LX450 LM4/4L60E Swap

[Albatross80]

I finally bought the oil pan used on LH8 V8 equipped 4wd Hummer H3 Alphas and Colorados. The pan looks like it will clear the driveline at stock height.

Before removing the 302-1 style pan, I removed the front springs to test driveline clearance. The front diff hits the oil pan before the driver's side bump stop contacts.

 

[White Stripe]

Do you know the part number for the oil pickup that goes with that pan?

 

[Albatross80]

Do you know the part number for the oil pickup that goes with that pan?

I don’t unfortunately. I ordered an eBay copy kit.

 

[Albatross80]

Finished installing the H3 pan today. It wasn't the final solution I was hoping it would be but I'm going to have to run with it for now.

There is now plenty of diff clearance at full compression; even enough for lateral movement that may happen with bushing flex. However, the H3 pan is taller and will barely touch the tie rod under full compression. Contact will definitely be more severe under more dynamic compression of the front end. Also, the pan only allows for one of the two bell housing bolts to be used. I'm not sure how bad this is but I'm all out of weekend and money.

As for the Labwork pan kit itself, I had to slightly bend the pickup support arm for it to match up with the crankshaft scraper tray bolts. Also, I had to trim the pan baffle slightly to clear the pickup.

For now, I'm going to get bump stop drops until I can afford the Holley 302-4 pan or until they make a knockoff one of those.

 

[Albatross80]

Theme of the first summer road trip: Heat Management

I discovered two main issues:
1. Air bubbles forming in the engine’s coolant passages
2. ATF temperatures climbing as high as +230°F while climbing the mountains toward Flagstaff

Despite these problems, I never fully overheated. My setup has been:
- TYC radiator
- Stock FZJ80 overflow tank
- GMC Traverse electric fans
- GM two-speed relay control
- 50/50 distilled water / Prestone

This combination has served as my daily driver for the past three years.

Coolant / Boiling Issues
During +100°F drives through Texas, stopping for gas would cause heat soak and localized boiling. Coolant would escape, and once the boiling stopped there wasn’t enough fluid left to be drawn back into the engine.

A new radiator cap initially fixed the problem. At altitude near Flagstaff, however, it would still boil over slightly.

By the end of the trip I switched to a GMC Sierra 1500 expansion tank. This completely eliminated the air bubbles and boiling-over issues. I haven’t seen anyone else discuss this approach, but I believe it’s the right way to go.

I fabricated custom brackets and mounted the tank as high as possible on the passenger-side firewall. The lower port on the Sierra tank is 1". I had to tee into the ¾" heater hose and use a reducer to connect to the 1" lower expansion hose. Connecting the steam ports was straightforward. I also modified the radiator overflow hose so it functions like a steam port (free flow in both directions) and used a Gates 42 psi “blanking cap.” The cap needed a thin layer of RTV on the seal because it was holding less pressure than the original GM overflow tank cap.

I’m planning to re-do the expansion tank setup properly once I’m back home in New Orleans. I’d like to find a tank that already has a ¾" lower port to simplify the hose routing. The mounting brackets I made on the road were a bit of a hack job, functional enough to continue the trip, but not ideal.

Transmission Temperature
For the high ATF temps I installed a NOS Tru-Cool M7B cooler I found on Facebook Marketplace for $60. It worked great.