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How to swap engines

farmtruc 10:10 AM 12-05-2007

Why on earth would GM put such an anemic transmission in a heavy Ѕ ton truck, Avalanche, or Escalade?

These transmissions barely hold up to the punishment a stock LSX based engine generates. Now add a few modifications to it, trust me, it won’t last long.

It’s great the new generation GM trucks with LSX engine variants are probably the most reliable and powerful engines out, but it would be nice if these transmissions would last a little longer.

Fortunately, GM does produce a beefier transmission that can handle any type of modification you install onto your truck and all the punishment you can throw at it.

They are only available in the HD ѕ trucks with 6.0L and 8.1L engines.

In stock form, I’ve seen these transmissions handle over 600fwhp for several years.

Add a few performance parts to them, and you have a transmission that will handle more than the engine can with full performance modifications. GM’s tough transmission with an overdrive is the 4L80e.

In this article, a fully built 4L80e from Finish Line Transmissions will be installed in place of the 4L60e.

This 80e has been proven in 1000HP+ vehicles.

Some of the highlights this transmission includes are the following:
  • 300M billet input shaft
  • 300M billet main shaft
  • Seal & gasket kit
  • Hi-energy clutches
  • Super sprag direct drum(large 36 element sprag)
  • FLT 2nd gear clutch kit
  • 6 clutches in direct drum
  • Bushing kit
  • overrun roller clutch
  • Bonded pistons
  • Transgo HD-2 shift kit
  • FLT extreme duty calibrated valvebody
  • Low roller clutch
  • All solenoids
  • Manifold pressure switch
  • Internal wire harness
  • Filter
  • Spacer plate
  • New speed sensors
  • Torrington bearing rear case
Finish Line Transmissions | Performance Transmissions | Torque Converters | Transmission Parts | Transmission Service

This article is specifically written for the 2wd GM truck owner with a 4L60e transmission. However, the majority of these steps will apply to the 4wd and AWD trucks, or at least give you a good understanding on what is involved.

This article is for all you LSX based performance truck enthusiasts.

Are you tired of going through those weak 4L60e transmissions? Read more about it below!

- Before starting the teardown, disconnect the battery.

- It helps to have a lift to assist; however, all you do-it-yourselfers will find it just as easy on jack stands. Use caution when lifting your vehicle!

- Removing the transmission can be a mess. Since this transmission pan doesn’t have a drain plug, remove the pan to empty the trans of the fluid.

Here’s what the fluid contained. As you can see there is a lot of material in the pan. The trans obviously chewed some clutches up and from the way it sounds, broke some internal parts.

- After all the fluid is removed, reinstall the pan and move to the driveshaft. Using the correct wrench, remove the driveshaft bolts then gently pry the caps from the yoke with a large screwdriver.

- Next, disconnect every electrical component on the transmission. For this application, we disconnected the gear selector switch, vss connector and main trans harness and gear selector.

- Now it’s time to remove the crossmember and exhaust y-pipe. Using a transmission jack, carefully lift up the trans until all the pressure is off the crossmember. Then, remove the transmission mount bolt. Once done, remove the four crossmember bolts. Remember to have a buddy hold up the crossmember when the last bolt is removed so it doesn’t fall.

Carefully let the transmission jack down and let the engine oil pan rest on the front crossmember. It’s now time to remove the y-pipe.

- Remove the four oxygen sensors from the y-pipe. Simply disconnect them from the main harness or tie them up out of the way. Spray the exhaust bolts with lubricant to allow the nuts to spin off easily. If you break or strip one of these nuts, whip out the air hammer or grinder. Depending on how many miles and rust has collected on the studs and nuts will determine how easily they come off. After the nuts have soaked a few minutes, it’s time to remove the y-pipe. Having the crossmember out of the way makes is a lot easier. The 2 15mm nuts will also have to be removed in order to drop the y-pipe.

- Remove the 2 13mm bolts in order to drop the starter. After that, it’s time to remove the two splash guards held on by 10mm bolts. Now you can access torque converter bolts. GM calls the circular, removable plate on the bottom of the transmission bell housing a torque converter bolt access point. I have no idea why since it’s impossible to access the bolts through this hole.

Some converter bolts are hex head and others have a typical bolt. Try to be careful when removing these bolts or they will strip and then it will back to the grinder and dremel to grind the head off.

To access each bolt, use the converter access hole to turn the flex plate with a screwdriver.

- Now it’s time to remove the bell housing bolts. The easiest way to remove the top, center bolt in the housing is to allow the engine and trans hang like currently are. Grab a 4 feet extension and impact. Using a 15mm swivel socket, remove the bolt.

Now, using the transmission jack again, raise the transmission to an acceptable height and use the safety chain to secure the trans to the jack. Remove the remaining bolts. There will be smaller 13mm nuts securing the dipstick and other lines.

Now that all the bolts are remove and the converter bolts are out, let’s pull this thing!

