Gear Change Thud / Clunk / Shunt

[eatmoreburritos]

Hi All
Sometimes when my 2.5L 2000 automatic Liberty changes up gears I get a loud thud and the vehicle is shunted forward. This started happening on odd occasions a couple of months ago and now happens most times i drive but only after the car has been running for a while (20 or 30mins).
Once the thud/shunting starts occurring it happens for the rest of the trip whenever the gears change up.
Every time this starts happening I also have loss of power at low revs (ie taking off from traffic lights).
I have checked the error codes and TPS codes shows up (No. 31). I have replaced the TPS but still have the problem.
Any Ideas?

[Robbks]

first thing with an auto issue it to check the fluid level
if that's ok then drain/ flush and re-fill the fluid.

also, unless you have reset the ECU/ TCU to clear the TPS code, it will still be stored in the ECU memory and show up whenever you read them, regardless of teh TPS operation.

[Ric]

I assume that model has a lock up torque convertor. It sounds like it is jamming on, when it should be off during gear changes.
Call into an auto transmission specialist and discuss it with them.

[eatmoreburritos]

Thanks Robbks, AFT levels are good and changed again over the weekend. I also cleared the codes and they have come back again.

Thanks Ric, this may be the issue. The other thing that seems to happen is when I take my foot off the accelerator i get a slight sense of compression breaking, but its an automatic!

[Robbks]

Thanks Ric, this may be the issue. The other thing that seems to happen is when I take my foot off the accelerator i get a slight sense of compression breaking, but its an automatic!

locked up torque converter

did you check the front diff/ torque converter oil levels too
they are separate to the rest of the box

[julianhaami]

I have a similar issue... Fortunately my ride is due for a service in a couple weeks, and i'm pretty sure my warranty covers tranny work.

It only occurs when shifting from 2nd to 3rd (5EAT) and there is a noticeable clunk in the transmission with a lurching sensation.

Also, under full acceleration there is a brief dead spot when 3rd engages (only a fraction of a second), where it sounds like an RPM drop or surge, but with no deceleration.

It happens in all RPM ranges and its no better or worse in the different SI Drive modes.

I thought it might have something to do with either the torque converter, carbon tax, or depletion of the ozone layer, any thoughts?

[youngy69]

If a convertor is locking up the engine will try to stall,good chance a shift solenoid is blocked (think its D) or worst case the valve body is blocked.
Cheers

[julianhaami]

Sweet cheers!

[julianhaami]

Had the TCM reflashed, codes cleared, and re-learn of all gears according to the invoice... $135 + GST.

The thud is still there from 2nd to 3rd less frequently however not as noticeable (it seems more noticeable under load like driving up hill), also the gear changes are somewhat smoother across the range.

In the meantime, can anyone explain how long the re-learning normally takes and are there any helpful precautions I should be taking to prolong the life of the gearbox in this electronic world?