What kind of mileage could I expect.

[rs74]

I know not to expect a whole lot of mpg's but here it is anyway. I am looking at swb 4x4 with a 305, 700r4 and not sure what gears. I am sure either 3.42's or 3.73's. This is factory suspension and factory size tires. The 305 is stock as is the whole truck with the exception of headers. I do have a 350 that runs well it might have a slightly bigger cam but it has a smooth idle. I would think about putting it in for a little more torque.

If I did anything to the truck suspension wise it would be a 4" lift and maybe 33's. Should I expect somewhere in the low to mid teens for mileage or is that asking too much. If it is going to be that bad then maybe I should think about a 5.3l. 4wd's and mileage don't go hand in hand but I would like to know what I am up against from the beginning. Not really comparing apples to apples hear but my 91 z71 short bed has a tbi 350 and 5-speed and gets between 20-22mpg with 3.42's.

[74 stepside]

My 99 silverado standard cab shortbed had 5.3 with 4L60E. It was 2wd with 6" lift and 285/75R16 which is about 33" tire. I averaged 15 mpg and that was with 4.10 gears. With higher gears you might get 1 to 2 more mpg, but my truck was more aerodynamic than a squarebody. So its a toss up.

[piecesparts]

Tall tires and tall gearing is a bad mix for most 350 combos. The tall tires and a set of 3.42 gears with a 700 R4 tranny will give you a low RPM on the highway, but the energy to get that rolling will eat up your economy. If you do any driving in the city or where ther are hills, then you will work your engine/tranny copmbo hard to keep the RPMs up. The 4-wheel drive resistance will add to that work that has to be done and then you will be sore about your fuel mileage.

Example:3.42 X 70MPH X .70 ODrive X 336 divided by 33" tall tire = 1706 RPM on the highway

Example 2: 3.73 X 70 MPH X .70 oDrive X 336 divided by 33" tire = 1860 RPM on the highway.

The carbureted GM 350 engine is most comfortable around 2000 to 2300 RPM for a cruising RPM range and will give you the best econonmy in this area. If you have a TBI or fuel injected engine, the economy will move with the RPMs and what the computer can control.

[79Betty]

My79 k10 eith 4" lift turnin 35's and 4.10's got 13 mog on the highway doin 55 that was right around 2300 rpmish. I loved it and then i got the 4 barrell to open on my q-jet... It went down to 8 lol
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[nobull2]

10 is the real world number

[Zane M]

I agree with nobull2. 10 is realistic, anything above that is gravy.

[rs74]

I kind of figured maybe it was more like that. Not something I wanted to hear but kind of thought so.

[martindc1]

My 87 had a 305 TBI, 700R4 and 3.08 gears with 32 inch tires. The 3.08 gears with overdrive IMO didn't work too well unless I was going 65 or faster - the word turd comes to mind. It literally got just as good mpg in Drive that it did in Overdrive. Fuel mileage ranged between 12-15. But 12 was more realistic for everyday driving. When I got it, it was getting around 7 mpg then I changed the MAP and O2 sensors and set the timing and the fuel mileage pretty much doubled. I think 4.11s would be good with the 700R4.

[rs74]

Nothing is set in stone yet but I think I am passing on this truck and going to build my own. I called about a frame today and I have an 85 long bed that I am going to take the cab, front end, axles and suspension and swap over. Not sure about the drivetrain. I think my axles are 3.73's and I have a 700r4 out of the 85 I can use if it is good or I can see about having my th350c switched over to a 4wd trans.