Torque Converter slippage (Help)

[GringoPete]

Originally Posted by Blue Bowtie

Has the fluid been changed recently? Has it been changed regularly? Using an incorrect fluid can contribute to clutch slippage.

It might be beneficial to check the line pressure with a gauge and compare it to what the internal pressure sensor array is reporting to the PCM. Weak/dirty internal pressure sensors can report higher pressures, causing clutch slippage. Obviously, internal wear and hydraulic leakage can also result in slippage.

One potential (but not always definite) way to check for low pressure is to start in Range 1 and manually shift through the ranges. The PWM pressure control is basically bypassed when in manual mode, allowing full line pressure to operate the clutches and servos.

Ok, Sorry i'm late getting back to you on this.

I manually put it in 1st gear and it did not do it.

It does it in drive and when it happens it seems as if the front end bounces up and down rapidly which makes me think that its the tires spinning from hitting the gas too hard when i have the wheel cut.

What do you think?

[GringoPete]

Originally Posted by BNaylor

Did you ever get it scanned with a trans capable scan tool or at least one that can read out GM extended DTCs like P1XXX? As I might have mentioned earlier certain DTCs related to PCS and internal slippage may not trigger the SES/CEL light but are stored when a fault occurs.

I dont have one of those scanners BNaylor.

[BNaylor]

Well, it sounds like you can rule out motor mounts. Classic 4T65E launch shudder. Meaning a flaky PCS. Definitely not good news.

As suggested get the line pressure tested at a transmission shop and they most likely have the proper scan tool to check for DTCs. In D1 the minimum line pressure ranges around 146-187 PSI. D2, D3, D4 is 74-86 psi.

[Blue Bowtie]

You could try the Saturn TAAT trick, and manually force the PWM solenoid to full on until the trans gets really good and warm, dump the fluid, change it, and return to PWM to see if it improves.

You should still follow Mr. Naylor's instructions and scan the trans data to see if the pressure switches are reporting actual line pressure. After all, the PCM can only work with the data is is given.

[BNaylor]

Originally Posted by Blue Bowtie

You could try the Saturn TAAT trick, and manually force the PWM solenoid to full on until the trans gets really good and warm, dump the fluid, change it, and return to PWM to see if it improves.

You should still follow Mr. Naylor's instructions and scan the trans data to see if the pressure switches are reporting actual line pressure. After all, the PCM can only work with the data is is given.

Not a bad suggestion Jeff but IMO no cigar yet. .......

Mr Naylor has further instructions and a better solution. This may sound radical but based on my research and experiences doing a work around which appears to be a good alternative solution. It has worked successfully in 3 GM test vehicles with the 4T65E autotransaxle. Beats replacing the PCS solenoid.

Dump Seafoam tranny additive (full container) into the tranny. Run it for a few days so the Seafoam does it's job. Then do a pan drop service. Drain out the old Dex III. Remove the 1-2, 2-3 accumulator and add spacers to firm up the shifts which will improve shift timing so the PCM module sees no issue and does not set any DTC like P1811 (max adapt, long shift). You can add a 3/4" spacer to the backside of the 1-2 and 2-3 pistons. On the front side of the 1-2, 2-3 piston add a 1/2" spacer to the 1-2 and 3/4" to the 2-3. Basically you are installing a shift kit.

Put it all back together with a new Filtran brand screen filter which is the same as the AC Delco TF304 screen filter. Now here is the best part so take note. Replenish with the approximately give or take 7.5 quarts of the new Dexron VI ATF.

The launch shudder will be history as will any P1811 DTC to include any hard upshifting.



4T65E 1-2, 2-3 Accumulator Disassembled