BMW 745Li Transmission Problems – Our List of Reasons and Fixes

The BMW 745Li is a 7-Series sedan that was introduced in 2002 and stayed in production until 2005. The luxury vehicle had an attractive, bold, and self-assured presence thanks to its sleek exterior and fashionable features. Not to mention, superior handling along with a high-performance engine that provided exceptional performance with maximum comfort.  

BMW 745Li automatic transmission highlights

• Average lifespan:190,000-230,000 miles
• Reliability Score:High
• Prone to minor issues:No
• Price for repair after failure:$1,300-$2,400
• Price for replacement:$5,500-$7,000
• Availability of parts:Good
• Common problems:overheating, slipping, strange sounds, limp mode.

What are the common transmission problems in your BMW?

The smallest transmission problem can affect your 745Li's performance and end up damaging the engine. Therefore, it is crucial to have some knowledge related to your BMW's transmission issues so that you can quickly diagnose and repair them on time. Below are some common reasons, symptoms, and fixes related to transmission problems that an owner of a 745Li BMW should be aware of and know how to deal with.  

• Low Transmission Fluid 

The transmission fluid in your 745Li BMW getting too low is without a doubt one of the most common reasons for having transmission problems. Although leaks are normally the main culprit of the issue, blocked transmission fluid filters along with old or cross-contaminated fluid can also cause troubles. Regardless, a low transmission fluid level left untreated can result in a full breakdown of your vehicle's transmission.  

The main purpose of the transmission fluid is to keep all parts of the transmission system well-lubricated. Also, the fluid helps reduce the high temperatures produced under the hood, especially while changing gears and accelerating. That is precisely why it is so important to check your transmission fluid at least every six months to monitor the level and quality of the fluid.  

• Leaks in the Transmission

Transmission should never run low and if you happen to notice any fluid under your vehicle, it is because it leaks somewhere. Transmission fluid is kept inside the transmission system by a variety of seals and gaskets. Due to wear and tear as your 745Li BMW ages, these seals and gaskets can easily start to fail.  

Although leaks can be internal, most often you will see some dark red fluid that smells a little sweet under the front of the vehicle. These leaks can be easily fixed by replacing the gasket or seals that are damaged or not working properly. It is much easier and way less expensive than having to replace the entire transmission.  

• Clogged/blocked Transmission Fluid Filter

While the transmission fluid continues to circulate through the transmission system, it can collect dirt along with built-up debris and sludge. To prevent this or at least slow it down, the 745Li BMW's transmission system comes with a filter to catch dirt, debris, etc. The main purpose of this filter is to keep the transmission system clean while the fluid runs smoothly through all the necessary parts.  

Unfortunately, after enough time and usage, these filters eventually will get clogged up. Therefore, the fluid will not be able to pass through the blocked transmission fluid filters and cause a similar scenario as having a low transmission fluid level. As a result, many parts of the transmission system will not get the fluid that is needed and end up malfunctioning.  

• Solenoid

Solenoid malfunctioning can also be a cause of transmission problems for your 745Li BMW. They basically control the fluid that flows through the transmission of your vehicle. Solenoid functions through voltage that is supplied by the transmission's computer.  

If you are continuously driving with a low transmission fluid level, it will eventually damage the solenoid after some time. The solenoid in your vehicle can also have electronic problems that can cause it to malfunction. Problems with the solenoid also have very similar symptoms to having a low transmission fluid level and can be replaced if needed.   

• Torque Converter

As manual transmissions have a clutch connecting the engine to the transmission, the 745Li BMW has an automatic transmission with a torque converter. Just like a clutch, it allows the engine to spin independently while transmitting the engine power to your vehicle's wheels. The torque converter not only allows the vehicle to come to a complete stop without stalling your engine but also gives it more torque when accelerating from a stopped position.  

Wear and tear over time can cause the torque converter to become worn out or damaged, which will have a direct impact on the transmission's functions. Your vehicle's transmission will get damaged because of the worn-out converter and may even fail to work completely. You will be able to hear grinding sounds while shifting gears and driving if the needle bearings are worn-out.  

