Bolting a 4L80E to a 2005 5.3: do I need a 6.0 flexplate with spacer, or the 5.3 flexplate with spacer?
The key is the converter bolt pattern, not the engine size:
Last updated
| Transmission | Converter bolt pattern |
|---|---|
| 4L60E, 4L65E, 4L70E | 11.062 in (sometimes listed as 11 or 11.08 in) |
| 4L80E, TH400 | 11.5 in |
| Powerglide, TH350, 700R4 | 10.75 in |
A 2005 5.3 usually came with a 4L60E, so its flexplate has the 11.062 in pattern — a 4L80E converter (11.5 in) won't bolt to it. You need a flexplate with the 11.5 in pattern, the kind used on LS engines that came with a 4L80E from the factory. A 2005 engine still has the 6-bolt crank flange (8- and 9-bolt cranks started in 2009).
What we can confirm: on an LS that came with a 4L80E from the factory, you use the stock flexplate for the 4L80E, and a spacer is used when adapting a TH400 to that factory 4L80E flexplate.
Our source doesn't spell out the spacer stack for a 4L80E on a former-4L60E 5.3, so confirm converter engagement and crank-to-converter spacing with your flexplate or converter maker before final assembly.
Look up the 2001-2006 2500HD 6.0L/4L80E application; that gets you the correct flexplate, spacer, crank bolts and torque-converter bolts. It isn't a 5.3-vs-6.0 question, since both engines backed both transmissions. The ATP Z270 flexplate/spacer/bolt package is the inexpensive route at around $50; alternatives are piecing the GM parts together or buying an aftermarket unit such as the Hughes HP4004X-EBP. If you're buying a converter anyway, you can have it built to bolt to the stock 4.8/5.3 flexplate.
Check this first:
- Confirm crank snout length (a 2000 6.0 with the long snout can't simply reuse donor parts)
- Verify converter bolt pattern against the flexplate
Based on what we've seen work across our own builds, our friends' builds and the wider LS community, reviewed by our lead shop tuner (over 20 years of LS and LT tuning experience). Every combination is different, so use at your own risk and check our safe tuning limits before any wide-open pass.
Go deeper
Check this first
- Identify which flexplate you have (flat vs dished).
- Check converter hub engagement into the crank with the trans bolted up.
- Confirm you have the longer crank bolts if using the spacer.
Try this, then this
- 1) Flat 6.0 flexplate + GM spacer 12563532 + longer bolts 19257940 with thread-locker.
- 2) Or ATP Z270 package as the budget all-in-one.
- 3) Or custom converter built for the 4.8/5.3 flexplate - no spacer needed.
How you know it's fixed
- Converter engages the pump properly (pulls forward ~1/8 in to the flexplate), no pump noise, no vibration.
Still not fixed?
- Re-measure spacing - the usual error is a spacer on a dished flexplate or the wrong bolt length.
Every option we know of
We may earn a commission when you buy through links on this page.
| Maker / product | Part # | Fits | Price | Where | Status / notes |
|---|---|---|---|---|---|
| GM 4L80E flywheel | 19260102 | 2002+ 3/4-ton 4L80E trucks; flat style needs spacer | verify current | Buy GM dealers, RockAuto | Current production Confirm flat vs dished before adding spacer |
| GM Crank spacer | 12563532 | Flat flexplate to 4L80E converter | verify current | Buy GM dealers, RockAuto | Current production Only with flat flexplates |
| GM Longer crank bolts (x6) | 19257940 | With spacer | verify current | Buy GM dealers | Current production Use thread-locker |
| ATP Flexplate + spacer + bolts package | Z270 | LS to 4L80E | about $50 | Buy RockAuto (~$50 reported) | Check stock Budget option; verify contents |
Prices are approximate as of September 2026. We list every option we know of, including small shops and used parts we can't link to. Confirm fitment with the seller.