NHRA - National Hot Rod Association

NHRA Expertise: Build a custom transmission dipstick for any car using AN fittings

Another use for AN fittings that you'll kick yourself for not thinking of sooner.
06 May 2020
David Kennedy
Racing Technology
Custom dipstick fix

Transmission dipsticks are one of the hassles of race cars. In factory applications their steel tubes snake up past the drivetrain and firewall to put the dipstick right where you need it. But in a one-off combination? Forget it. About the only thing more certain than a factory dipstick tube hitting the engine, chassis, or firewall in a race car is the guarantee it’s going to split and leak if you try to bend or reform it.

Enter this AN-fitting solution

You can clock, adjust the length, or speed up transmission swaps by making a multi-piece transmission dipstick tube. Here's how. It turns out most transmission dipstick tubes are ¾-inch diameter. So you can treat them like you would a -12 AN hard line. We created this custom dipstick tube with an extra bend using a pair of -12 AN tube nuts, sleeves, and a male-to-male union to splice two ¾-inch-diameter dipstick tubes together. When you make this kind of modification, you can’t alter how much of the dipstick itself goes into the transmission (lengthen or shorten it as necessary) or the ATF fluid level will never be correct.

Start by installing the transmission dipstick tube into the transmission to see where the interference is. In this case the dipstick tube hit the exhaust manifold. Mark the dipstick tube where you want to splice in a new section, and then remove the tube so you can cut it with a tubing cutter.

Using a 37-degree AN flaring tool (we got this Nitrous Outlet Ratchet Flare Tools 00-56003 from Summit Racing) we fit a -12 AN tube sleeve and tube nut over the shortened dipstick tube and flared the end.

Then we added a -12 AN male-to-male union that mates up against the newly flared dipstick tube. We tightened the nut and union together with AN wrenches.

We used a curved section from a scrap dipstick tube to make the top half of the dipstick tube. We flared it 37-degrees and connected it to the other side of the -12 AN male-to-male union. Again, when you make this kind of modification, you have to make sure you’re not altering how much of the dipstick tip goes into the transmission. Lengthen or shorten it as necessary to ensure the ATF fluid level reads correctly.

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