4.56 or 4.11 gears? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ROAD DOG · 12-28-2003, 08:08 PM

I'm about to change my gear ratio. I had been thinking 4.56 gears.. But now I'm debating on 4.11 gears. The truck is a 1970 K-10 with a built 355. sm465 4 speed tranny with stock 3.07 type 3 carrier gears. Running on 31" MT tires.
The calculator says

3.07@65mph = 2163rpm
4.11@65mph = 2896rpm
4.56@65mph = 3213rpm

My cam doesn't make serios power till around 2400 rpm
But after that its 400+torque monster. Right now its a pig off the line. You get to 75mph on the freeway@2500 rpm and you could pass any car on the road. I just want to know if 4.56 is too much or just enough. I go 4 wheeling quit a bit but want a ratio I can drive 70mph to get there.thanks.

Destructo · 12-28-2003, 08:15 PM

I wouldn't run gears that are going to put your cruise rpm above 3k. I would like something right around 2500 rpm cruise.

**Stocker** · 12-28-2003, 08:50 PM

Yeah, my 4:10 (4:11?) gears are fine on 2-lanes with 55 mph limit, but at freeway speeds, it's as low as I'd want - I think you'd regret 4:56s.

BTW that's with 33-12.50/16.5s, about 32.3" tall.

Destructo · 12-28-2003, 09:25 PM

I'm planning on running 35" tires and using 4.56 gears, but I also have OD so i'll only be turning about 2000 at 65mph.

**kwmech** · 12-28-2003, 10:50 PM

If you are going to do serious towing I would look at the 4.10s if not I would run a 3.73 with the 31'' tire. OR you can buy the 4.56s and then call me and purchase an NV4500 and matching t-case I have for sale

ROAD DOG · 12-29-2003, 12:30 AM

Yep it's looking like 4.11's. I havent done a rear gear change before,I wonder how the truck will act with 4.11's.
Up from the stock 3.07 I'm expecting alot.

rogf4 · 12-29-2003, 12:33 AM

I hope your motor has a serious bottom end if you decide to go with the 4.56 gears without over drive

earl87gta · 12-29-2003, 01:19 AM

You may be agle to find a good set of axles with 4:10 in them cheaper then changing gears you may want to look in to guy a complete set of axles I sold a the d44 and 12bolt out my blazer for 250 with 4:10s in it when I whent to D60 and 14b. Im running 4:10 in the new set up with 36 in tires, my old tow rige had 4:56 with 31in tires and it was horible if you had to drive it over 55.

ROAD DOG · 12-30-2003, 02:11 AM

Good feed back on this post, right on!

I've been looking through salvage yards, junk yards and old farmers backyards here in denver metro. for a couple of months. And haven't found nothing more then 3.73's. From spining tires counting driveshaft revolutions, to pulling covers counting teeth,
You'all know the deal. nothin,

On the parts board a guy from washington that has both axles with 4.10's for $200 obo!!!!!! If he was within 500 miles they would be mine!

Anyways I just dropped $290.35 to Summit for richmond 4.10's and install kit for the rear. What sucks is I'll have a two wheel drive truck until I save the dough for the front.

12-28-2003, 08:08 PM	#1
ROAD DOG Top of the foodchain Join Date: Oct 2003 Location: 3.5 miles from Mile Hi Stadium Posts: 127	4.56 or 4.11 gears? I'm about to change my gear ratio. I had been thinking 4.56 gears.. But now I'm debating on 4.11 gears. The truck is a 1970 K-10 with a built 355. sm465 4 speed tranny with stock 3.07 type 3 carrier gears. Running on 31" MT tires. The calculator says 3.07@65mph = 2163rpm 4.11@65mph = 2896rpm 4.56@65mph = 3213rpm My cam doesn't make serios power till around 2400 rpm But after that its 400+torque monster. Right now its a pig off the line. You get to 75mph on the freeway@2500 rpm and you could pass any car on the road. I just want to know if 4.56 is too much or just enough. I go 4 wheeling quit a bit but want a ratio I can drive 70mph to get there.thanks. __________________ 1970 K-10 4x4 1975 Jeep CJ-5 4x4 1990 Jeep XJ 4x4 Smell the Magic!

12-28-2003, 08:50 PM	#3
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Yeah, my 4:10 (4:11?) gears are fine on 2-lanes with 55 mph limit, but at freeway speeds, it's as low as I'd want - I think you'd regret 4:56s. BTW that's with 33-12.50/16.5s, about 32.3" tall. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay Last edited by Stocker; 12-28-2003 at 08:53 PM.

12-28-2003, 10:50 PM	#5
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,630	If you are going to do serious towing I would look at the 4.10s if not I would run a 3.73 with the 31'' tire. OR you can buy the 4.56s and then call me and purchase an NV4500 and matching t-case I have for sale Last edited by kwmech; 12-28-2003 at 10:53 PM.

12-29-2003, 12:30 AM	#6
ROAD DOG Top of the foodchain Join Date: Oct 2003 Location: 3.5 miles from Mile Hi Stadium Posts: 127	Yep it's looking like 4.11's. I havent done a rear gear change before,I wonder how the truck will act with 4.11's. Up from the stock 3.07 I'm expecting alot. __________________ 1970 K-10 4x4 1975 Jeep CJ-5 4x4 1990 Jeep XJ 4x4 Smell the Magic! Last edited by ROAD DOG; 12-29-2003 at 12:32 AM.

12-29-2003, 01:19 AM	#8
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	You may be agle to find a good set of axles with 4:10 in them cheaper then changing gears you may want to look in to guy a complete set of axles I sold a the d44 and 12bolt out my blazer for 250 with 4:10s in it when I whent to D60 and 14b. Im running 4:10 in the new set up with 36 in tires, my old tow rige had 4:56 with 31in tires and it was horible if you had to drive it over 55. __________________ Earl 68 2500 4x4 GMC Burb

12-28-2003, 08:15 PM	#2
Destructo Registered User Join Date: Sep 2003 Location: Lewisville, NC Posts: 1,836	I wouldn't run gears that are going to put your cruise rpm above 3k. I would like something right around 2500 rpm cruise.

12-28-2003, 09:25 PM	#4
Destructo Registered User Join Date: Sep 2003 Location: Lewisville, NC Posts: 1,836	I'm planning on running 35" tires and using 4.56 gears, but I also have OD so i'll only be turning about 2000 at 65mph.

12-29-2003, 12:33 AM	#7
rogf4 Registered User Join Date: Nov 2003 Location: whitesburg,Tn Posts: 223	I hope your motor has a serious bottom end if you decide to go with the 4.56 gears without over drive

12-30-2003, 02:11 AM	#9
ROAD DOG Top of the foodchain Join Date: Oct 2003 Location: 3.5 miles from Mile Hi Stadium Posts: 127	Good feed back on this post, right on! I've been looking through salvage yards, junk yards and old farmers backyards here in denver metro. for a couple of months. And haven't found nothing more then 3.73's. From spining tires counting driveshaft revolutions, to pulling covers counting teeth, You'all know the deal. nothin, On the parts board a guy from washington that has both axles with 4.10's for $200 obo!!!!!! If he was within 500 miles they would be mine! Anyways I just dropped $290.35 to Summit for richmond 4.10's and install kit for the rear. What sucks is I'll have a two wheel drive truck until I save the dough for the front. __________________ 1970 K-10 4x4 1975 Jeep CJ-5 4x4 1990 Jeep XJ 4x4 Smell the Magic!

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