Tech Question - Do I Need New Springs?

Dear Eaton Tech Person,

I am rebuilding a 1978 Ford, 4x4, F150, Standard Cab, 400 cu In. engine, truck for a series of articles.

Even though the vehicle's front springs appear to be fine, and it was not overly low in the front end on teardown, I am considering the replacement of the springs.

The springs are rust free.

Perhaps it's the fact the vehicle is 30 years old or perhaps the many miles...many miles!

But, this all begged the question of why?

Why am I doing this?

How do I know if this or any coil sprung front end needs springs or not?

How do I test them?

Is it the length unsprung?

Or, should I just assume any spring with 30 years life and a few hundred grand on the truck's odometer needs springs?

I would sure appreciate some help on this question and any suggestions you might have.

I'm happy to quote you as the source of info in the article etc.

Thanks for all the help.

Love your web site, good webmaster you have.



Very good questions with very simple answers.

Looking at the coil springs, whether they are rusted or not, will not tell us anything unless of course they are broken.

Checking the free unloaded height of the spring will not give us any answers, because even though a spring does not lose spring rate, they do lose the ability to carry weight.

So the spring height can still be to specs, but not be able to carry the load.

Load testing the spring is the surest way to tell if it is any good or not. However, who has a spring load test machine handy?

So let's look other ways to tell if the coil springs need replacing.

There are 3 quick ways to tell if a coil spring needs replacing.

The first will seem to be very obvious, the spring is broken.

However with many coil springs the breakage occurs on the bottom coil and can not be detected unless the spring is removed from the vehicle.

Just jacking the truck up to get the weight off the spring and looking may not expose the break.

One has to physically remove the spring and hit the coils to reveal the break.

The second way is to look at the vehicle.

How does it sit empty?

How does it sit with a load?

If it looks fine, then chances are the coils are fine.

However, if it looks low or leans to one side chances are the springs are bad.

The third and final way is how does the vehicle ride?

Again, check it with and without extra passengers or a load.

Bad springs normally will bottom out when traveling over uneven surfaces.

If the vehicle fails any of these tests, then replace the springs.

Then there is reality, when redoing a 30 year old truck with a bunch of miles on it, it is just a darn good idea to replace the springs.

And don't stop at the front springs, check the rear leaf springs and all 4 shocks.

I hope this helps you and to learn even more about both leaf and coil springs download a copy of our Spring Tech 101. And feel free to use this information in your article.

You may also want to look up some of our Other Tech Questions.


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