4:56 gears need to change - The 1947 - Present Chevrolet & GMC Truck Message Board Network

theside00 · 09-10-2007, 09:48 PM

Went on a camping trip and drove a couple hours on the freeway and was pushing 3,000 rpms with a 454 just to go 65-70. I am thinking about raising the gearing to 4:11 or higher. Anybody think this is a good idea?
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69halfton · 09-10-2007, 10:19 PM

been thinking of some 4.56 gears in my truck, although i have a 12 posi. do they even make 4.56 gears for a 12 bolt? never run across them?

wibilly · 09-10-2007, 10:35 PM

you must have some pretty tall tiresif thats all the rpms you are turning. i used a calculator online somwhere and came up with 2600rpms at 64. somthing with 4,10s and 33"tires

theside00 · 09-10-2007, 10:51 PM

I am running 39.5s right now and thinking about going down to 38 and that is going to kill the highway travel even more. Figure that 3,000 RPMs on the highway is a little to much for the 454 for long periods of time.

wibilly · 09-10-2007, 10:53 PM

yea they are som big as tires

bad6772 · 09-10-2007, 10:59 PM

im running 4.56 gears in my lwb 26 inch total tire wheel combo... its a pain on the freeway. 60 is about the max....3400 rpms.....and it tops out at about 90 mph ...but does it real quick....when i did a little friday night racing went to 10.5 mickey thompsons, 29'' tall. rpms was alot better

Twistedsteel · 09-10-2007, 11:05 PM

Quote:

Originally Posted by 69halfton

been thinking of some 4.56 gears in my truck, although i have a 12 posi. do they even make 4.56 gears for a 12 bolt? never run across them?

Yeah I got em in mine, I run 35's and it's not a nice freeway cruiser.

theside00,
What kind of tranny are you runnin? I wouldn't go any lower(number wise) than 4.11 with those big tires. If your runnin an auto it will kill it quick. Maybe put in a overdrive trans or a overdrive from gear vendor.

Albie

Twistedsteel · 09-10-2007, 11:08 PM

Quote:

Originally Posted by bad6772

im running 4.56 gears in my lwb 26 inch total tire wheel combo... its a pain on the freeway. 60 is about the max....3400 rpms.....and it tops out at about 90 mph ...but does it real quick....when i did a little friday night racing went to 10.5 mickey thompsons, 29'' tall. rpms was alot better

Damn! I run about 3000rpm goin 55-60 with 4.56 and 35's and a th350

theside00 · 09-10-2007, 11:08 PM

There is just a th350 so running smaller might kill the tranny. If the th400 final drive ratio the same as the th350? That is a swap I would like to do to have a tranny that can handle the power from the built 454.

Twistedsteel · 09-10-2007, 11:16 PM

Quote:

Originally Posted by theside00

There is just a th350 so running smaller might kill the tranny. If the th400 final drive ratio the same as the th350? That is a swap I would like to do to have a tranny that can handle the power from the built 454.

Not sure on the final drive gears but a Th400 would be nice and I would look into adding a overdrive on it. Not sure how much power the overdrives handle, might want to look into that.

wheels67 · 09-11-2007, 12:12 AM

hmmm My original 327 with a th400 and 3:73 gears are killing me as
well on the freeway.

A 200r4 is almost a direct bolt in but are weak.
A 700r4 requires driveline shortening and crossmember movement
but can be rebuilt to handle the load......the overdrive swith can be mounted down by the dimmer switch on floorboard........the projects never end...lol

1LoC10 · 09-11-2007, 07:26 AM

I have 4:56 gears in my 12 bolt with a 3 on the tree and 255/70/15 tires... sucks on the highway, adn im shifting into 2nd before i leave the driveway

grayw0lf · 09-11-2007, 09:48 AM

4.56 here w/ 12 bolt, Th350 & 255/60/15's.

It sucks!

AlienYouth · 09-11-2007, 11:06 AM

final drive in TH350 and 400 are both 1:1

gkolmatycki · 09-11-2007, 03:05 PM

I have the same problem you do & know your pain. I have 235/75/R15's with a 283/TH350 combo & 4.56 gears in the rear end. On the highway at 70 MPH she's at almost 4000 RPM's. But she gets there pretty quick!!!

mnunn454 · 09-11-2007, 07:11 PM

I like working these equations from the mathmatical side first.

