They may have tuned the trans to be garbage too.

 

Is it possible the shorty headers are causing some reversion at lower RPM that goes away at 3K

 

9* of overlap: This is my thinking. I didn't think I had gone TOO radical to not be streetable, hence why I'm confused as to why it just falls on its face...

Transmission slippage is definitely mechanical/hyd in nature. Story time:

Back when the car was stock, it would slip out of OD when cruise control was enabled after 15-20minutes. After figuring out how to duplicate the symptoms, I rebuilt the transmission. Since I is smart, I figured it wouldn't be complicated. Transmission ran fine for about 2000 miles, then the same symptom started again.

I immediately took the transmission to a shop they rebuilt it. Saying some seals weren't replaced that should have. I had replaced all seals that came with the kit, but w/e. Since I was broke and in college, and took them the just the case, it came with no warranty. 2k miles later, started slipping again, same symptoms.

I did an intake swap and had the car speed density tuned, removed the MAF and the slipping stopped. After doing some research I ran across some information that said at times the transmission will interpret the signal from the MAF. I do not know how true this is. Since the MAF was removed, the transmission had stopped slipping.

Fast forward to now, the car had been sitting for 3 years. The engine was rebuilt, the transmission was left in a bag with all fluid that it would hold still in the pan. After install, the fluid level was checked while running, after the engine had reached closed loop, and all seems normal from the outside. Some sources online state that the 4l60e is only rated for about 350/350 stock.

After doing more research on transmissions, I'm torn between, having the transmission rebuilt 1 more time, buying a beefed up 4l60e, getting a junkyard 4l80e and have it rebuilt, or buy a beefed up 4l80e.

But we've deviated waaaay away from a dead spot in the power. I'll try to get the tune file.

 

Get RPM or FLT to rebuild it. I wouldn't trust anybody else to touch a 4L60. If you want someone else to touch it, the 4L80 is a better option. But, the 4L80 is not geared for a low power car. You don't have an 800rwhp turbo build where you want less first gear. With a 400rwhp LS1... you want the advantage the 4L60 gives you in gearing.

 

I figured the shortys might be counter productive.

 

https://ls1tech.com/forums/generatio...l#post19204452

Over in the internal section, this thread got partially gobbled up in a shorty vs long tube discussion. I linked straight to Martin's post about the differences. This was the main reason I brought it up. Shorties will scavenge fine at higher RPM, but down low, might be acting no different than stock manifolds