date: Feb 2008 Location: Shelbyville, KY Posts: 51	Re: What rear gear ratio is good for highway??? My '72 had the original 307 2bl, three on tree and 3.73 gear when I purchased it. I drove an hour one way to work and ran around 70. The motor sounded like it was really turning at that RPM. Now the stock cam and little carb like low RPM,s ,but the motor will not fly apart or anything like that. You can swap out the rear from a truck with a 308, but you will loose any ability to pull from a stop with your current motor/trans setup. In fact if you have tried to pull/haul any real weight yet you have already found that the stock first gear seems a little high for that 307...... If it where my choice, I would swap the cam for a reproduction 350hp 327 cam, and install a 600 holley and intake. This will give you more power, and allow the motor to "feel" more relaxed @ highway speeds. Remember that we have driven overdrive cars for so long that we forget what it felt like before them............

01-15-2010, 02:58 PM	#30
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,586	Re: What rear gear ratio is good for highway??? A fixed-blade fan will pull a lot of air and make it sound like the engine is running faster than it actually is. If you still have one, consider a clutch fan. Not only will it cool better (get a recovery tank and sealed-system cap, also) but you won't have the constant roar at highway speeds. If nothing else, it makes for more relaxed highway driving. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

01-15-2010, 03:09 PM	#31
Oldesole7472 Registered User Join Date: Jan 2010 Location: Hanover, PA Posts: 18	Re: What rear gear ratio is good for highway??? yeah first gear does feel like its a lil high

01-15-2010, 05:04 PM	#32
Blackbird66 Registered User Join Date: Feb 2008 Location: Shelbyville, KY Posts: 51	Re: What rear gear ratio is good for highway??? I blew up the original 3 speed. ( actually had pieces laying on the ground ) After that I went with a tremec 3550 five speed. That gave me a first gear that I only needed to pull a load with, and a super smooth cruise at high speeds. My gas milage did not improve at all, contrary to popular theory. Though I am very happy with my setup, it is not a low cost fix. I still think that putting a little more cam in your motor would be the lowest cost solution for both high speed cruising, and still being able to pull a load from a stop.

01-16-2010, 08:29 PM	#33
johndawelder Registered User Join Date: Jan 2010 Location: Loudon,TN Posts: 101	Re: What rear gear ratio is good for highway??? I have a 67 C-10 custom with a 69 vette 427, 400 turbo trans,3:07 gear in a 72 rear end.I run 32 in. tall tires on the rear.I'm running 2300 rpm's at 75 mph.As you know speedo only reads 100 mph, I've broke speedo cable twice already.As for gas milage,I have no idea.

01-16-2010, 11:57 PM	#34
'72customdeluxe Registered User Join Date: Jan 2008 Location: Tejas Posts: 691	Re: What rear gear ratio is good for highway??? My truck did 100+ pretty easily when it actually ran. 3.73 rear and 28" tires. 3.08's are a crap compromise unless you have a torque monster engine that just overpowers the tires anyway. You lose the acceleration and around town mileage of the shorter gears while still getting crap mileage on the open road. I would hold out for overdrive __________________ '72 cheyenne super step, '05 long bed gmc

01-17-2010, 01:53 AM	#35
gonzo6869 Cops, ha, catch me if you can! Join Date: Jun 2009 Location: Santa Barbara, CA. Posts: 271	Re: What rear gear ratio is good for highway??? I can tell you that you have 3.73's. I was in your same situation, I finally got a tach, at 60mph i am at about 2800-2850rpm. I was thinking of changing my rear end as well, but after doing some research and pricing, I felt like my money would be better spent on a new 200R4 Tranny. It will only be a few hundred more, and its pretty much a direct swap unlike a 400 or 700. Last edited by gonzo6869; 01-17-2010 at 02:12 AM.

