Can too much transmission fluid cause speedometer malfunctions?

Shortly after I had my entire automatic transmission rebuilt, I received two traffic citations. I later had my oil changed (by a different auto shop), and they found that my transmission was over-filled.

I know enough about cars to know that too much transmission fluid will cause a transmission to "slip". However, I need a Toyota transmission expert to reply to this message, and indicate the "possibility" or "probability" that a speedometer can malfunction when there is too much fluid in the transmission.

My car has 130000 miles.
My car has an automatic trans

Experienced mechanics share their insights in answering this question :
Hi there. In most cases when you overfill the transmission fluid it can cause excessive foaming of the fluid or possible internal component failure due to excessive pressure inside the hydraulic lines. Sensors like the speed sensors however are rarely impacted by this situation. However, in regards to the possibility of probability of this; I would say perhaps a 10% chance.

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Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Transmission fluid will become foamy if there is too much fluid. Excessive fluid prohibits proper lubrication and cooling and slows the rotating crankshaft, similar to the effect of running through water.
When the internal engine or transmission sensors determine a fault exists inside the transmission (which can be triggered by too much hydraulic pressure due to excessive fluid), it tends to create a limp mode, so you can slowly drive the vehicle to a repair facility.
Over time, the transmission speed sensor can go bad due to wiring issues or just outright failing due to it constantly being used every time you are driving your vehicle. If the sensor is magnetic, it can go bad from iron sticking to the tip of the sensor, which will cause an inaccurate reading.
Automatic transmissions are very susceptible to damage from overfill. This occurs because auto transmission fluid expands a lot (well, a lot more than engine oil, for instance). The problem it can create is blowing the seals, like where the torque converter rides.
#1 Cause of Failure

The optimal temperature range for transmission fluid is 175 to 220 degrees. Above that, for every 20 degrees bad things happen, starting with formation of varnish at 240 degrees, followed by seals hardening, plates slipping, seals and clutches burn out, carbon is formed, and, ultimately, failure.

Unfortunately, neglecting to change transmission fluid regularly can have severe consequences. As transmission fluid degrades over time, it becomes less effective at protecting the gears and clutches. This can lead to increased friction and wear that can result in decreased vehicle performance over time.
Speed sensors, the MAF, MPS and TPS; to name just a few of the essential monitors within your engine. All of these send signals to the control units, so as with faulty wiring, if one of these monitoring units is not functioning correctly, then it could send a message that causes the car to enter limp mode.
The output speed sensor is also known as the vehicle speed sensor in a vehicle. It transmits a signal to the transmission control unit, informing it of the vehicle`s speed. Failure of the speed sensor is a common reason for taking the car to the mechanic.
The most common causes of a speedometer that stopped working include are a faulty speed sensor, a broken gear on the speedometer, damaged wiring, or a faulty engine control unit.
Transmission fluid ensures that the gears shift smoothly, but there will be a clunking sound in manual transmissions and whining sounds from automatic ones if it is low.
When your vehicle starts to shake convulsively, it may seem like your transmission is significantly damaged and about to shut down completely. However, the primary cause of a shuddering transmission is simply contaminated transmission fluid.
There are two lines or marks on the dipstick labeled either; “Hot” and “Cold” or “Full” and “Add.” The fluid needs to at least be between these two lines. If it is below the bottom line, then more fluid needs to be added.
The ideal maximum transmission temperature is 200 degrees. This is important to know because for every 20 degrees your transmission goes above 200, its life span is cut in half. Think about it. At 220 degrees, your transmission`s life is cut in half.
However, the answer is yes, in a manual shift car (automatic gearboxes are a different matter) the gears and the gear ratios affect the top speed. If the gears get too long – although theoretically allows for a higher top speed- have the adverse effect.
If the transmission fluid begins to leak, your car will start to rev to higher levels (due to torque converter or gearbox band slippage). This may be accompanied by delayed or erratic gear shifts.
If you have a faulty transmission, it will affect the smooth run of your engine which in turn makes you frustrated. In a situation where there is leakage or low transmission fluid, the engine would not provide maximum speed your vehicle.
Not being able to shift is a direct result of having low transmission fluid. Slipping Gears – On the flipside, slipping out of gear is another side effect of having low transmission fluid. For example, you may be maintaining your current speed, then suddenly feel your vehicle downshift or shift to a higher gear.
Gears That Slip

The dirty fluid cannot flow through the system properly, and that hurts the pressure in the system. Changing the fluid allows it to flow, and this fixes the problem.

How fast does a car go in limp mode? Limp mode will likely reduce your maximum speed to anywhere between 35 and 45mph, and revs (RPM) will be limited to 2,000 or 3,000. This is to allow you to continue driving at a safe speed until you`re able to stop and seek help.
Transmission won`t shift – If your car`s automatic transmission is stuck in one gear, often second or third, it very well could be a limp mode activation. It prevents a car from accelerating quickly from a stop and limits the speed once moving.
Disconnect the sensor from the housing on the transmission, as indicated in the repair manual for your car. Disconnect the sensor`s wire coupling. Using the multimeter`s voltmeter connect the probes to the ground and reference wires in the connector. If no voltage is received, the sensor is faulty.
When your vehicle starts to shake convulsively, it may seem like your transmission is significantly damaged and about to shut down completely. However, the primary cause of a shuddering transmission is simply contaminated transmission fluid.
There are two lines or marks on the dipstick labeled either; “Hot” and “Cold” or “Full” and “Add.” The fluid needs to at least be between these two lines. If it is below the bottom line, then more fluid needs to be added.
When your vehicle starts to shake convulsively, it may seem like your transmission is significantly damaged and about to shut down completely. However, the primary cause of a shuddering transmission is simply contaminated transmission fluid.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Can too much transmission fluid cause speedometer malfunctions?
ANSWER : Hi there. In most cases when you overfill the transmission fluid it can cause excessive foaming of the fluid or possible internal component failure due to excessive pressure inside the hydraulic lines. Sensors like the speed sensors however are rarely impacted by this situation. However, in regards to the possibility of probability of this; I would say perhaps a 10% chance.

