55 mph on highways ?

[berserk]

Truck is a K10 Th350 and 4.10, 33" tires so it revs at higher speeds. Been under construction for 2 years and finally used it to haul a small equipment trailer 40 miles last week. I have a driveline vibration that I'm about to tackle and it really only starts above 55-60 mph so.... I run right at 55mph lately. It keeps my rpm down and is a little better on gas, that and the mud tires ride terrible at higher speeds.

I have property in rural Oklahoma and you cannot drive there without hitting the rural 2 lane highways. Unless you are willing to drive a 15 mile section on rough neglected mud/gravel roads. My back won't appreciate that.

So here I am running 55 mph in a 65 zone, only a shoulder and steep rolling hills. A guy in a Tacoma 4 cars back decided to pass on a double yellow, on a blind hill. Must have been doing 100 mph after passing through 5 cars including me.


Scariest part he BARELY avoided a head on collision because there was a blind hill and oncoming traffic. I moved onto the shoulder because I thought he was going to clip my front fender. 😡


I'm worried to drive on the Interstate and highways now. These people are insane and regularly drive 10-25 mph over the speed limit and road rage seems to be a common trait in Oklahoma.


What are your experiences with these old trucks with high gear ratios and no OD running on the highway? Any advice? My dad said he just stares straight forward and ignores the traffic behind him lol

 I feel like installing auxiliary red flashing lights for hazard signals. I waved as many as I could around me in safe spots and would creep on the shoulder to give them more passing room.  I want a 4l80e but the funds have run dry.

[ehjorten]

My '77 K20 has 4.10:1 rear gears and 31.6" tires (265/70R17). It also has a THM350. I have run that on highways for countless miles. Yes, it is a little high-rev'ing due to the gearing, but I can run it 70 miles per hour all day. 70 MPH is about 3,100 RPM for me. For you with 33" tires, that same 70 MPH should be just a hair under 3,000 depending on converter slip. So...you should be able to run 65 no problem. 65 should be somewhere between 2700 and 2800 RPM.

[Shifty]

4:10/TH400 here, 33"'s, and the poor old guys screams in agony on the interstate.....

[berserk]

My '77 K20 has 4.10:1 rear gears and 31.6" tires (265/70R17). It also has a THM350. I have run that on highways for countless miles. Yes, it is a little high-rev'ing due to the gearing, but I can run it 70 miles per hour all day. 70 MPH is about 3,100 RPM for me. For you with 33" tires, that same 70 MPH should be just a hair under 3,000 depending on converter slip. So...you should be able to run 65 no problem. 65 should be somewhere between 2700 and 2800 RPM.

It just feels wrong to spin the engine at 3000 rpm sustained 😂 glad I put quiet mufflers back on the truck, the 2 chamber welded mufflers would be deafening at that rpm.

[ehjorten]

Marine 350's will cruise at that RPM all day! As long as you don't have a cooling issue, it will be fine.

[berserk]

Marine 350's will cruise at that RPM all day! As long as you don't have a cooling issue, it will be fine.

I have a monster 4 row aluminum rad and a plate stack trans cooler I just installed this summer. I also have a 6" cowl hood which should pump a lot of air under the hood.

Guess I'll just let the rpm's sing and just keep an eye on the temp and oil pressure. Thanks

[ehjorten]

It is fatiguing for long road trips. I never noticed it with my 4.10:1, lowered '68 C10, or my 4.10:1 '77 K20, but when I got my '91 V3500 with the overdrive, I then started to realize that long road trips with loud, high-rev'ing engines tends to tire you out.

[Shifty]

Erik, how many years between them?  I had a 68 Chevelle with 4.88/th350 that I drove from Phx, AZ all the way to Bowling Green KY, and it didn't bother me a bit....nowadays, I'd be stopping at every motel along the way....

