4l60e sliping 4th on light cruise

Hi all, first post after a lot of reading.

I have had issues slipping 4th on slight inclines with very little throttle. eg: slight accent on the road roll off throttle into ascent and speed drops off, rpm climbs like severe clutch slip. eg: 5000rpm 4th no response until i pedal or grab 3rd. I had replaced trans a couple of thousand ks ago after burnt 3/4 due to same slippage with Mrs driving. Under load even towing trans feels great 100%.

pressure gauge doesn't drop, fluid levels are fine, temp within reasonable range. I'm worried by the time i diagnose issue 3/4 will be gone like before rebuild. Trans builder set tune. I am hoping for a fix to lockup 4th until sort out engine tune as i feel its triggering the slip.

Log file shows slip 30:5 minutes in. Trans log added shows PWM spike 96.9%



Car is 2004 Holden Adventra. LS1 5.7 with 4l60e, US Friends its like a GTO AWD wagon.


Mods: cam 234?/238? 114, 3 inch exhaust, OTR intake. Converter fash @ 4000 rpm. Nothing special with 230kw @ tyre.

(Edit better example of log) Attachment 96206

im no tune expert but from ur tune file and ur data log it looks like it wasnt a slip but more of a downshift.... given u where traveling at 54 mph and at certain hill throttle % went to 45% and in ur tune file traveling in 4th gear and then applying 45% throttle anything over 38mph it will command a downshift to third...

Id suggest using BC Trans tool and see if your tune needs adjusting. This program works very good and makes transmission tuning very easy and less aggravating.


https://forum.hptuners.com/showthrea...Table-Software

Quote:

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Originally Posted by Jlram10

im no tune expert but from ur tune file and ur data log it looks like it wasnt a slip but more of a downshift.... given u where traveling at 54 mph and at certain hill throttle % went to 45% and in ur tune file traveling in 4th gear and then applying 45% throttle anything over 38mph it will command a downshift to third...

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Quote:

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Originally Posted by Jlram10

im no tune expert but from ur tune file and ur data log it looks like it wasnt a slip but more of a downshift.... given u where traveling at 54 mph and at certain hill throttle % went to 45% and in ur tune file traveling in 4th gear and then applying 45% throttle anything over 38mph it will command a downshift to third...

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Thanks for the reply guys. I have done a better data log that indicates the slip. very close on the end of the short file. The BlueCat tables did improve the overall driveability but the slip still occurs under certain conditions. Road undulation when of the throttle and on accent, warm 170f. I can see a section of road and know its going to slip. log 1:18 . log 2 is another example. RPM Climbs speed drops due to slip.

Attachment 96204
Attachment 96205
Attachment 96207

I know this is an old thread, but just in case this helps the OP or anyone else with the same problem, I just solved the same issue on my GTO. The culprit was cross leakage in the servo. There was excessive play in the separator plate around the servo pin. This would allow enough leakage for the band to slip, until apply pressure came up enough to overcome the leakage.

I could see this same behavior happening on any leak anywhere in the 4th apply circuit.