Hi Fellows,
I have used this site from time to time for help with restoring my F-100 shortbed. It is a working truck not just a poser so I am concerned what I am hearing locally about towing with this machine.

First of all the mods to this truck.
390 w/edelbrock cam, lifters, dual chain timing set, aluminum intake manifold and high performance water pump.
Holley 750 carb.
All MSD ignition including distributer.
Hedman ceramic coated headers into dual exhaust with great sounding exhaust.
Heavy duty extra capacity radiator with new core and heater core.
C-6 transmission rebuilt extra heavy duty with a large transmission cooler.
New driveline.
Differential is untouched and is a 3.23 ratio.
New springs front and rear, air bags in rear, heavy duty sway bars front and rear, all bushings in front end replace with polyurethane, including sway bars.
Newly rebuilt steering box. (manual steering)
New professionaly installed king pins. The front end of this truck is TIGHT.
Michelin LTX 9.50 x 30 x 15 tires.

Front to rear that is basicly what I have done to this truck over the last 3-4 years. The engine was set up for ignition and carbueration on a dyno and it puts out around 325 HP and has around 400 ft. lbs. of torque.

Now the problem I am having in a nutshell.
With all that has been done to the suspension I cannot tow a trailer straight down a hiway. It has had a 4 way alignment done and it is perfect. The trailer (4,000 pounds) has been professionally hitched with a weight distributing hitch.
The old guy that has done the alignment has told me that the twin I beam suspention is the worst ever put under a truck and that he can do no more with it.

Have I just spent thousands of dollars and spent uncounted hours in the last four years on a truck that cannot tow a modern trailer above 45 MPH without wandering around the whole road?? The local experts are telling me this is as good as it gets with this truck. Are they right??

I am obviously dissappointed and really mad that this has happened and am pleading with you that can give me good advice to please help an old truck.

Scott

 

i think that these experts are idiots. i use my truck to tow a 4000 pound car trailor with a 4000 pound car in it. i would take the truck to someone who knows about the suspension. at one time mine was wandering all over the road and it ended up being that my tires were not all equally inflated. just some thoughts.

 

Try another alignment shop that specializes in HD and over the road trucks. The regular alignment shops can not handle the TIB suspension.

 

I do not know what to think anymore. The guy's I have talked to are supposed to know their stuff, but it seems to me that Ford made these twin I beam systems for a long time. Surley towing should not be a big deal.
Tires, I have them at 50 PSI and they are just one of the good things done to this truck to make it a towing machine.
I hate to think that I will have to buy a more modern machine.............payments, bah!

Scott

I have had the truck to two of these shops now including the last one that specializes in "Twin I Beam".

 

Are your rear air bags isolated from each other? If they are tied together thru a Tee the air pressure will transfer side to side and cause roll steer in a leaf spring suspension.

 

Air bags are seperate and since I put in the new springs and 1" sway bar they are not even being used.


Scott

 

Have you measured the suspension height at all 4 corners unloaded and loaded? If one of those "new" springs is weak it can also cause imbalances.

If the front wheels lift when loaded you can loose your caster which can cause instability. If so reduce your tongue weight.

Personally I think the Twin Idiot Beam suspension is junk and was an advertising gimmick (Ford's better idea) turned horribly wrong. I am changing mine over to a 3/4T GMC suspension.

 

Eric,
Yes all of the measuring has been done. The truck rides like the proverbial buckboard when empty it is so stiffend up from suspension mods.
GMC parts huh? I threatend that very thing when faced with the news about terrible I beam suspension. Have you looked into the cost and feasabilty of doing that?

Thanks for your interest by the way.

Scott

 

I bought two complete GMC suspensions with a frame for one for $125. I got both power steering boxes, and pumps also along with a HD sway bar. Many new parts on both units. It takes a lot of fabricating to blend the two suspensions tho. I have figured out two ways of doing the conversion, both are WORK! One keeps the upper 2" of the Ford frame rail so your body mount points are intact. The other method just splices the GMC rail to the Ford under the cab which means you have to fab up all of the body mount points. Either way will require custom engine mounts.

Glad to be of assistance.

 

What would y'all think of a steering stabilizer? Converting to power steering?

I am searching........

Scott

 

have ou tried another trailer?

preferably one without a weight distributing hitch on a 4000lb load. That seems over kill to me.

 

Yes I have tried another. I also have a Wells Cargo 14' and it is the reason I have done so much work to the truck. It does tow this trailer much better but still is not "right".
The travel trailer in question has a 450 pound tongue weight that needs to be distributed around the truck.

Scott

 

Tongue weight is a good thing. 10-15% of the trailer weight should be on the tongue. I prefer to lean more toward the 15% if possible.

Make sure the hitch on the truck end is not unecessairly long past the bumper; if possible, have one custom made to bring it in as close as possible.

You removed quite a bit of weight from the front when you swapped-in that aluminum manifold for your 390. You might want to add an auxililary battery under the hood, or something to bring some weight back to the front and see if that helps. I have found that when I am towing my 3-place snowmobile trailer behind my '76 Bronco, that it rides much straighter when I have the detachable winch on up front.

Weight distributing hitches help, but they also make anti-fishtail attachments for problem trailers that work great also.

If the Twin I Beam suspension is so bad, then why do they still use it on the new Super Duty trucks?

 

not to be a turkey, but, how much experience do you have pulling a trailer?

Since you ruled out tounge weight (trailers weight distribution), and the alignment is done proper, possibly you have a dud trailer?

I once rented a u-haul trailer that made my truck a living nightmare to pull. Constant tail wagging the dog situation, and down grade highway situations were beyond scary.
I later rented the same size/style/modle trailer, and I was forgetting it was back there...this even having removed my vehicles rear sway bar, which in theory ought to have made things worse...

Is there a way to check for alignment/lineararity of the trailer?

If the trailer checks out, maybe you should consider one of the hydrolic anti-sway strut deals.

Of course a short wheelbase rig is not ideal, but, it should handle a properly weighted 4000lb load trailer without so much trouble...

Good luck.

 

The TIB suspension is robust or durable, that is all I can say for it. Ford will keep using an idea until they can't, it is just a corporate philosophy. Those A/C connectors are another example of a proven bad design that they were determined to make work. This conversation is not sticking to the problem this user has with his truck. Let's keep focused on his problem.

If his front end is rising with the weight of the trailer the caster may be decreasing in the front like I have said before.

Steering stabilizers are usually only required when you have big floppy tires or large amounts of slop in front end components.