The 4L60E is a for speed automatic transmission with a .70 overdrive. The overdrive gear is gear number four. As the 4L60E ages, one of the most common problems that it develops is that it won’t shift into overdrive anymore.
Without overdrive, your vehicle turns into a time machine and takes you back to an era where it was the norm for a vehicle to scream down the highway at 3000 RPM. We’ll cover the common causes that can put your Overdrive out of commission.
A couple of things to consider before moving on to the problems that cause the overdrive/4’th gear to go out in the 4L60E. There area few conditions that can feel like you are losing reverse, but you really aren’t. We’ll cover them briefly here. If you have no doubt, go ahead and skip to the next section.
The most common problem that is a false flag for the loss of overdrive would be when the torque converter fails to lock up. When the torque converter doesn’t lock the vehicle will travel at a higher rpm down the highway. The whole point of the locking converter is that it is supposed to create a direct 1:1 connection between engine and transmission.
A good way to tell if this is the case is to look at the vehicles RPM on the highway. If the needle moves up and down with the most minor of rpm input change, than it is likely that the locking mechanism has failed. It feels so different going down the highway that it can be confused for a lack of overdrive.
4L60E No Overdrive Causes
Here is where you need to start diagnosing why your 4L60E won’t shift into overdrive. It either can’t, or it won’t.
If it can’t shift into fourth anymore, that means that there is a mechanical issue at hand. These things wear out and eventually even a well maintained automatic transmission will fail. We’ll cover them below.
Can’t is often more difficult to figure out than won’t. If it won’t, that means that the computer has either entered into limp mode (discussed directly below) or that it has a trouble code that is keeping it from shifting into fourth.
The best thing you can do is plug a code scanner in and see what issues may be going on with it. If you don’t have one, just head on down to your local AutoZone (or it’s equivalent) and have them do it for you free of charge. If there are any transmission related codes, you have a great place to start.
Limp Mode– When the 4L60E enters limp mode, it takes overdrive out of the game. It also takes first out as well. You can manually operate the 2-3 shift with the shifter. If you think that you may have a vehicle that has entered limp mode, go ahead and use the how to fix limp mode page on this site to help you diagnose what’s going on. Maybe you’ll get lucky and it’ll be an obvious wiring issue.
Linkage Issues– Before taking anything apart, make sure that you aren’t having an issue with the linkage physically putting the transmission in OD. A good way to do this is to put it into OD. Now go down to D,2,1. Did you get three clicks? If you couldn’t feel three distinct clicks as the gears changed, you very well could have an issue with the transmission going into the gear you are looking for. There’s a reason that this is before the next item. It only takes a second to do and can save you a ton of money if it is the cause.
Band Failure– Most of the time the overdrive gear is going to fail to engage due to the wearing of the band for the Overdrive. The servo will no longer be able to engage it because of this wear. This is the physical problems that stops overdrive most of the time if no other issue is detected. Bands are pretty affordable.