Overall, you'll want about a 10:1 ratio on low (with a normal, say 28-30" tire diameter). With monster tires that are (say 30% taller), you'll want to go to about 13:1 in total ratio in low. (Gear Ratio in low times R&P ratio)

For highway, a 2.8 to 3.0:1 final drive ratio (again with a "normal" tire) is a great target to keep the RPMs driveable at highway speeds. With a 30% larger tire, this should probably be in the 3.73 R&P range (assuming your tranny is 1:1 in high gear).

Sure you can live with more or less than that, but it'll only cause you either fuel wasting or acelleration lacking problems.

JMO.

theside00 · 09-11-2007, 08:58 PM

Arent the 700r4 weak and not worth the swap for a 4x4? What kind of add on overdrives are there?

Twistedsteel · 09-12-2007, 12:17 AM

Quote:

Originally Posted by theside00

Arent the 700r4 weak and not worth the swap for a 4x4? What kind of add on overdrives are there?

Yeah I've heard that they can be weak, but I've also heard that if you find the right year and build it with the right parts that they will hold up but I dunno. Here's the link to the overdrives

http://gearvendors.com/

09-10-2007, 09:48 PM	#1
theside00 Registered User Join Date: Jun 2007 Location: Seattle WA Posts: 38	4:56 gears need to change Went on a camping trip and drove a couple hours on the freeway and was pushing 3,000 rpms with a 454 just to go 65-70. I am thinking about raising the gearing to 4:11 or higher. Anybody think this is a good idea? Sorry I had to edit your post. You need to be a subscriber to trade, want to buy or sell. oldiron forum staff See link below to subscribe. http://67-72chevytrucks.com/vboard/payments.php Last edited by oldiron; 09-11-2007 at 12:46 AM.

09-10-2007, 10:19 PM	#2
69halfton Registered User Join Date: Apr 2007 Location: King City, Ontario, Canada Posts: 974	Re: 4:56 gears need to change been thinking of some 4.56 gears in my truck, although i have a 12 posi. do they even make 4.56 gears for a 12 bolt? never run across them? __________________ - Jason If you can turn, Youre not going fast enough. Favorite caption: first car to 200 mph in the 1/4 mile, no parachute, drum brakes all the way around.. ..back when men were men.

09-10-2007, 10:35 PM	#3
wibilly Senior Member Join Date: Nov 2005 Location: northwestern wi Posts: 2,111	Re: 4:56 gears need to change you must have some pretty tall tiresif thats all the rpms you are turning. i used a calculator online somwhere and came up with 2600rpms at 64. somthing with 4,10s and 33"tires __________________ common sense isn't so common anymore

09-10-2007, 10:51 PM	#4
theside00 Registered User Join Date: Jun 2007 Location: Seattle WA Posts: 38	Re: 4:56 gears need to change I am running 39.5s right now and thinking about going down to 38 and that is going to kill the highway travel even more. Figure that 3,000 RPMs on the highway is a little to much for the 454 for long periods of time.

09-10-2007, 10:53 PM	#5
wibilly Senior Member Join Date: Nov 2005 Location: northwestern wi Posts: 2,111	Re: 4:56 gears need to change yea they are som big as tires __________________ common sense isn't so common anymore

09-10-2007, 10:59 PM	#6
bad6772 Official Site Guitar Shredder Join Date: May 2006 Location: Oz Posts: 3,955	Re: 4:56 gears need to change im running 4.56 gears in my lwb 26 inch total tire wheel combo... its a pain on the freeway. 60 is about the max....3400 rpms.....and it tops out at about 90 mph ...but does it real quick....when i did a little friday night racing went to 10.5 mickey thompsons, 29'' tall. rpms was alot better

09-10-2007, 11:08 PM	#9
theside00 Registered User Join Date: Jun 2007 Location: Seattle WA Posts: 38	Re: 4:56 gears need to change There is just a th350 so running smaller might kill the tranny. If the th400 final drive ratio the same as the th350? That is a swap I would like to do to have a tranny that can handle the power from the built 454.