- Before we remove the trans we have to disconnect the fluid lines. Using a small pick, simply remove the retaining clip. After that, the line will pull free. Keep a shop rag handy, it’ll make a mess.

Removing the transmission can be tricky. Lift the trans to the factory angle. Place a wedge between the oil pan and crossmember. This will allow the engine to remain in its factory angle and the bell housing will break away from the engine a little easier.

You may have to aggressively shack the trans back and forth in order to free the trans.

A small pry bar will also aid in breaking the dowel pins that align the trans and engine.

If your truck has about 50K miles on it like this one does, it may take some shaking and prying to free the trans, but it will break free, just be careful.

As your lowering the transmission, be sure all lines and wires are free. Pulling an electrical connector from its device or bending a line will cause issues.

- We chose a Yank torque converter from for this application. The larger makers of converters can usually adapt the front cover of the converter to meet your needs. In this case, we ordered a standard HD 80E 2800 stall converter.

This means, you must replace the factory 5.3L flex plate with a flex plate and spacer from any 2002+ ѕ HD GM truck that originally came with a 4L80e transmission.

The space allows the factory 80e flex plate to have the correct offset so that is lines up with the starter. Plus, the converter for this application has 6 converter bolts, so does the flex plate.

Since we have a spacer between the flex plate and engine, longer bolts will also have to be ordered.

Install the spacer on the back of the engine or tap it into the flex plate. Take notice that the spacer and flex plate have an alignment hole; be sure to align these holes. The rear of the crankshaft also has a matching hole, be sure to align all three when install the parts.

The flywheel is marked engine side.

Using red loctite, apply a small dab on each flex plate bolt.

Tighten the bolts in a star pattern to allow the plate and spacer to sit flush.

Once done, torque all bolts to 75lb/ft.

Here is how the finished product should look.

- It’s time to install your new HD 4L80E transmission. We chose the best performance transmission builder for our LS based Avalanche, Finish Line Transmission, check them out at FLT’s transmissions will hold up to any punishment you can throw at it. From stock 4.8/5.3L engines to high performance LSX engines.

- Now it’s time to install your new converter. This must be done correctly or you can damage the transmission and converter. Last thing you need now is to prolong the installation by destroying your expensive parts.

The easiest way to install a converter on the 80e transmission input shaft is to sit the transmission on the tail shaft. If you received your transmission from FLT, this is going to make a mess because FLT tests every transmission on their transmission dyno, which means the trans still has fluid in it. So, it’s best to sit the trans upright on a drain pan.

Before stabbing the converter on the trans shaft, pour about Ѕ quart of trans

fluid in it and let it soak in. This will ensure the converter isn’t dry during start up.

Next, carefully sit the converter over the input shaft. This step is very important; the converter must seat correctly into the shaft and pump. If you’ve installed a converter before, you know the feeling when the converter is seated correctly. If this is your first time, spin the converter and it will fall down one step, continue spinning it until it seats again. The converter must seat/fall twice.

Performance converters can be tricky to install. The snout that protrudes from the converter is cut straight and the factory snout is chamfered. On our converter, we had to grind/file the two flat spots on the side of the snout so that the snout would slide into the pump easier.

Notice it wasn’t recommended on how to lift your 80e upright, this is completely up to you, just be very careful. This transmission is very heavy and may fall or slip out from under you. Get a buddy to hold the trans while the converter is installed.

This is the amount of offset the converter will have when compared to the front of the bell housing. It’s about 1.5 inches.

- Before installing the trans, it's a good idea to clean the transmission lines, cooler and any external coolers with a can of transmission line cleaner. You can do this by spraying into one trans line and holding a bucket under the other. You can ensure they are clean enough when the fluid comes out clear. To finish the cleaning process, blow some air through the lines. This is very important if you're swapping transmissions due to breakage or clutch failure.

- Two dowel pins align the transmission and engine. These pins will sometimes get stuck in the engine. Be sure they are installed in the new transmission.

- Now that the converter is seated correctly, lift the transmission on the jack and secure with a safety chain. It’s now time to stab the transmission.

Before lifting the transmission into position, we’ve found it easier to set the dipstick tube up into the firewall. Let it hang into position while you lift the trans. Once the trans is lifted high enough, install the tube into the trans grommet. Speaking of dipstick tube, you will need a dipstick tube from a 2002+ HD truck. The dipstick will be reused.

Carefully lift the jack up while paying attention to all the wires and trans lines until the two dowel pins are align with the transmission holes.

Wiggle the trans forward and immediately get four transmission bolts started.

At this time, ensure the converter will spin freely. If it does not, the converter is not seated correctly. You must remove the transmission and try again to seat the converter in the shaft and pump.

Do not proceed if the converter does not spin. Tightening the bell housing bolts will crush the pump and possibly damage the converter.

If the converter is seated correctly, the converter will be about 1/16th inch from the flywheel.

If the converter does spin freely, snug the bolts down while making sure everything is lignin up correctly. Now you can tighten the bolts up.

Lower the trans jack just enough to access the top, center bolt. Install the bolt.

