Making a drastic gear change on an L27 will kill you at the track. If you're already 3.06, I'd suggest you leave it. The L27 needs far more help at the top end than it does off the line. They have short legs.

L27s run out of breath about 4k on up to the 5500 rpm limit. I have been working on a highly ported and polished lower intake from an L27 for a while now (I am almost done with it, but haven't done much with it since I am juggling other projects). I can tell you that there is room for improvement with the lower intake manifolds. Same with the heads.

I've been told that the L27 in my SSE is a factory freak. It *seems* to put out more than any other L27 that has been driven. Why this is so, nobody seems to know. But I can tell you that every system on that engine (electrical, fuel, ignition, exhaust) is 100%. They make good power when they are nice and happy.

I got a list printed of all my RPO codes... I have a 35/35 and a 2.84 FDR. So to get the FDR of 3.06 that WillWren reccommends I need a Sun gear and differential gear. My dealer parts guy couldnt find a gear actually named Sun gear. Nor could he find anything else I needed. razz. Are there other names for these gears? Which cars carried the compatable 3.06 FDR "diff" and "sun"? If it helps my actual trans code tag says 4YMW.

Unless you want to pay $1k for a diff and sun gear, go to a junkyard and pick up used parts and inspect them.
The junk yards around me always have 4t60-e'* still in cars from people just grabbing the motor.
You just have to:
pop the axle tulip out if it'* still in the trans
Unbolt the diff cover
You'll see the diff is held in by a C-clip that'* on the end of a shaft that goes through the diff. Pop that off with 2 flat heads and the diff will come right out.
The sun gear is on that shaft and goes into the diff. You'll see what I mean.
Just look for the proper RPO before you start pulling it.

And get the same year tranny too. There are differences in the pitch and direction of the planetary pinion gears in the 60 diffs.

To clarify a little bit.
The diff is a carrier with 8 gears.
4 planetary pinion gears are arranged in the 12, 3, 6, and 9 positions on the one end and they have a spiral shape.
The sun gear goes between these 4 spiral gears and is shaped the same.
Those 5 gears differ between different FDR diffs..
There are also 4 gears in the center of the diff, side gears and spider gears. 2 parallel sets that are perpendicular to each other and turn each other. This set of gears allows the wheels to turn at different speeds. 1 of the 2 sets is held in place by the infamous Diff Pin that has a tendency to loose lubrication and either elongate the pin and snap it or blow up the spider gear.
Then there is the vehicle speed sensor rotor that is on the outside of the diff opposite to the spider gears that tells the VSS how fast the diff is spinning.
(p.*. I incorrectly called the planetary pinion gears spider gears in an earlier post)
Heres a pic:
Diff:

Sungear:

Thats an immense help 95naSTA! Thanks a million. Would like to know what 94s would likely have the right Arrangement and exactly what the 94 4T60E code I am looking for is. thanks, Kris

Well, It will say FW2 on the spare tire cover on the trunk..
I think that the manual I have at home will list what the code on the trans should be. I'll look it up when I get home.

Ok Iooked it up..
For a 94 3.06 FDR 60e heres the list with the teeth on the VSS in parentheses.
(Your VSS rotor has 30 teeth)
4YZW (30)
4WAW (31)
4PFW (31)
4KUW (31)
4BLW (31)
4PBW (30)
93 3.06 FDR 60es are:
3YRW (30)
3CWW (30)
3WAW (31)
3CXW (31)
3CTW (31)
3BYW (31)
You can find these in H/C/W/U body cars.

Those should all work, you'll just have to have Ryan account for the different FDR and VSS tooth count.

Thanks, really. That was fully informative. I ll call the wreckers when the weather and my wallet are more cooperative. To ask of the last straw, I need the gears of any of the transmissions that have a tag that matches any of the codes on your list that end in (30)? That and only those 93s that are otherwise compatable?

I wouldn't ask for "the gears" because they will think you mean the drive and driven gears inside the trans.. They are on the driver'* side of the trans and connect the crank/flexplate/torque converter centerline with the rest of the trans that is down behind your engine. They are much harder to get to..
You're looking for the differential and sun gear from any of the above listed with the (30).
Ask Ryan (gmtuners/sinister performance) if he would be able to compensate for a VSS with a different number of teeth in addition to the FDR change. I'm sure he can but just ask, and if he says yes, then you can use all of the above codes.
92-94 should work according to my manual, but I figured I would post 93-94 to be on the safe side..

That pretty much covers it for me. Its unbelievable the help you guys provide. I ll be hoping To show you what came of it at WCBF 08. wink smile