Fixing One of GM’s Great Ideas

GM made some great cars but some of them were afflicted by not-so-great ideas, such as the infamous GM side-terminal battery set-up.

Pretty much every other car company’s vehicles use batteries with top-mounted terminals for the obvious reason they’re easier to get at. This makes it much easier to remove the battery when it’s time to replace it – and to install the new one, because it’s easy to get a wrench or a socket on the clamps that hold the positive and negative cables to the battery.

Side-mounted terminal connections are much-less-easy to get at – and much-less-easy to get a wrench or socket on. There is usually very little clearance, in the first place. The side terminal’s positive side is in some cases maybe two inches from the inner fender well, which is made of metal. That can easily result in sparks flying if your metal wrench or socket touches the metal (i.e., the ground) while it is also touching the positive terminal.

The negative side – on my car’s battery – is awkwardly close to the windshield washer reservoir.

The job of disconnecting the cables is made even more more fun via absurdly tiny 5/16 bolt heads. While almost everyone has a crescent wrench, adjustable pliers or similar tool handy that can be used to easily disconnect top-terminal battery cables, many non-wrencher types do not have a tiny 5/16 open-end wrench, which you have to have to loosen/tighten the battery clamps on a GM side-post battery because of the clearance issue; it’s difficult if not impossible to use a 5/16 socket because there’s not enough room to work with. A vice grip might work, if you can get the thing on the stupid 5/16 bolt.

That means a 5/16 open end wrench, which is awkward to use in this usually very tight spot. You also have to use your fingers to get the cable bolts “started” when you’re trying to get the battery cables hooked up. This can be exasperating, because the threaded tips of these cable bolts are typically very stubby; you may have half-an-inch to work with. And trying to get the bolt aligned correctly with the threaded hole in the battery while you try to hand-thread it in that really tight spot down there is even more challenging (and far less rewarding) than fumbling with a bra strap in the back of a car on prom night. It is very easy to get the bolt misaligned (and cross-threaded).

Then you’ll have a bad connection and when you go to start the engine, it might not. 

Top mount terminals are superior as connection points. You have these big, protruding lead terminals to clamp the cables to – making a strong, positive connection much more likely. It’s easy to physically see and feel the clamp and thus ascertain whether the connection is tight and right – and also because it is impossible to cross-thread a clamp.

I recently decided to fix what GM broke.

I wanted to do this in a way that wasn’t visually obvious, because my ’76 Trans-Am is an antique car and I sometimes take it to antique car shows. Antique car people try to keep their antique cars as original as possible because they are into preserving the historicity of the things. Modifying my car in a visually obvious way – as by installing an incorrect top-terminal battery – would cost me points as well as money (I’d have to replace the perfectly good side terminal battery with a new top terminal battery, plus replace the factory side-mount cables or mutilate them in a visually obvious way).

Instead, I decided to modify the factory side-terminal cables’ heads, by removing the obnoxious (and stubby) 5/16 headed, barely-threaded studs from the cable with a same diameter bolt but longer-threaded and with a 9/16 bolt head. This is easily done. Just work the original 5/16-headed stubby bolt (see pic at the head of this article) out from the rubber that encases the cable end. It slips through a “O” loop within the cable that’s connected to the wire that transmits the current.

Once that’s done, you’ll be able to run the new, longer-threaded bolt (an extra 3/4 of an inch or so makes all the difference) through the cable head’s “O” loop. It may be necessary to use a metal spacer (a hollow brass tube cut to the length you need using a hacksaw works perfectly) to assure a wiggle-free/tight connection. Don’t forget to use a washer under the threaded head, to distribute clamping forces evenly.

That 9/16 bolt is much easier to turn by finger at first – to get it threaded straight – and much easier to tighten up with a 9/16 open-end wrench. It’s also much easier – and arguably, much safer – to get a jumper cable’s alligator clamps affixed to. If you have ever tried jump-starting a GM vehicle with 5/16 side terminal posts, you already know what a treat that is!

Once done, the fix is very difficult to discern because you still have side-mount cable connected to the positive negative terminals. It takes a keen eye to notice the bolt heads are larger than 5/16. Few will.

Once fixed,you’ll never feel like smashing something again when it comes time to replace the battery or jump-starting the engine.

. . .

If you like what you’ve found here please consider supporting EPautos.