boxburn

Hi all. I'm just wondering how I'd know if my torque converter is actually locking up? I've only had this Jeep for 4 months and am starting to question whether it is or not. It's a 1995 Jeep Cherokee XJ, 4l 4 speed auto.

Thanks

dave1123

If you're going 60 or so and you lift your foot, the rpms will slowly decrease, not suddenly lose 200 rpm. When it's locked up, it acts like it's a standard shift with a clutch, not the slippage of a torque converter. Tap the brake and it should disengage.

boxburn

Thanks for the reply. I'll have to take note next time I'm going to be at those speeds, whether that's Km/h or Mph.

dave1123

You see? This is why it's important to know your location. If I knew you work in Km/h, I could have spoken your language! I'm saying about 100 Km/h.

boxburn

Now I thought you may have been talking in Km/h. I'm in the UK so we're still using Mph so 60 it is.

Location updated.

dave1123

Excellent work! I have an interest in anything British. Like MGB's and Triumph motorcycles, and BSA's are nice too. You can keep your Whitworth threads though!

I've been driving my 2000 Grand Cherokee (WJ) for over 5 years without the lock-up converter functioning, mainly because I won't tear it apart just to replace the converter to save a little petrol. I've checked everything else that controls it and it IS the converter. Like I said, all the lock-up does is reduce the rpms by about 200 at highway speeds and I really haven't noticed any difference in fuel mileage. I've had to work around that check engine light (P0740) for inspection purposes, but I've done so pretty well. I just clear it, do the drive cycle until the emission monitors have reset, then quickly get it inspected before that stupid light come on again. IDK what the code is for your 95 or even if it matters.

jordan96xj

If the torque convertor lock-up is working correctly the following will be observed:

1. Establish a comfortable cruising speed (90-100 kmh)
2. Note the RPM at that speed (typically around 1850-1900)
3. Without taking your foot off of the accelerator, tap the brake pedal (just enough to flash the lights, but not enough to engage the brakes).
4. RPM should quickly jump up by about 200-300
5. After 1-3 seconds, the RPM should reduce back down to the RPM noted in step #2

(The brake pedal switch tells the computer to disengage the lock-up clutch, and the RPMs race a little, then after 1-3 seconds the computer commands the torque converter to lock back up again)

dave1123

Okay, someone HAD to post the official service test procedure! Sorry I'm a putz.

boxburn

Well I don't get any check engine codes relating to the gearbox, just the occasional blip which goes when I turn it off and start it up again. I have put that down to the LPG conversion and the Jeep noticing that something isn't stock. All I can get out of it are flash codes and finding anybody over here within a local distance with a DRB II to read the thing is hopeless.
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As for the braking test, I cannot say that I've ever noticed any change in RPM when blipping the brakes to disengage cruise control so maybe the lockup isn't working. However it's not something I've set out to look for.

Thanks for the replies.

00t444e

A torque converter that isn't locking up creates more heat, and can shorten the transmission life. If it's not locking I would recommend fixing it as soon as possible.

dave1123

That may be true, but my lockup hasn't worked in almost 100K miles and my 42re is still working perfectly at 244K miles. All I've ever done to it is change the fluid and filter several times and a solenoid pack once.

cruiser54

That's not true with all automatic transmissions.
I know it is with a couple GM transmissions.

cruiser54

In my garage and for sale.

dave1123

"Are you talking to me?" I just bought an XJ! My plate is full. Nice car though.

cruiser54

yep.