09-11-2007, 12:12 AM	#11
wheels67 Registered User Join Date: Dec 2006 Location: southern Utah Posts: 103	Re: 4:56 gears need to change hmmm My original 327 with a th400 and 3:73 gears are killing me as well on the freeway. A 200r4 is almost a direct bolt in but are weak. A 700r4 requires driveline shortening and crossmember movement but can be rebuilt to handle the load......the overdrive swith can be mounted down by the dimmer switch on floorboard........the projects never end...lol

09-11-2007, 07:26 AM	#12
1LoC10 Insert Title Here Join Date: Feb 2006 Location: Dyer, Indiana Posts: 5,679	Re: 4:56 gears need to change I have 4:56 gears in my 12 bolt with a 3 on the tree and 255/70/15 tires... sucks on the highway, adn im shifting into 2nd before i leave the driveway __________________ BOBBY _69 SWB_ 1000 pics of 67-72's>> http://s193.photobucket.com/albums/z...-72/?start=all <<

09-11-2007, 09:48 AM	#13
grayw0lf Registered User Join Date: Apr 2004 Location: Clanton, AL Posts: 1,253	Re: 4:56 gears need to change 4.56 here w/ 12 bolt, Th350 & 255/60/15's. It sucks! __________________ 85' CUCV M1009!!! The newest addition! 6.2diesel, Th400, NP208, & only 36k miles! 70' C-10 LWB Fleetside - Looking good these days! 05' Dodge Neon 88' Winner Escape Sport 1750 - 4.3v6 94' Seadoo SP 84' Honda TRX200, bare nekkid. Just a frame & tires. Always looking for another project or any good deal!

09-11-2007, 11:06 AM	#14
AlienYouth Registered User Join Date: Apr 2007 Location: Westminster, Maryland Posts: 411	Re: 4:56 gears need to change final drive in TH350 and 400 are both 1:1 __________________ Picturesss 71 C10 383/TH400 13.65 @ 99... 2.06 60' spinnin :/

09-11-2007, 03:05 PM	#15
gkolmatycki Love that '69 Join Date: Oct 2005 Location: Sherwood Park, Alberta, Canada Posts: 109	Re: 4:56 gears need to change I have the same problem you do & know your pain. I have 235/75/R15's with a 283/TH350 combo & 4.56 gears in the rear end. On the highway at 70 MPH she's at almost 4000 RPM's. But she gets there pretty quick!!! __________________ I AM CANADIAN & PROUD OF IT!!! 1969 Chevy C10, SBC V8, TH-350 Transmission, Metallic Blue, B&M Megashifter, GT Grant Steering Wheel, 2.25" True Dual Magnaflow Exhaust System w/ SS Magnaflow Embossed Tips, 700W Rockford Fosgate Stereo System, Lowered 1" Front & Stock Rear, 4.56 Rear with Positraction, 15" Chrome Rims w/ Chevy Center Caps & Michelin Tires, 4.5" K&N Air Filter, Edelbrock 'Elite' Engine Accessories, Chrome Powdercoated Engine Parts 2001 Cavalier Z24, 2.4L DOHC, Silver, Spoiler, AEM Intake, 2.25" Magnaflow Exhaust System, Clear Euro Tails, Tinted Windows, 400W Clarion Stereo System Last edited by gkolmatycki; 09-11-2007 at 03:06 PM.

09-11-2007, 07:11 PM	#16
mnunn454 Registered User Join Date: Dec 2006 Location: Rhode Island Posts: 602	Re: 4:56 gears need to change I like working these equations from the mathmatical side first. Overall, you'll want about a 10:1 ratio on low (with a normal, say 28-30" tire diameter). With monster tires that are (say 30% taller), you'll want to go to about 13:1 in total ratio in low. (Gear Ratio in low times R&P ratio) For highway, a 2.8 to 3.0:1 final drive ratio (again with a "normal" tire) is a great target to keep the RPMs driveable at highway speeds. With a 30% larger tire, this should probably be in the 3.73 R&P range (assuming your tranny is 1:1 in high gear). Sure you can live with more or less than that, but it'll only cause you either fuel wasting or acelleration lacking problems. JMO. __________________ 69 C-10 SWB Fleetside 454/TH400 (For Sale) http://67-72chevytrucks.com/vboard/c...ct=1299&cat=12 70 El Camino 454 TH700 29 Model A 4-DR Sedan Deluxe

09-11-2007, 08:58 PM	#17
theside00 Registered User Join Date: Jun 2007 Location: Seattle WA Posts: 38	Re: 4:56 gears need to change Arent the 700r4 weak and not worth the swap for a 4x4? What kind of add on overdrives are there?

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