V8 swap or differential swap?

ANYTHING TO DO WITH MAKING YOUR VAN MOVE EXCEPT FOR THE ENGINE ITSELF.
Post Reply
User avatar

Topic author
H2OJoe
I finally get the smurf thing
Posts: 188
Joined: Wed Jan 05, 2011 7:49 pm
Location: White Salmon, WA
Been thanked: 1 time

V8 swap or differential swap?

Post by 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
2001 Astro LT AWD "Redneck Edition", 4" Custom Lift, 30x9.5R15LT on stock wheels, Hightop conversion, custom interior, custom roof racks, external solar shower, front recovery points. SOLD

1997 Astro LS AWD Starting build soon.
User avatar

arlon
I finally get the smurf thing
Posts: 164
Joined: Wed Dec 28, 2011 8:56 am
Location: Midland Texas
Contact:

Re: V8 swap or differential swap?

Post by 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.. (-:}
2004 AWD Astro 2" lift, overnight-able
2003 Dodge/Cummins Quad cab
2006 Nissan X-terra MT
1985 LTD LX 5.0 HO
Plus wife's and kid's cars to take care of...
User avatar

1Gary
I have my van tatooed on my cheeks
Posts: 2743
Joined: Wed Oct 07, 2009 4:18 am

Re: V8 swap or differential swap?

Post by 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.
1979 Malibu drag race only car
1999 Sonoma 4.3 5 speed-Rufus
1989 Astro-Ole Yellar cancelled-still selling off parts
1985 Astro-shop van R.I.P. my friend
1994 Astro LT RWD W4.3 rod knock RIP
1982 Winnebago single rear wheel-Chevy 350 Scraped 1/28/13-broken dreams......


Rochester,NY

LiftedAWDAstro
I have my van tatooed on my cheeks
Posts: 4379
Joined: Sat Sep 09, 2006 3:35 pm
Location: New Haven, NY

Re: V8 swap or differential swap?

Post by 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.
Current rides:
2013 Toyota Tundra DC 4x4
2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special Edition

Mileage spreadsheet

Vans owned:
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy
User avatar

Topic author
H2OJoe
I finally get the smurf thing
Posts: 188
Joined: Wed Jan 05, 2011 7:49 pm
Location: White Salmon, WA
Been thanked: 1 time

Re: V8 swap or differential swap?

Post by 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.....
2001 Astro LT AWD "Redneck Edition", 4" Custom Lift, 30x9.5R15LT on stock wheels, Hightop conversion, custom interior, custom roof racks, external solar shower, front recovery points. SOLD

1997 Astro LS AWD Starting build soon.
User avatar

1Gary
I have my van tatooed on my cheeks
Posts: 2743
Joined: Wed Oct 07, 2009 4:18 am

Re: V8 swap or differential swap?

Post by 1Gary »

If MMead ever gets his LS 5.3 swap done,you'll see the mileage he gets.
1979 Malibu drag race only car
1999 Sonoma 4.3 5 speed-Rufus
1989 Astro-Ole Yellar cancelled-still selling off parts
1985 Astro-shop van R.I.P. my friend
1994 Astro LT RWD W4.3 rod knock RIP
1982 Winnebago single rear wheel-Chevy 350 Scraped 1/28/13-broken dreams......


Rochester,NY
User avatar

1Gary
I have my van tatooed on my cheeks
Posts: 2743
Joined: Wed Oct 07, 2009 4:18 am

Re: V8 swap or differential swap?

Post by 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
1979 Malibu drag race only car
1999 Sonoma 4.3 5 speed-Rufus
1989 Astro-Ole Yellar cancelled-still selling off parts
1985 Astro-shop van R.I.P. my friend
1994 Astro LT RWD W4.3 rod knock RIP
1982 Winnebago single rear wheel-Chevy 350 Scraped 1/28/13-broken dreams......


Rochester,NY
User avatar

T.Low
I plan to be buried in my van
Posts: 1768
Joined: Wed Jun 06, 2007 7:11 pm
Location: Bellingham, Wa
Been thanked: 1 time

Re: V8 swap or differential swap?

Post by 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. O:)
ImageImageImageImage
AstroLander Build Slideshow
Church bells ringing in the middle of a gunfight.
User avatar

doyoulikeithere
ASV Supporter
ASV Supporter
Posts: 2060
Joined: Tue Nov 17, 2009 8:27 pm
Location: Misty Mountains of Cowichan BC.

Re: V8 swap or differential swap?

Post by doyoulikeithere »

H2OJoe wrote: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...
2021 Yamaha Tenere 700 - Blue.
2016 Yamaha XSR900 - Silver.
1990 Astro - AWD - Brown.
1987 Astro - With 5 Speed & 4wd - Silver & Blue.
Post Reply