Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic -- Hot Rod Forum

Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> General Rodding Tech> rear end
User Name
lost password?   |   register now

Thread: rear end Reply to Thread
Send Trackbacks to (Separate multiple URLs with spaces) :

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Additional Options
Miscellaneous Options

Topic Review (Newest First)
04-13-2006 03:05 PM
red65mustang welcome....and just to help you feel better about bad mpg.....

a picture of my son's toy.....hell, the four tires weigh 2,000 lbs!
04-13-2006 02:36 PM
Originally Posted by glen_roepke@yahoomai
i am the new kid please help i have a 78 chev 4x4 full time 4x4 with 307 gears how can i get better gas milage i get about 6 miles a gallon thanks


Did you buy my son's worn out 454 4x4 ???? There was NO HOPE for it.

We increased gas mileage 200% (from 5 to 15) by buying something different and only was out of pocket $ 100. no joke
04-10-2006 09:39 AM
farna To see how tire size affects engine rpm, go to and check out the gearing calculators. You need to keep the engine up to 2500-3000 rpm at cruising speed (say 70-75 mph, if that's how you drive). A lot more (or less) and mileage will suck. If you have a lot bigger tires than stock, it's the same as reducing the gear ratio. That in turn over works the engine. If you have stock gears, you need to keep very close to stock tire size. If you put big tires on, you have to change the gears (in front AND rear -- they MUST be the same in a 4x4) to compensate for the tire size. Like I said, use the gear and speed calculators on to see how tire size really changes things. You can't change one thing without affecting others.
04-09-2006 11:00 AM
M&M CUSTOM I had a 1978 GMC ton 4X4 with the full time hubs and transfer case.
I never removed the solid hubs, or installed the part time kit in the transfer case, but I did rebuild the rear axle because it leaked from everywhere.
I ran a 305 with a new cam and lifters slightly over stock specifications, the TH-350 transmission got rebuilt as it lost first and reverse along with leaking from every place it could, I had a set of 31X10.5X15 tires and the gears in it were 3.55, I got 18 mpg when I did more highway driving.

I had a 77 Chevy that came form the factory with a 400, TH-350, NP-203, and after replacing the engine with a 350 (the 400 spun a rod bearing) and swapping a set of 33X12.5X15 tires on it, I got a rough average of 13 mpg, and this truck had the part time kit and hubs BUT had a set of 3.08 gears.

Over the years I ended up using the engine out of the first above mentioned truck, the transmission out of the second above mentioned truck and a NP-205 transfer case along with a 1983 8.5 inch GM front axle and 1974 10.5 inch rear axle containing 4.10 gears, along with the 33X12.5X15 tires from the second above mentioned truck and got an average of 14 mpg.

Your mileage will vary greatly with the amount of highway use, stop & go traffic, idle time, etc. but the tires need to match the gearing you have to keep the engine rpm's in the lower end of the power band to get better mileage, a general rule of thumb for mileage and power trade-off is keeping the engine revving around 2100 rpm's.
04-08-2006 08:56 PM
lakota Get that front end out of full time. If you have a 3:07 rear then it's not in sync with the front. Most Chevy 4X4's are 3:73 or 3:90. You don't need to change the rears. The 3:07 will give you good highway speeds and fair MPG's. Just get your front end to freewheel. 6 Miles to the gallon??? My 80,000 LB, 880 cubic inch 6 cylinder, 18 wheeled Peterbuilt got 7 MPG.
04-08-2006 02:53 PM
30desoto glen
Are you sure you have 307 gears, I have never seen a 4x4 with those gears or you would get better milage than you say most gears are closer to 390's on 4x4. Do you have a 350 in the truck what size carb, do you have headers, have you thought about putting in hubs it would help a bunch in milage to get it out of 4 wheel drive, what size and type of tires are they big lug or all weather, how does she run, does the carb need rebuildt, when did you change the oil last, how is the air filter, what type of air filter, when was the last tuneup on your rig, I know these are all small problem questions but each one can make a difference in your milage.

By the way welcome aboard

04-08-2006 08:42 AM
Originally Posted by glen_roepke@yahoomai
i am the new kid please help i have a 78 chev 4x4 full time 4x4 with 307 gears how can i get better gas milage i get about 6 miles a gallon thanks

I moved this thread here from the tranny & rearend section.

It seems to be a general question about fuel mileage that could use many different answers to help with the MPG of the vehicle.

We need more information on the truck. Model 1/2 or 3/4 ton , engine , tranny type, tire size ??????
04-08-2006 01:08 AM
rear end

i am the new kid please help i have a 78 chev 4x4 full time 4x4 with 307 gears how can i get better gas milage i get about 6 miles a gallon thanks

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

All times are GMT -6. The time now is 04:16 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.