Project: '72 Family Hauler

[shearjs]

What began as a mostly simple fuel tank install turned into a cnotch install, which turned into a rear end cleanup, which turned into a full rear end rebuild and disc brake conversion. These are all things that I had planned on doing eventually, but I figure I might as well dive in while it’s all apart. I likely scraped off 10 lbs of gunk and dirt from the rear end. I’ve been doing a little research to determine exactly what gear combination and traction device would give me the ride I’m looking for. With a final gear ratio of .75 on the 4l60, a 29.3” tire height, and 3.73 ring and pinion, I should be around 2096 rpm at 70 mph. My old GMC was around 2350 rpm at 70 and that felt a little high for my preference. I’m currently trying to decide between the Eaton Posi and Eaton Detroit Truetrac and leaning toward the Truetrac. Does anyone have any prior experience that might persuade one over the other?

[polishspy]

Originally Posted by shearjs

What began as a mostly simple fuel tank install turned into a cnotch install, which turned into a rear end cleanup, which turned into a full rear end rebuild and disc brake conversion. These are all things that I had planned on doing eventually, but I figure I might as well dive in while it’s all apart. I likely scraped off 10 lbs of gunk and dirt from the rear end. I’ve been doing a little research to determine exactly what gear combination and traction device would give me the ride I’m looking for. With a final gear ratio of .75 on the 4l60, a 29.3” tire height, and 3.73 ring and pinion, I should be around 2096 rpm at 70 mph. My old GMC was around 2350 rpm at 70 and that felt a little high for my preference. I’m currently trying to decide between the Eaton Posi and Eaton Detroit Truetrac and learning to the Truetrac. Does anyone have any prior experience that might persuade one over the other?

If you are going to drive it regularly, a posi is the way to go. The true trac is more of a racing rear end.

[04ls1gto]

I put a true Trac in mine with the 3:73 but I am running a 6l90 which has another overdrive. I highly recommend the trutrac as it drives like a open diff and is nice and quiet. Honestly made the drivability a lot better then the open diff.