the truth about 700r4's ??

[no1udknow]

Hey guys, I have read many forums about 700r4's and I feel like many of them are blowing smoke up my a$$. Who is running one, and what kind of milage are you really getting. my current setup is a 350 (383) with a edle-brick 750, th350 and 4.11s. I need to be able to drive this thing to work once in a while with out selling any organs. I'm not expecting the fuel economy of a sub compact, but I would hope to be able to achieve the high teens if not 20mpg by swapping the carb, rear end gears, and the trans. I have access to a 700r4 which is why I'm asking. but I might be open to other options if they are cheap. 4l80e's seem to be expensive as are t56's

[MARKDTN]

I have an '83 K20. It had 42K miles when I got it. It has 350, 3.42 rear, 700R4 trans. It always got about 14 mpg city and 17 highway (unloaded). I swapped to TPI fuel injection and now I get 17 city and 20 highway.

[67ChevyRedneck]

You do not want a 4L60e or 4L80e, those require an $ stand alone harness to run if you're not already running an LS motor, which you're not.

67 C10, 350/700R/3.73. Had the 700R since 2002. I get about 12 around town and 16 highway. Low to mid teens is average depending on how you drive, expect 15-17mpg highway depending how you drive. The 4.11 gear is a bit steep. The 3.73 seems to be the best all around, I've read many guys have swapped back from a 3.08 to 3.73 because the motor was always lugging. A 3.42 would be great, but they're hard to find, unless you buy a new gear set.

[nightmare]

Originally Posted by 67ChevyRedneck

You do not want a 4L60e or 4L80e, those require an $ stand alone harness to run if you're not already running an LS motor, which you're not.

67 C10, 350/700R/3.73. Had the 700R since 2002. I get about 12 around town and 16 highway. Low to mid teens is average depending on how you drive, expect 15-17mpg highway depending how you drive. The 4.11 gear is a bit steep. The 3.73 seems to be the best all around, I've read many guys have swapped back from a 3.08 to 3.73 because the motor was always lugging. A 3.42 would be great, but they're hard to find, unless you buy a new gear set.

Agree with 67ChevyRedneck. Stock 350, Edelbrock 1406 (600cfm carb), 700R4, 3.73 posi rear end.

I'm getting slightly less, only because of the whole lwb vs swb thing, but still decent mileage for a 40 year old brick.

[GASoline71]

The 700R4's are great trannys! Best part is they are plentiful and affordable. Only thing you need to remember is that once you start putting serious TQ through one... It will need major upgrades. Behind a warmed over 350 or a not so radical 383 they will last forever with very inexpensive rebuilds and mods.

But if yuo're trying to push over 400hp and 400 lb ft of TQ... they won't last long in stock form. They need major upgrades to take it. But when they are upgraded they are simply a great transmission that doesn't require any electronic gizmos to work.

One thing to consider also is a 200-4R. They are the same size as a TH350, and can be built to handle TQ as well.

Gary

[michael bustamante]

Make sure you get a tranny guy to adust your tv canle brfore ypu drive it though. Very very important. Also theres alot of info on how to use a brake switch and vacuum set up and it works but id suggest getting a tv kit.from reliable vendor. You wont regret it

[Z10]

I'm running a new ZZ4 350 F.I.R.S.T TPI FI with about 3k miles. A GM rebuilt 700r4 from a 91 Corvette, 373 rear, & 29" tires. I just drove 300 miles, 90% highway, a couple of weeks ago running about 70mph with cruise control and the truck returned 15.3 mpg.

I'll be changing to Mobil 1 synthetic at around 5k miles. Hopefully the oil and a looser engine will give me a mpg or two?

I'm happy, the truck used to get 10mpg on the highway. 50% improvement is not shabby.

[Fitz]

Originally Posted by no1udknow

Hey guys, I have read many forums about 700r4's and I feel like many of them are blowing smoke up my a$$. Who is running one, and what kind of milage are you really getting. my current setup is a 350 (383) with a edle-brick 750, th350 and 4.11s. I need to be able to drive this thing to work once in a while with out selling any organs. I'm not expecting the fuel economy of a sub compact, but I would hope to be able to achieve the high teens if not 20mpg by swapping the carb, rear end gears, and the trans. I have access to a 700r4 which is why I'm asking. but I might be open to other options if they are cheap. 4l80e's seem to be expensive as are t56's

Some like them, some don't. The first generation of this trans broke easily but later models fixed the weaknesses as long as you don't try to put too much torque through it. Your 383 won't break it and you will like the low final drive ratio so go for it!

[GuyO]

350 w/700r4+ 3.73's with 31" tires = 15 mpg average for me.

[piecesparts]

Originally Posted by no1udknow

Hey guys, I have read many forums about 700r4's and I feel like many of them are blowing smoke up my a$$. Who is running one, and what kind of milage are you really getting. my current setup is a 350 (383) with a edle-brick 750, th350 and 4.11s. I need to be able to drive this thing to work once in a while with out selling any organs. I'm not expecting the fuel economy of a sub compact, but I would hope to be able to achieve the high teens if not 20mpg by swapping the carb, rear end gears, and the trans. I have access to a 700r4 which is why I'm asking. but I might be open to other options if they are cheap. 4l80e's seem to be expensive as are t56's

