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Old 04-09-2009, 11:34 AM   #1
JJanzen
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Differential, Transmission & Motor Combo Opinions Needed

For the last year and a half, like a lot of us, I have been collecting parts to re-do my 72 SWB Cheyenne Super. I have come to the conclusion I have so many parts that maybe I should just build a new truck. So, I purchased a new shortbed frame and am having a lot of the parts powder coated and/or replaced. In cleaning up the rear end, I looked up the code and found that it is a 3.07. Here's my dilemna, I purchased a slightly used (200 mi.) HO 350 GM crate motor (330 HP) and my initial thoughts were to put in a 700r4 tranny. Now that I know I have a 3.07 rear end I have read and heard that combination isn't a good one. I would love to hear opinions on which way I should go. I live in the city and most of the driving with this truck will be short interstate (25 mi. plus/minus) and just cruising on city streets. One other thing I might mention, I am at 5280 feet above sea level.
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Old 04-09-2009, 11:38 AM   #2
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Re: Differential, Transmission & Motor Combo Opinions Needed

My favorite combo is a 350, TH350, and 3.07 gears. I've run a bunch of different ones, but for me, this is the one I always am most satisfied with.

For me, it's a lot about economics too though. A 3.07 rear is usually cheaper to buy than a 3.73 (they are in more demand it seems), and a TH350 is way cheaper than a 700R4 is.
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Old 04-09-2009, 11:43 AM   #3
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Re: Differential, Transmission & Motor Combo Opinions Needed

Kevin,
Is that combination going to be a bit "doggy" from a standing start?
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Old 04-09-2009, 11:51 AM   #4
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Re: Differential, Transmission & Motor Combo Opinions Needed

In my current shortbed:

Bone stock 170k mile 350 from a 77 model truck. Edelbrock performer intake, 600 vac secondary Holley, stock ramshorn exhaust manifolds, dual glasspacks

Bone stock 170k mile never touched TH350

3.07 rear diff with 275/60/15 tires.

From a standing stop, it will burn both tires through first and about 1/2 way through 2nd gear.

Not a hot rod at all, but I've never been dissapointed with it.

I get 12 mpg every tank.
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Old 04-09-2009, 11:56 AM   #5
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Re: Differential, Transmission & Motor Combo Opinions Needed

From your description of driving type, I'd go for 3:73's.
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Old 04-09-2009, 12:07 PM   #6
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Re: Differential, Transmission & Motor Combo Opinions Needed

My combination is a Small Block 406 (420 Horse Power to the wheels) with a built TH350 and 373 gears. My truck does not get driven alot but maybe 100 miles a month give or take so fuel economy is not important to me. Truck is stupid fast I can not get on the throttle at no speed less than 50mph because it breaks the tires out of control loose. I am very happy with my combo...
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Old 05-17-2009, 09:19 AM   #7
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Re: Differential, Transmission & Motor Combo Opinions Needed

The 700 and 3.73 gears are hard to beat. You might as well do it now and have the flexibility later if your driving style changes.

R/

PS Where are the pictures?
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Old 05-17-2009, 01:39 PM   #8
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Re: Differential, Transmission & Motor Combo Opinions Needed

I have run a 350/700R4 w/3.42 posi for well over 100000 miles. I pull hills, Zip down the Freeway and tow heavy (14' enclosed & Car trailer) @ 70mph it would tach about 2400rpm w/26" tall tire(295/35R17). It gives you an all around use. 700R4 gives you a 5% lower 1st & 2nd gear over a TH350/TH400.
Although a TH350 w/3.07 would be the less expensive, it is all what you want to spend.
A quality 700R4 will set you back 1800.00+ now days. I purchased mine from the Toy Shop. I have used 4 of these for different friends rides, all are still in service. Quality Fluid & Coolers are a Must!
I use a Hydrotex HytorqueZ and a B&M Super Cooler, routed thru the Radiator cooler then thru the external cooler.
But it all comes down to the $$$$$$$$ you want to spend.
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Old 05-17-2009, 01:47 PM   #9
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Re: Differential, Transmission & Motor Combo Opinions Needed

I love a 700r4 and 3.73 combo. Great all around combo.
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Old 05-17-2009, 08:17 PM   #10
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Re: Differential, Transmission & Motor Combo Opinions Needed

whats the best diff for gas mileage?

Last edited by dga93; 05-17-2009 at 08:17 PM.
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