I'm curious as to whether the Powertrain 4L80E fitted to the XJ81 has the same problem as the X305 models did early on, like mine.

The transmission is slow to engage Drive, particularly when engaging 2nd gear in Normal mode. It is something that I live with, but is rather annoying at times. It can be annoying for other drivers too, as I have to wait a lot longer before I can get in gear and go! Up to 5 seconds delay.

Conversely, the transmission is quick but very harsh when engaging Reverse from Park or Neutral.

Its hard to believe they would have let these cars go from the factory like this. However there is a TSB from 1996 regarding the problem, whose only remedy is to replace the entire transmission with a revised unit.

Interesting that shifting Drive to Reverse is prompt and smooth as butter. And operation while in gear and driving, flawless.

I know there's not many of you out there, but if you see this, please share.

 

It certainly doesnt seem normal. Id suggest that a Reputable Transmission Person may be able to help since its not really exotic.......

 

I wonder where I can find a reputable transmission person?

It is a bit of a mystery. According to the TSB, the dealers were replacing entire transmissions instead of servicing the installed units. That had to be a huge expense. If it was a simpler fault like mis-adjusted valve body ***** or a pressure regulator not being correct then why in the world would Jag replace the entire unit?

Transmissions are complicated and I don't fully understand how they function. But as you say the 4L80E is well known in the US. But then you have the Jag adaptation which I'm sure no one will know about! My best estimate is that it has to do with too low of fluid pressure used to engage drive.

It is a possibility that my car did not show this behavior until after the warranty ran out. But... it has been displaying this behavior from the day I took ownership more than 10 years ago at 66k miles, and has not changed or improved at all, even with a gradual changeover to synthetic fluid.

So, I will continue to investigate and find some transmission techs to talk to. Thanks, Jerry. Anyone else? Al R?

 

Google "4L80E Delayed engagement". Lots of info out there. Any decent trans shop should be able to help. Anything there is to know about the '80E has surely be learned and practiced by now.

I had the same problem with my 4L80E. I don't think I ever fixed it. I do remember replacing the shift solenoids and speed sensors.....but can't remember why.

Just for giggles carefully check the wiring bundle going into the trans. It's fairly common to find connector problems or stretched wires here, due to the very loosey-goosely trans mount which allows a lot of movement and tugs the wires

Cheers
DD

 

It may have been traced to a problem that isn't practical to fix in the field. A casting problem in the case which bollixed up the fluid pathways, for example. Or, sometimes they just don't want dealers messing around with stuff. It was probably a joint decision between Jaguar and TurboHydramatic Division of GM who, at the end of the day, probably carried most of the expense

Cheers
DD

 

G'day Gents,

I've recently had the autobox in my X305 rebuilt after years of problematic operation which slowly got worse and eventuated in the rebuild.

As soon as I described the symptoms to the technician he said it's probably your AFL valve. WTF is that I asked?

This following article explains it all better than I could, the AFL valve apparently is a horizontal steel shuttle valve which runs in the light alloy valve body and eventually wears the operating cylinder out of round and then problems start to appear. Anyhow here is the article.

AFL Valve.

1993 to 2018 General Motors vehicles equipped with 4L60E, 4L65E, 4L70E, 4L75E and 4L80E automatic transmissions often wear out the actuator feed limit (AFL) valve bore. As a result, inadequate pressure rise and shift solenoid feed oil loss can occur. This can cause trouble codes, wrong gear starts, falls out of gear and clutch plate burn-up.

The purpose of the actuator feed limit valve is to limit the pressure going to the actuators (aka shift solenoids). The AFL valve spring is calibrated to prevent the pressure from ever exceeding a predetermined pressure, no matter what the main line pressure is. This is necessary to prevent more fluid from being fed to the solenoids than they can physically exhaust and to limit the maximum line pressure output.

On one hand, if the pressure feed to the ON/OFF shift solenoids is higher or lower than intended, the shift valves controlled by those solenoids may not do what they should. For example, too much pressure could flood the shift solenoids, making them act as mechanically stuck closed solenoids. Alternatively, not enough pressure could make them act as mechanically stuck open solenoids. As a result, the transmission can have wrong gear starts, or fall out of gear.

On the other hand, for pulse width modulated (PWM) solenoids like the line pressure control solenoid (PCS), if the feed pressure is too high or too low, the consequences can be detrimental. The PCS output controls the line pressure based on the calculated load from the computer. Consequently, if the AFL pressure feeding the PCS solenoid is too high or too low, the line pressure output will also be too high or too low. As a result, the transmission will either slip and burn frictions, or have hash shifts.


PWM/TCCValve

1991 to 2013 newer General Motors vehicles equipped with 4L80E and 4L85E automatic transmissions often wear out the torque converter clutch (TCC) regulator valve bore in the valve body.

The TCC regulator valve function is to regulate the torque converter clutch apply pressure. The computer varies the pulse width modulation of the TCC PWM solenoid, which regulates the apply pressure of the lock-up clutch. Because of the constant PWM solenoid induced oscillation, over time, excessive wear of the bore occurs. As a result, the computer loses the ability to control the lock-up clutch apply rate and slip rate properly due to the loss of TCC apply pressure.

I hope this info is helpful, cheers,
Jeff.

P.S. If I'd had the AFL valve fixed years ago I probably wouldn't have needed the rebuild. BTW the car has over 220,000 miles on it and now going better than ever.

P.P.S. Fault codes indicating dodgy shift solenoids will be displayed but changing them will make no difference because the dodgy AFL valve is the culprit.

 

Wow Jeff those are good examples of the complexities of the auto trans.

Touch wood that the driving operation of my transmission is correct, with gear changes that are swift and positive. The harshness at the shifter between P, R and D is in stark contrast. I think it is related to fluid pressure delivery during engagement, an example being that a shift from D directly to R produces a smooth and prompt transition, as if the fluid pressure to engage R is already at the correct level coming from D. It's a theory. I will do more research. The problem might be within the valve body, which would not require a rebuild.

My original curiosity was to find out how widespread this problem is, how many owners have seen this. But there are simply not many cars out there anymore, some may have been repaired long ago, and/or many owners are not Jag Forums users!