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#1 |
Registered User
Join Date: Oct 2008
Location: richmond, kentucky
Posts: 30
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i need more speed/mileage
i got a 72 lwb chevy with a 350/350. i'm not gettin the best milage, and don't have a very high top speed. i'm startin to think the 350 tranny has to go. lookin to put somethin with overdrive in. maybe even a 5 speed. automatic only, i have a low hump floor, and so on. what do you guys think?
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#2 |
Tot Roddin'
Join Date: Apr 2005
Location: Mid-MO
Posts: 24,461
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Re: i need more speed/mileage
You can do a 700R4 swap fairly easy and IIRC can even reuse your old tranny member.
Of course you could also drop in a 250 w/ powerglide like my '69 and pull in 21 mpg. ![]() It won't get you there the quickest but you'll have a few cents extra in your wallet.
__________________
-Nate ![]() 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package) |
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#3 |
Registered User
Join Date: Oct 2008
Location: richmond, kentucky
Posts: 30
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Re: i need more speed/mileage
is the 700r4 4spd+overdrive? i forget
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#4 |
Watch out for your cornhole !
![]() Join Date: Jun 2003
Location: Azle, Texas
Posts: 14,162
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Re: i need more speed/mileage
A 700 is a 4 speed trans. Third is 1:1 like your current TH350 and 4th is .70 overdriven.
__________________
I'm on the Instagram- @Gearhead_Kevin |
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#5 |
Registered User
Join Date: Oct 2008
Location: richmond, kentucky
Posts: 30
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Re: i need more speed/mileage
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#6 |
Tot Roddin'
Join Date: Apr 2005
Location: Mid-MO
Posts: 24,461
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Re: i need more speed/mileage
Of course you could also keep your TH350 and throw on a GearVendors OD, but you would probably be money ahead with the 700R4.
__________________
-Nate ![]() 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package) |
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#7 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: i need more speed/mileage
how many miles per gallon do you get and about what speed are you trying to achieve?
__________________
71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#8 |
Registered User
Join Date: Oct 2008
Location: richmond, kentucky
Posts: 30
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Re: i need more speed/mileage
i don't get much right now, less than 15 for sure. as far as speed goes, maybe 110 or 120. that's not as important as being able to cruise 75 on the interstate without runnin 3grand lol. where im goin to school next year im gonna be hittin the interstate every mornin...
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#9 |
Registered User
Join Date: Oct 2008
Location: richmond, kentucky
Posts: 30
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Re: i need more speed/mileage
well, sounds like 700r4 is the way to go. where should i get one? how hard will the swap be? how much is this gonna set me back?
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#10 |
Registered User
Join Date: Aug 2007
Location: greenville,ms.
Posts: 47
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Re: i need more speed/mileage
maybe try swaping some 3.07 gears.
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#11 | |
blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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Re: i need more speed/mileage
Quote:
otherwise www.bowtieoverdrives.com is a good reputable shop with quality stuff and lots of valuable tech help. |
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#12 | |
Senior Member
![]() Join Date: Jan 2009
Location: Austin, TX
Posts: 1,079
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Re: i need more speed/mileage
Quote:
It might cost you a little more because I was given a 700r4 core to rebuild
__________________
-- Josh Instagram: @americanmusc1e OLD SKOOL-- 1970 C10. 454/Th400/3.07 posi Build Thread FARM TRUCK----1949 Chevrolet 3800 Power Wagon Hauler Build Thread 1999 4wd OBS Tahoe - daily. DM me if you can't see photos i posted |
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#13 | |
Senior Member
![]() Join Date: Jan 2009
Location: Austin, TX
Posts: 1,079
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Re: i need more speed/mileage
Quote:
bottom line: I would not use a 700r4 and 3.08's together, the 700r4 works better with a 3.50 to 3.73 rear end
__________________
-- Josh Instagram: @americanmusc1e OLD SKOOL-- 1970 C10. 454/Th400/3.07 posi Build Thread FARM TRUCK----1949 Chevrolet 3800 Power Wagon Hauler Build Thread 1999 4wd OBS Tahoe - daily. DM me if you can't see photos i posted |
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#14 | |
Registered User
![]() Join Date: Apr 2008
Location: Sacramento, California
Posts: 62
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Re: i need more speed/mileage
Quote:
The Turbo 350 doesn't run too bad with the taller gears. My old truck was a '73 C20 with same engine/tranny (350/TH350) with 4:11 gear ratio; I looked into it and it would have been cheaper to just rebuild the TH350 and change the rear gearset than to go with a 700R4 swap. Plus dialing in the 700R4 with that TV cable gets to be real fun (insert sarcasm here). Basically, if you are going to change something, be sure to consider how the tranny and gearing work together.