I have an 84 GMC SWB with a 383 with a comp roller cam and T-700 tranny. It is a 700 R4 without a lockup converter, but my converter is a 2400 stall. I also run 3.73 gears and a lower profile tire, so I can keep my RPMs in the range where I do not generate too much heat in the tranny from slippage. I have ocnsidered going to a slightly taller tire to drop my RPMs another 100 on the highway, but it has not happened, yet. I have driven many highway miles with the truck and it runs around 2500 RPM at 75 to 80 MPH. I have a 650 CFM Edelbrock carb on it and I get a solid 15 MPG on the truck. For the HP it has, to me this is not a bad number. I did have a 750 Edelbrock on the truck, but found that to be a hinderance in daily driving and it did not work well with low speed and general street driving and my cam. The 750 is good at RPMs above 2500 and lighter vehicles like a Camaro, but it slobbers up on a heavier vehicle like a truck. I talked to several carb suppliers (Edelbrock, Holley, and Carter), they all say the trick is not the total flow, but the air signal from the rate of flow, so a smaller carb will be more effective on the street in a heavier vehicle than the 750. The other side of this, the 750 provides a higher amount of fuel available at higher RPMs, so you have to target what you want out of the engine. What you drive in daily will set the standard as to what you select for gears and tire sizes. City driving (Stop and Go) will eat up mileage on a taller tire and highway driving will kill you on a smaller tire. Look for an RPM, that you will get the optimum performance from your engine and then select tires and gears to put you at the point that you drive the most. There is always a "Sweet Spot". The exhaust and air intake setups make a large difference, also.

[no1udknow]

Originally Posted by GASoline71

The 700R4's are great trannys! Best part is they are plentiful and affordable. Only thing you need to remember is that once you start putting serious TQ through one... It will need major upgrades. Behind a warmed over 350 or a not so radical 383 they will last forever with very inexpensive rebuilds and mods.

But if yuo're trying to push over 400hp and 400 lb ft of TQ... they won't last long in stock form. They need major upgrades to take it. But when they are upgraded they are simply a great transmission that doesn't require any electronic gizmos to work.

One thing to consider also is a 200-4R. They are the same size as a TH350, and can be built to handle TQ as well.

Gary

well, my motor setup is a 350 crank, bored .080 over medium cam, torquer intake, and a edlebrick 750. supposedly the motor makes about 350-370hp. I have a spare 600 cfm at home I was considering putting on it to lighten up the fuel consumption but we will have to see how it runs.

[mechanicalman]

What transmission you have makes no difference on cruise gas mileage, only final drive ratio. People who get good mileage have the right combination of parts, no one thing is a magic bullet for gas mileage. IOW, an overdrive with a 4.11/1 rear axle is roughly equivalent to a non-overdrive with a 3.0/1 axle.

Fuel injection systems have at least two advantages when it comes to gas mileage.

1. They usually control the ignition timing close to ideal calibration, and that includes a knock sensor to keep the engine in one piece.

2. They usually have O2 feedback and close to ideal fuel calibration.

That being said, you can tune your carb and your distributor to get very close to FI numbers, but it takes time and patience. First, your compression ratio has to match the cam, then the cam's "cruise RPM" needs to match your actual cruising RPM, then you need the most cruise timing you can get without ping (vacuum pod with adjustable tip-in plus a stop to adjust total vacuum advance). You will need a hand held vacuum pump and use the pump as your vacuum gauge while driving cruise so you know when it tips in.

In order to achieve that much cruise advance, the distributor will also have to have to proper curve to match the engine before this part of the calibration can take place.

Jets, primary metering rods, primary metering rod springs, etc. Some engines even like EGR, and most factory EFI's have that. Not good with a bigger cam, however.

It's not a 700R4 issue.

[67ChevyRedneck]

Originally Posted by mechanicalman

What transmission you have makes no difference on cruise gas mileage, only final drive ratio. People who get good mileage have the right combination of parts, no one thing is a magic bullet for gas mileage. IOW, an overdrive with a 4.11/1 rear axle is roughly equivalent to a non-overdrive with a 3.0/1 axle.

Go to any classic Mustang site (I'm currently installing a 5 spd T5 in my 289 '65) and prepare to laugh your ass off...

I can't tell you how many times people have posted they want to save fuel mileage and lower their highway RPM, but then they swap in a T5 and put a 3.23 or 3.5 or steeper gear out back from a 2.8 or 3.0 rear, many don't realize they're right back where they started, and they'll swear they're getting 25mpg

The T5 I'm using comes from a 98 V6 mustang with a 2.73 rear and similar sized tires. I'm keeping my 2.8 rear. I mentioned that in one of my threads and people told me my car would be a dog with that gear? My 289 should have similar, maybe a tick more HP than the 98's V6. Also, a C4 has a 2.46:1, 1.46:1, 1.00:1 gearing for 1st, 2nd, 3rd. My new T5 has 3.35, 1.93, 1.29, 1.0 and 0.73:1 ratios.

My car will actually be "quicker" now all the way up through 3rd gear and have the advantage of OD.

Sometimes I don't think people quite get the math on how it all works, and absolutely, going from a 3.08 to a 700R w/3.73 will see a minimal gain in fuel economy, however, drivability will be much more fun, especially with the low 1st gear the 700R's have!

But, if you're converting from a 4.11 with a 1:1 final drive ratio to a 3.73 (or even keep the 4.11) and a 0.7 final ratio... that's gonna be a nice improvement.

[IwantaK5]

I am happy with the 700r4. without having an accurate fuel gauge i figure i get about 12/14 mpg. But that is with 4x4 ,6in lift and 35x12's.

[GASoline71]

Originally Posted by no1udknow

well, my motor setup is a 350 crank, bored .080 over medium cam, torquer intake, and a edlebrick 750. supposedly the motor makes about 350-370hp. I have a spare 600 cfm at home I was considering putting on it to lighten up the fuel consumption but we will have to see how it runs.

Hold up... you have a 350 bored .080 over??? With a 350 crank??? How are you getting 383 cubes? The most any 350 should be overbored is .060, and that is pushing it in most cases.

Gary