Is my TCC bad

[Joel_SS]

The other day I noticed that it felt like my TCC was slipping when commanded locked.. I looged some data and was wondering of anyone would confirm that the TCC slip RPM should be alot lower than it is monitored? See my logs.. I suspect when the TCC is locked the TCC slip rpm should be little to none..

[joecar]

Joel,

I'm having trouble opening the zip (aarrgh, I'm having problems on my home pc), so I haven't looked at your log... but...

some slip is acceptable (say no more than 50-100 rpm) since the stock TCC is only "half" a clutch (torque can make it slip easily);

and you have to correlate the slip amount with TCCMODE... slip should be low when TCCMODE is locked/applied, slip can be anything otherwise.

if you could post a screen shot (PrntScreen, save into file, reply to post, do Manage Attachments, upload) of your chart dashpage that will help me... thanks.

Joe

[Joel_SS]

Here is some screen shots.. Forst is idle and second is cruising @ 50mph..

[joecar]

Joel,

Can you log TFT (trans. fluid temp.) also...?

Do this...

At steady cruise, record the MPH and RPM...

Then use this formula to see if the MPH and RPM correlate correctly:

RPM = MPH * 336 * gear_ratio * axle_ratio / tire_diameter

where tire_diameter is in inches;

if they correlate correctly, then the TCC may not be slipping, but probably the PCM is computing incorrect data or the TCCSLIP PID scaling is incorrect.

Joe

[wait4me]

Maybe you just have a broken TCC soloniod case?

[joecar]

wait4me has a good point...

Joel, how many miles are on your trans...?

[Joel_SS]

wait4me has a good point...

Joel, how many miles are on your trans...?


Brand new just re-built 1200 miles ago.

[wait4me]

That part could have gotten cracked if they forgot to pull it out before pulling the front pump. USUALLY that is a part they wont replace because it is the whole trans harness also.

[Joel_SS]

Well I can command the TCC to lock via the scan tool and nothing happens.. I tried it while stopped and I guess if it engaged it would kill the motor, but it did not the RPMs stayed at a steady 1000rpm idle speed. SO I would guess the TCC soleniod is shot?

[joecar]

Joel,

I assume you commanded both solenoids, right...?

It seems to me that the PCM requires several conditions to be met before it allows the TCC to be overriden:
- GEAR must be 3rd or 4th
- VSS must be above some minimum
- ECT must be above some minimum
- some others that I don't know

The PCM is trying to protect the TCC and the vehicle;
So you have to either lift the rear (30-40 mph is good, don't go above this, and make sure the vehicle is SECURE... safety first!), or take a buddy with you on the test drive;

When overriding the TCC, if you monitor the various TSTATE pids (in addition to TCCMODE and TCCDC) you'll see that the PCM does not command the TCC while the conditions are not met...

(this makes me think there are some unknown tables for setting the condition parameters for TCC override)

It may be wise to pull the pan and inspect the solenoid and it's wiring;
I think I saw a solenoid kit where you cut the old one from the harness and crimp on the new one (using specially supplied piercing crimps... this is how it's done on other GM trannies)...

Like Jesse said, the TCC sol. may have been damaged when the pump was pulled from the front of the case with the solenoid still in the bottom of the pump (it requires quite a bit of force to pull the pump as it fits very snug in the case);

Joe

[Joel_SS]

Update: Put the stock converter back in all is good..

[joecar]

:cheers:

[Doc]

Whoa! Did you send the Yank off to get checked?

[joecar]

Sounds like the lining failed...
I don't know if it could leak pressure internally inside the TC... I don't think that could happen... unless maybe the plate had cracked or something drastic,but I can't image it doing that.