[78 Chevyrado]

I had a guy road rage on my back in 2021.   I was going 65 on the freeway and he passed me on the shoulder and shot rocks all over my truck.  I blew the train horn on him through his open drivers side window.  Dude drove 2 miles down the road in the fast lane before he decided he was mad enough to cut over to the right lane and lock it down.  I swerved past him, ended up in front of him.  He rolled up on my back bumper like he was gonna do something.  Well a bunch of other cars had a pileup because of him.  He got scared and tried to run but I was in the way.  he drove right through my back bumper while I was holding the brakes.  left his hood, bumper, rh mirror and half the fender on the side of the road.   I chased him a bit to get the tag but no tag.  likely stolen.  Pulled off at the next exit and called the cops.  They gave me a report.   
Cops told me yeah everybody that called in said this white beemer hit an old truck and they both took off.   I quit chasing him because he started splitting lanes in an suv.   It was a Sunday too.  likely he hurt a lot of people.

My truck has the right to be out there like anyone else.  minimum speed on the freeway is 40.  they can deal with it.  I go 70.  I have a 3/4 ton with a 3.73 gear and no OD and 33.5" tires.  turns about 2900rom at 70.   Old truck held up. 

Dude hit me cuz he was mad, which I can let that go but if he had come up to my window he'd have learned a smith and lesson.  That will not end well for you.  Always be prepared.  Yeah your slow and gonna make people mad.  thats their problem not yours.  that being said be prepared to defend yourself.

Pic is at the walmart I stopped at at the next exit to have the cop come meet me.

[78 Chevyrado]

Straightened out the bumper and added a spare piece of lower tailgate trim I had and added a dent to it to match the tailgates new shape...    Sprayed some color match paint around the tail light hole after I straightened it as best I could.  it looks dull cuz i never cleared it..   still have a piece of the cars something I dug out of the tail light hole.   Since the bumper paint is screwed why not add a FAFO emblem to it.  ya know...  pic from tonight.

[berserk]

☝️ That's what I was worried about, I was almost fully on the shoulder and the Tacoma had maybe 100 yards before a head on collision before he whipped into my lane!

One of my biggest issues right now is a driveline vibration. I can't run faster than 60 or it feels like the truck will shake apart. I already had the rear drive line completely gone through. And while it helped my pinion angle is off because of 2.5" lift springs I just installed.

I'm going to abstain from highway driving until I get the issues fixed so I can run 70 smoothly. Maybe that way I won't end up with someone up my rear bumper like happened with you.

[Shifty]

Wow Kenny, I'm glad that you're ok enough to post that!  Did the rager get charged?

[ehjorten]

Erik, how many years between them?  I had a 68 Chevelle with 4.88/th350 that I drove from Phx, AZ all the way to Bowling Green KY, and it didn't bother me a bit....nowadays, I'd be stopping at every motel along the way....

Shifty, I've had my '69 Chevelle since HS, my '68 C10 since college, the '77 K20 when I was a few years out of college, and the '91 V3500 in my late 30's. I am 50 now and still can grind harder than most kids these days, including my 19 year old son. The high-rev'ing, loud engine on long drives is still more fatiguing than the '91 with overdrive. I still do it all the time.

[Shifty]

I'm glad that you can represent us old dudes Erik....I take a lot of meds for that...

[78 Chevyrado]

☝️ That's what I was worried about, I was almost fully on the shoulder and the Tacoma had maybe 100 yards before a head on collision before he whipped into my lane!

One of my biggest issues right now is a driveline vibration. I can't run faster than 60 or it feels like the truck will shake apart. I already had the rear drive line completely gone through. And while it helped my pinion angle is off because of 2.5" lift springs I just installed.

I'm going to abstain from highway driving until I get the issues fixed so I can run 70 smoothly. Maybe that way I won't end up with someone up my rear bumper like happened with you.

You have no obligation to run 70 or even 60 or even 50 on any road anywhere in this country.   That being said, do what makes you most comfortable.