Full Frame for SAS

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eidgenosse
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Full Frame for SAS

Post by eidgenosse » Tue Dec 25, 2007 3:28 am

Well it has survived the transfer
Me and Gary both posted while Justice was trying to find the correct file to edit to put up the rediect message on the old forum.She grabed them for me ;Thanks Justice
Here are my original post and Garys reply
Has anybody contemplated modifying an Astro to full frame for SAS.
I have noticed some cracking and resulting leakage along various calked body lines after wheeling on some washed out forest service roads last summer. My Astro has a 4" OLV lift and a Dana 44 HP, Ford 9" and S-10 NP231 are sitting in the back yard. I'm also in the market for a 3.9L Isuzu 4BD1T diesel engine out of a NPR truck. The added torque and the radius arm placement ( if I go with the coil spring front SAS from the 1979 F-150) might justify building a full frame for the Stro.

Gary: I have to admit in this area I don't have any help for you.The mod for this section could help and I would think is out enjoying the holiday with his family.
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Re: Full Frame for SAS

Post by LiftedAWDAstro » Tue Dec 25, 2007 5:04 pm

There have been a couple pics posted over the years of some Blazer or short bed truck frame swaps. Ususally these turn out to look like crap with the body just sitting on top of the high points of the frame. You end up with 6-8 inches of air gap between the bodies and frames. :vom:

To do it correctly would require cutting the body open to allow the body to sit down over the frame to make it look factory. I think I would just build a new frame using some rectangular tubing and make it fit the body. You can then build the spring hangers and mounts where you want or need them.

As for the radius arms and coil mounts, I would go that way if you have the parts available.
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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

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eidgenosse
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Re: Full Frame for SAS

Post by eidgenosse » Tue Dec 25, 2007 6:04 pm

I was thinking of fabing up a new frame from scratch.
Modifying an existing truck frame seems like more work and would never look as clean as a purpose built frame.
Correct me if i"m wrong, but minor trimming on the rear structural members on the existing uni-body in order to tuck a new frame up in there, should be OK. Also some added reinforcement at body mounting points in the rear would be advisable.
The other way would be to seam weld the body and ad an integral frame,scrapping the front sub frame all together, sort of like they do on uni- body rally cars. This path seems would stiffen up the ride a lot, to the point of uncool for a daily driver.
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Re: Full Frame for SAS

Post by madslammer » Fri Dec 28, 2007 1:00 am

What about adding some sub frame connectors like the Street Machine guys do?
Just My 2 cents. . . :partyman:
'97 Astro 2wd, lowered 4" w/Belltech spindles and drop leafs.
'87 Astro 2wd, lifted, pretty close to 4" all around.

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Re: Full Frame for SAS

Post by eidgenosse » Fri Dec 28, 2007 5:05 pm

That was the first solution I thought of to. Further thought brought out the theory that resisting flex, like sub frame connectors or stitch welded rally roll cage bodies do, will lead to material fatigue at some point. Letting a frame flex and absorb the energy and isolating the body seems like the way to go. On Unimogs for example the cab and the bed (or what ever is in the rear) are independent and each only mounted to the frame at three points, allowing the frame to flex /twist. That said at what point does the street ride suffer and get sloppy?
Guess I need to check out some full size vans, see how the frames are fitted there.
BTW I'm not fixed on full frame, its just as fare as I have come, contemplating it on my own in my the basement, so I figured it was time for some outside ideas.
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Re: Full Frame for SAS

Post by madslammer » Fri Dec 28, 2007 5:13 pm

You have really done your homework man. . . =D>
'97 Astro 2wd, lowered 4" w/Belltech spindles and drop leafs.
'87 Astro 2wd, lifted, pretty close to 4" all around.

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Re: Full Frame for SAS

Post by eidgenosse » Sun Dec 30, 2007 7:08 pm

Here's a pic of a tubular frame that looks like something to start with.
I think the color and pinion angle of the front drive shaft are especially important :-k
Attachments
astro frame 1.JPG
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Re: Full Frame for SAS

Post by eidgenosse » Sun Dec 30, 2007 7:32 pm

Has anybody else had any problems with body flex?
I bent my rear door about a year ago and it just occurred to me that the rear doors might make up some sort of stiffening member in the design of the body.
My doors still close, but the passenger side one is bent out at the top about 1/2".
In some pic somewhere a saw Dean's rig had a dent at about the same location as mine.
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Re: Full Frame for SAS

Post by LiftedAWDAstro » Mon Dec 31, 2007 7:59 pm

The doors that were dented were the barn doors in my old 95 that skippy has now. In my 98, I have never had any issues with body flex. I have had mine on 3 wheels many times and occasionally balanced on just 2 and never had a problem.
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

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Re: Full Frame for SAS

Post by GEJ » Mon Dec 31, 2007 11:59 pm

Coming from a drag race backround on tube frames I will tell you those frames are only as good as the roll cage that transfere's force and ties the front to the back and makes every thing stiff.How well it is z'ed and x'ed in is key.The 2x4 tube frame and round tube frame will still flex greatly without a well designed roll cage.I posted a project which is call "Pro-Mod Street Rod" that has a designed roll cage where you can see what I am talking about.Even thro it is designed as a drag race low rider the same concept applies to your uses.I seem to remember the Big Foot type of trucks tilt the drivetrain a lot to make up angles for the driveshafts.

