Duramax Allison Transmission Fluid Type and Maintenance Guide

In short, if you want the best fluid for your Allison Transmission, you should pick one that is factory specified. There is one specific fluid type that will work amazingly with your Allison Transmission: ACDelco Dexron VI fluid, which combines great value with high quality. 

Fluid change in transmissions highlights

• Level of importance:High
• Time interval:Once every 60,000 miles or 10 years (if other not stated by the manufacturer)
• Needed expertise:High
• Needed tools:Basic set of car maintenance tools, plus car lift
• Time taken:2-4 hours
• Possible issues:Fatal failure of your transmission, jerking, harsh work, vibrations, limp mode, no shifting.

What is a Transmission fluid and what does it do?

Transmission fluid is a base oil equipped with different types of additives. Transmission fluid lubricates moving metal parts and bearings that are in the transmission. It makes the whole process of shifting gears easier and smoother. Choosing the right type of transmission fluid for your Allison Transmission is really important, and it requires caring maintenance if you want to achieve the long-lasting reliability that Allison's transmissions are capable of.  

Types of Transmission Fluids for Allison Transmissions

As mentioned earlier, Allison Transmissions are made to last for a very long time. However, it is crucial to choose the right transmission fluid in order to achieve long-lasting functionality. Obviously, there are various types of transmission fluid to choose from. As a brand, Allison approves two types of fluids: 

• On-Highway Fluids
• Off-Highway Fluids

It's important to mention that these Allison-approved transmission fluids are synthetic, but don't worry, these types of synthetic fluids compared to regular fluids based on petroleum offer viscosity and thermal advantages. 

If you want to find out your change interval detailed information, you can find Allison's Fluid + Filter Calculator at this link.

Best Transmission fluid for your Allison Transmission

Allison's TES 668® Approved Fluid is a next-generation fluid that has a lot of advantages compared to non-synthetic fluids that are mineral based. This transmission fluid is made for Allison 1000 Series, 2000 Series, 3000 Series, 4000 Series, and hybrid H 40/50 EP automatic transmissions. 

Compared to mineral-based fluids, TES 668 provides better oxidative stability, anti-wear performance, and friction modifier durability. Thanks to TES 668, the quality of the shifts is improved, and noise and vibrations are reduced. With better friction performance, the clutch application is more consistent, even in quite high or low temperatures and with heavy loads.

TES 668 ensures the ideal and smooth operation of Allison Transmissions and is key for great performance and long-lasting reliability.

How often should you change your Transmission's fluid?

After some time period, transmission fluid becomes contaminated with particles and debris. If not changed, it can make some serious damage to your Allison's transmission and therefore shorten the long-lasting durability that it's capable of. The good thing is that you don't need to change your transmission's fluid as frequently as motor oil. Despite this, you should check it regularly in order to avoid problems in the future. 

You should follow the manufacturer's recommendations for your specific vehicle. Depending on various factors, such as your driving style or the specific type of transmission your car is equipped with, it is recommended to change your transmission fluid every 50,000 to 100,000 miles.

How to tell your transmission's fluid level is low

You may be wondering how to know that your transmission fluid level is low. But don't worry, we got you. Here you can find a brief list of warning signs that you should be aware of:

• Puddles:If you noticed the formation of puddles under your car, your transmission fluid probably leaks.
• Color:If your transmission's fluid turned from a light, clear-colored fluid to a darker brown or muddy green color it can indicate that you should change your transmission fluid.
• Chattering:If your car's engine is chattering while starting, it can be a sign of low transmission fluid level.
• Difficult shifting:If there are any delays or weird sounds you should check your transmission fluid.
• Transmission slipping:This can indicate that your transmission's fluid is at a low level and that there is insufficient fluid to submerge the fluid pick-up within the pan.

Most common problems with Allison transmissions

Despite the fact that Allison's transmissions are known for their reliability and long-lasting performance, there are some problems that may occur. Now, we're going to discuss them.

• Limp mode:If you have an Allison transmission 1000 model, you might face this problem. The Limp mode is a feature that locks transmission into third gear. The limp mode activates automatically when it senses too much overheating or when you are towing a very heavy load. The thing is that limp mode can't be reversed by the driver. If you are struggling with limp mode, you should have your transmission inspected and reset or repaired. If you want to avoid this problem, you should maintain your Allison transmission 1000 model well.
• Wrong installation:Another problem can occur even when transmission itself is alright. You should check your vacuum lines and other parts connected to the transmission.
• TCM Module:Allison's transmissions from the mid-2000s were withdrawn from the market and replaced because of their faulty TCM modules. If yours was not replaced, you should contact your dealer and ask for a replacement.

Service tip #1

This first servicing tip may be helpful for you if you want to know more about Allison's transmission servicing. GM recommends that the Allison 1000 transmission fluid should be changed every 45 000 miles, or when the HD's oil monitor says so. 

Despite this, you should have your eyes and nose on guard, since from the color or/and the smell you can tell when the transmission fluid needs to be changed. 

The truth is, that the transmission fluid should be reddish and it should not smell burnt. If it has this kind of color or smells, you should have your internal filter changed and the transmission fluid itself changed too.

Service tip #2

This second tip may help you in terms of maintaining your Allison transmission well. It can save you a lot of money you would have to spend in the future.

• Inspect the drain plug magnet for any signs of metal:If there are obvious signs of metal on your magnet, it may signal some serious internal problems. If you can't see any signs of metal, that's a great sign.
• Replace the magnet on top of the filter:This magnet should be cleaned and replaced if needed. Many owners forget to do so. You shouldn't.

Conclusion

We hope that this article helped you find the information that you were searching for, regarding Allison transmission fluid type and maintenance, as well as some servicing tips that can save you a lot of money in the future. Remember to maintain your Allison transmission well and to follow the given intervals, or change the fluid earlier if needed.

If you find some of the indicators of low fluid levels that were mentioned, make sure to change the fluid as soon as possible. With this caring maintenance, your Duramax Allison transmission will work great for a very long time period and provide excellent performance, even in high temperatures or with heavy loads.