I have a guy I built a trans for explaining something to me and I wanted to get some opinions here first. 320 hp bolt on LS1 camaro, about 3600lbs. He explains that on a shift (specifically the 2-3 shift because he usually is just rolling then stabs the throttle, doesn't really take off from a dead stop) the car will make what feels like a solid shift but the rpm's will hang out at about 4400-4600 rpm for about a second or a second and a half before they actually start to climb and the motor change pitch. It just sounds "flat" for about a second and a half before the motor changes tone and starts to climb rpm again.

This has an 8 clutch B/W High Energy setup, .030 clearance, and line pressure is about 220.

He says it sounds to him like clutches "slipping then grabbing" but...in a fresh trans with perfect pressure and good clutch setup...I really am not buying it. It's the same setup I've used in much higher HP builds without issue.

He says it's a 3200 stall converter, i believe from PATC (if it matters) that he installed at the same time as the trans.

sounds to me like just converter shift extension. Other opinions?

 

Yes, converter extension is real!!!! And a good thing! The way you tell the difference is mph. If mph during the dead spot suffers, its the clutches, if mph pulls strong, its converter extension. Try this thread to help better illustrate.

https://ls1tech.com/forums/multimedi...uge-shots.html

On the 45-90 video, watch how the rpms pause (at like 4800) immediately after the 2/3 shift, but mph stays steady, then rpms start climbing again in unison.

 

That can be eliminated by modifying the valve body, blocking a hole in the separator plate and making 3rd feed big and band release bigger than normal.
You will feel the 2-3 shift regardless of converter.

I'm not getting into all the modification specifics.

 

Valvebody modifications wont stop converter extension. Sorry sir you are mistaken.

 

Like I said, the shift will be felt. Didn't say it'll stop converter extension.

 

mmmk. Its too early in the day to be drinking buddy.

 

He sent me a video!! Now I can actually see what he was talking about. It does sound flat. And the mph does seem to climb but not anywhere near at the same rate as I would expect with normal shift extension. Unless it's just the most inefficient torque converter ever? IDK

Now, at the end of the video, I can hear/see in the mph when it seems like it "grabs"

This is clearly not a 2-3 flare as it drops the rpm's down right away. But it almost seems like 4th instead of 3rd based on how it doesn't really want to pull. I'm starting to wonder if the band isn't releasing fast enough. So when it brings on the 3/4 clutches, the band is still applied (giving 4th) until the band finally releases and gets back into 3rd.

Thoughts?? Opinions? I've built probably 50-100 of these and this is a first for me.

 

Almost looks like it's going right into lock up at the gear change then unlocks

 

I'm running a different transmission, but look at this and see if you are experiencing the same. If so, you probably have nothing to worry about. On the 1-2 shift, the tach is a bit static.... but it's still pulling.

 

Lemme check the vid tomorrow.on the laptop to give a full opinion. But patc, is junk. They are local to me. Bad bad place. Nothing would surprise me coming out of that place.

 

This gets my vote. Ask him what his shift extensions are or have him make another video of the 1-2 shift. 4000 rpm shift extensions seem pretty low. If he is getting around 45-5000 rpm shift extensions on the 1-2 I would say you are on the right track. Those 4000 rpm shift extensions is what I would expect from a 2-4 shift. Not a 1-2 or 2-3.

 

This would actually seem to make the most sense. I'll get with him at lunch today and go for a rip. I have HP Tuners on my laptop so I'll watch whats happening and see if I can figure anything out.

I'm really thinking its not the band. The more I got to thinking about it, the more I realized the last 10 builds identical to this almost have had all my same specs in it. From clutch clearance, band clearance, feed hole sizes (based on converter diameter, rpm, etc etc), endplay, boost valve, yadda yadda yadda. The list is about the same. And they've all worked fantastic. And putting a gauge on this one lead to about 220 psi at WOT.

I'll look into the converter locking deal first with him at lunch and report back to everyone.

 

There is most definitely a pause in acceleration around 88-90mph while the rpms pause. Before AND after that acceleration is faster. Before condemning the trans/converter, could it be something simple like a slight bog related to AFR or reduced timing?

 

If it is locking right at the shift and he's got torque management still on the the quick engagement of the clutch and loss of that many rpm's at the same time will trigger massive kr and tm timing pull at the same time. The higher the timing pulled the longer it holds the timing out before adding back in. Which explains the slow acceleration and engine tone during the problem.

 

Any explanation as to why it might be trying to lock the converter right on the shift? I'll look at the tune too if there's anything I can change to make it not lock up on the shift.

It shouldn't try to lock the converter at all on the shift right?

 

is start with a log run first to see what you can find. Look for tcc apply, any timing being pulled at shift whether it's kr or tm and the actual rpm movement. But that little 2-300 rpm increase after the flat spot in rpm looks just like the converter unlocking.

 

Ok, went for a ride. Converter definitely locking right on the 2-3 shift. No idea why.

I opened the controls in hptuners and commanded the torque converter off and the trans made 3 back to back, abusive 2-3 shifts at WOT. Crisp as a pringle chip. Motor pulled great. I didn't save any logs (sorry) but it was definitely locking the converter...or at least trying to...
there was still 4-5 % slip with the converter "locked" on the 2-3 shift.
around 11-14% in 3rd gear when I forced the converter unlocked.
oh, and at the top of 2nd at about 6100 rpm, the converter slip is only about 3-4%

If I post up the tune, would anyone be willing to look at it and tell me if they can see any reason the converter would lock up on a 2-3 shift on it's own?

 

Here's the tune file I pulled from it.
I'm far from an expert, but there's nothing that's screaming at me as the problem. Maybe someone else can look it over and tell me I'm missing something.

Also, put a gauge on it, and it is in fact making about 220 psi line pressure on the 2-3 shift.

Any help would be very greatly appreciated.

 

Lockup tables look stock (so it should be fine). I see it still has TM. Id personally remove that crap and tune shift feel off the shift pressure tables, which look like junk, stock i assume. I like to have full clamp by 300ft/pounds. I have no experience with TM, so i wont comment but i can promise WOT lockup with burn the converter up quick.

 

Check this video out, i think his converter was locking during shifts. Bad bad deal. At 2:45.