Crossposting from the Diesel section, as it's probably more appropriate here.

I have a 1989 F350 that's been lengthened 30 feet to be a car hauler.

Problem is, the rear end is too high. When I drive a car up the ramps, I scuff the front bumper on the ramps and drag the exhaust on the pavement when it's up.

If I were to lower the truck, the rear would drag when I drive up a hill. There's maybe 10 feet of overhang behind the rear axle.

What I'd like to do is airbag the rear end so that I can lower the truck when loading, then raise the truck when driving in hilly areas.

Unfortunately, to get airbags that'll adjust ride height, I'll need to pitch the leaf springs and put in a 4 link suspension...

Does anyone have any experience doing this? Are there 4 link kits for these trucks? The truck is a 2wd with dual rear wheels.

Thanks in advance.

 

If you want to go the 4 link route and bag it, you shouldn't have any problems really. I'd give a call possibly to Jegs or Summit and talk to one of the techs there to see which kit you might possibly need. There's a place here in Indy called Automotion that builds a ton of race cars and suspension systems. I'll give Rick a call tomorrow and see what his suggestions might be. The only other thing you'll really have to do a bit of looking into will be the bags you use and the price. You're going to need something substantially more heavy duty than just the standard Ride-Rite bag everyone is using nowadays to put their car or truck on the frame at shows.

 

I'm used to making trucks go UP... Cranking torsion bars, Adding leaf springs and spacers, Drilling holes in old hockey pucks and such...

Making trucks go so low as to have parts rubbing the drivetrain, wheels, and possibly ground seems a little absurd. I feel like a part of me has died...

Still, this is utilitarian.

At least my wheels won't spin while the truck is not in motion.

 

Nahhh, no need to feel like you're betraying yourself, besides, even with the bags and the 4 link, you'll still retain the factory ride height. All you're really doing is making your hauler more functional. If you think of it that way your conscience will be intact. lol

 

I saw a pickup front end welded/connected to a car trailer without the tounge on it. I guess it was a 4 wheel drive running in 4 hi with no rear drive shaft, like a front wheel drive. It was a Chevy 2500 or something.....was still cool looking.

 

Nah. With this thing, they took an incomplete chassis crew cab F350 XLT Lariat and cut the frame right behind the cab. Then welded 10 or so feet of I-Beam between the cut. They built a platform of angle iron and sheet steel with diamond plate and put it on top and used additional sections of 2 or 3 piece driveshaft to connect the drivetrain.

 

So anywho, I talked to Rick today to find out his suggestion. He said there are several great 4 link kits available and just about any of them should work for what you're needing. On the airbags, he said to give a call either to a heavy truck supply shop or maybe an RV sales center and use the same type of bags they use in the rear of those, that way you'll never have any weight issues.

Hope this helps you out a bit.

Rob

 

If you can weld, making your own 4-link isn't very difficult. Essentially it's four arms that locate the axle where it should be, going forward to a set of bracketry mounted on the frame. A panhard rod goes from one side of the axle near the hubs, to the frame on the other side - which keeps the axle from moving side to side.

And the air bags go on the existing leaf spring perches, to new mounts you make on the frame. Probably two bags per side, one outside the frame one inside, and then you can easily raise and lower your truck for loading/unloading.

I actually started a 4-link for my F350 crewcab, however what got started is 3 hours from my house at a friend's at the moment, otherwise I'd offer you pictures. It's really fairly simple.

I intended to "bag" the front and rear, and do a homemade suspension lift to add about 4" to the ride height. Then lower the truck to slightly below it's current ride height, to make getting in and out, and (unloading) the bed more reasonable. Then air up for a slightly lifted look.

All engineered, just not complete and I didn't take pictures yet. I used mostly 3/8" plate for bracketry and the links hae 1" ID rod ends and the rods themselves are 1.25" OD with a 0.25" wall, meaning all I had to do was drill and tap the ends - all mild steel, and definately strong enough.

 

I'll look at what they use on the busses at work next time I'm at a garage... I work for the local Mass Transit organization. If it'll support a city bus, it'll support my truck.

Why do I need four arms? Why not just two, one per side? Where would I put the other two arms?

I'd like to see what you did there "frederic" and perhaps see how it works out for you. I'm inclinded to use off the shelf parts, so I'll look around at the scrap yard next time I'm there and see what I can scrounge up.

 

Wth two arms, the differential pinion angle will change as the truck lifts and lowers. With a well designed 4-link, you can keep the angle "correct" at all times.

This way you can adjust the height as necessary, and sitll drive without destroying your u-joints.

 

Hmmm... That makes me wonder, should I get an off the shelf bolt on kit or fab it up myself...

I have been looking for a good excuse to buy a MillerMatic 210. Then again, I don't know how well I can make up a suspension from scratch.

 

My answer to you depends on if you can weld *well* or not. If you're not sure, welding something you need to stay together might not be a good project

But assuming you can, here is more or less what you want to make. You might be able to google some additional results. I wouldn't worry so much about googling for F350's specfically, as for pickups they are more or less the same design - just that the mounting brackets would be different because the frames are slightly different, and have holes in different places, for Dodge, Ford, Chevy, so looking at other kits for different brands might give you more ideas.

http://www.stengelbros.com/catalog/8...63_5212876.htm

http://www.airbagit-store.com/produc...t.asp&ID=92981

http://www.stylinconcepts.com/parts..../categoryid/30


This 6mb PDF gives you details in how to install it, which you might get enough detail to design your own:
http://www.linkmfg.com/PDFs/Updated%...174_060323.pdf

Some of the designs above are 2-arm designs, which work but I'd still be worried about the pinion angle changing while the suspension travels under load. Like you said, transit bus type vehicles have this feature nowdays - they're called kneeling busses. They drop the front at the curb so passengers can step in and out easier as the floor of the bus' stairwell is lowered to curb height.

BTW, the longer the 2 arms, the less the pinion angle is changed with suspenion travel - one of the reasons why a lot of off-road guys do use 2-arm rear suspensions and have the links mounted under the cab...

 

That's a good point frederic, I didn't think about the two arm offroad style setup, and the kneeling bus idea was something I had thought about too, but wasn't sure how that setup would transfer to the rear. As far as putting a kit together by just buying the needed parts off the shelf, keep your eyes open since steel prices have been going up, that was the main reason I suggested buying a prefab kit, they're a bit cheaper than just buying all the steel yourself and then having to cut and measure.

 

I was just gonna look at the bus parts for the airbags themselves. If it's beefy enough to support the bus and a whole herd of people, it should support the rear end of my truck and a car. If I need more load capacity, I can put more airbags in parallel and just "T" the air lines in.

I see that with a four arm setup, I have two links that bolt to a bracket attached to the axle, one above the axle plane and one below. The upper link gets bolted to the frame closer to the axle and the lower link gets bolted to the frame a bit more forward.

I'll see what i can scrounge offa other vehicles. Any vehicles have a 4 or 2 link suspension from the factory?

 

Gm had something similar to a 4 link setup that they used on the old Chevelle's and Grand Prix's, even some years of the El Camino, not too sure about Ford, let alone how they are under extreme weight.