What parts and wiring do I need to swap a 4L80E in place of a 4L60E in a GMT800 truck?
- The Quick 4 kit includes both the early large and late small output-speed-sensor harnesses, with black and purple wires terminating in the controller's white TSS connector.
- For 4L80E installations the Quick 1 manual says to connect the solenoid and TSS cables keyed correctly, connecting both TSS cables according to their labels.
- For 1999-2007 Gen III truck/LS-style harnesses, the 4L60E-to-4L80E conversion guide moves the transmission-connector brown wire from cavity U to cavity S, and repurposes the removed white wire (cavity S) and tan/black wire (cavity T) for the 4L80E input-speed sensor.
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Confirm against the instructions for your exact parts before wiring. More: Transmission control in our tuning guide.
Swapping a 4L80E in place of a 4L60E in a GMT800 comes down to nine things. (1) a 32-spline slip yoke with a shaft no longer than 5.75 in and at least 0.75 in of slip (the 4L60E is 27-spline), which may save you from cutting the driveshaft, plus a conversion U-joint to mate the existing shaft; (2) a 6.0 flexplate, spacer and longer crank bolts with thread-locker, like the ones off an '02 2500; (3) six converter bolts instead of three; (4) a trans mount, since the 80E is usually 2-bolt against the truck's 1-bolt crossmember; (5) cooler lines, since the 80E's 3/8 in hard lines don't mate to the 60E lines, so either run AN braided hose or cut, double-flare and extend them with trans hose and clamps. The rest is the crossmember, which we've seen cut with the center moved back 6 in using 3/16 plate while keeping the same overall width, an HP Tuners segment swap for the trans and trans diagnostics using a matching OS, and adding a VSS wire to the PCM, since the 4L60E setup doesn't have one. Done yourself, the whole swap can come in under $5K.
Check this first:
- Measure slip yoke length and slip travel before cutting the driveshaft
- Get a segment-swap file that matches your PCM's OS
- Get the VSS sensor plug and PCM terminal pins
- Confirm the crossmember and mount line up with the 80E's 2-bolt mount
Careful: Skipping the segment swap will leave you with a CEL and trans codes, and the crank bolts need thread-locker.
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
- Confirm donor 80E year, 2WD/4WD, and ISS presence.
- Measure driveshaft and crossmember implications.
- Check HP Tuners credits and OS compatibility.
Try this, then this
- 1) Hard parts: yoke, flexplate/spacer/bolts, mount, cooler lines, crossmember.
- 2) Wiring: repin for 80E, add VSS wire and ISS pins.
- 3) HP Tuners segment swap with matching OS; verify shifts and TCC.
How you know it's fixed
- All gears, correct shift points, TCC lockup, no codes, no leaks or vibration.
Still not fixed?
- Wrong shifts = segment swap/OS issue; no VSS = wiring; vibration = yoke/pinion angle.
Every option we know of
| Maker / product | Part # | Fits | Price | Where | Status / notes |
|---|---|---|---|---|---|
| GM 4L80E donor (2002+ 3/4-ton) | OEM | GMT800 swap | $800-1,500 | Salvage | Plentiful used Confirm 2WD/4WD and ISS |
| HP Tuners VCM Suite + credits | n/a | Segment swap and diagnostics | about $300-500 | HP Tuners | Current Needs matching OS |
| Spicer 32-spline slip yoke + conversion U-joint | application-specific | 4L80E output to existing shaft | about $150-250 | Driveline shops | Current production Shaft <=5.75 in, >=0.75 in slip |
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.