View Single Post
Old 03-24-2015, 02:58 AM   #1 (permalink)
oil pan 4
EV convert
oil pan 4's Avatar
Join Date: Jul 2011
Location: NewMexico (USA)
Posts: 8,765

Sub - '84 Chevy Diesel Suburban C10
90 day: 19.5 mpg (US)

camaro - '85 Chevy Camaro Z28

Riot - '03 Kia Rio POS
Team Hyundai
90 day: 30.21 mpg (US)

Bug - '01 VW Beetle GLSturbo
90 day: 26.43 mpg (US)

Sub2500 - '86 GMC Suburban C2500
90 day: 11.95 mpg (US)

Snow flake - '11 Nissan Leaf SL
90 day: 141.63 mpg (US)
Thanks: 212
Thanked 2,895 Times in 2,259 Posts
Fuel economy of 7.4L (454) powered 3/4 ton suburban

In addition to the little 7.4L engine it has a 3 speed automatic transmission and 4.10 fuel economy gears.
What, 4.10 gears are great for economy compared to optional 5.13 gears.
I don't know what it gets for gas milage but I am going to find out.
I have been told anything from 10 highway to 8 city to half that.
Its got 140,000 miles on it, that means its burned at least 14,000 gallons of gas. Soon it wont be burning any gas.

Well the bad news is the numerically lowest gear ratio I can locate for the full float GM 14 bolt 10.5 inch axle are 3.42:1 gears. The same gears my half ton suburbans 8.5 inch 10 bolt semi float rear has.
I wanted to pick up some 3.23s, but that's not happening.
Edit: It is happening. NitroGear makes 3.21 gears, the numerically lowest ratio known to have ever been produced for 14 bolt full float. But they are $600. NitroGear is the only producer for 3.21 gears, they are aware of this and have priced this gear set accordingly.

The 454 and 3 speed are only going to be in there till I can pull my 4 year old diesel engine out of my rusted out half ton and repair, update and improve its 700R4 transmission and move it all over. The current 700R4 shattered its torque converter lockup, a 27 spline lockup converter on an obsolete 27 spline input shaft and I cant even find a replacement lock up torque converter because everyone has gone to 30 spline which GM started using in 1985.
Edit: I have found some 27 spline options but they are limited to say the least.
I have almost infinite options available for 30 spline torque converters, (almost) nothing for 27 spline. But swapping to a 30 spline input shaft and drum will fix that.

This 3/4 ton suburban has a few important improvements over the half ton. Mainly the 3/4 ton frame, full float heavy duty axle, bigger brakes, class 4 hitch, working trailer brake controller, 40 gallon road warrior fuel tank and its not rusted out.

Its running really painfully rich, I have an edelbrock performer carb on the way and I am going to take the wide band O2 sensor meter out of my Camaro and dust off my advanced edelbrock carburetor tuning kit and get that thing running the correct A/F ratio.

I filled up the 40 gallon fuel tank from about 1/2 tank, took 20 gallons, so it looks like the gauge reads correctly.
Then I am going to weigh it tomorrow and drive it around for a few days and see what it gets for MPG, I am sure the as is FE will be disastrous. I am not sure what day the new carb is getting here let alone when I will be able to put it on and tune it.

1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.

Last edited by oil pan 4; 05-28-2015 at 01:36 AM..
  Reply With Quote