Heres a link to another thread I made, but heres the short of it.
https://ls1tech.com/forums/drag-raci...unch-60ft.html

Basically I have a stock cube LS1 with good rod bolts, fresh bearings and rings. Less then 1k on it. Fast 92mm intake, PRC stage 2.5 heads with valves recessed for MS3. Yank 4400 convertor, 4l65e and a 9" with 3.70s. So built the motor 6 months ago and had an MS3 in it. Had a vig 3200 which was way to small. Had it restalled to a 4k and still was way to tight and not right at all. Stepped up to Yank PT4400.

Car still seemed like a dog down low, no power under 3k. Go to track and cant 60ft at all. 2.0s all night long. 12.40s at 114 all night.
So.....
Have Pat G spec me out a cam. 230/234 .600 .602 111+3 Swap out cams, retune and now the car feels great. Lots better down low.

Take it back out to the track tonite. Same times, almost identical. But the kicker, I lost mph. Only trapping like 110 now. We cannot figure out what the problem is. Car seems to be hooking just fine. Its not blowing the tires off. Running bigs and littles, 26x10.50 Et streets. Car has stock springs up front with strange coil overs. Stock springs and shocks out back with about 1 1/2 coils cut in the rear.



Fast forward to this last weekend.

Pulled valve body off trans. Found the pulse width modulation valve that came in trans go shift kit was trashed. So we had a theory that we were getting pressure bleed off and that it was trying to apply lockup clutch when I go wot. Got a stock valve and new spacer plate. Bought a cheap B&M shift kit and installed it with stock valve body. Car shifts way firmer now and has no more 2-3 flare issue. But still wont launch.

Scanner says that lauching it off 1000 rpm, it will only flash the convertor to about 2400. Brake stalling it, it will only stall to about 2800 and then it just pushing through the brakes. Stalling it as high as I can on the brakes, it will only flash to about 3200 when I mat it. Its a PT 4400.

Convertor acts great though other wise. From a roll the car is stupid. I had the ET street rolling smoke from a 10 mph roll. Car shifts at 6800 and only drops to 5500 so shift extensions are fine too.

This really seems to be a convertor or trans issue to me. Input would be greatly appreciated.

 

Vids of car at the track.....
First run is just off idle to the floor. Second is loading the covertor till Im about to push through the brakes. Notice how it sound like somethings lugging the motor really hard when I launch?

http://www.youtube.com/watch?v=lYee5y0S_tQ
http://www.youtube.com/watch?v=27LANuccJSY

 

Anyone?

 

all i can say is that im having the same exact problem so im also waiting for someone to chime in!

 

Did you have it on the dyno to check tuning?

Also

Did I hear some bouncing off the rev-limiter in that second vid?

 

This is interesting to me because I have a problem thats maybe similar.In my case my car has slowed up a few tenths.When I compare my old timeslips I see my 60 ft times are off some but it shows up more at 330 ft out to 1/8 mile.Car has lost a couple mph and its off by the 1/8 mile-car pulls just as hard thru to the 1/4 stripe.I thought I must have a converter or transmission problem but it doesn't seem that is the case.I am as frustrated as you must be trying to figure out where the problem is.Good luck and be sure to post if you find your problem.

 

Sounds like you are having 2 issues. The first seems to be the converter and the second is the transmissiom. I was having the same transmission problems as you so I went with a TH350 and a 8" converter to solve the shifting issues. I would pull the converter and either get a custom one built built for your setup or have the one you have now rebuilt.
Good luck man. BTW that converter isn't stalling to 4000rpm. I did have the same issue when I went from being a bolton car to a H/C/I car. You move the peak torque up in your curve so the converter doesn't stall as high.

 

well i dont think you have converter or trans issues. On the first video right when you mash it it sounds like it has a hell of a hesitation. Maybe a fuel bog or something. Also maybe a tune issue as well as your hitting the rev limiter in both videos pretty hard. I would look at that first before you dump a bunch of money in the trans. Can hear a deffinate engine hesitation in the first vid. Anybody else hear that??

