As you may or may not know, transmission fluid is designed to be changed at regular intervals just like any other fluid on vehicles. There are very few that do not require such service, such as a completed sealed unit with no way to drain the fluid. However many are still serviceable.
If you neglect to change your fluid or worse, wait until you start having a transmission issue before you change it, it can have negative consequences on the transmission and can reduce the lifespan. If your fluid has never been changed before, replacing it with new fluid can cause the transmission to start slipping, even if it wasn’t slipping before. This is because the old fluid will contain clutch material from being in there over time and can actually be helping the transmission to still shift gears.
With that said, should you change the transmission fluid? How often should you change it?
Changing your fluid cannot cause any damage by itself, if everything is fine inside the transmission. The issues start to appear when you change the fluid if your clutches are already worn or damaged from use. If you go and replace the fluid after they are already worn out. this can cause slipping. The old fluid had contained particles that actually helped shifting, making it grittier to allow better gripping. New fluid doesn’t contain this material and may not grip as well, causing slippage.
So although new fluid may cause the transmission to start having issues, in reality, the issues were already there, you just brought them to light after changing the fluid.
Should you change the transmission fluid on an unmaintained vehicle?
Particles and debris are flushed out when you change the fluid on a vehicle. If you don’t ever drain your transmission fluid, these will remain circulating in the transmission. Although they may not damage the transmission itself, they actually allow the transmission to shift properly as the miles accumulate.
After fluid is old and clutches wear down, you may want to think twice about changing your transmission fluid if you have an older vehicle that hasn’t been changed as recommended. Just because it hasn’t been maintained doesn’t mean changing it will for sure cause any issues, but it is very common that most shop s will warn against it if it has never been changed before.
Should you change the transmission fluid on a properly maintained vehicle?
As long as the fluid is changed periodically, you don’t have much worry when it comes to your transmission. The fluid is designed to be replaced at recommended intervals, so it is a good idea to keep up with the maintenance schedule as defined by your vehicle manufacture, especially if it is still under warranty.
What if I don’t know when it was changed last?
This happens a lot, you buy a car and don’t know if it was ever changed before. Should you change it or should you leave it alone? It really depends on the last time it was changed.
- Ask for Service Records / Carfax: This is an easy way to see the maintenance history of a vehicle. If it was done at a shop or they have a purchase receipt showing it was performed at X miles or X years then that is a good sign for you to continue on with servicing it, as long as it is within the next scheduled service – not 100k miles past when it should have been done.
- Inspect the fluid: Most older vehicles and some newer ones still do have a dipstick to check the fluid. Pull it out and make sure that it is within range, not too low, overfilled or really dirty looking. The ideal color is bright res and clear/ This indicates it was recently serviced. If it is dark red, brown or looks like a ton of particles floating around, it hasn’t been serviced recently.
What do I do if it is slipping?
There are many reasons a transmission can slip. Automatic transmissions can slip from low fluid, wrong fluid, internal failure and more. On manual transmissions, they will slip as clutches become worn. Not all unmaintained transmissions will start to slip after having the fluid changed, however it’s common enough that many mechanics warn against doing it.
Another easy and cheap temporary fix that you can attempt before having your transmission rebuilt or replaced it to pour a transmission stop slip product into your transmission to see if that helps the situation or not, such as Lucas Transmission Fix. It is designed to be poured into your transmission in an attempt to keep your transmission from slipping and jerking through gears. Although this is no guarantee, what do you have to loose to give it a try? It can buy you some time to put back for the eventual repair.
How often should transmission fluid be changed?
The recommended intervals are determined by your vehicle manufacturer, as a general recommendation however, most will be between 30,000 – 60,000 miles. Changing it before the recommended service interval will not harm anything and can help keep the fluid cleaner longer. Just ensure you use the proper fluid and keep up with the schedule, as once you stop, you may think twice before doing it again.
Is it better to flush or change the transmission fluid?
Having your fluid changed or flushed has always been up for debate. Having it changed or draining the old fluid out and replacing it with new fluid is definitely the safer option.
A transmission fluid flush forces fluid through the transmission and can cause debris to circulate around and clog up parts of your transmission. That said, having it flushed can actually cause more harm than a simple drain & refill.
