2000 Classic K2500 LS swap

[00CrewCab]

So tried searching the forums and didn’t get much luck, got a 2000 Classic K2500, motors been drinking oil (454) and waiting for it to blow, but now the trans (4l80) is hard shifting, so I wanted to do a 6.0ls with 4l80, but I found a Allison trans with transfer case for $1k. Is the Allison possible? Worth it? Engine and trans will remain basically stock for the time being. Eventually pulled for mild build, maybe boost. Who’s the go to for wiring? And brackets? I’ve seen plenty for the 1/2ton trucks but can’t find much for the 3/4 tons. Thanks guys!

 

[HotWheelsBurban]

So tried searching the forums and didn’t get much luck, got a 2000 Classic K2500, motors been drinking oil (454) and waiting for it to blow, but now the trans (4l80) is hard shifting, so I wanted to do a 6.0ls with 4l80, but I found a Allison trans with transfer case for $1k. Is the Allison possible? Worth it? Engine and trans will remain basically stock for the time being. Eventually pulled for mild build, maybe boost. Who’s the go to for wiring? And brackets? I’ve seen plenty for the 1/2ton trucks but can’t find much for the 3/4 tons. Thanks guys!

Have you checked the fluid level in the transmission lately? While it's running, after it's been driven a little bit and run through the gears? 4L80Es are pretty sturdy transmissions but they like the fluid level correct like any other automatic.

 

[00CrewCab]

Have you checked the fluid level in the transmission lately? While it's running, after it's been driven a little bit and run through the gears? 4L80Es are pretty sturdy transmissions but they like the fluid level correct like any other automatic.

I have not, would still like to do the Allison if it’s a reasonable idea. I really haven’t heard much bad about the 4l80, and so far it’s served well, but it’s been towing all its life, started as a RV puller, then it was used for construction, now it’ll be used to tow derby cars, so want to make sure I’ve got a beefy trans behind the motor I put in it.

 

[L31MaxExpress]

I have not, would still like to do the Allison if it’s a reasonable idea. I really haven’t heard much bad about the 4l80, and so far it’s served well, but it’s been towing all its life, started as a RV puller, then it was used for construction, now it’ll be used to tow derby cars, so want to make sure I’ve got a beefy trans behind the motor I put in it.

Allisons do not like high rpm and rob loads of power.

 

[HotWheelsBurban]

It's much cheaper and easier to change the fluid and filter on the 4L80E that's already in your truck, than to swap another transmission that isn't designed to fit in the older truck....
If the fluid looks or smells dark red or burnt, that's what you need to start out with.

 

[df2x4]

The Allison swap is a bad idea IMO if you ever want to do any type of spirited driving in this truck. The Allison is basically a bus transmission. GM never offered them with the 6.0L in the GMT800 trucks, only the 8.1L as far as I know.

They did offer the 4L80E behind the 8.1L in 3/4 ton Avalanches though...

The 4L80E is a very strong transmission in stock form and drives much nicer than the Allison under most conditions. There are people running them basically unmodified in 1K+ HP drag trucks, I doubt you'll hurt one hauling derby cars with a stock-ish 6.0L. Even if your 4L80E is injured, I'd just have it rebuilt or swap another one in. You can find good deals on them in known good condition at salvage yards.