There is automatic transmission fluid in a manual transmission. Is it okay to leave or do I need manual transmission fluid?
ANSWER : This would depend on what the manufacturer recommends. Many manual transmissions do take automatic transmission fluid. If your transmission has ATF in it, it is very likely that it is supposed to have that in there. If not, it is likely that the transmission would not function properly with the wrong fluid. Many manual transmissions will also take engine oil as a lubricant. The best way to know for sure is to check your owner’s manual or call your local General Motors dealership to inquire.

New cars don’t have transmission fluid dipsticks Transmission fluid changing
ANSWER : That’s a very good question. The reason they have gone with no dipsticks is because they don’t want people messing with transmissions other there at the dealership. Some cars went through that a couple of decades ago. They make it a very involved, convoluted process all through, in order to change the fluid on these modern cars. They have special adapters you have to put. Some of them have to have scan computers in order to read the data and what’s in there, and then be able to change it. A lot of these companies claim that this new fluid is the "lifetime" fluid.

Most new use synthetic fluid can last a long time but any fluid is going to get dirty and wear out over time. I would change it at least every 80,000 – 100,000 miles but if you’ve got one that is really hard to change, you are better off hiring a mechanic to do it.

On some of the cars, it would be too hard for the do-it-yourself because of all that equipment you need. The professional mechanics already have that. Just call any good mechanic, like one from YourMechanic, and they will be able to perform a transmission fluid service for you.

Can I use alternative Transmission fluid to the quotes recommended fluid if i’m bringing my own parts?
ANSWER : I would recommend buying the correct fluid. The reason is because I want to make sure your car is taken care of and is running as long as possible. You wouldn’t want to put something foreign in your car that it may not accept unless you’re willing to accept risks. Different fluids have different chemicals in it. It may cost more right now, but you won’t have to spend money buying a new transmission or having one rebuilt.

Hey Peter, about how much would 2 year maintenance be on a Ram 3500? Transmission fluid, 4×4 fluid, air filter, etc… dealership
ANSWER : Hi Tim,

Thank you for contacting YourMechanic! I have emailed you the quote # 1753289 for the 39,000 miles maintenance service. Remember that this is only an estimate and the total price might change after you add your full address and VIN.

I hope this helps!

Best regards,

Erick
YourMechanic Customer Service Team

My car is leaking transmission fluid – I can’t diagnose the leak
ANSWER : Based on the NHTSA database covering consumer complaints, as well as government mandated recalls and factory service bulletins, for your specific year, make and model, I do not see evidence of widespread complaints about transmission fluid leaks. Such leaks are, in fact, common in transmissions made by any car company, particularly if the transmission is older than say 10 years. There is a manual shaft seal, oil pan gasket, output shaft seals, case seals, torque converter seal (inaccessible) and so forth all of which are potential leak points on your transmission.

If you want to identify and resolve these leaks, certainly a certified Mechanic from YourMechanic could come out and perform a transmission leak inspection and let you know where the leak points are and what it will cost to resolve them.

how much automatic transmission fluid to switch for 2007 camry
ANSWER : Hi there. I’ll try to clarify this for you as it can be a bit confusing. When you replace the standing oil (or oil inside the pan of the transmission) it typically is around 4 quarts of ATF. During a standard transmission oil change, that’s how much fluid is typically used. However, the transmission is comprised of multiple hydraulic lines that have fluid inside them under pressure. This fluid does not "drip" to the pan. It is removed during a transmission flush. The amount of transmission fluid inside these lines, the torque converter and other transmission components equals about another 4 quarts. So, when we complete a transmission fluid service, we are fully flushing all old transmission fluid from the entire unit; which is where we get the 8 quart requirement. It’s always a good idea to have the transmission fluid FLUSHED instead of simply changing 1/2 of the fluid.

Transmission fluid comes up out of the transmission vent tube attached to the transmission dipstick tube
ANSWER : Hi there. Fluid seepage out of the vent tube can sometimes be normal, but can also be caused by overfilling. Has a service been performed recently? Perform a fluid level and condition inspection by having the engine at idle, on a level surface, warmed up engine, and remove the dipstick and cleaning it with a shop towel. Reinsert the dipstick and fully remove to a horizontal position for inspection. Make sure the fluid is not milky, very dark, or has contamination. The level should be in the safe zone marked on the stick.

Have an inspection by a qualified technician determine if any problems truly do exist and provide you with some assurance. YourMechanic has several technicians available that can assist you with a transmission leak inspection and can perform a transmission fluid service if needed.