1995 Impala SS LS Swap 6.0 with 6L80e Transmission

. The LS 6.0 with 6l80E showed up

Most of the fitment challenges with a 6L80/90 are at the back just before the tail shaft housing. With a ~1" body lift it took another 1" of floor deformation to make it (barely) clear. The fortunate thing is that it's right in front of the front seat and there's plenty of "compliance" in the carpet. The other place that requires some massaging is for the u-joint out of the back. This one is more difficult since it's actually under the seat and there is a reinforcement brace there which doesn't move very easily.

Were I to do it again, I'd cut the floor down the center, from the floor brace ahead ~8", split it open and weld in a filler strip. The carpet will still fit no problem and you'd never otherwise know, however the center console...????...I've a wagon. Seems like a solvable thing though given all the other things that need to be done to fit a 6L80/90?

This is the back end of a 6L90E vs 4L60E side by side. The 6L doesn't "taper" near as much as the 4L does as it goes toward the back. Lots of room up front by the bellhousing, not so much at the tail housing.


Another challenge is how low the transmission oil pan hangs - it's about 1.5" below the front crossmember. It's a tough pan, but I'm still not a fan of anything hanging below the front crossmember. I've heard rumors of a Cadillac low profile pan and filter, but was never able to find one or even verify their existence. The most you can gain is ~3/4" before you start running into solenoids. My front cross member is 1.5" lower than stock so I'm good on clearance and have decent driveline angles and the pan is parallel with the frame. You'd need to move the engine and transmission up 1.5" to keep the pan above the bottom of the front crossmember and the frame along with decent driveline angles. I built a trans crossmember, and ended up using OEM holes in the frame to mount it.

The rest is relatively straight forward (relative to an engine/trans swap) - Cable shifter, cooler lines, dipstick tube, wiring harness, etc.

The wiring itself - Park/Neutral/Reverse logic, tow/haul switch, tap up/down shifting, etc is all handled via the body control module on the donor vehicle - no direct inputs/outputs from the transmission. The transmission wants to see a stoplight switch input (+12v when brakes applied) Not sure how the sedan with a console handles transmission position. Non console cars have the transmission position sensor switch at the base of the steering column which handles a lot of different things (door lock/unlock, brake to shift interlock, trunk release (sedans) or rear glass release (wagons). All of these circuits will need to be integrated (or eliminated) and/or go with a standalone system for the transmission. 6L80E/6L90E Standalone Controller

It's going to have to get both wider and taller, but mostly taller. On mine, the u-joint on the back of the transmission came from a G4500 van so is massive in size compared to 'stock' B body stuff. There might be (likely is?) smaller u-joints from other vehicles like camaro's and similar that will help a lot on clearance there. One should definitely pursue that option for several reasons (having a driveshaft built is one one of them)

I'm using stock LT1 motor mounts, but adapted to a different engine along with significant crossmember modifications so the factory crank centerline is long gone on my car. However, it's not far enough out where body clearance behind the front seats should be affected. Make sure to double check your pinion angles when setting up the transmission crossmember.

There's a 6L90 and a 4L60 in the shop - I'll try to get some better pictures next time I'm there.

Regarding a skid plate...the front of the pan is around where the front body mounts are just behind the front tires. You might be able to put some something like a piece of 3x3x3/8 angle iron to protect the leading edge of the trans oil pan, but it would have to be removable.

Needless to say, this is not a bolt in affair, but it can be done.

I finally remembered to take some pictures of the 6L90E vs 4L60E and I threw in a 4L80E in just for fun

First the 4L60E vs 6L90E - Sorry the 4L60E is for a 4x4, couldn't find a 2wd one handy, but this will get the idea across well enough...




This shot really shows the height difference between the two. It doesn't look like it's much bigger in the above pictures, but once you try to actually put it in the tunnel, things get "cozy" pretty quickly.


The left side of the 6L90E has quite a "bulge" that requires additional width compared to the 4L60E


There happened to be a 2wd 4L80E there too so I slid it over for a comparison shot...It's on the floor vs the other two on the cart, but the bellhousings are lined up true to each other. As you can see a 4L80E will drop in more/less no modifications.

Out with the LT1

KDS mount painted
Converted to truck style accessories drive due to ac clearance issues to the frame, I want to run the AC down low
Test fitting ac compressor
Test fitting oil pan-F body pan—ended up using the TSP Pan 81073

Had to cut the truck alternator bracket to clear the L77 intake. Relocated the idler pulley, using a 2010-2015 Camaro SS water pump for shorter coolant hose routing.

Motor dropped in like it was meant to be there.
Shaved the Transmission a few spots, it’s snug in the tunnel. I did not modify the tunnel except I flattened the body seam lip at the top of the tunnel. If I had removed the intake, it would have been easier to maneuver the drivetrain.
modified the stock crossmember, ended up dropping the transmission mount area by 1/8” for a bit more clearance.
Motor is pushed all the back on the KDS adapters for best clearance for the long tubes.
Engine looks good in the bay, decided to pull engine out to paint the bay.

Pulled the engine out to paint the bay. Notched the frame for AC clearance. AC compressor is for a 2012 GMC Sierra, it would have cleared without notching the frame except I was test fitting the with F body pan, with the F body pan, I was unable to have the motor sit all the way due to F body Pan hitting the crossmember. This was when I decided to get the TSP 81073 pan or Holley 302-2 would have worked also. The TSP Pan have way better clearance and it was way easier to drop the motor in with the TSP pan. I still notched the frame for additional clearance in case I ever change the accessory to the corvette style.
Pull the front clip to paint everything, ziplock bags to label everything! Wire wheels and rustoleum rust reformer for the win, then coated everything with semigloss black paint. Installed new upper control arms too since the old ones was worn out! Way easier with everything out of the way. Fresh Nicop brake lines was installed too.

Engine & transmission installed, long tubes installed had to modify the frame braces for clearance, started to install the front clip parts . Fresh knurled upper control arm bolts for a second Camaro is a good replacement for the B body, fresh bilsteins as the old shocks was non-existent.

On to the wiring fun yes it rat nested but I labeled everything!, drive by wire is fun. I started with one item at time, first I connected the left bank injector wire on the LS doner harness to the LT1 left bank injector wire(pink) on the fuse box. I highly recommend LT1 swap.com for wiring info and pin outs. Then I moved on the other parts of LT1 fuse box, matching everything from the LT1 fuse box to the LS harness as much as possible. On the LT1 harness some sensors shares the same power and grounds, I reused those junction splices as much as possible. Easier said than done, this is tedious and if you can afford it, there’s plenty of reputable harness builders for LS harness for the B bodies.
Drilled and taped the oil block off for oil pressure gauge, reused the LT1 sensor and connector. I did not touch the LS oil pressure sensor and left it hooked up. Bought a C6 corvette gas pedal, match the harness to the pin on the gas pedal.

C6 pedal installed.
On to gas pedal fun, bought the bracket from Tejas steelworks, this bolts up to the firewall, no drilling required. Due to the pedal design, I welded an additional tab to the bracket to move it a bit closer to the brake pedal (not pictureex). 3 self tapping screws and the pedal is installed, I reused the same Hole for old throttle cable on the firewall to run the wires for gas pedal.