Hi,

I'm really beginning to think about a swap from a t56 to an auto in my 02 Z28. My car is currently just a bolt-on car and I probably won't do too much to this car since it's my DD and I already have a racecar, but I still like to have fun and sometimes take it to the track.

Because my curiosity gets the best of me, what is the ET difference between similarly setup 4l60/4l80's? I just wonder because of the slight weight difference and possible parasitic losses?

Thanks,
Josh

 

Great question, i am wondering the same thing.

 

Many, many people report a lower ET going from 60e to 80e. Gearing in the 80e is just more desirable for 60 ft times and between shifts. Don't get to involved in the weight thing. You're looking at 30-35lbs more. According to Jake's Performance(vendor) power loss is very little. I don't remember the numbers. Maybe he'll chime in on this.

 

A customer posted dyno results from a T56 to 4L80E swap a few months ago. Very little loss.


GENERALLY,
A 4L60E should ET better in a lower power or heavier combo because of the additional gearing in low, assuming the converter gives decent shift extension.

A 4L80E should be more consistant to hook and ET better in big power cars.

 

Thanks guys, I appreciate it. My car currently is full weight and has gone 12.7 @ 113.5 with a 2.09 60ft. Just looking to have fun with a bolt on car that has gotten a best of 31 MPG on the highway The only downside to going auto lol

 

I thought I would pick up going to a turbo 350 over the 4l60e. Nope. Less weight less gear.

 

in a 500ish RWHP car, with about 3600 lb curb weight

assuming zero changes other than the transmission itself...
going from a t56 to a 4l60 with a 3600 ish stall... you can expect as much as 4 to 5 tenths decrease in time...
going from a 4l60 to a 4l80 with no changes you can expect to see an additional 1 to 2 tenths

this comes from a friend of mine who actually did the swap.

 

Great info, thanks

 

and to be clear... that was me saying 4l80 is faster than 4l60

 

I was also wondering if the 4L80E might give a better ET than a 4L60E because the 4L60E has such a huge difference between the gears - the 1-2 shift drops you from e.g. 6500 rpm to just 3500 which is too low for a hot cam.
I considered the tighter ratio 4L60E gears available from PATC which they claim will reduce the ET by 2 or 3 tenths. However, the gears alone are $1150, and you have to rebuild the trans AND you still end up with only a marginally-strong 4L60E.
While I believe their lower ET claim, I'll save the money for a 4L80E instead.
Just my thoughts; I look forward to more experienced opinions.

 

I dont see how that is possible. When we swapped out C6Z from a 6 speed it was making 965rwhp. After we swapped the 4L80 in it made 830rwhp and went 8.81 at 154 like that.

 

Converter locked on the dyno or?

 

Yes it was.

 

With a locked converter, if you lost 135 HP something was very wrong, with either the car, dyno, etc.

I would expect to see 20-40 HP, but not 135. You will always show loss through an unlocked converter, but typically the torque multiplication will more than make up for it on the track. However with a locked converter you don't have much more HP consumption happening, your running the pump, and a small amount of loss due to rotating weight but that is more dependent on the rate of acceleration.

 

I swapped from a T56 to a Jakes 80,, I can tell you right now, I lost close to 30 HP wiht the converter unlocked, (on the same dyno) Only regret I have, is I wish I would have done it a long time ago, I miss bangin gears, but when I stage the car and let off the tbrake it runs the same et to the hundreth, that says alot for consistency,, AND with the auto, the wife can drive it, and dont complain nearly as much about how much money the car eats..

 

It's looking like 20rwhp on 570rwhp. My 4l60E lost about 10 locked when converting from a t56. 20 rwhp seems bout right... I'm expecting the 4l80e will QT lower and trap higher with the better use of ratios and my 5200 flash stall, than a similar 4l60e. Time will tell.....

 

Wasn't there a correlation on loss of power with high HP and the 4l80? Meaning, until you get into the low 10's, power loss is insignificant between the two A4's. Jake's performance(IIRC) explained the theory a while back about having to accelerate the mass so quickly at that level is why the higher losses, which is with any transmission.The 4l60 has for the most part given up anyway at that level so, you need to run something different that'll hold up. This is where "Jake's Performance" comes in to explain.

 

So does anyone know what the hp loss is between the 4l60 vs 4l80?

 

It is not a static number.
HP loss due to rotating weight is MOSTLY dependent on the rate of acceleration. The faster the acceleration the more the power loss. So an 8 second car will suffer more losses out of any transmission than a 12 second car.

It also varies depending on who built the unit somewhat. We do several mods to reduce parasitic losses on the units we build.

 

On a Transmission dyno there is less than 2% Parasitic loss difference Between the 4L80E and the 4L60E using a Y combo converter with a 122 K factor and 1.60:1 Torque multiplication. That's basically a stock configuration Converter, I have seen this in person with my own eyeballs. The biggest issue with the 4L80E et drops is the Gear Ratio, which I cannot imagine somebody making this conversion without using the 2.75 1st and 1.57 2nd gear planet set. This gives you the gear ratio of a 2004R for 1-3, Nice and tight. Both Coan and PATC sell these planets and I have also used the 2.97 1st and 1.57 2nd in a lot of 3/4 trucks with nice results.