Background:

346ci stock 4L60E trans 37000miles 3.07:1 Aussie Ute.
222/224 112 Comp Cam, 4:1 1.75" Short , 4" high flow cats.

Installed a 3200 2.1STR converter, 24k cooler, new filter and fluid last weekend, When I pulled the pan it had about a 1/4 teaspoon of metal powder on the magnet but oil was clear red (never been changed up to then).

I have HPTuners and adjusted shift points down to avoid hitting rev limiter and all shift speed and rpm OK. No codes thrown.

Problem:

I'm now getting slip at all shifts both full and part throttle (even 20% or less). Fluid was about 1 pint low during first drive (about 5 miles) and on full mark thereafter.

Shifts are taking up to 2 seconds to complete, have increased shift pressures and it's still the same, have also tried increasing Force motor current by 20% across the board. Neither of these seem to have made a difference to the slippage but once shift approaches completion its now quite firm at part throttle but not vicious, still soft at WOT. Tried stock tranny settings and still the same.

I have done some pulls commanding each gear manually using HPTuners (so it takes off in gear commanded and does not up or down shift automatically) and from a standstill and flooring it (uphill) I do not get any slip in 1st 2nd or 3rd (flashing to about 3000rpm) - wheel spin city in 1st and a little in 2nd. The clutches and bands seem to be able to hold full power even with STR multiplication of 2.1

The slip is only during the shift and not after it has been completed. Shifting manually still slips the same as having it in drive. (I haven't tried commanding shifts with HPTuners yet but will do so if anyone thinks it will help diagnose)

Pulled the pan and changed the fluid and filter again today and as expected some clutch material in the fluid (smelt fine - no burn smell) no discernable metal on magnet. (it's my DD so I did about 300miles - mostly freeway locked up in 4th - over the week). Went for another drive and still slipping on changes.

Have not seen more than 167f temps (drops back to about 140 when cruising)so seems temperature is not a factor. Air temps are around 60f at the moment.

I'm figuring either electrical or something that is specific to shifts rather than a pump pressure, clutch or band problem. Hoping someone can give me a pointer into the possible problems. (hoping it an accumulator problem or such but strange this should happen as the same time as a converter change - no signs of any slippage before the converter change)

Cheers
Jamie

 

I am assuming your using the scanner to look at the slip , And heres the problem theres probably nothing wrong, The PCM looks at the engine RPM verses the OUTPUT speed. With the higher stall and loosenes the PCM may read that the shift is taking longer due to the slip in the converter (looseness). Now while I dont suggest this at full throttle to get a real idea of whats happening if your tuner/scanner has the capability lock the converter in second gear then make the shift to third locked and then look at the elapsed time, Thats how long its really taking to make the shift, The numbers shown with the high stall and converter unlocked are not and acurate depiction of whats actually going on . High stalls particulary at lower throttle positions will any times feel like they are very sloppy during the shift when they really are not, I comonley use the pillow cushion comparison because thats the effect a high stall with have on the shifts.

 

Thanks performabuilt, yes I was scanning using HPTuners, I will upload a tune and give it a try locking the converter at part throttle from 2nd to 3rd with converter locked (fuddle HP/Street which is supposed to take WOT locked so should be able to handle part throttle locked during changes but don't want to push it). Will post how I go later today.

Hope I'm concerned at nothing (although the amount of clutch material in the oil within 300miles still concerns me unless it was from when it was a pint low).

Cheers
Jamie

 

Ok, these are the shift times reported with HPTuner with Converter locked during shifts:

Shift @ RPM - Throttle - mA - Shift Time

1-2 @ 4500RPM - 34% - 100mA - 0.2sec
1-2 @ 5300RPM - 74% - 100mA - 0.6sec

2-3 @ 3300RPM - 34% - 100mA - 0.1sec
2-3 @ 3700RPM - 36% - 100mA - 0.1sec
2-3 @ 4000RPM - 45% - 100mA - 0.2sec
2-3 @ 4700RPM - 64% - 100mA - 0.2sec

3-4 @ 2900RPM - 17% - 660mA - 0.4sec

2-3 seems ok at part throttle not sure about the 0.6sec 1-2 though. Box is stock as per Pontiac GTO (ie no corvette servo)

FWIW converter slip reported during changes was between 2 and 9 rpm.

Thanks
Jamie

 

Those numbers are within normal range for a stock trans with no shift kit.

 

Thanks heaps for your help, now I can sleep a little easier.

Regards
Jamie