Rpms at highway speeds

[1985c20]

Hello everyone

My truck is a 1985 C20 350/400 4.10 32" tires. The engine was overhauled about 18,000 mi ago bored +.030.

At 70-75 mph the engine sounds like it is ready to come out from under the hood,it tachs about 3050rpm at 70mph.

 

My wife and I were going to take it on an 1800mi round trip by I am worried that the engine will have premature wear at those rpms, and prolonged operation at 70-75 mph will harm the engine.

 

For reference I have another truck 302 AOD 3.25 30" tires that at 70-75mph turns about 1800-1900 rpm

 

any help will be appreciated

 

Jeff

[AG Bill 05 Z71]

Unfortunately when you have an older truck with no overdrive and 4.10s, it results in high RPMs at highway speeds. Looking at the positive side, at least the trans is not shifting up/down for small hills and you have good pulling power!

 

I don't think you have to worry about premature wear or harm to the engine. The biggest worry is paying for the gas when you are getting 10-12 MPG...

 

The best recommendation is to bring some good tunes, be nice to the wife and slow down to 65-70 MPH for less noise and a little better gas mileage.

 

As a point of reference, with 31" tires and 4.10s, my 05 is running 2150 at 70 MPH.

[1985c20]

Unfortunately when you have an older truck with no overdrive and 4.10s, it results in high RPMs at highway speeds.  Looking at the positive side, at least the trans is not shifting up/down for small hills and you have good pulling power!

 

I don't think you have to worry about premature wear or harm to the engine.  The biggest worry is paying for the gas when you are getting 10-12 MPG...

 

The best recommendation is to bring some good tunes, be nice to the wife and slow down to 65-70 MPH for less noise and a little better gas mileage.

 

As a point of reference, with 31" tires and 4.10s, my 05 is running 2150 at 70 MPH.

 

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Thanks for answering,

I my take our other truck :it has 302 3.25 rear 30" tires and automatic overdrive and turns around 1850 at 70 mph and gets about 17mpg as well.