Built 4l60e vs. built 4l80e

[srh3trinity]

Open to opinions on a built up 4l60e vs built up 4l80e. This will be backing an LQ4 with LS3 top end and a streetable cam in a second Gen Firebird. There isn't much cost difference between the two, I know there is a weight difference. The 4l60e's are more plentiful around here. Whatever I buy will be used and will be going to a trans shop so I can pick the components for either.

[Fras]

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[Fras]

Sorry, my reply didn't go through with the pic. I have a LQ lower with Ls3 top end in my 68 Camaro and went with the 4L80e. They are a stronger tranny than the 60 and wanted to error more on the side of "over building" it. Enjoy the motor.... It's badass

[srh3trinity]

What cam are you running? Any hp/tq numbers?

[Fras]

Cam was spec'd by Patrick G and is 222/230 .597/.609". Ls3 heads and intake and 96mm tb It's tuned to extremely streetable. Its right at about 550hp at the crank.

[Fras]

Actual is 551hp @ 451 tq

[srh3trinity]

Any other thoughts?

[Poorhousenext]

With the HP an TQ engine will make, 4L80 would be my choice. You will always be pushing the limit of 4L60 capability to handle the power, even the best built ones. Picking the right builder for 4L60 at that HP/TQ is more critical too. With the 4L80 you have a transmission that will allow you to keep increasing HP & TQ without having to upgrade from the 4L60 later or maybe even sooner with power you will have now.

Might want to look at gear ratios and shift extension RPM Retention and Loss between shift too. THe 4L80E has the better RPM Retention between gear shifts.

4l60
3.06
1.62 -- 52.94% (high) RPM Retention 47.06% RPM DROP
1.00 -- 61.73% (high) RPM Retention 38.27% RPM DROP

4l80
2.48
1.48 -- 59.68% (high) RPM Retention 40.32% RPM DROP
1.00 -- 67.57% (high) RPM Retention 32.43% RPM DROP

As you can see the 4l60 has the absolute worst ability to keep the engines RPM's high with each shift. That means the engine has to drop to a low RPM and lug itself up to speed again. When you factor in the loss of momentum between shifts due to the transmissions design, you see why it's essential that the transmission BANG into gear to minimize that loss. That however puts a strain on the trans/clutches each bang-shift.

Conversely, the 4l80 offers the best RPM carry over (or minimum RPM loss) and clutch hand off between gear shifts. However, it's first gear ratio to get the ball rolling offers the LEAST amount of torque multiplication.

Torque converter stall ratio and rear end gearing need to be taken in to consideration with both to get the most out of them.

Talk with Bowler Transmission here as well as shop that specializes in 4L80s, Jakes Performance.

[srh3trinity]

Thanks for that response. Very helpful. I have the luxury of time, so I will watch for a 4l80.