Thinking of ditching the 78mm and going back to 67mm
02-15-2017, 10:50 PM
#1
Thinking of ditching the 78mm and going back to 67mm
Turbos in question ... On3 7875 vs. Pricision PTB505-6765
When the 67 failed due to a cracked head and coolant in the oil, I also completely rebuilt the kit while I was taking everything apart and finished it as a flipped manifold setup. While I was at it, I thought "why not go bigger" and put in the 78 as it was cheap (and I was in a mild rush and didn't wanna wait a month for rebuild) and put the 67 on the shelf. Well a friend was asking about recently and so I sent it out to be rebuilt ... 580$ was the quote for new turbine wheel, bearing housing, backing plate, and bearing components, which isn't bad. It's already got the billet wheel and anti-surge housing upgrade/etc. and was pretty $$$ new.
It performed good on the old kit with the 4L60E putting down north of 510rwhp at about 12psi taking it easy due to still running a stock trans and fuel pump. It was a hoot to drive and burned up the trans a time or two (previous owner was a friend and I've known truck since new). One of the many reasons I bought it.
Didn't really drive it much after the 4L80E swap as the turbo failed. However the 78 setup is laggy as hell with the 3.42 gearing and the 4L80E trans low gearing ... and am running a stock converter. So that's made things worse as the lag is annoying too. I actually prefer my wife's Armada right now haha.
Didn't have luck with a 3200 stall I had for a short time as it burned up the TCC twice ... not sure if that was due to trans/tune (was still figuring out the swap/wiring) or the converter itself. Also got sick of having to Rev so much to get going and would prefer a quick truck for around town shannanigans ... so the 68 seems logical.
What do you'll think? 4.10 gears first?
When the 67 failed due to a cracked head and coolant in the oil, I also completely rebuilt the kit while I was taking everything apart and finished it as a flipped manifold setup. While I was at it, I thought "why not go bigger" and put in the 78 as it was cheap (and I was in a mild rush and didn't wanna wait a month for rebuild) and put the 67 on the shelf. Well a friend was asking about recently and so I sent it out to be rebuilt ... 580$ was the quote for new turbine wheel, bearing housing, backing plate, and bearing components, which isn't bad. It's already got the billet wheel and anti-surge housing upgrade/etc. and was pretty $$$ new.
It performed good on the old kit with the 4L60E putting down north of 510rwhp at about 12psi taking it easy due to still running a stock trans and fuel pump. It was a hoot to drive and burned up the trans a time or two (previous owner was a friend and I've known truck since new). One of the many reasons I bought it.
Didn't really drive it much after the 4L80E swap as the turbo failed. However the 78 setup is laggy as hell with the 3.42 gearing and the 4L80E trans low gearing ... and am running a stock converter. So that's made things worse as the lag is annoying too. I actually prefer my wife's Armada right now haha.
Didn't have luck with a 3200 stall I had for a short time as it burned up the TCC twice ... not sure if that was due to trans/tune (was still figuring out the swap/wiring) or the converter itself. Also got sick of having to Rev so much to get going and would prefer a quick truck for around town shannanigans ... so the 68 seems logical.
What do you'll think? 4.10 gears first?
02-16-2017, 07:48 AM
#3
Precision rep said I'd only expect 5-600 with this turbo. So wondering if the units others are having luck with are different. The guy Turbo Tim said he was pushing 25# on it!
02-16-2017, 12:59 PM
#4
I'd do the gears, if you do not make long highway drives daily. Also check your turbo and make sure its turning freely.
4.10 gears you will think you add 100hp to the truck. They'll allow the engine to RPM and be happy.. 3.42 are just lugging the combo..
66 exhaust wheel will feel great and quick spool on a 5.3 but not gonna make big power..
PT hp rating is at the engine and the edge of its flow and not on an LS v8.
4.10 gears you will think you add 100hp to the truck. They'll allow the engine to RPM and be happy.. 3.42 are just lugging the combo..
66 exhaust wheel will feel great and quick spool on a 5.3 but not gonna make big power..
PT hp rating is at the engine and the edge of its flow and not on an LS v8.
02-16-2017, 02:38 PM
#5
Well I just had a conversation with Precision and they're upgrading me to a 66mm turbine wheel and .96 a/r exhaust housing for about the same price. (usually a $550 upgrade alone). So even if I decide to not do this, it's gonna be a pretty decent turbo with 1yr warranty that I may be able to sell.
02-16-2017, 02:41 PM
#6
I'd do the gears, if you do not make long highway drives daily. Also check your turbo and make sure its turning freely.
4.10 gears you will think you add 100hp to the truck. They'll allow the engine to RPM and be happy.. 3.42 are just lugging the combo..
66 exhaust wheel will feel great and quick spool on a 5.3 but not gonna make big power..
PT hp rating is at the engine and the edge of its flow and not on an LS v8.
4.10 gears you will think you add 100hp to the truck. They'll allow the engine to RPM and be happy.. 3.42 are just lugging the combo..
66 exhaust wheel will feel great and quick spool on a 5.3 but not gonna make big power..
PT hp rating is at the engine and the edge of its flow and not on an LS v8.
Yeah gear install should be about $200 for the partial kit. Is the 2009 a 8.5 or 8.6? I keep getting mixed results when I search.
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02-17-2017, 04:25 PM
#8
"The 6765 was actually 67.4, so the housings they used were labelled as 68’s. We changed to a more standardized part numbering system a few years ago. As for the upgrade, the turbo will take slightly longer to spool due to the increase in AR size, however the newer wheel is also more efficient so it shouldn’t be super noticeable. Also by going this route you will increase power up top"