• Clutch

The clutch in your 745Li is found within the torque converter and can occasionally get jammed. Once the clutch in the torque converter jams, the solenoid locks, and the transmission fluid within the torque converter is not correctly calculated. Being related to a fluid issue, a malfunctioning clutch has the same types of effects and symptoms as having a low transmission fluid problem.

Symptoms of Transmission Problems

Transmission problems will cause your 745Li BMW to underperform or not work at all. During hard acceleration or turning, your vehicle may display a Transmission Failsafe Prog or go in Limp Mode if there isn't enough transmission fluid for the oil pump. Your vehicle goes in Failsafe Prog or Limp Mode to preserve itself and prevent further damage to the engine, transmission, and other related parts.  

Low transmission fluid, damaged or worn-out solenoid, and malfunctioning torque converter/clutch are just a few of many reasons that can arise issues with the transmission of your 745Li. Whatever the actual cause may be, it should not be left unattended and dealt with immediately. Fortunately, there are some very common symptoms and tell-tale warning signs that will alert you and help detect most transmission problems at an early stage.  

• Grinding or Shaking in Gears

Grinding or shaking in gears is a common symptom of a failing transmission. The transmission in your 745Li BMW is designed to shift smoothly from gear to gear without any hesitations. So if you feel any grinding or even shaking when switching gears as you accelerate, that is due to transmission problems.  

• Slipping Gears

The transmission of your vehicle knows when to shift from one gear to another through a computer system built within your 745Li BMW. If the computer malfunctions or has a faulty transmission, you will end up in a very dangerous situation on the road. While driving, if your vehicle seems to slip out of gear, try to give it more gas for a better pickup and to get to the nearest auto repair shop.  

• No Response/Delay to Switch Gears

Along with slipping gears, you can also experience a delay or no response at all from the transmission when going into drive, reverse, or accelerating. This could be due to bad/contaminated transmission fluid or an issue with the built-in computer system that was mentioned earlier.

A transmission flush can resolve the issue related to the fluid issue and resetting the computer system by disconnecting the battery for about 30 minutes may fix the tech problem.  

• Strange Noises/Sounds from the Transmission

Strange noise coming from under the hood of your vehicle is never a good sign and most often is due to transmission troubles. Whining, humming, and clunking noises are very likely to be related to transmission fluid issues. The transmission's components and other related parts are kept lubricated as the transmission fluid circulates through the transmission system.  

Due to old/contaminated or low fluid levels, the transmission fluid fails to keep all parts of the transmission system lubricated and working smoothly. Those dry parts start grinding against each other and the friction causes the noises. Immediate action is necessary for this situation as the parts causing the noises inside of the transmission will most likely get damaged and break down from the frictions.  

• Burning Smell

If you are detecting any burning smell/odor while driving, your 745Li BMW definitely has a problem with its transmission and needs your undivided attention. That smell that you're picking up is due to overheated transmission fluid. That means the transmission fluid is failing to lubricate all parts and keep everything under the hood at a normal temperature.    

Whether the overheating is due to low fluid levels or just bad transmission fluid that needs replacement, your transmission is on the verge of breaking down. Keeping all parts of the transmission system well lubricated and cool is the key to a healthy and well-performing transmission as well as the engine. Therefore, if you sense a burning smell coming from your 745Li BMW, you need to get it serviced before it is too late and the transmission system fails completely.  

Conclusion

The transmission is considered to be the heart and soul of your 745Li BMW as it is the connection between the engine and the wheels. After all, the transmission is what directs the power from your engine to the driveshaft. Furthermore, allowing the wheels to turn and change gears as needed for you to drive at your desired speed.  

Regular and proper maintenance will help your vehicle's transmission to perform better, need fewer repairs, and last much longer. Paying attention and caring for the transmission fluid should be on the very top of your maintenance checklist. As recommended, the transmission fluid for your 745Li BMW should be inspected and if needed, replaced every 30,000 to 60,000 miles for best results.  

A transmission has many parts inside and can fail for too many reasons. Even a minor transmission problem unattended over time can have you stranded with your vehicle on the side of the road. Moreover, cause great damage to the engine and other parts that may require some very expensive repairs and replacements.