Just some thoughts,

Gary
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Re: Full Frame for SAS

Post by astrozam » Tue Jan 01, 2008 12:39 am

Theres just no way, no how, you could ever get one of these vans with just 1 wheel in the air,or is there,LOL

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Re: Full Frame for SAS

Post by eidgenosse » Tue Jan 01, 2008 6:05 pm

Some times I over think things. I just don't feel like doing it twice, like when I built my long shaft mud motor for my duck boat I obsessed about rusting; rust is going to kill it, rust is going to kill it, rust is going to kill it, so I built the whole thing in stainless ( had the stuff laying around, did not go out and buy it ). Maybe all I need is someone to tell me shut up, build it and fix it if it does not work.
Might help to clarify what I am planing to use the van for. Lets be honest 98% street driving, forest service roads, some of witch are washed out but by no means rock crawling, towing my duck boat in and out of places one does not tow boats in and out of and the occasional safari camping trip. Mod that are planed are: solid front axle, coils and radius arm suspension in the front ( wish I could do a tri-4link in the back but that might have to wait), 4x4 transfer case, diesel engine ( gone from Cummins 3.9l 4bt to Cummins 3.3l QSB International 2.8l back to Cummins 3.9l and finally to Isuzu 3.9l 4bd1t or 4bd2tc) and ~31" tires . I travel for work and often end up sleeping in the van so some interior mods might happen to.
PS: Have recovered my neighbors full size Chevy plow truck with sander out of numerous ditches. I am assuming that might happen again, considering he is missing one eye. :rolleyes:
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Re: Full Frame for SAS

Post by astrozam » Wed Jan 02, 2008 1:28 am

It sounds like a great project,if you end up going diesel even cooler,between your ideas and the help of members here you'll be well on your way.

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Re: Full Frame for SAS

Post by mdmead » Wed Jan 02, 2008 2:54 am

garysgifts wrote:Coming from a drag race backround on tube frames I will tell you those frames are only as good as the roll cage that transfere's force and ties the front to the back and makes every thing stiff.How well it is z'ed and x'ed in is key.The 2x4 tube frame and round tube frame will still flex greatly without a well designed roll cage.I posted a project which is call "Pro-Mod Street Rod" that has a designed roll cage where you can see what I am talking about.Even thro it is designed as a drag race low rider the same concept applies to your uses.I seem to remember the Big Foot type of trucks tilt the drivetrain a lot to make up angles for the driveshafts.

Just some thoughts,

Gary
Yeah, what Gary said...

I had written a response to this post early on but I must have screwed up and not gotten it sent. Basically I mentioned that in addition to frame rails (hooking in with the front subframe), some type of cage (interior or exterior) would be needed to make the van rigid. Basically, you need to tie it together three-dimensionally to eliminate the flex.

Regarding flexy bodies and these vans, mine is less than inspiring. Granted, my factory top was compromised as it was removed and a fiberglass high-top was added. In theory, this new top should have actually improved things if mounted properly, but my top has several stress cracks that are a result of flex. I've also found I get some really scary noises if I drive down a gravel road and the slider isn't fully closed. Something in the body is flexing and it sounds like the van is being ripped apart. (OK, maybe not quite that bad....)
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Re: Full Frame for SAS

Post by SAS H3T » Sat Jan 12, 2008 2:21 am

I have driven my Van for two years on the very system you propose. The three link (two radius arms and a trac bar) is one of the easiest systems to adapt to any vehicle. I've put it under 6 vehicles before the van was done...from a CJ-8 Jeep , a couple of XJ Cherokees, right on up to a Comanche pickup and even a 1500 series GM truck. I'm currently designing radius arms to attach a Dana 60 one ton up front to compliment my Sterling 10.5 Superduty rear out back.

Only at the point where I intended to add two doors and a cab with rear window from a dually GM to a stretched wheelbase on my van, did I start fabricating a frame for it. You're slightly ahead of me in the deisel option, however.
I just went to look at a 6.5L GM engine complete with tranny, and I walked away wondering if I could even fit it into the van....
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