Piston Slap: Tighter truck turns via OEM+ upgrades?

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Michael writes:

I have a 1994 GMC long bed pickup. My problem/gripe is the turn radius, as the USS Missouri has a smaller turn radius. I did come across an article that said a set of 1998 control arms would help but that article was very vague. It’s said the problem is the tires hitting the control arms. If you have any ideas or a solution I’d really appreciate it. I’m wanting to rebuild the front end and address this problem while I’m doing it.

Sajeev answers:

The answer depends on your drive configuration (two- or four-wheel drive) and whether you have stock-sized tires. If you have a 4×4, the front axle geometry is your limiting factor, as you never want to stress/bind the CV joints just to get a tighter turning radius. If you have a 4×4 with beefier tires? Well, you probably already know the answer (i.e. return it back to the stock size).

Generic advice aside, you are right about the GMT400 platform having an upgrade for both the upper and lower control arms. It is derived from the newer C/K 2500 and 3500 front suspension, and the bits are easy to find online or at any parts store. I am a sucker for these OEM+ upgrades, but only in theory: Steering limitations from things like your pitman arm, steering box, etc. might keep you from enjoying the extra room offered by those control arms.

No matter—here’s one example of the bulky, stamped steel affairs on your truck.

GMT 400 Control Arm old
AC Delco


And below is an example of the slimmer forged steel (?) control arms from a newer 2500/3500 series truck. (I found these for a 1998 model.) After upgrading my 2006 Crown Victoria Police Interceptor to the aluminum lower control arms from a Mercury Marauder, I know which ones I want on your Sierra!

GMT 400 Control Arm new
AC Delco

But don’t trust people on the Internet, especially me. Ask your preferred parts vendor to get you an example of both and ensure that the hard points match. I’d be tempted to purchase both old and new designs of all four control arms (eight total) just in case the newer control arms didn’t work. Nobody likes leaving a project up on jack stands, and parts stores mark up their stuff for good reasons—they don’t want their liberal return policies to put them in the red.

Let’s hope that new front suspension gives you a little more turning flexibility. If not, maybe we’ll need to dig deep into steering parts. Who knows, maybe the Internet didn’t lie this time.

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