Changing Gears - The 1947 - Present Chevrolet & GMC Truck Message Board Network

48 ish · 03-24-2008, 05:08 AM

I just dropped in a 427 with a t400 in my 67 C-20 with an HO 70 rear. It's got all balls I can ask for, but with the 4:10's in the rear it passes everything but a gas station. I want to drop the ratio to 3:55 or 3:70, but all the guys up here that do that sort of stuff say I'm out of luck. I know I may end up swapping it out for a late model, which may not be a bad thing as I tow a 5th wheel and could use a rear disc set up, but sometime's I'm a little old fashioned and would rather keep the original rear if possible. Anybody have any ideas?

crazy longhorn · 03-24-2008, 05:57 AM

Leaf or coil ?

Longhorn Man · 03-24-2008, 07:08 AM

you should have the HO52 rear... the HO72 was for one tons.
4.10 is as good as you'll do without some real luck. There were aftermarket 3.90 (I think?) but they are all gone and very far and few between.
Axle swap, or overdrive.

ed2552 · 03-24-2008, 07:14 AM

He has one already, read his sig

Longhorn Man · 03-24-2008, 07:21 AM

gear vendors doesn't drop the RPMS as much as a real overdrive.
But it is 100 times stronger though.

ed2552 · 03-24-2008, 07:28 AM

And it turns a TH400 from 3- 6 spd

Longhorn Man · 03-24-2008, 07:33 AM

could turn it to a 12 speed, but it won't help drop the cruise RPMs as much as a real overdrive.

What kind of RPMs are you spinning on the freeway in 3-hi?

crazy longhorn · 03-24-2008, 07:48 AM

What the OD ratio on that..... .8? that should knock that 4.10 down a tad anyway(about 3.28 on my calc). crazyL

48 ish · 03-24-2008, 08:03 AM

Coil springs. I don't have a tach on it yet, but it feels like it should shift about three more times (slight exageration) running down the road at about 65 mph. I can't imagine not having the o/d. Last time I checked I got 11.5 mpg comb city/hwy. I know I may just have to be happy with that without changing to a later model.....Thanks guys

crazy longhorn · 03-24-2008, 08:16 AM

Quote:

Originally Posted by 48 ish

Coil springs. I don't have a tach on it yet, but it feels like it should shift about three more times (slight exageration) running down the road at about 65 mph. I can't imagine not having the o/d. Last time I checked I got 11.5 mpg comb city/hwy. I know I may just have to be happy with that without changing to a later model.....Thanks guys

thats not bad.....my 383 gets 9-10 mpg (OUCH)!

Longhorn Man · 03-24-2008, 09:04 AM

11 is about the average for these.
Considering you have a big block... smile.

**El Jay** · 03-24-2008, 09:39 AM

The last time I checked, a Gearvendors "under/overdrive" was about $2500/2600, + some drive shaft mods.
I think the ratio is about .78.

They're durn near bullet proof.
Some motor home builders install them as a "factory" option; there's more than a few straight line races that use them.

That's definitely on my "to do" list.

haysonj · 03-24-2008, 05:37 PM

I had a gear vendors in my 60 1/2 ton short step side and it didn't help the mileage much but was sure fun to drive Had a Hurst ratchet shifter with the OD on a floor mounted switch and it was like driving a six speed.

**El Jay** · 03-25-2008, 02:58 AM

Quote:

Originally Posted by haysonj

I had a gear vendors in my 60 1/2 ton short step side and it didn't help the mileage much but was sure fun to drive Had a Hurst ratchet shifter with the OD on a floor mounted switch and it was like driving a six speed.

My uncle has one in his 1 T dually.
He says it helps his gas mileage some when running empty.
And when pulling his 5th wheel, getting up & down hills is a LOT easier because he can shift that 1/2 a gear, instead of a whole gear.

And, I'm willing to bet that when you started banging off shifts,you turned more than a few heads.

03-24-2008, 05:08 AM	#1
48 ish Registered User Join Date: Mar 2007 Location: Kennewick, WA Posts: 65	Changing Gears I just dropped in a 427 with a t400 in my 67 C-20 with an HO 70 rear. It's got all balls I can ask for, but with the 4:10's in the rear it passes everything but a gas station. I want to drop the ratio to 3:55 or 3:70, but all the guys up here that do that sort of stuff say I'm out of luck. I know I may end up swapping it out for a late model, which may not be a bad thing as I tow a 5th wheel and could use a rear disc set up, but sometime's I'm a little old fashioned and would rather keep the original rear if possible. Anybody have any ideas? __________________ hooberjon@yahoo.com "Life's Been Good To Me So Far" 1941 Chevy PU (new project, right out of the field) 1948 P/U: 350/700r4, Nova Clip,Chevelle rear, air ride suspension, custom door handles, custom firewall, custom dash, buckets and console, visor 1967 C20: 427 Tall Deck, Turbo 400 with Gear Vendors aux tranny, 5th wheel, 3500 bucket seats and console. 1996 Geo Tracker 2x4 1996 Geo Tracker 4x4

03-24-2008, 05:57 AM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Re: Changing Gears Leaf or coil ? __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

03-24-2008, 07:08 AM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Changing Gears you should have the HO52 rear... the HO72 was for one tons. 4.10 is as good as you'll do without some real luck. There were aftermarket 3.90 (I think?) but they are all gone and very far and few between. Axle swap, or overdrive.

