frying 3-4 packs under medium acceleration

[98 SS]

2006 2wd TBSS, scaled tune with 10psi of boost.

Trans is a 4l70e. From front to back: Circle D stage 3 billet multi disk 3600 stall, billet input shaft, billet pump rotor, Sonnax pump spring, boost valve, boost valve spring. Pump has been modified for oil return off the front seal. Wide drum with wide kevlar band, Sonnax input drum with reinforcement sleeve, circle D billet piston. 3-4 pack setup with 9 .062 BWHE clutches and 8 .078 steels, had to take out one steel in the middle of the pack and put two thinner steels back to back to get a clearance of .035. DID NOT put back in the spring clips with the new sonnax springs. Beast shell, billet output shaft. Valve body has all sonnax goodies with an 07 seperator plate. TCC slip programming has been eliminated, Billet servos.

Problem
I burnt up a 3-4 pack about a year after a rebuild. I attributed it to abuse and adding the blower. The rest of the trans looked great, but I picked up the new converter, did some valve body work, and added the new sonnax drum. The 3-4 lasted about a week.

The 3-4 held up great under WOT, Both times I have burnt them up are under 50-70% throttle. First time was on a highway on ramp, second time was going from a 70mph cruise trying to catch up to the convoy, but not enough to downshift.


The tune is scaled for 60lb injectors. Running an LS7 maf. I havent touched hptuners in over a year due to a deployment, and I know this tune is FAR from being correct. Im just wondering if there is anything obvious that sticks out that would attribute to part throttle 3-4 burnup.

Here is the tune I had the first time, and revision 2 was the one I had this week when I burnt it up.

And here is a log and config from when I put it all back together.

[snowvette]

I would assume you have a auxiliary trans cooler also. The one in the radiator is far from sufficient.

[98 SS]

Yup, auxillary cooler, tci deep aluminum pan that holds an extra gallon, and I was running max shift from TCI.

The temps stayed at 150 pretty consistantly, even after hammering on it. But as soon as the 3-4 started slipping on the highway it jumped from 150 to 165, then cooled back down. The slip was for approx 3-4 seconds.

[98 SS]

For clarification.... this is the new sonnax smart tech drum that gives you a solid apply plate and bolt on backing plate. No more c-clip in the drum. No coning of the clutches at all! (Which the last 3-4 pack was coned like crazy)

[IJ.]

Happen shortly after a kickdown to 2nd under power/load??

[98 SS]

The first one, I beleive was on red altos, it fried while getting onto the highway after grabbing some food. Wife was drivng, she got into it, but not full throttle, it shifterd into third and I could tell it was slipping. I yelled for her to get out of it, but it was too late by the time she figred out what was going on.

This set, the BWHE's, We were cruising locked in 4th, I got into it some but not much at all. I think it kicked down from 4th to 3rd but didnt unlock the converter. Otherwise it stayed in 4th and unlocked the converter. There wasnt a big enough rpm jump to be unlocked in 3rd. Something didnt feel right, so I got out of it, watched the temp spike, then realized that the 3-4 was slipping under load, but holding at steady state driving. We pulled off for gas, and I had to manually shift through 1st and 2nd to get the truck up to speed before putting it in D to let it lock up and hold so we could cruise. I could speed up slowly without slipping, but any real load and the rpms would start climbing

[IJ.]

As fas as I can work out it's an issue with the 3/4 pack not venting fast enough on kickdown and it pulling another gear that kills them (in the same boat here as of 2 weekends ago)

My other car has a stock 5.7 so I drive it on the shifter a lot and it's never shown any sign of distress, I'm currently awaiting a bunch of Sonnax parts to rebuild mine along with the new CircleD TC this time.

The Boys at PATC are rewriting a Trans File and I think I'll look at changing the kickdown behaviour..

[snowvette]

Im no expert, but are you locking the tcc at the same time you make the 2-3 shift. That seems like it would be rough on the trans. your wot tcc apply and normal apply don't match either. Your Baseline file looked better than your rev 2.

