From a standing start all thru 1st, and second, which shifts into 3rd at 92+mph it is a constant steady pull. When I make shift into 3rd it pulls, flattens and then starts to pull hard again.
Is this the TC locking up or ? It happens at about 4400rps +/- and only after 3rd.

 

I think thats the ratio in the trans.

My 5.3 w/ 4l60 did the same thing. It sucked. From 90-110 was dead!

 

Sounds like it's the convertor locking to me.Are you running the stock Radix tune or do you have tuning software?

 

Tuning by Rick@SynergyMotorsports. Feels like the converter locking. I can have him tune it to not lock, right?

 

Yes you can,but you probably just want to delay it,because you actually can put more power to the ground with the convertor locked.If you delay your lockup until your motor hits the sweet spot in the powerband your trapspeed will be higher.What gearing are you running and what rpm are your shift points?

 

4x4
Gearing is 3.73
Shifting at 6600 rpm
Peak hp = 6300
peak tq=3700
TC=2800

 

You are hitting a flat spot with the big drop off in gearing going into 3rd gear,the convertor is extending your rpms from 4000 to 4300 rpm,you need a bigger convertor with more shift extension.4L60E transmissions have a huge gear spacing from 2nd to 3rd.A set of 4.10s would help too.What kind of 1/4 mile trapspeed are you seeing?

 

It is the hydrualic lock-up in the converter. I had the same question when Dave at Rock On was tuning my transmission. Thats what he told me.

Have you checked you speeds when it happens? What caught my attention was that the rpms went flat but the mph continued to increase. Someone else posted about this a few weeks back also.

 

Feels like converter,
It shifts, pulls hard (now in third) goes flat, and then pulls hard again.

 

Man, my car is unloading in thrid...
Its your fuel map, you have a nasty hole...

I would fix that before you blow your intake mainfold bolts!!!!!