03-24-2008, 07:14 AM	#4
ed2552 Registered User Join Date: Jan 2007 Location: Charles City IA Posts: 1,626	Re: Changing Gears He has one already, read his sig __________________ '67 C20, Under the Knife!, LWB, Eaton HO-52, Rear Coil Springs 72' GMC C2500, 350, TH400(?), Dana 60 '67 K10 4-spd., 305, SM465, Dana 44, 12 Bolt, RUST! '65 C60 292, 4 spd, 2 spd Rearend, 15' Grain Box, MINT! 09 Yukon Denali 82k Miles 6.2L/6A

03-24-2008, 07:21 AM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Changing Gears gear vendors doesn't drop the RPMS as much as a real overdrive. But it is 100 times stronger though.

03-24-2008, 07:28 AM	#6
ed2552 Registered User Join Date: Jan 2007 Location: Charles City IA Posts: 1,626	Re: Changing Gears And it turns a TH400 from 3- 6 spd __________________ '67 C20, Under the Knife!, LWB, Eaton HO-52, Rear Coil Springs 72' GMC C2500, 350, TH400(?), Dana 60 '67 K10 4-spd., 305, SM465, Dana 44, 12 Bolt, RUST! '65 C60 292, 4 spd, 2 spd Rearend, 15' Grain Box, MINT! 09 Yukon Denali 82k Miles 6.2L/6A

03-24-2008, 07:33 AM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Changing Gears could turn it to a 12 speed, but it won't help drop the cruise RPMs as much as a real overdrive. What kind of RPMs are you spinning on the freeway in 3-hi?

03-24-2008, 07:48 AM	#8
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Re: Changing Gears What the OD ratio on that..... .8? that should knock that 4.10 down a tad anyway(about 3.28 on my calc). crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

03-24-2008, 08:03 AM	#9
48 ish Registered User Join Date: Mar 2007 Location: Kennewick, WA Posts: 65	Re: Changing Gears Coil springs. I don't have a tach on it yet, but it feels like it should shift about three more times (slight exageration) running down the road at about 65 mph. I can't imagine not having the o/d. Last time I checked I got 11.5 mpg comb city/hwy. I know I may just have to be happy with that without changing to a later model.....Thanks guys __________________ hooberjon@yahoo.com "Life's Been Good To Me So Far" 1941 Chevy PU (new project, right out of the field) 1948 P/U: 350/700r4, Nova Clip,Chevelle rear, air ride suspension, custom door handles, custom firewall, custom dash, buckets and console, visor 1967 C20: 427 Tall Deck, Turbo 400 with Gear Vendors aux tranny, 5th wheel, 3500 bucket seats and console. 1996 Geo Tracker 2x4 1996 Geo Tracker 4x4

03-24-2008, 09:04 AM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Changing Gears 11 is about the average for these. Considering you have a big block... smile.

03-24-2008, 09:39 AM	#12
El Jay Gone to greener pastures Join Date: May 2007 Location: Gateway to the Delta Posts: 7,354	Re: Changing Gears The last time I checked, a Gearvendors "under/overdrive" was about $2500/2600, + some drive shaft mods. I think the ratio is about .78. They're durn near bullet proof. Some motor home builders install them as a "factory" option; there's more than a few straight line races that use them. That's definitely on my "to do" list. __________________ '69 Chevy 1/2 T LWB Stepper: Daily Beater '72 GMC 3/4 T Fleet: Another Daily Beater '72 Plymouth Gran Coupe: ? "Ah women. They make the highs higher and the lows more frequent." Friedrich Nietzsche "Never kick a fresh turd on a hot day." Harry S. Truman GUN CONTROL: Never having to say, "I missed you." Always fire two warning shots into your attacker's chest area before putting a bullet between his eyes. Paraphrased from Louis Awerbuck

03-24-2008, 05:37 PM	#13
haysonj Registered User Join Date: Dec 2007 Location: Santa Maria, Ca. Posts: 1,423	Re: Changing Gears I had a gear vendors in my 60 1/2 ton short step side and it didn't help the mileage much but was sure fun to drive Had a Hurst ratchet shifter with the OD on a floor mounted switch and it was like driving a six speed. __________________ 69 Chevy 4x4 383 Power



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