6.0 vs. 5.3 conversion questions

[deerhunter1970]

Thank you for the real world experience deerhunter1970! Are you a 3/4T with the 4.10 gear? I didn't think 4.10 gears were available in the 1/2T truck/suv? Or did you change to 4.10 to compensate for tire size larger than stock?

No, it's a stock Yukon XL 1500 SLT. It has the GT5 option gears, ordered that way by my father-in-law. I'm not running big tires and wheels - 265/75/16 BFGoodrich All Terrain T/A KO2s, so it spins pretty fast on the highway, but it rarely ever kicks down out of 4th, even with a load on it. I really think that's how the original engine and trans lasted so long (471,000) as it didn't have to work so hard pulling the beast around.

 

[mattt]

No, it's a stock Yukon XL 1500 SLT. It has the GT5 option gears, ordered that way by my father-in-law. I'm not running big tires and wheels - 265/75/16 BFGoodrich All Terrain T/A KO2s, so it spins pretty fast on the highway, but it rarely ever kicks down out of 4th, even with a load on it. I really think that's how the original engine and trans lasted so long (471,000) as it didn't have to work so hard pulling the beast around.

Thanks. Learned something new today. When the original engine and trans gave up the ghost at 471k, was it catastrophic or just a slow dying death?

 

[deerhunter1970]

Thanks. Learned something new today. When the original engine and trans gave up the ghost at 471k, was it catastrophic or just a slow dying death?

Blew a head gasket after overheating due to a blown plastic heater hose connector! The trans was still in good shape, but since I was replacing the engine, figured I might as well do the trans too as a package.

Most everything else (axles, transfer case, alternator, etc.) is original and still working fine. I drive like an old person, gotta make this thing last as long as possible

 

[zraffz]

Most everything else (axles, transfer case, alternator, etc.) is original and still working fine. I drive like an old person, gotta make this thing last as long as possible

You're very fortunate lol. I assume front CV shafts have been changed? My old girl eats CV shafts annually cause of the lift.

 

[deerhunter1970]

As far as I know - they are original!!! I don't have any lift...if anything its lowered, as I'm sure the bars have sacked a little...

It needs shocks, but I'm hesitant to mess with it. I'm sure once I do, it will start breaking on me

 

[mattt]

The 317s are similar to the 243/799s, they have the same intake port design, the same size intake and exhaust valves, only difference is 71cc combustion chamber vs 64cc combustion chamber...you can pull the 317 heads and have them milled at a machine shop...every .006~1cc so you could have them milled ~.040 to get down to a 64cc combustion chamber instead of buying another set of heads

One plus I thought of for using the 243/799 instead of having the cut 317's is the more the stock 6.0 head is cut, you could run into an issue with intake manifold fitment, as the heads become shorter, the distance between heads will grow larger.

 

[01FormulaTA]

One plus I thought of for using the 243/799 instead of having the cut 317's is the more the stock 6.0 head is cut, you could run into an issue with intake manifold fitment, as the heads become shorter, the distance between heads will grow larger.

.040 is the max you can go without running into issues

http://www.ls1truck.com/forums/powertrain/20902-milling-317-heads.html

https://www.performancetrucks.net/f...-modifications-158/mill-317s-how-much-431884/