TrickyTransAm

I had my truck tuned by a local business and since then my 4L60E shifts from 1-2 and 2-3 slip badly at half to wide open throttle. WOT is a guarantee it will slip bad.

The trans was just rebuilt about 20K ago and hadn't been abused, and I haven't carried any heavy loads or towed. I paid extra cash to make sure it had good parts put in it.
At least 18K of the miles were with my half dead 5.3L which I was pampering along as I knew it wouldn't last long, now with the 6.0L.
I will say since around June of this year it was acting a little funny and seemed to have some slippage with the old engine. I never really got on it that much, only rarely to pass or get out of someones way. When I did, it would slip slightly at WOT. Mabee with the refreshed engine it's now forcing the trans to show its weaknesses?

My tuner is telling me despite increasing the line pressure, the trans wouldn't respond to tuning, and that it's definitely a mechanical issue.

Is there anything in the PCM that could be set incorrectly causing it to slip badly? I noticed after the tune, my shifts are firmer and the slippage is getting worse by the day.

iamkeniff

iTrader: (16)

low on transmission fluid?
if not then something is wrong with the tranny. what converter is in it? i would pull the pan and double check for clutch material on the magnet/in the pan. mine doesnt slip but it was starting to "pause" between shifts at part throttle and wot so i pulled it before it left me stranded

1FastBrick

iTrader: (17)

Check fluid level first. But I would say its a failure inside the trans... Not sure but have you ever changed the fluid since it was first built??? Good transmission builders are hard to find.

TrickyTransAm

Trans fluid looked full on the stick when checked hot, in park, and idling.
No, I didn't change the fluid since it's been rebuilt. Didn't want to touch it as it was professionally done by a long time trans builder in the area.

The Converter was replaced when the trans was rebuilt. Stock Replacement style converter.
It seems to be heating up a bit more than normal in this cool weather. It's not really hot, but more than where it normally sits. Normally it sits around 110-120F, today in traffic on a 37F day, it was around 150F. Not hot by any means, just an observation. I haven't seen it that warm since July sitting in traffic on a hot day.

I wasn't sure if others had the same experience or "things to check" with the tune.

1FastBrick

iTrader: (17)

Have you spoken to the builder???

baSICK5.0

iTrader: (1)

I would say you are likely to need a trans rebuilt. Seems like the new power is finding the weakness. Did they take the torque management out? Which dumps timing between shifts and pulls thru them instead of nosing over. I was told that on my high mileage 60e this would likely shorten the life behind my LQ4. The truck is strong and i havent felt it slip yet but i did add a corvette servo and external cooler to try to protect it.

baSICK5.0

iTrader: (1)

BTW I noticed you said increase in line pressure.....Lots of people do this to firm up the shifts..but i had been told its a sure fire way to fry your tranny. My tuners didnt touch the pressure. Simply up'd the points, took out the torque management.

TrickyTransAm

Yes, he's going to look at it after the holiday weekend is over.

The trans has Raybestos Z-pack clutches, vette servo, dual cage input sprag, beast sunshell, and regular improvement goodies, all new electronics, and a new torque converter since the last trans was flooded with water. NO shift kit.
The truck already has a stock cooler, and normally stays around 110F on the E-way, but climbs to around 150 in town.

Honestly, I haven't really romped on it as the 5.3L that was in it was on its way out, and I wasn't ready to drop in this 6.0L. But when the oil pressure said bye bye, I had no choice. Based on the RWHP, I would estimate the power and torque to be around 380-400 at the flywheel, which is less than many bone stock setups. So that's why im questioning if I need to change something in the tune or...if it was just a bad trans build.

Guess we'll find out this week!

smokeshow

iTrader: (16)

Firmer feeling shifts come from reduced torque management, but holding a gear under power is reliant on the ability of the clutches to remain engaged. He won't need to worry much with the z-pak clutches, but pulling out torque management and expecting the stockers to handle the load during a shift without increased apply pressure is just asking to burn up the tranny.

1FastBrick

iTrader: (17)

My understanding In regards to durabilllity and longivity for the transmission as far as tunning goes, Is that you leave the line pressure stock and leave some of the torque managment in.

In regards to the transmission, when it starts slipping Its usually a mechanical issue. Assuming the electrical part of the transmission is functioning properly. It could be several things so with out a tear down Its hard to pinpoint the root cause.

If it was exibihting any kinds of sliping with the 5.3 they would only be exagerated when you put more power through it.

Keep us posted and let us know what happens.