RSIV

In short, I'm doing an LS swap. Rear end gear ratio is 3.73. 5th gear is 0.753:1. I'm thinking my RPM's will be around 3200 cruising in 5th at 70mph. I could be wrong, but it would be close to that. Is that bad for a 5.3 to be constantly running at that RPM. Will this wear down the engine faster? I have a friend that's sure this is not good for it since originally that engine is designed to cruise at low RPM on the highway. What are your thoughts? Thanks for any feedback.

wretched73

What size tire?

That's high, you're fuel mileage will be beyond trash

EddieK

I think you are wrong. Assuming your tire is 28" tall, my calculation shows 85mph at 3000rpm, 71mph at 2500.

68Formula

So you're running 20.6" tall tires? Are you swapping an E-Z-GO?

RSIV

225/50r16. 24.9" tire diameter. My question is will it be bad for the 5.3 to turn that kind of RPM for long out of state trips? Other than bad fuel economy will the engine fail soon at some point?

EddieK

75mph at 3k rpm, 88 at 3500.

RSIV

Well, that sucks. I don't think I want to turn that much revs crossing 4 states.

"When this baby hits 88mph, you're going to see some serious ****."

FirstYrLS1Z

iTrader: (4)

I'll relay my conditions. 98Z A4 stock un-modified engine, bought used in 2001, currently approaching 190,000 miles, it's a traveler. In 2007 I put in a 4.56 rearend, I work on rears so I built a complete from a housing and 'parts' I had. It's easier to swap an entire rear than it is to just swap gears in rearend in car. Ran the 4.56 rear for 7 years until 2014 when I put the 3.23 rear back in. Put the 4.56 rear back in 2018. For those 7 years with the 4.56, it went on 5 trips to Florida (from Cleveland Ohio area). Trip cruising RPM was 2500 at 60mph and 3000 at 72mph, RPM read off ScanGaugeII and MPH off GPS. Comparing MPG with 3.23 vs 4.56, the 3.23s gave 24.5mpg and the 4.56s' gave 21.5, the computer did a good job of MPGs'. Once on the way back on I26 in S.C., we hooked up with a fast moving group of cars and was in cruise control at 4000rpm for about an hour. Does the LS handle extended high rpm, in my case, very well. And it runs stronger as time goes on.

LetsTurboSomething

You can cruise at 3000rpm forever basically. It's going to be annoying but mine does 65mph at 3k on my th400 and I can rev it to 3500-3700 for an hour without having any engine or engine compartment issues. Now, you may need to change the oil around the 2000 mile mark instead the the 3k mark. Enjoy watching the fuel gauge drop like its on time lapse.

GM engines in marine applications run 3000-4500rpm at a constant for 2000 hours. As long as nothing is overheating and nothing in the engine compartment is melting its all good.

Cherry84

iTrader: (7)

I do 3000 plus I everyday for last 5yrs avg 100 miles per day.. 4:10 gears /4l80e/ 3000 stall/& Detroit locker with drag radials...😈