 

What about the engine bouncing off the rev limiter on the 2-3 shifts? I didn't notice much of a engine hesitation off the line as much as it seemed as though his converter wasn't stalling as high as it should. When I was a bolton car my converter was built to a 3600rpm stall. Then I went to H/C/I and my converter was only stalling up to about 2400rpm and bogging the engine on the launch. I had to pull the converter back out and have it recut for the engine modifications because now my peak torque was higher up in the rpm range than it was when I was a bolton car.

 

I do think the converter is too tight but in the first video when the car leaves from an idle there is a deffinate studder when the throttle is mashed. Not so much a bog its a studder.

 

I watched it again and still didn't notice a studder in the engine. I did notice he didn't clean the engine out after he did his burn out. That has always made a difference in my car. Try pulling the converter and sending out to be recut or if you like I have a PTC4000 stall that I was cutting 1.46 60ft. with with my stock bottom end full weight H/C/I 346ci LS1. I could make you a good deal on it. PM me know if you are interested.

 

How does it act on the street? Does it bog?

I had a simular problem when I hade the 4l60e. After I did a burnout in "D" it would launch in 2nd gear. Are you sure this isn't happening? Try after the burnout putting it in park. Give it a sec and then put it back in "D" and stage. Hopefully this will solve your problem.

 

car doesnt sound right ... check the tune ? sounds lazy... full weight?

 

It does sound like the tune is off. Maybe a little hesitation off the starting line. I'd double check the timing tables and make sure you have plenty of timing down low. Also make sure it's not pulling timing for some reason...

 

Im glad someone else hears that hesitation from the engine off the line. even if that converter is alittle tight it should still 60ft better than it does. Get that hesitation straight and there will be a big improvement. still need the converter fixed though

 

If you talked to me real sweet, I might let you install my tranny for a pass or two. Of course pending you help me put it back in my car when I get back!

 

Im surprised no converter companys have chimed in....would like to hear what they have to say.

 

With this note it sounds like the converter is not the issue:
Convertor acts great though other wise. From a roll the car is stupid. I had the ET street rolling smoke from a 10 mph roll. Car shifts at 6800 and only drops to 5500 so shift extensions are fine too


But I have seen many times the the transmission front pump halfs and not flat and allowing oil to bypass from the line pressure port to the lock-up clutch passage.
This will bring the clutch on under torque at the point the STR is in effect.
What is happening is torque will twist the stator support and deform the pump even more as the pump bends the oil applies the clutch and stops the converter from flashing and working as designed.
You can remove the lock up control on the valve body and run the car that way you will not have lock up but the converter will be fine to use till the repair is done on the transmission.

 

What you are saying is the same thing my trans guy was guessing could be problem! He was thinking there could be pressure bleed off somewhere in the trans and it would be forcing on the lockup clutch when I go wot and the line pressure spikes. But it would never show in the scan cause it would be doing it without the command of the computer.

Thats why we pulled the valve body to see if there was a problem in it. But he was also saying there could be an issue in the pump and the orings that are on the input shaft too. Sounds like I need to pull the trans and pull that pump out.

My 2-3 shift problem is gone now after we put different valve body and shift kit in. It shifts perfect now.

 

Hey man, I just wanted to let you know that I went to the track 2 days ago and was having a similar issue to you. I just installed a new TH350 tranny and 8" PTC converter in my car. I finally had a chance to take it to the track and see what she could do. Well, I lost 2 tenths on my 60ft from my previous transmission setup. Seemed as though my car was bogging off of the line. Well yesterday I called PTC and questioned them on the new converter and he told me that they wanted to build it tight but could have made it to tight. He instructed me to go in first gear at 1500rpm and stomp it to see where the converter is flashing to. To my surprise the converter was only flashing to about 3000-3200 rpm. So this explains my lost in 60ft at the track. I am going to pull the converter back out and send it back to them to be recut to the stall that more fits my setup. Hope this helps you figure out your issue.