This summer the 4l60e in my 2004 1500 4x4 reg cab/short bed died. Rather than rebuild the 4l60e, I went to the wrecking yard and got a 4l80e from a running truck (hit in the side). There are numerous 4l60e to 4l80e swap threads all over the internet, but there are none specific to a regular cab/short bed truck. So I thought I would highlight the few items that I ran into, namely driveshaft options.

Rear driveshaft:
4l80e is longer than the 4l60e. As such, the 4l60e rear driveshaft will not work. Most people go have a driveshaft made, but I was able to find a rear driveshaft from a 1999 4wd tahoe which worked ($50 at the wrecking hard). It's slightly shorter than optimal, but only around an 1"-1.5". My truck does not have a lift, so a lifted truck might get away with/need the 4l60e driveshaft length. There's plenty of spline engagement with the tahoe driveshaft, but I also don't use my truck for anything but daily driving/very light towing, so I'm not stressing the shaft at all.

Front driveshaft:
Because the 4l80e moves the transfer case back 2", the front driveshaft is shorter than ideal. Unlike the rear driveshaft, the front being shorter does not prevent it from being installed/functioning. However, because the shaft is short, the boot that covers the splines doesn't reach the output shaft. This results in grit/dirt/rust on splines/etc. happening. I went looking for a front driveshaft from a 2500 with a 6.0, but every one I found was the same length as the 4l60e front driveshaft. I measured the front driveshaft on my LB7/allison 2500HD, realized it was the right length, and dug one of those up at the wrecking hard ($50). Like a glove!

Cooler lines:
Prior to this swap, I had already removed all of the hard lines and converted to 6AN fittings with 3/8" braided hoses due to leaking fittings at the transmission. I live in central KY so while everything worked fine in the late summer/fall, when winter came and I had -20 degree mornings, I found that the 4l80e did not perform as expected until it warmed up a bit. I quickly deduced that this was a fluid issue and upgraded to 8AN fittings with 1/2" braided hoses. This resolved the issue. So it seems the 4l80e requires more flow than the 4l60e, which can be problematic in cold weather with 6AN lines. In above freezing weather, 6AN seems to be adequate. I'm running a 40,000 btu aux transmission cooler in addition to the engine radiator integrated cooler. Cooler was installed at time of 4l80e swap.

Side note:
I also swapped out the factory NP246 (autotrack) transfer case for a NP261 (manual shift). My NP246 was trashed inside (250K miles) and I prefer manual shift anyways. Overall it is a direct swap, however you will need to do some rewiring. I pulled the factory transfer case harness, cut out the unnecessary wires related to the NP246, and added the correct plugs for the NP261. One issue I hit was the "service 4wd" message. I looked all over, but could never find a clear answer on how to resolve this. Everything mentioned to remove the transfer case controller (TCC), but this alone did not resolve the message. What gets left out is that it also requires unhooking the battery, keying on to clear any memory, and then hooking the battery back up. This clears the BCM's memory of the TCC being in the vehicle. After doing so, the BCM thinks the vehicle was always a manual shift TC vehicle. No BCM programming is necessary.

 

Cool, thank for sharing this 👏. I have always wondered about this swap on a 1500 4x4, now I know.

I think the AutoTrac transfer case is actually the 246, no? 🤔

 

Thanks, yes, 246. Had a moment.

 

Just a note on your install of 4L80:

In my case, it was very quick and easy to cut 1.6" off the rear driveshaft. I used a chopsaw, dressed the tube with a file, cleaned up the yoke with a 4" side grinder, tapped it back in the drivshaft tube with a dead blow hammer, measured a few times with a carpenters tape measure ( STRAIGHT ) and MIG welded it together. no expert, but it's smooth through 130mph.

As to cooling, the 40K cooler needs to be plumbed in BEFORE the radiator cooling loop, ie, the transmission fluid needs to be WARMED UP by passing through the radiator on the return line. Below a certain fluid temp, the TCC will not lock.

In my initial install, I had left the radiator loop OUT of the ATF cooling circuit, and transmission would not warm up to operating temperature. COLD tranmission is long term detrimental.

 

Good point.
For my install, I put a thermostat on the external cooler. Until the fluid reaches 180 degrees, it bypasses the external and only goes through the internal.