The 5.3 LS to 4L80E Flexplate Fiasco (And the $85 Part You Can't Forget)

If you’ve ever done an LS swap or mated a 5.3L (LM7) to a 4L80E transmission, you know that "bolt-on" rarely means just bolting it on. Last week in the shop, we hit a roadblock when we realized our original flexplate wasn't going to cut it. Fast forward to last night’s build session: We unboxed the new flexplate, and before we even got the old flexplate off, we ran headfirst into another classic LS swap puzzle.

Here is what went down in the bay, what went wrong, and the exact parts you need so you don't get stuck midway through your build.

Step 1: Shiny New Parts & High Hopes

There’s nothing better than opening up fresh parts for a project. We grabbed a brand-new flexplate designed specifically for the 5.3 LS (LM7) to 4L80E drivetrain.

• The Flexplate We Used: If you're running a similar setup, you can grab the flexplate by clicking this link here - > Replacement 5.3 LS Flexplate on Amazon.  (Full disclosure: We use affiliate links for the parts we use in the shop. If you grab your flexplate through our links, Amazon throws a few cents our way to support the channel. Thanks for backing The ROY Garage!)
  

Step 2: The "Spot the Difference" Game

Above and below is the old flexplate that we haven't removed yet. Take a close look at it. Then scroll down and take a look at the new one we got from Amazon.

Below is the new flexplate. Can you tell what's different?? We tried making it easy to see lol. If you can't tell what's different, that is okay; we explain it further down :) 

When you look at the spacing between the stock flexplate and the engine block, you'll notice something crucial: the factory plate actually has a dish/curve built into it that offsets it away from the block.

The new heavy-duty flexplate? Completely flat.

Without that factory curve, a flat flexplate sits too far back. That means your torque converter snout won't properly engage the crank, and you're going to have a massive air gap between your torque converter feet and the flexplate mounting pads. Try to pull those together with bolts, and you'll ruin your transmission pump in seconds.

To make a flat flexplate mate up properly to a 4L80E torque converter on a standard dished 5.3 crank, you need an LS flexplate adapter spacer.

The Lifesaver Adapter: Don't stall your build as we did—grab the LS Flexplate Spacer Adapter on Amazon so you have it ready on the bench! (Again, we get a little kickback if you use this link - Thank you for your support!)

See It In Action (Shop Short)

Here is a little behind the scenes from filming when we figured out we didn't have all the parts we needed... You can hear the frustrations, but I hope you read this article first so you can order all the parts you need before you start wrenching!

Summary:

You will need two key parts to adapt your LS LM7 to a 4L80E:

• The Flexplate
• The Spacer

We hope you enjoyed this blog, and you consider subscribing to our email list so you get notified when we finally get this full how-to video put together and live!