Figure 1

Whenever a new transmission or transaxle comes out, most guys try to compare it to something they're familiar with. I think this helps all of us adjust to the change more easily. How many times do you still hear people refer to the 4L80E as the electronic 400? Way too many: As we all know, the 400 is a three speed, and the 4L80E is a four speed, but they do have many similar parts.

The 4T60E and the 4T65E would be a lot closer comparison. At first glance they appear to be the same; they even have the same clutch and band application. However, once you start to look more carefully, you'll notice external differences which we will cover in more detail a little later.

Don't get the idea that these two units are so similar they use the same gasket kit or the same parts: they don't. As you'll soon see, the 4T65E is unique.

General Motors' Outlook

Before we dive into this unit, you should know that GM published a powertrain product service bulletin on this unit. The purpose of this bulletin was to introduce the 4T65E to its dealers. The bulletin goes on to explain GM's service policy. As you've probably seen, when a new transmission is introduced, the manufacturers often place a sticker on it saying, "Do not service this unit," and provide an 800 number to call. There are a few reasons for this: The primary reason is it provides the manufacturers the opportunity to evaluate any field problems and perform some "root cause analysis" on why the unit failed. So, up until the start of production in 1998, or until further notice, the powertrain policy states that only limited on-vehicle service should be performed to this transmission. If the problem can't be corrected in the vehicle, the unit must be replaced with a SRTA (Service Replacement Transmission Assembly) unit.

Of course, most of us, always wanting to be the first on the block to work on something new, never let a little thing like a sticker stop us from diving into these preliminary units.

Where will you find it?

Figure one is a list of the vehicles that use the 4T65E transaxle. One thing I usually do when a new unit comes out, and recommend to others, is to spend a night visiting the local new car dealership. I like to get a firsthand look at some of these modelsbefore they find their way into the shop. If you're a little creative with the salesman (and he thinks you're likely to buy) you may even get to road test one of these new units. The vehicle I drove was a Grand Prix; the transaxle performed perfectly.

External Appearance Differences

Figure 2  Figure 3

When you get past the first glance at a 4T65E, you'll notice that the case connector is located on top, toward the back of the bellhousing. It's in the twelve o'clock position, facing the fender (figure 2).

The servo cover design has changed: It's now a flat cover, without the ridge that characterized the 4T60 servo cover since 1984.

This transaxle is fully electronic; it has an electronic pressure control solenoid to control line pressure, so it no longer needs the vacuum modulator. The area where the modulator would have been (if this were a 4T60E) now houses the actuator feed limit valve. This is a pressure regulator, similar to a modulator valve, but instead of influencing line pressure, it feeds the pressure control solenoidwhich, in turn, influences line pressure (figure 3).

The Electronics

Removing the side cover provides access to all of the unit's electronics and its valve body. Figure four identifies each of these solenoids. The pressure control solenoid and the TCC solenoid are pulse width modulated (PWM).

Take a good look at where the pressure switch manifold is: Hopefully, these won't fail too often, because it's a job-and-a-half to get this side cover off in most models. Don't over look the fluid temperature sensor, located in the internal wiring harness.








Figure 4

Pressure Tests

Well for you guys that hate to check transmission pressures, the 4T65E has only one pressure tap: It's for checking mainline pressure (figure 5). And even better, this tap is in a location that seems fairly easy to reach.

Valve Body

The valve body looks very similar to the 4T60E; however, the two valve bodies aren't interchangeable. Figure six shows all of the valves, and figure seven shows the checkballs.

Figure 5

Figure 6a  Figure 6b

Conclusion

Those of you folks who've read my articles in the past know I try to provide as much information as possible on any new transmission coming down the highway. Unfortunately, until these 4T65Es begin to make their way into the repair shops, there's only so much we can learn about them. And once they start hitting the bays, we'll all be scrambling to find out as much as we can. Let the learning curve begin!








Figure 7