Transmission Master Kits vs. Overhaul Kits

We want one thing to be absolutely clear to transmission rebuilders everywhere: when it comes to what rebuild kit you buy, you definitely have options to choose between. Rebuild kits come in some different shapes and forms, and depending on the characteristics and setup of your shop, they're not necessarily all equally beneficial for you. That's why we're taking the time to walk you through the differences between two of the main types of transmission rebuild kits on the market: master kits vs. overhaul kits.

To learn what you can expect to find in typical transmission master kits vs. overhaul kits as well which might be best to use for a certain job or shop, keep reading.

Master Kits vs. Overhaul Kits: What's Inside 

Depending on what your kit supplier or distributor offers, you might not know what the difference between a master kit and overhaul kit really is. While you can use either kit to rebuild a transmission, the key to telling them apart is by looking at what actually comes inside them. Here's our breakdown of the differences:

• Transmission overhaul kits contain all the "soft parts" you need to rebuild a transmission—that is, the typically non-metal parts that take a lot of wear and tear. The contents might vary by manufacturer but typically include sealing O-rings, lip seals, D-rings, lathe cut seals, sealing rings, metal clad seals, paper gaskets, bonded pistons, etc.

• Transmission master kits contain everything that you'd find in an overhaul kit, PLUS some additional parts like friction clutch plates and steel clutch plates. These additions can be classified somewhere between soft and hard parts because they typically withstand a higher level of wear than soft parts but aren't necessarily considered a hard part like pumps and gears. 

Therefore, while an overhaul kit is the foundation for many transmission rebuild jobs, a master kit can do thesame job plus a bit more. However, one type of kit is not necessarily "better" than the other in every case. The next section of this post will discuss how to choose which kit might be the best fit for your rebuild job or your shop as a whole.

Choosing Master Kits vs. Overhaul Kits

Deciding whether a master kit or an overhaul kit better fits the requirements of a rebuild job depends completely on the policies of your shop (for a discussion on the shop policies that affect the cost of doing a quality repair, check out our recent blog post). If you're concerned about your liability, you might opt for a more complete rebuild on every transmission job, whether the parts are worn out or not. Transmission master kits would make a good blanket option in this case, especially on a low volume unit.

If you're looking for flexibility, customization for each job, and in some cases, a lower cost, transmission overhaul kits might be a great choice for you. Many of the additional parts found in master kits can be ordered separately, so you only need to pick and choose based on what needs replaced in the unit and what doesn't to accompany the overhaul kit. Many shops choose to order parts such as clutch plates and steels separately on higher volume units and order a master kit on the "one off" units that they see occasionally. However, it's important to be sure to have all the parts you need for a complete rebuild. Check out our recent post on some advancements in transmission technology that might affect future rebuilds.

However, one more factor that may influence on what parts are replaced is the length of the warranty that the shop/rebuilder offers. If a shop or remanufacturer is offering a shorter warranty period, they may option to only install the seals from an overhaul kit along with parts that don’t meet inspection, while a longer warranty that needs to hold up for a longer period might benefit from the additional replacement parts. Whichever way you choose to get the parts you need for the transmission rebuilds you perform, rest assured that there's a kit option out there to suit any situation your shop might be in on a given day.