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Discussion Starter · #1 ·
I just finished putting a 4bta 120 in my 71 chevy 4X4. I have a 700r4 and 31X10.50 AT radials. I am not sure what gears I have I am thinking they are 3.56 or 3.73. My only mod is a 3200 rpm spring. I have checked mileage twice now and am getting 22 MPG. I have accounted for a 10% error in my odometer already. I hear about lots of guys getting 25mpg +. Is there a way to tune the pump for better mileage, not just more power??
 

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I punched in your basic stats into a gear calc program:

http://www.f-body.org/gears/

using diameter of 31", either axle ratio, redline of 2500, and
1st through 4th as 3.06, 1.63, 1.00, 0.70

The 3.56 ratio should give you good economy. Look at the
table and see where your shift points are. Do you have a tach
installed? Probably need to see what your rpm is at cruise
(assume about 65mph). Seems to be around 1750 rpm using
the 3.56, which is very good with a light load on level highway
(best case scenario).
 

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A sloppy torque converter can rain on your little parade too!
 

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Do you have the Torque Converter lockup enabled? That'll be good for another couple of MPG..
 

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Absolutely make sure the convertor locks up!!! Trans temps go out of sight when TC doesn't lock. Mileage too!

I'm looking at tires for my '03 Ram. I'd like ATs but am gonna get Toyo HTs so I don't screw up my milege.
 

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If it's got the stock 12 bolt rear under the 71 it's got 3.73. Most of the half ton trucks came with a 3.07 or 3.73 rear. The C/K20's had up to 5:13's in those eaton rears. Remember you're driving a truck about as aerodynamic as a brick - 55mph and/or around 1600-1800Rpms will net you the best mileage.
 

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But think about this. A first gen Ram is about as aerodynamic as a brick as well, and first gen 12V Cummins get about the best MPG of all of them.

Best all around rpm and speed for my 3.73 geared 48RE trans '03 is 1800rpm and 63.5ish mph. On pure flat land 1500 at 53ish is of course better. But 63.5mph gets me there.

1900rpm at about 67-68 doesn't hurt things TOO bad if I'm in more of a hurry.
 

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Discussion Starter · #10 ·
Thanks for all the info. I have the 12 bolt so I guess it's 3.73. It could be 3.07 as the engine feels like it's lugging and vibrating if you go up a slight hill at speeds less than 65 in OD. TQ is locking up, but Having a hard time setting up shift points. I had a guy put heavier weights and springs on the tranny GOV for earlier shifts as per advice saying "you should put a diesel GOV in the tranny" I listened to this before I tried it with the original Governor in the tranny. It shifts into OD at less than 40mph and lugs the tranny. I have trouble getting it to upshift into 2cnd unless I back off the gas slightly at about 20mph. TV cable is such a pain to adjust and setup properly. I wish someone would make a electronic control box for a 4l80e or 4l60e for a reasonable price like say $200 maybe more people would be using them and programing shift points in.
 

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Wow, all those issues and you're getting 22mpg!??

Mileage can only get better! Hope the gas-700R doesn't break
during all your "field testing"...
 

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Thanks for all the info. I have the 12 bolt so I guess it's 3.73. It could be 3.07 as the engine feels like it's lugging and vibrating if you go up a slight hill at speeds less than 65 in OD. TQ is locking up, but Having a hard time setting up shift points. I had a guy put heavier weights and springs on the tranny GOV for earlier shifts as per advice saying "you should put a diesel GOV in the tranny" I listened to this before I tried it with the original Governor in the tranny. It shifts into OD at less than 40mph and lugs the tranny. I have trouble getting it to upshift into 2cnd unless I back off the gas slightly at about 20mph. TV cable is such a pain to adjust and setup properly. I wish someone would make a electronic control box for a 4l80e or 4l60e for a reasonable price like say $200 maybe more people would be using them and programing shift points in.
sounds like the issues that I am having. I have the 4L80E in the garage waiting for the controls and a torque converter.

At low speeds I shift to 3rd, keeps the converter from locking up. You are having problems getting it to shift out of 1st into 2nd? I'm having the exact issue. All the research i have seen point to the TV cable/ TV itself, namely the TV sticking and not working correctly. I also noticed on mine that it does not shift back to 1st, so from a stoplight I start out in 2nd, didn't notice it at first, this thing's got low end torque for sure!

good luck, I can't wait for my 4L80E to go in, just need to find the money...
 

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I can sure understand why many 4BT swappers run standard transmissions!

I like the 48RE in my '03 2500 a lot! It sure does seem that someone should make it fairly easy to use an E trans.

All I know is I do pretty good on mileage with an 8,000LB 2500.
 

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The fun I've had with the Throttle Valve adjustment on the 700R4 on some prior builds is part of the reason I've decided to go a different path for the transmission on my swap.

Even if you're using a TV kit, such as the ones at www.bowtieoverdrives.com, it can be a bear to get it right. If you're "rolling your own" on the TV connection to the throttle.. Then things can get REAL fun. In "stock" installs, such as my 90 C2500, the throttle arm rotates about 90°, and the "pull" on the TV cable is fairly linear, with the angle established between the throttle shaft, TV cable attachment point, and the TV cable hitting 90° at about the half-way point in the pull. (Actually a bit before that, but not by too much..)

If the angles of a custom install don't match these, then things can get real ugly trying to get all the points to line up, and you likely will wind up with some VERY non-linear operation even if you get idle and WOT licked. And, if the total rotation of the throttle shaft / levers is something other than about 90°, it's going to be just about impossible to get it right w/o some custom linkages. I've not looked at the total throw / angles of the VE throttle levers that much with TV in mind, but I know when I was first thinking 700R4 something in my mind went "that's not gonna be easy.."

One thing I can say is this: You WILL need a pressure gauge to have a hope of getting it correct for all modes.

The other thing that can be a battle is the governor. If you just put in the "diesel" governor, it's not going to be correct for our application. I noted you indicated that you had the shop put heavier weights on it, but what's the thing actually set for? And, you'll need a different setting depending on what your actual attainable RPM is out of the engine.

A very good writeup on TV and getting it right is here: http://www.tvmadeez.com/article/index.php
 

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I am in the process of putting a 4BT in my 3/4 ton 'burb. I am using the 4L80 that was in it. It had the 6.5 diesel. I will use the existing computer and electronics. I am using the 6.5 crank trigger and MAP sensor, and will add a cable linkage to the fly by wire throttle. I'm working on the motormounts at the moment. I'll post some pics once I get it done.
 

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just dich the auto and go 5spd. O.D. WITH 3.08 OR 3.42 GEARS. i,am building a 1 ton 1972, 6bt 12 valve, ve stock pump, stock cpl, 3.21 gears & 19.5 rims. i expect to do 20-30 mpg on highway. why the 3200 rpm gov spring ? your gonna blow it up if you rev it that hi on a stock bottom end. these arnt race engines there work horses. dont try to make em do somethingthere not designed to do. try to cruise at 1600 rpm,s...
JMO
BOB
 

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interesting. lots of good info. im hoping to put a 4bt into my 79 plymoth trail duster(dodge ramcharger) i got a d 60 front and rear np205 and hoping to get a nv4500. planning on running 4.10 with 35" tires. what do you think my cruse mpg will be? i have herd "storys" of guys who have 350 hp and 700 tq who get 35mpg? are they just blowing smoke?(no pun intended)
 
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