The 4T65E is for the most part a fairly reliable transmission. It is the successor to the 4T60E. Variations of this transmission have been common since the 1980’s. By the 2000’s most of the kinks were worked out. But, like everything else, it’ll break and wear out with mileage and time. So without further fanfare, here are some of the most common 4T65E Problems.
Before you go any further with your 4T65E diagnostic quest, make sure to hook in an OBDII reader if the service engine soon/transmission light is on. The advanced diagnostics built into modern cars will often tell you the exact part that may need replaced, saving you a load of time.
Only 1’st, 2’nd, and Reverse Work
If you have a situation where Drive and 3’rd gear stop working entirely, you know how terrible it is to drive home with your vehicle screaming down the highway. The situation is most likely going to be caused by a broken forward apply band.
Harsh or Jarring Shifts
One of the most common issues with the 4T65E is that it’ll suddenly start shifting really hard. There are a few different issues that can cause this. The good news is that it usually throws a trouble code. The most common code is P1811.
In my experience, this is the most common code that registers for this problem. The ECM will begin registering this code whenever it detects shift times that are outside of its normal operating parameters.
Once the code is thrown the transmission will begin to operate at maximum line pressure. While not a full limp mode, the transmission at full line pressure shifts incredibly hard. The reasoning for this is the shorter shift time will save the transmission
The real problem with harsh shifting is that many issues can cause it. Most of them have to do with the transmission being just wore out. Here are the most common ones.
- MAF sensor causing the transmission lower command line pressure to be to low. This creates sluggish shifts do to lack of pressure.
- Valve body wear.
- Clutch wear.
- Bad Pressure Control Solenoid.
- Worn or bad seals and rings.
Here’s a great video all about what causes the P811 code.
Won’t Move In Any Gear
If your 4T65E doesn’t move at all whenever you put it into gear, it’s a good idea to start with the transmission fluid. It could be out or extremely low. Get to know the signs of low transmission fluid so that it doesn’t happen again.
A broken shift linkage could also be responsible for the vehicle not moving in gear. This is espescially worth considering if you recently had some ice or a hard freeze. The linkage can freeze. It’s not very common, but it certainly can. Typically, when this happens it should feel like the shifter is stuck until you break it free. But what has really happened is the shifter has been pulled off of the linkage.
Won’t Move When Warmed Up
This has to be one of the most baffling things that can happen to someone. The scenario would be that the vehicle works fine when cold, but whenever it warms up, the transmission just stops working.
This is most commonly cause by the damage to the transmission filter caused by damage to the torque converter. It’s a chain reaction that can leave you stranded. The maddening thing is that the 4T65E will work fine again when it gets cold.
Reverse hardly ever fails on these transmissions. When it does, it’s almost always something that you’re going to have to open the transmission up to investigate. Here are the most common issues that may cause reverse failure in the 4T65E include:
- Reverse Apply Servo- Sealing lip seal may be failing
- Reverse Boost Valve- Worn so much it’s stopped engaging
These are some of the most common issues and problems with the 4T65E. If you have a question I might be able to answer feel free to leave a comment or use the contact page. Remember, while these are the most problems and solutions, there are any number of less common things that can cause the same issues. When in doubt, take it to a professional.