silver-mod-o

iTrader: (15)

I guess a big enough converter would make up for it... but you would have to be making SERIOUS power to warrant the swap IMO... it takes more Hp to turn the big bitch over... plus the first gear issue... Which is probably why the TH400 guys havent complained... if you are making enough power to need the swap, the extra loss wouldnt be noticeable IMO...

LS1rulz

iTrader: (1)

Not necessarily. I mean, yes, I'm heads/cam/spray, so it's worth it for me. But look at it from all viewpoints. It's also worth the power loss because it's so tough. Most of us would trade some power for more reliability over these junk 4L60e's, and most of us need overdrive. It's the only smart option.

Also, the 4L60e can be a turd beause of the wide spread between 1st and 2nd. I mean, the 1st gear on the 60 is TOO LOW for the times we need. Even a stock car with a decent stall will run better times with that taller first gear.
Here's the ratios, for those who want to chime in:

Gear--------1-------2--------3------OD
4L60e-----3.06----1.63-----1.00-----0.70
4L80e-----2.48----1.48-----1.00-----0.75

silver-mod-o

iTrader: (15)

my shift extension is about 5K RPMs with the stock 60E gearing and SS3600... so its no too bad...

DeltaT

iTrader: (5)

You may be right - I assumed it was an add-on unit but forgot that there is a tailpiece on other configs as well. Thanks for pointing that out.

Jim

Ragtop 99

iTrader: (7)

I have to raise the flag on this.

There's about a 20% difference in first gear from 2.48 to 3.06, so let's look at a 2.73 and 3.23 car. I have never seen a stock 2.73 car that is faster than stock 3.23 with any size stall from 2800 to 4400 when both cars have adequate tires and the only difference is the rear gear. You'll see .05 -.1 in the 60' with 3.23s depending upon the stall size.

The same is true when going from 3.23s to 3.73s. Just about everyone with a stall who is not traction limited gains about .1 in the quarter mile with .05 coming in the 60'. I've never seen anyone run slower, so long as they don't run out of room at the top of third.

If you're in the high HP leagues and running a restricted tire size, I could see where the longer 1st gear becomes an issue. Its the classic debate of going with a PG v. TH350/400.

LS1rulz

iTrader: (1)

I guess. I'm hearing it way different from the racers who I talk to.

Ragtop 99

iTrader: (7)

No need to guess. Just look at the stock internal top 50 list.
https://ls1tech.com/forums/drag-racing-results/628613-quickest-stock-internals-list-11-79-bump.html

On an eyeball basis, roughly 40 of the cars are A4s. Not a single one has 2.73 gears.

LS1rulz

iTrader: (1)

Remind me of where the 2.73 gears came in. I'm not talking about them. I'm talking about the same gear ratio as the TH400.

SVT THIS

iTrader: (27)

How about a parts list for a 4L80e swap into a 4L60e equipped LS1 car...
-built 4L80e trans
-Driveshaft? Which one? 300m from FLT? Somewhere else?
-converter-which would you reccommend? N20 is probably in the future..
-Cross member? Torque arm? Wiring harness? Shift linkage? Anything>\?

Ragtop 99

iTrader: (7)

I used 2.73s as an example because it creates a longer first gear. A 2.73 car with a 3.06 first gear has the same effective gearing as using a 4l80 with 3.23s. So if a longer first gear made a stock internal car faster, you'd see them on the stock internal list.

The point is that 60' time is a direct function of 1st gear if we hold all other things (e.g. stall size and motor mods) constant. If using a lower 1st gear ratio (i.e. 2.48 vs 3.06) improved 60' time, we would see that a 2.73 car would have a lower 60' time than a car with 3.23s or higher gear. The fact is that in a properly set-up car, the lower 2.48 gear is of no benefit until you hit very high HP levels, levels far beyond heads/cam/mild spray.

I do understand the value of close shift ratios. The exception I would make to the above is if you are willing to shift into 4th and use a much higher gear ratios. You could take advantage of the shorter shift drops by running 4.56 gears to make up for the long first gear, but that would suck in a street car that sees much highway use.

BTW, you can get a higher first gear as an option on a TH400 from some builders.

LS1rulz

iTrader: (1)

Yeah, I know.

My interest in this comes in that I'm trying to decide between 3.42 and 3.73 for my upcoming 4L80e swap. I know the 3.73 may be a little better at the track, but is 0.1sec worth the loss in gas mileage? I'm stuck on that dilemma.

T/A KID

iTrader: (12)

I am doing 3.42's with my 4l80E, Hell I even thought about a 3.23 since I am reving the car to only 6200 (speeding the Blower up)

MIGHTYMOUSE

iTrader: (59)

i have 3.42's they are a nice compromise, but even with 3.73 you could get into 135mph trap speed territory without being terribly tough on rpm's

i run about 2500rpms locked up at 75mph in OD

T/A KID

iTrader: (12)

MIGHTYMOUSE
what is your Cruise Speed at 60mph??? 2,000?