Economy modding my Chevrolet Astro work van (diesel 5-speed conversion)

[JB3]

Originally Posted by slowmover

Great news on the axle/gear swap!!

Can't remember if tires were discussed. Truck-spec closed-shoulder highway rib tires would be my choice for another "major" change. Or, what is best suited to climate/terrain and truck use in a premium brand of tire if time/miles anticipated warrant it (MICHELIN, not BFG; Bridgestone, not Firestone. Etc). Tires are not the place to go cheap. They'll more than pay for themselves on a work truck. Same with shocks: Bilstein over Monroe, etc.

Has brake drag been looked over, front and rear axles? Same for steering slop, from column out through end links . . big truck manufacturers note this as a measurable FE problem.

The precise steering and "feel" of a tight front end, well-adjusted brakes/bearings and no-slop steering system coupled to premium tires/shocks is the feedback needed for low fuel burn tactics on a truck. The pieces needed to fit within a "smart use" strategy.

.

I rebuilt the front end a couple years ago, and its reasonably tight. There is a bit of play in the steering box, but its not much.

I am coming up on tires being needed. I have some cheaper pep boys tires on there that were rated at 40k and are at less than 20k with about 15% treadlife left, but are starting to show some serious dry cracking.
Definitely going to go higher quality this time, these tires are only 2 years old, so that was a serious waste of money, however they were useful as test tires while I worked out the alignment. Basically they are so crappy I didn't care if I sanded them down.

Brakes also have to be adjusted, I have yet to install a working parking brake in the rear, and then need to dial in the drum brake setup.

[JB3]

have some good 4.56 diff mileage info now. this weekend drove down to PA, about 600 miles total and got some good reading on the new economy. Its a very consistent 28mpg now. Drove down towing a (valueless as related to economy) very small trailer unloaded I was dropping off, about 5 feet long parts bin on wheels basically, and my economy was 28.9, probably because I was keeping my foot out of the throttle trying to preserve the trailer from destruction as it flew around over bumps, on the way back did 28.3 and made a little better time.
Cruising speed I am estimating was about 60-65 with some bursts to 70. (estimated this by using a clock and mile markers)

[Jasen]

JB, nice to see it come together.

I didn't see if you posted your progress over at astrosafari.com, I know a few were pretty interested in your build.

[mikeyjd]

Nice work

[JB3]

new update, the 616 4cyl diesel was trundling along fine and I put about 8k on it, but the lack of power for work reasons and towing was getting a little stale, so ive swapped out the 616 diesel for a 617 5cyl diesel instead, which has approx twice the HP.
Another reason is better stock oiling, and I wanted to redo the motor mounts among other things also. I didn't see any reason to keep the lower hp motor in there if I could fairly easily install the larger plant.

Ill post new economy stats with this change. I expect it to go down somewhat, but the added power should mean the engine is working a lot easier to maintain highway speeds, so it could go either way.

here is the 617 motor about to go up-



and installed-

[Miller88]

Excellent! One thing I hate about living in NY is these diesel swaps are nearly impossible on vehicles that have not rusted into oblivion.

Very neat that you are pushing 30MPG with it. Wonder if the fuel mileage will get better with the more powerful 617 swap. I know the 617 are somewhat popular in the Jeep community.

I thought the Astros were a unibody / "uniframe" design similar to the unibody Cherokees / Grand Cherokees? But you did a body lift and the body is completely removed in the one picture.

Did you divide by zero and body lift a unibody vehicle??? Haha.

My guess is it's some sort of hybrid unibody / full frame like a Jeep Comanche?

[JB3]

Originally Posted by Miller88

Excellent! One thing I hate about living in NY is these diesel swaps are nearly impossible on vehicles that have not rusted into oblivion.

Very neat that you are pushing 30MPG with it. Wonder if the fuel mileage will get better with the more powerful 617 swap. I know the 617 are somewhat popular in the Jeep community.

I thought the Astros were a unibody / "uniframe" design similar to the unibody Cherokees / Grand Cherokees? Clearly it's not as you did a body lift and the body is completely removed in the one picture.

Yeah, in your area depending on EPA rules, you really need to find a cherry car thats still 25 years old, a lot harder to do up there. I lucked out with this van, it has some repairable rust holes, but I wouldn't call it rotten.

Ironically I started with a Rochester astro, but it was too rusty to swap.

I think technically you are right in that these are classified as unibody vans, but they have a removable 6 bolt subframe/engine cradle, so its possible to drop the important bits out of the unibody by removing the subframe. Its kinda half and half in my view. I think a lot of unibody vehicles are built like that though.

Here are some videos of the test starts of the new motor-

first one with big air pocket-

http://www.youtube.com/watch?v=n41CPUq6kyY

second one runs well. I also got to try out out an open vac shutoff I read about that I now love-

http://www.youtube.com/watch?v=vCy6p5eDw2c

[JB3]

Tirerack claus came through and some much needed but taller rubber has arrived. Old tires are dangerously cracked and worn on the front.

With the bigger motor, twice the power, and same gearing, I can afford to play some games with the rear tire to alter the gearing ratios to increase the cruising economy hopefully



Im interested to see if these tires really fit on the front of these vans. The size difference is several inches, but some astro people say they fit and look good. looking forward to having them installed as soon as I get the tranny put back up and seeing for myself if they do. There are a lot of conflicting first hand accounts, so it seems like a van by van thing. Im convinced the van will look good with these tires, but looking good and turning are different things.

The stock size is 205/75 R15, but ive jumped up to 235/75 R15s instead with the same ground footprint, but much taller sidewalls

stock compared to new-

[cRiPpLe_rOoStEr]

Are you still keeping the 616 to eventually use it in another project?

[JB3]

Originally Posted by cRiPpLe_rOoStEr

Are you still keeping the 616 to eventually use it in another project?

yeah, if nothing else, it makes for an excellent spare motor for my DD. Ill probably slowly clean it up.