So way back in the '70s, it was normal to use a big car, like the Cadillac with the 500-cube V8, for towing rather impressive trailers.
They were ladder-frame cars, not so different from today's full-size half-ton pickup-based SUVs.
That went away with the late '70s move toward unit-body econo-boxes, and stayed away as pickups became the thing in the late-'80s, becoming more comfy.
I have in mind an '80s car, RWD, factory-rated to tow 2K with a bumper hitch, and I'm not looking to be bashed. I'm challenging you guys to see, and type, ways to make this work, rather than reasons against it.
This car has aftermarket subframe connectors, and is getting an aftermarket roll cage. For a rear axle upgrade, a Dana 60 is a very real possibility.
And before I spill the beans, I've already begun this project, with a build thread, on another forum that none of you will ever think to check.
I propose to fit an in-trunk, through-the-bumper, hidden-by-the-license-plate, class 3 hitch, tied into the cage, AND tied into a GN plate which also ties into the cage and the subframe connectors. This plate rests on the tops of the rear coil springs, and I figure 1/2"-thick is ideal considering the car is my '84 Trans Am, with a big brake upgrade.
This isn't how much can I tow. This is can I safely equal the Cadillac without ripping the car apart. Testing will be done on a neighbor's potholed 3/8-mile driveway, not public roads.
If anyone gets negative, I won't show my progress. If you're against this, fine, just don't pollute this thread by explaining.
Edit: update: this sort of is becoming what-can-it-tow, a 5er ( fifth wheel ) hitch is getting added in.
* This post was
edited 06/03/12 11:30am by whisperide *
'06 GMC C2500HD RCLB gasser 4.10:1, 4L80E, custom camshaft
'84 Trans Am 6.2 diesel, 700R-4, custom Class-3 receiver
'69 F350 dually. GM 6.2 diesel, turbo, 700R-4, NP208 all pending.
I should also note that I will use many gussets, and many sandwich plates so as to clamp as much of the car's structure as possible. This is standard practice for installing cages into these unibody cars, but I'll add even more for the hitch.
Of course you can do it, and it will probably do what you want it to well and safely.
My only question is, now that you are getting into this, why not go all the way and put the full running gear out of a 3/4 ton 4X4 under there?
As the old song goes, just "knuckle down, buckle down, and do it , do it, do it!"
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Here are the first 3 pics. I'll upload more when my phone is re-charged.
In this first pic, I'm standing on the left side of the car, near the rear, looking down on the top of the sub-frame-rail. Notice how I've scraped away all the glue so that the new steel can sit flat
Now leaning in, standing a bit forward, looking toward the rear
Now same thing, but looking at the passenger side instead
Notice I have the deck all scraped, hammered, and smoothed flat for the GN plate
Here's as far as I got before I ran out of blades ( and drill bits )
and here's a close-up
First, on those rear subrame rails, I will put a pair of 12" lengths of 3" x 3" x 1/4" angle iron. Then across the tops of those I will set the 46.5" cross-tube of 3" x 3" x 1/4"-wall square mild-steel tube. This will be spot-welded. Then I will clamp the center-tail-tube under the cross tube, so I can mark where to cut the back wall of the trunk. Cut made, repeat for cutting the bumper. Now fit and spot-weld the tail tube. Pull the whole assembly, all 6 pieces, out for full welding plus gussets. Re-install for drilling. Make sandwich plates and drill those. Bolt the whole deal in place permanently.
Move on to the GN plate:
test-locate, drill 2 locating holes, bolt. Measure for final location of ball. Mark. Remove plate for cutting. Measure for cutting deck to match location of ball. Ball will also sandwich some of the deck. Plate back in, ball in hand-snug, 2 locating bolts in. Get underneath and drill up through car and through plate. Make, drill, and install sandwich plates.
Install Competition Engineering cage per instructions. Add gussets. Weld to cross-tube, add bars to GN plate at rear springs. Add bars between cross-tube and rear of GN plate. Add bars from front of GN plate to SFCs.
Now the tongue weight, from either / both hitches, gets transferred directly to the tops of the rear springs, while the towing stresses get transferred to the rear trailing arms, which is what the axle pushes on.
If you're caging the car with a full cage, front to rear, I don't see there being a problem, provided your design for the whole cage/frame/hitches is good. If you're just attaching hitches to the thin sheet metal of the unit body that are not all tied together with a full cage front-to-rear, top-to-bottom, I see the possibility of a lot of welds being torn out along toe on the sheet metal side of the weld. Remember, that sheet metal the unit body is made of is thin, 16 to 18 gauge, maybe 12 or 14 gauge at the very thickest parts, and you're attaching 1/2" and 1/4" plates/angle/flat bar, etc to that thin sheet. Be very careful and thorough with your cage/frame design, accounting for all the forces involved, and it can work. Hobble it together and it could be a disaster.
How's your welding ability for welding thick to thin, out of position, in difficult to reach areas? What process and filler are you intending to use?
My immediate reaction is - WHY?
If you were doing this to a full frame car I would not hesitate, but the TransAm is a hybrid of Unibody with front and rear subframes.
If your roll cage anchors those frames together, OK, otherwise the body sheet metal will be carrying a lot more load than it was ever designed for.
Not saying it can't be done, but just a word of caution, that's all.
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