V8 swap or differential swap?

[H2OJoe]

So I finally installed my 4" lift and got 30x9.5/15 tires on the van. As expected, I have experienced the loss of mpg after installing the lift/bigger tires. I think if I keep the 3:42 gears and replace the 4.3 with a 275-300 hp small block Chevy I will increase my mpg to upper teens or lower 20s. I don't do any hardcore offroading. It's mostly driving on the beach, on forest service roads and in snow.
What do you guys think?

Thanks,

Joe

[arlon]

When I added taller tires I had the same issue. You could really feel the difference. I doubt it would tow my Casita very well now. I've considered 4.10 gears, V8 swap, power adders, 4bt cummins swap, etc.. V8 sure would be nice but I'm not sure if the expense and effort is worth it. 4.10 gears will probably be my next addition. A bottle full of nitrous for when I need to pass would be nice.. (-:}

[1Gary]

The gear swap is a precursor to a V8.Having a big picture of what V8 it is going to be, dictates which gear ratio.
Having swapped in a LSx engine will certainly get you there over a first gen SBC.After you get through messing with a first gen SBC,the end of the day costs are close with the first gen not providing you the gas mileage a LXs can and will.

[LiftedAWDAstro]

I mostly recommend swapping 4.10 gears. I will say in this case if you can afford the cost of a V8, that is definitely a better way to go. I am not sure you'll see upper teens and low 20's mpg wise but drivability will be greatly improved. With the V8, 3.42 gears will probably be ideal.

[H2OJoe]

Thanks for your input guys. A guy I work with has a 2005 GMC Savanna with the 5.3 and AWD and gets about 17 in town and 23 on the hwy. I thought if I put a similar engine in my Astro it should get the similar or better mpg because of the weight difference. So many decisions, so little time and money.....

[1Gary]

If MMead ever gets his LS 5.3 swap done,you'll see the mileage he gets.

[1Gary]

I went back and checked to see you have a AWD.They don't get great gas mileage.

The way to judge which gear ratio to have is to look at where a torque curve just begins on what ever engine you have.So don't be afraid to spin up a 4.3 mainly because of it's size it needs a higher rpm to develop reasonable torque and your are using a larger tire killing off some of that rpm.Same applies to a V8 where you want to set the cruise rpm just at the beginning of the torque curve.Here is a link to figure what rpm your spinning at what mph given you set-up.

http://www.wallaceracing.com/Calculators.htm

[T.Low]

Great replies and info guys.

Swapping in 4:10's put my van back in it's happy place. Performs great.

Yes, a v8 would be awesome, no doubt...

But I've had 50,000 trouble free recreational use miles on this van with just the gear swap. If the economy would have held and I was still making great money, I'd have spared no expense to button up a sweet V8 swap, but at the end of my day in the new economy, the cost/benefit factor simply wasn't there for me to pursue it.

That being said, I always enjoy reading about a good V8 swap.

[doyoulikeithere]

So I finally installed my 4" lift and got 30x9.5/15 tires on the van. As expected, I have experienced the loss of mpg after installing the lift/bigger tires. I think if I keep the 3:42 gears and replace the 4.3 with a 275-300 hp small block Chevy I will increase my mpg to upper teens or lower 20s. I don't do any hardcore offroading. It's mostly driving on the beach, on forest service roads and in snow.
What do you guys think?

Thanks,

Joe

I think I saw a guy on this board with some AWD V8 motor mounts for sale. You do Know that they are not the same as 2wd mounts, right?
I was thinking about them for myself, but I already have my hands full and dont have time for another project...