Tranny swap. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tynee · 12-20-2002, 09:23 PM

I'm looking at a deal for a 700r4. I've been threatening to swap my th350 for one since I got the truck. My thinking is that it will increase my MPG, and will increase longevity of engine because of fewer RPM @ highway speeds. Am I correct in the assumption that it will improve MPG (mostly in-town driving)?
Also, what is it gonna take on a scale of 1 to 10 to do the swap? 1 being a direct bolt up; 10 being a torch, an act of congress, and the will of the almighty himself.

Project1970 · 12-21-2002, 05:27 AM

Look in the FAQ, I wrote one up that covers everything I could think of at the time.

Don't even try to justify it on a cost basis; you're looking at a lot of miles before the MPG improvements show up as a fatter wallet after taking the hit that a 700R4 is. Do it for the lower cruise RPMs and shorter first.

You will gain in MPG; the 700R4 is what pushed my truck from a 10mpg wonder (TH400) to a 14mpg wonder. I have clocked it as high as 17 if I drive reeeeeeally carefully.

Scale of 1-10, I'd say a 4...it's really not too far beyond a bolt-up, but there are a few technical bits (namely, TV cable and TCC wiring).

Just FYI...your new cruise RPMs at a given speed will be, at most, 74% of what they are now, and that's if you either didn't put a locking converter in the 700 or if your TH350 has a locking converter. That's one of the other reasons I like it, is the 4th gear lockup.

3damnboyz · 12-21-2002, 12:34 PM

I plan on doing the 700r4 thing to my 72......its 30 miles to anywhere i want to go so i figure its gotta help my mileage! from what i hear i will have to get a few inches taken off the drive shaft, the other things are simple wiring and linkage installs. i got some of my parts and information from the folks at 700r4.com. i hope it all works out!

Tynee · 12-22-2002, 03:19 PM

Thanks, Guys. Goos stuff

busterwivell · 12-22-2002, 07:27 PM

Bottom line, if you install it CORRECTLY, you'll love it!

12-20-2002, 09:23 PM	#1
Tynee I miss this truck. Join Date: Dec 2001 Location: Lexington, KY U.S.A. Posts: 2,863	Tranny swap. I'm looking at a deal for a 700r4. I've been threatening to swap my th350 for one since I got the truck. My thinking is that it will increase my MPG, and will increase longevity of engine because of fewer RPM @ highway speeds. Am I correct in the assumption that it will improve MPG (mostly in-town driving)? Also, what is it gonna take on a scale of 1 to 10 to do the swap? 1 being a direct bolt up; 10 being a torch, an act of congress, and the will of the almighty himself. __________________ '07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT.

12-21-2002, 05:27 AM	#2
Project1970 14.1 @ 96MPH Join Date: Jul 2001 Location: Mesa, AZ Posts: 2,811	Look in the FAQ, I wrote one up that covers everything I could think of at the time. Don't even try to justify it on a cost basis; you're looking at a lot of miles before the MPG improvements show up as a fatter wallet after taking the hit that a 700R4 is. Do it for the lower cruise RPMs and shorter first. You will gain in MPG; the 700R4 is what pushed my truck from a 10mpg wonder (TH400) to a 14mpg wonder. I have clocked it as high as 17 if I drive reeeeeeally carefully. Scale of 1-10, I'd say a 4...it's really not too far beyond a bolt-up, but there are a few technical bits (namely, TV cable and TCC wiring). Just FYI...your new cruise RPMs at a given speed will be, at most, 74% of what they are now, and that's if you either didn't put a locking converter in the 700 or if your TH350 has a locking converter. That's one of the other reasons I like it, is the 4th gear lockup. __________________ Project1970 - LS1 Swap Complete!

12-21-2002, 12:34 PM	#3
3damnboyz Registered User Join Date: Dec 2002 Location: east texas Posts: 42	I plan on doing the 700r4 thing to my 72......its 30 miles to anywhere i want to go so i figure its gotta help my mileage! from what i hear i will have to get a few inches taken off the drive shaft, the other things are simple wiring and linkage installs. i got some of my parts and information from the folks at 700r4.com. i hope it all works out! __________________ 72 short wide 55 stepside- 2nd generation "come on honey, we need more old trucks to fix up for the boys to drive, they will be driving before ya know it!"

12-22-2002, 03:19 PM	#4
Tynee I miss this truck. Join Date: Dec 2001 Location: Lexington, KY U.S.A. Posts: 2,863	Thanks, Guys. Goos stuff __________________ '07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT.

12-22-2002, 07:27 PM	#5
busterwivell Registered User Join Date: Jan 2002 Location: Sahuarita, AZ USA Posts: 2,033	Bottom line, if you install it CORRECTLY, you'll love it! __________________ Bill - Tucson, AZ 47 Chevrolet 2 dr sedan 56 Chevrolet 210 2 dr sedan 66 Chevrolet Malibu 2 dr 4 speed 71 Chevrolet C30 Longhorn 86 Chevrolet Monte Carlo SS (Sold) 01 Chevrolet Tahoe IM - BUSTERWIVE@aol.com

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