Reinstall the fuel line bracket and vent tube bracket that are held in place by the bell housing bolts.

- At this point, decide if you want to install the torque converter bolts. They can be done at a later time. Make sure a small amount of red loctite is used on the bolts.

We used after market converter bolts that were stronger than stock bolts; however, stock converter bolts can be used.

- The 4L80E has a lower, removable bell housing cover. This part can be purchased for the same truck as all the other parts.

Install this lower piece and the starter if you’ve already installed the converter bolts.

- Reinstall the y-pipe and all O2 sensors.

- In order for the transmission to shift correctly, a conversion harness must be purchased. This harness repins the 60e configuration to the 80e pin configuration. The harness simply plugs into the main harness and installs into the factory transmission connector.

- The 80e trans is longer than the 60e transmission so the stock crossmember has to be modified. There are numerous methods of doing this, but the easiest way so far seems to be like this:

While being as straight as possible, cut the ends off the crossmember. Be sure the center section that remains is wider than the transmission.

Install the two ends and the center section. They will look like this:

Obtain some metal stock that is 4” wide by ј” thick. This will be used to connect the center section with the ends.

Cut 10” lengths of the metal plate.

You can then tack the metal plate in position. While doing this, be sure everything is square and each side measures the same. Allow the plate to overhang a little bit to ensure a good weld is made.

(insert cm1 to 7)

Remove the newly fabricated crossmember and fully or partially weld it.

Gussets may be installed on the corners, however, after this piece is fully welded, you’ll notice how strong the crossmember is.

- Now install the modified crossmember and lower the transmission onto it. Don’t forget the center bolt that bolts to the transmission mount.

Here are some pics of the finished product:

- The factory transmission lines are not going to line up. The front line can be straightened out so that is pushes in to the front trans line connector.

The back line needs to be extended. There are several ways of doing this; this is how we did it:

- Now it’s time to reinstall the driveshaft. For this particular application, it was decided that the factory driveshaft would not be reused. The factory driveshafts for the Avalanche are made of extremely thin aluminum. Cutting and welding on the factory driveshaft wasn’t an option for us.

Luckily, the Avalanche has the same chassis as a Suburban. The Suburban was available in Ѕ ton and ѕ ton. All ѕ HD trucks had the option of having a 4L80E transmission. This means we we’re able to use a factory Suburban HD driveshaft.

We also got lucky because this particular driveshaft is a monster; it measures 5” in diameter.

Anyone who has destroyed a driveshaft at high speeds knows this isn’t fun at all. The larger diameter will help increase the critical speed of the shaft and allow it to turn higher RPM’s.

Here is a comparison of the stock driveshaft and HD driveshaft.

The HD driveshaft obviously had no issues fitting into the transmission’s tail housing. However, the Avalanche is a Ѕ ton truck and it gets a smaller 10bolt rear-end. The rear-end unfortunately has a smaller yoke. To remedy this issue, a larger 1350 yoke was purchased and installed.

Notice the rear-end seal also had to be changed. For some odd reason, GM decided to change the rear-end yoke. The factory yoke has a pressed on ring that requires a larger inside diameter seal. GM used this larger inside diameter seal on the old body style trucks. We simply changed out the factory seal with an old version. The new, larger 1350 yoke sealed nicely and the driver shaft was installed. The retaining nut that holds the yoke in place is not reusable. It’s designed to go on one time. It’s a inexpensive part, so replace it.

Be sure to use a small amount of loctite to ensure the bolts stay put.

- Finally, recheck all you work and install anything we forgot to mention in this article J

Before the truck is operational, you must have your PCM programmed with an 80e calibration.

Fill the transmission with about 8qts of Dexron III fluid. Start the engine and ensure each gear engages. This also allows the valvebody to open all its orifices and valves.

Recheck the fluid and let the transmission reach operation temp. Recheck the fluid one more time.

With the addition of the higher stall converter, a larger transmission cooler is required. We went with the largest B&M cooler we could find. Temperatures are under control during any type of driving. They average about 140degs on the highway with 70deg weather.

So why did we go overboard and choose a transmission that can handle 1200hp? Well, we’ll be pushing this Avalanche to the limits with its current setup. After that, we’ll abuse this transmission with a smaller stroker and 25psi! Trying to propel a 6,000lb vehicle requires a transmission that can handle the punishment.

Parts needed to complete the 4L60E to 4L80E transmission swap:

FLT fully built 4L80E – Finish Line Transmissions

4L80e torque converter – Yank Converters

Dealer OEM items:

80e flex plate – PN:12551367

Flex plate bolts – 12563533

Flex plate spacer – PN:12563532

Torque converter bolts – local parts store

Lower bell housing – PN:15765723

Lower bell housing bolts – PN:11516328

80e gear selector cable bracket – PN:

HD truck dipstick tube – PN:15832205

Transmission mount – reuse PN:22201140

2002 ѕ ton HD Suburban driveshaft – PN:15771996

1350 series rear end yoke – local gear shop

Category: Forex

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