L86 to L8T in '19 Yukon XL Denali

[chevman88]

After reading through @L8T BURB thread, I decided to swap out the broken L86 (Thank you GM DoD) out for the L8T. So far smooth sailing, separating the l86 from the 10l80 required a wood chisel to wedge in and work around the block until they separated. Now that the new L8T is set in place there is about 1/4" gap between it and the trans and I'm wondering if I'm going to have to use bolts to pull them together. The torque converter spins freely and I don't see anything that may have been caught between the two. If I use a pry bar to rock the motor up and down, they pivot on the dowels but won't seat all the way. Thought?

Pics for reference

 

[Bigburb3500]

No thoughts… but subscribed to follow progress. Sorry I’m no help.

 

[chevman88]

Consensus reached after talking to some of my fellow gearheads was to pull the motor just enough to wrap some emery cloth on the dowels (If I can reasonably remove them, do that) and sand them down just a touch and verify they are indeed what's hanging it up (and give her some lube). Gonna have to wait until tomorrow due to working out of a shorter garage and the weather turning to nasty sleety BS.

 

[Fless]

Good plan. I was going to suggest NOT using bolts to get a full mate.

 

[RoadTrip]

After reading through @L8T BURB thread, I decided to swap out the broken L86 (Thank you GM DoD) out for the L8T. So far smooth sailing, separating the l86 from the 10l80 required a wood chisel to wedge in and work around the block until they separated. Now that the new L8T is set in place there is about 1/4" gap between it and the trans and I'm wondering if I'm going to have to use bolts to pull them together. The torque converter spins freely and I don't see anything that may have been caught between the two. If I use a pry bar to rock the motor up and down, they pivot on the dowels but won't seat all the way. Thought?

Whoa up! I broke a transmission pump on my Chevy forcing the engine and trans back together.

There are 3 spline sets that have to line up with the deepest being the trans fluid pump. If you are successful pulling the two halves back together without breaking the mounting flanges on the transmission, the loud pop you hear will be your transmission pump breaking.

On the SECOND installation, I had a friend rotate the engine slowly with a breaker bar as the transmission was close, like yours, until the crank splines lined up and then it seated easily.

It's been some years since this project and maybe others here have more recent experience. There may even be some YTvids to show the best process.

You don't want to have to do this again.

 

[chevman88]

Whoa up! I broke a transmission pump on my Chevy forcing the engine and trans back together.

There are 3 spline sets that have to line up with the deepest being the trans fluid pump. If you are successful pulling the two halves back together without breaking the mounting flanges on the transmission, the loud pop you hear will be your transmission pump breaking.

On the SECOND installation, I had a friend rotate the engine slowly with a breaker bar as the transmission was close, like yours, until the crank splines lined up and then it seated easily.

It's been some years since this project and maybe others here have more recent experience. There may even be some YTvids to show the best process.

You don't want to have to do this again.

Agreed, I don't think I'm in this same boat as my torque converter still freely spins, however, better safe than sorry. I've broken a trans pump myself on a 4l80e and it's no fun to have to pull it all back apart to fix that.

 

[chevman88]

Pulled the motor out a tad, saw that the dowels were being self clearanced by the block and proceeded to sand them down and put some axle grease on them. Set the block back in place and the gap was smaller, but still there. Based on the dowel condition, the fact that the converter still freely spun, and how much of a pain it was to separate them to begin with I decided to use the four bolts surrounding the dowels and tighten them a bit at a time while checking the converter and only going 1-2 turns at a time before moving on to the next bolt. She's now seated all the way, so it's time to start buttoning everything else up hoping to get a first fire by tomorrow afternoon/evening.