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"Two rules get you through life: If it's stuck and it's not supposed to be, WD-40 it. If it's not stuck and it's supposed to be, duct tape it." |
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#15 |
Old Skool Club
![]() Join Date: Jun 2001
Location: Benton, AR "The Heart of Arkansas"
Posts: 10,880
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Re: i need more speed/mileage
Custom Classic Trucks magazine had an article in the March issue about GM automatic transmissions. Until I read the article, I didn't have a high opinion about the 200R4. They say it is good for up to 800 horsepower, when built. It will also bolt to any GM engine. If it doesn't have the TV cable issues, it will get my interest piqued. There was a post a few weeks ago, and someone was talking about hooking a 200 to a Cadillac 472.
__________________
Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was. |
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#16 | |
I really hate wet sanding!
![]() Join Date: Dec 2008
Location: Brookfield, MO
Posts: 601
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Re: i need more speed/mileage
Quote:
http://www.tciauto.com/Products/TechInfo/trans_dims.asp I will eventually go this route, but for now my newly rebuilt 350 will have to make do, I don't have to drive mine everyday so fuel mileage is not that great of concern ![]() |
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#17 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: i need more speed/mileage
in reality, you'll be hard pressed to get more than 15 MPG... the typical MPG is 10 - 12 on these trucks.
You need to figure out what gears you have in the rear axle before you make any plans here, MPG can drop if you lower your RPMs too much. |
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#18 | |
Registered User
Join Date: Feb 2000
Location: Center City, MN, USA
Posts: 3,254
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Re: i need more speed/mileage
Quote:
2wd trucks get better but 15 and higher is the exception not the rule. Once you figure out what you get for mileage you have to decide how much you want to spend to "save" money. If you need to spend $1500 on an overdrive 700r4 or similar, and it will take 10 years to pay back, you might want to reconsider. If you run 4.11 gears, a swap to 3.07 gears will give you almost the same benefit as leaving in the 4.11 and putting in a .7 overdrive like a 700r4. And it will be a whole lot cheaper. To make a really long post short, you need to calculate your real mileage, figure out what rear end you got, and do some math.
__________________
'70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN |
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#19 |
Registered User
Join Date: Sep 2007
Location: Vilseck Germany (currently)
Posts: 317
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Re: i need more speed/mileage
How much longer is the 700r4 than a TH350?
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#20 |
I really hate wet sanding!
![]() Join Date: Dec 2008
Location: Brookfield, MO
Posts: 601
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Re: i need more speed/mileage
Oh yeah I forgot, the 700 is a shade over 3 inches longer than the short tail shaft 350, 27 11/16" versus 30 3/4". See site I mentioned in other post for all kinds of trans info.
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#21 |
Registered User
Join Date: Apr 2008
Location: Smithville, Ontario
Posts: 38
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Re: i need more speed/mileage
well from the LITTLE I know...more speed seldom = more mileage.
If you got the cash a gear vendors is too cool...6 speed auto. Check E-bay n they usually can be had for $1500 (+driveshaft mods). |
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#22 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
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Re: i need more speed/mileage
It`s always the same.You can spend a bunch of money to gain a couple mpg or save your money for fuel.The other benefits of o/d make it worth it more than fuel consumption.
__________________
"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
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#23 |
Blank
Join Date: May 2005
Location: Southington, CT
Posts: 221
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Re: i need more speed/mileage
2004r is great bolts right in, the crossmember has to be moved back a few inches but my frame already had holes for a different trans option. No drilling required, driveshaft bolted right up. got mine from a 86 monte carlo ss but many gm cars had them in the mid 80's
__________________
![]() 1969 lwb 4/6 drop 17x8-18x10 torque thrust II's 327-420hp 2004R 3.73 posi. 1977 Corvette 350-375hp 4speed, silver show car. 2002 S10 xtreme, work truck 2004.5 VW jetta GLI 1.8T 6speed, weekend warrior. 2013 Audi A3 TDI, the wife's car |
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#24 | |
Registered User
Join Date: Oct 2008
Location: richmond, kentucky
Posts: 30
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Re: i need more speed/mileage
Quote:
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#25 |
Registered User
Join Date: Oct 2008
Location: richmond, kentucky
Posts: 30
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Re: i need more speed/mileage
i'm not sure what my gears are now, but i know it was a quarry truck for the allen company new, and it was bought with the lowest gears it could be bought with. its a heavy duty truck- it's a 72 CHEVY 2wd with rear leaf springs. the only other 72's i have seen with leaves where GMC's.
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