transmission "slip" below 2500 RPM?

[Jberger]

Guys, I need help, I think my transmission is having problems. 1990 Q45 with external cooler, regular flushes and mobil 1 JWT ECU/TCU Combo.

I haven't driven the car much lately so I'm not sure what has happened, but here goes. I've been thinking that the transmission was sluggish lately, it just didn't seem to be right. Today, it was very apperant. The car seems to be slipping below 2200-2600 rpm. Above that, it's fine and shifts normally, but @ 2700 or below it seems to slip.

I've checked the fluid level and it's fine. I added fluid a few weeks ago since it's got a small leak somewhere. I'm planning on doing the transmission test as stated in the service manual this weekend. But all thoughts are appreciated.

Any chance it's the Torque Converter? The RPM relation makes me think it's possible, but I don't know how to diagnose it.

[greg_atlanta]

The transmission test only takes about 5 minutes. I'd do it now. Doesn't sound good.

Did you ever get a new car as daily driver? Remember you were looking forever.

[Jberger]

Hey Greg, I haven't replaced the Q yet, I was all set on a new Q45 but then saw the FX pics and decided to wait, still waiting on the FX45 to arrive. Just waiting until I have enough time to find the leak and the perform the test. Guess I'll just have to move it up on the agenda.

[DougQ45]

I would suggest you: i) drop the transmission pan, ii) clean the pan and magnet really well, and iii) replace the metal mesh trans filter and o ring inside the trans. The filters tend to plug with repeated flushings and deprive the transmission of fluid. Then the slipping starts!! This fixed my 90Q with 86,000. Takes a couple of hours, and costs only $50 or so!! Make sure you buy 4 or 5 quarts of fluid for what comes out of the pan.

[Jberger]

Doug, I agree, I have a full flush and filter change annually, and the last one was about 4-5 months ago. I"ll probably end up doing another one too, after I run the transmission test this weekend. Thanks!

[911/Q45]

Did you change the filter yourself? Many places automatically say flush and filter change, but unless it's T3 I'll bet they just flushed the fluid and you've got a clogged filter.

[Jberger]

I'm a T3 guy, they've been taking care of the car since I "met" dennis in the old yahoo forum. So I'm sure the filter was changed and I paid for the flush, and pan drop, etc. My standArd routine is to buy all the fluids and just tell them to do whatever Dennis suggests or has done to his car. The only problem is the distance, I've got a 2 1/2 hour road trip to get it serviced, but they do an outstanding job.

The main thing that's puzzling me is the "slip" below 2500, once the torque converter locks up, it appears to be rock solid. I do have a small transmission leak, that I've been unable to trace, but I just make sure it's topped off regularly. 90% of the miles are highway since I work from the house there's not really any stop and go driving.

It's strange, I've never experianced a torque converter failure, but that's what I'm guessing. Thanks for the replies, hopefully I'll have more info after I put it up on the stands this weekend. I just haven't had time to get to it this week. Gotta get some business done before everyone abandons the office for the holidays.

Anyone ever had a torque converter fail? What were the symptoms?

[Jberger]

Okay, I can't believe I was this dumb, but the problem was low fluid. I had just topped it off last week, and didn't think that could be it, but it was. I never got the AT Check to execute. I could get the dash display to read "AT CHECK" but never actually display the OK status after the tests. Any Ideas?

But here's the scary part. The leak was from the external transmission cooler. Appearntly, the return line was loose from the cooler itself. At rest, the line was not stressed and kept a fairly good connection. When running or under load, the line pulled away from the fitting and leaked a tremendous amount. That helped explain why I could only see a small leak in the garage, it was all leaking out on the road.

So go check those hoses and clamps!

Now, should I go have another Flush, pan drop and filter change?The last one was not long ago, but I figure the fluid probably should be changed and the pan/filter dropped to get rid of the heat related trash.

[PalmerWMD]

I do both every 18 months.

Fred..

[Q451990]

Do you still have your OEM TCU or is it JWT... I'm not sure about the self-test on JWT units. The "AT Check" staying on can mean several things... transmission not warmed up properly before test... incorrect selector positions when putting it in drive... not waiting long enough, etc. Does the square on the far right of the display flash on and off for a while, and then stay on? If so then the test result is "AT Check" and according to the manual it means "Inhibitor switch, 1 range switch, kickdown switch, idle switch or diagnostic information display system circuit is disconnected, or A/T control unit is damaged"

Heath

[Jberger]

I'm running both the JET ECU/TCU Combo. I assumed that's why the AT Check did not work. The display is fine, but when I used the presribed AT Diagnosis in the service manual, I only get the AT CHECK in the display, no blinking squares, no OK, no numbers. It's like I didn't perform the sequence correctly.