01-17-2010, 02:01 AM	#36
'72customdeluxe Registered User Join Date: Jan 2008 Location: Tejas Posts: 691	Re: What rear gear ratio is good for highway??? ^What he said. Both the 700r4 and 2004r have a deeper first gear ratio than non o/d transmissions, so you get even better performance along with the rpm drop in 4th __________________ '72 cheyenne super step, '05 long bed gmc

01-17-2010, 04:49 PM	#38
Blackbird66 Registered User Join Date: Feb 2008 Location: Shelbyville, KY Posts: 51	Re: What rear gear ratio is good for highway??? 200r4 is NOT a direct bolt in for any manual transmission truck. You will need an auto column, or aftermarket floor shifter ( witch may not clear your bench seat), and you will need to ditch the rear motor mounts in favor for a cross member and trans mount, as your three speed does not use a trans mount. And you may still need to modify the drive shaft. I'm not sure the trans yoke is the same on three speeds, as that for th350 or 200r4....... Did I miss anything else? Oh yea, you will need the kickdown/tv cable brackets....

01-18-2010, 12:14 AM	#40
gonzo6869 Cops, ha, catch me if you can! Join Date: Jun 2009 Location: Santa Barbara, CA. Posts: 271	Re: What rear gear ratio is good for highway??? What I said was that it is almost a direct swap, I believe he has a TH350, as I do too. So for us with auto's the 200R4 is a good choice, it is the same size as the TH 350, but like you said, it is not a direct bolt in, it needs minor adjustments in order for it to work.

01-21-2010, 06:44 AM	#42
hippie-46 Registered User Join Date: Dec 2009 Location: cincinnati ohio Posts: 28	Re: What rear gear ratio is good for highway??? i agree with longhorn man i think you got other problems . maybe clutch or pressure plate slipping .

01-21-2010, 10:56 AM	#44
Oldesole7472 Registered User Join Date: Jan 2010 Location: Hanover, PA Posts: 18	Re: What rear gear ratio is good for highway??? i highly doubt anything is slipping...but it could be...i am going to replace the clutch, throwout bearing, etc.



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01-21-2010, 11:00 AM	#45
Oldesole7472 Registered User Join Date: Jan 2010 Location: Hanover, PA Posts: 18	Re: What rear gear ratio is good for highway??? i love the nostalgia of the column shift...im going throw a tach in her, and see what its pullin...and if its high im going to put an OD in the trans...are all of the original 3sp trans Saginaw trans? I heard Saginaws are crap trans...is this true? my gut tells me that they are fine...mines lasted 40 years...thats gotta mean something...right?

01-21-2010, 11:49 AM	#46
gonzo6869 Cops, ha, catch me if you can! Join Date: Jun 2009 Location: Santa Barbara, CA. Posts: 271	Re: What rear gear ratio is good for highway??? I stand corrected, did not remember seeing that post. Are the gear ratios different for the auto and manual trannys? __________________ 72 C-10 Stepper 350/TH350 3.73 in the back Edelbrock intake and Carb Hooker Comp Headers 275/60R15 on Rallies

01-21-2010, 12:21 PM	#47
tjsblazer Registered User Join Date: Oct 2009 Location: Great White North Posts: 1,520	Re: What rear gear ratio is good for highway??? Don't know if this will help you or not but it is an awesome calculator. check out the link. http://www.grimmjeeper.com/gears.html __________________ Jeff. '72 Blazer K5 "Camshaft opinions are like belly buttons; everyone has one and no two are alike" My Blazer Build: http://67-72chevytrucks.com/vboard/s...d.php?t=626752 My Engine Build: http://67-72chevytrucks.com/vboard/s...d.php?t=637336

01-22-2010, 11:25 AM	#48
Oldesole7472 Registered User Join Date: Jan 2010 Location: Hanover, PA Posts: 18	Re: What rear gear ratio is good for highway??? ok...just got off the phone with the transmission place...apparently they cant put an overdrive in my original 3sp...i have to find one that had one in it from factory...

01-22-2010, 11:43 AM	#49
Oldesole7472 Registered User Join Date: Jan 2010 Location: Hanover, PA Posts: 18	Re: What rear gear ratio is good for highway??? are there any direct swaps for my manual trans that would allow me to keep the shifter on the column???????????????????

01-22-2010, 05:22 PM	#50
Blackbird66 Registered User Join Date: Feb 2008 Location: Shelbyville, KY Posts: 51	Re: What rear gear ratio is good for highway??? no your column shift will only work a three speed manual. the column shift also makes for a more roomy cab. I still say that, for the money, put in a slightly hotter cam and 4bl carb. This will make your motor "feel" more comfortable at speed, and the added power will help you pull from a stop better as well.

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