Blog posts of '2023' 'April'

How to Select the Perfect Dual Case Kit for Your Next Auto Project

Dual transfer case kits are how serious rock crawlers and off-road explorers get even more torque from their vehicles. They act as a reducer to add another set or two of low gears to what the main transfer case already produces so you have plenty of options. This guide looks at the factors you should consider when choosing a dual transfer case package so it gives the right amount of control for the terrain you want to tackle.

Crawl Ratio

Any transfer case installation or modification should be done with the crawl ratio in mind. Also known as the final drive ratio (FDR), this number reflects how much pull you have in the lowest possible gearing. Let’s say your goal is to have at least a 110 FDR for rock crawling, but your factory transmission and transfer case only produce a 40 FDR. That means your dual transfer case will need at least a 2.75:1 gear ratio to achieve the appropriate crawl ratio. Check the available gearing options to make sure the final combination meets your needs.

Matching the Spline

No matter what gear ratio you choose, the input shaft needs to match the gears. This lets the reduction box connect to the transmission and the main transfer case. For example, V8 Toyota trucks from the 1980s and 1990s generally have 21-spline transmissions while V6 trucks and four-cylinder turbos are 23 spline. Check your transmission to see what the factory input requires; if the dual case kit doesn’t match as-is, adapter couplers may be available.

What Is the Adapter Made of?

Your dual transfer case adapter is going to take a lot of abuse. Therefore, it needs to be constructed from high-quality materials. While full transfer cases are often made of cast iron, heavy-duty dual case kits are more likely to be crafted from aluminum. This is 20-30% lighter than cast iron while still being plenty strong for its purposes. With the adapter, you also don’t have to worry about internal part failures destroying it like you would an aluminum transfer case. Make sure it’s a high-grade aluminum like our 356-T6 heat-treated alloy.

Single or Twin Stick

Just like with regular transfer cases, the reduction box (aka crawler box) can have a single stick or twin stick shifter. A single-stick setup lets you switch between low- and high-range gears as you drive while the twin-stick configuration also lets you independently go between 2WD and 4WD. This ultimately comes down to personal preference; being able to switch drive engagement while moving has benefits, but some find the extra stick cumbersome and confusing.

Stock or Aftermarket Gears

In many doubler setups, you have a choice between keeping the OEM gears or adding lower aftermarket gears. Sometimes, you can combine the two. If you want to personalize the gearing, make sure your reduction housing will accept the desired gear set before purchasing. You don’t want to buy what you think is your dream combination only for them not to get along.

OEM Parts 101: What Are OEM Parts?

Anyone who has ever needed auto parts has heard or seen the term “OEM.” Understanding what this means is important for all vehicle owners — but especially for DIY mechanics and restorers. Our experts have put together this guide to OEM parts so that, whether you shop at Advance Adapters or through your local dealership, you know when OEM is the right choice.

OEM Parts Explained

OEM is short for “Original Equipment Manufacturer.” These parts are identical to what was on the vehicle when it left the factory. For newer vehicles, OEM components are made by the same company that designed and produced the original. In the case of older vehicles, other companies are sometimes contracted to make officially licensed parts using the OEM specifications and materials. An example of an OEM parts company is Mopar, which was created by the Chrysler Corporation solely to make authentic parts for their vehicles.

By purchasing OEM vehicle parts, you can expect the quality, fitment and performance to be the same as what you’re replacing. The parts are also more consistent, and they’re always backed by a warranty in case of failure. In other words, OEM is the “old reliable” of vehicle maintenance and repair. Occasionally, you can also get OEM performance upgrades. On the downside, OEM parts can be up to 60% more expensive, and availability may be limited for certain vehicles — especially if your vehicle is an older model or wasn’t as popular as other models.

OEM vs. Aftermarket Parts

You typically will have a choice between OEM and aftermarket parts for your project. Aftermarket car parts are made by independent manufacturers to replace the OEM parts. Some aftermarket parts look and operate like their OEM counterparts while others are designed to improve performance in some way. A few companies, like AC Delco, make both OEM and aftermarket parts. Manufacturers can make a huge range of aftermarket components or specialize in certain vehicles and types of parts.

There are a few advantages to buying aftermarket parts. Equivalent parts are often less expensive and have more variety, which is great for modding. These alternative components are easier to find, too. However, to the uninitiated, aftermarket parts can feel like a bit of a “Wild West.” While some parts are better quality than OEM, others are worse quality, and so-called universal parts might not be a great fit. Not all aftermarket parts have warranty coverage, either. This means doing your homework to make sure you’re buying a good part from someone reputable.

Which Parts Should I Buy?

The choice ultimately comes down to your preferences and project goals. Order OEM if you’re happy with how the original part performed and are willing to pay more for a sure thing. If you want customization and high-performance options, or the OEM component is no longer available, then go with aftermarket parts. Advance Adapters is known for quality conversions products and backs them with a warranty of up to one year so you know you’re getting the finest OEM and aftermarket 4WD components.