[wyochimneysweep]

I had a same thing with a stock avialance and it happen to be the one way sprag slipping and would burn the three-four clutches. This was with the monster in a box kit. Make sure there's no signs of slipping or heat on the one way sprag. I put three sets of clutches in before finding the new sprag had went bad.

[wyochimneysweep]

The first one, I beleive was on red altos, it fried while getting onto the highway after grabbing some food. Wife was drivng, she got into it, but not full throttle, it shifterd into third and I could tell it was slipping. I yelled for her to get out of it, but it was too late by the time she figred out what was going on.

This set, the BWHE's, We were cruising locked in 4th, I got into it some but not much at all. I think it kicked down from 4th to 3rd but didnt unlock the converter. Otherwise it stayed in 4th and unlocked the converter. There wasnt a big enough rpm jump to be unlocked in 3rd. Something didnt feel right, so I got out of it, watched the temp spike, then realized that the 3-4 was slipping under load, but holding at steady state driving. We pulled off for gas, and I had to manually shift through 1st and 2nd to get the truck up to speed before putting it in D to let it lock up and hold so we could cruise. I could speed up slowly without slipping, but any real load and the rpms would start climbing

This is actually what it did to me also with the sprag slipping

[IJ.]

Pulled my Dead one down this morning, destroyed the 3/4 pack no other damage.

Missing Friction material and severely bowed discs.

[98 SS]

I was playing with locking the converter all the time at wot. I probably didn't do it right at all. The converter is a multi disc, so I wanted to see what all the fuss was about. But I didn't think I wanted to change the part throttle to be locked?

I was wondering about the line pressure tables and shift time tables. I've never touched the line pressure tables, but I'm fairly sure they aren't stock. I need to compare them to my stock file.

As for the coning, $500 for the new sonnax drum. It mills off the c-clip tabs and bolts on a solid backing plate that stops the coning.

[98 SS]

Also wondering if my scaled tune could be the problem, or that I'm running in man only right now.

[IJ.]

I was playing with locking the converter all the time at wot. I probably didn't do it right at all. The converter is a multi disc, so I wanted to see what all the fuss was about. But I didn't think I wanted to change the part throttle to be locked?

I was wondering about the line pressure tables and shift time tables. I've never touched the line pressure tables, but I'm fairly sure they aren't stock. I need to compare them to my stock file.

As for the coning, $500 for the new sonnax drum. It mills off the c-clip tabs and bolts on a solid backing plate that stops the coning.

My Sonnax Drum is somewhere between the USA and Australia right this minute....

Keeping the TC locked during shifts is VERY harsh, If you're on a scaled tune again my understanding is you need to shift your shift pressure back into line with reality so yes this could be some of your issue at part throttle.

Banish covers this in his advanced tuning DVD, well worth a look in your case, how are you finding the CircleD TC?

I'm very impressed with the service and packaging, mine is sitting on the bench awaiting the arrival of the new parts for another attempt.

[98 SS]

I think circle D is great. Customer service is top notch, and if you ever need anything done to the converter, chris is great. Im loving the new converter, it is a heavy beast though!!

[IJ.]

I think circle D is great. Customer service is top notch, and if you ever need anything done to the converter, chris is great. Im loving the new converter, it is a heavy beast though!!

Thanks and I agree Chris has been brilliant, LOL yeah +5Kg's to a normal Converter!

I was expecting MUCH more damage when I pulled mine down, it was good to see it was only a dead clutch pack after all, I broke my case awhile back and swapped in an eary case I had here, this is a good opportunity to swap in a correct late case.

[jimmyblue]

When you say "scaled tune" that makes me think your
air mass (VE, MAF) values may be hokey and if so you
are telling the trans pressure control "stuff" that it's
seeing less load than it really is. How does your
Delivered Torque - Trans value compare to your dyno
#s (if you have them)?

I'd be looking at the commanded line pressure values
at the troublesom pedal-level, and bumping down my
force motor table profile to get it "all in" (10mA or so)
by that point. You can't really get at the trans line %
vs load, except in a few OSes that have Trans General
Pressure support, but you can grab it by the neck and
make it push full pressure under mid-high load anyway.