Square on the Interstate

[Wrighteous17]

I've driven my square as a daily driver for a few years now since highschool, and my route to my new college takes me on an interstate where cars are whizzing by at 70+. Can these old trucks handle the interstate? Mines an '87, so it has the TBI 350. I've been on the interstate a few times before with it but I'm scared to cruise at 70 in an (almost) 30 year old truck. But the engine has never given me any problems. Anyone else have any experience driving the interstate in their square?

 

[yevgenievich]

Cruise at around 80mph in a square suburban if in a hurry, otherwise a lot more fuel efficient at 65mph. A bit faster if loaded(due to gearing). If you have 700r4 and not too steep of a gears in the differential, should not be a problem. Even with a th350 or th400 70mph should be ok depending on the gearing.

 

[rich weyand]

I've done 175 mile shots from Bloomington, IN to Champaign, IL at 75 all the way on the interstate multiple times. Ran 320 miles each way from here to my bro's in IL at 75 all the way on the interstate. Mine's a '78 carbed 350 with TH350 and 3.73 gears.

As for mpg, I get 10 in town, 12 at 65, and 10 again at 75. That's in a K, with hubs free.

 

[crazy4offroad]

I've been wanting to put an NV4500 in dad's truck and daily drive it. If it had air it would be a great candidate for daily driving duty.

 

[Old77]

I drive my 87 on the highway daily with no issues. Usually keep it around 65-70

 

[h3adbang3r14]

81 k20 with sbc 400 sm465 and 4.10 gears

i drive my 81 k29 with above combo at 75 on interstate all the time average 11 mpg in dry conditions and minimum wind

 

[da_raabi]

I drive my 87 on the highway daily with no issues. Usually keep it around 65-70

Same here. 86 1-ton with TH400 and 4.10s. I keep it between 60-70mph and cruise that way for as long as I like. It seems to like it right around 60, but I think that's the 4.10s. Never had any trouble with it, except the 6-7 mpg I get. Well maybe closer to 10 on the interstate.

 

[Derick C.]

We do regular 6 hour trips to the dunes towing our 7k lb trailer at 75 and 80 at times. Squares are just fine on the hwy

 

[Wrighteous17]

Thanks y'all, I feel a little bit better about driving it on the interstate now. Since the speedo maxes out at 85mph I was never sure.

 

[mistaake]

my 3/4ton suburban with 350 v8 and th350 (3spd auto) doesn't like going above 75mph. i don't have a tach but the engine sure does get noisy.

 

[smoothandlow84]

Bury the needle at 85...no problem. The truck will outrun what the speedo reads. Gm topped out the speedo at 85 to slow the public down. Earlier speedos read up to 100mph

 

[74propu]

my 74 don't start running good till around 80 and likes 100 as a cruse speed that's when it is happy about 4 pounds of boost so go for it

 

[7903sc]

430,000 miles 90% towing 79 C30 dually> I would drive it anywhere our speed is 75 on the hwy and if you go 75 you get run over.

 

[throttle out]

I drive my 87 V10 LS swapped short bed on the highway on a daily basis. I'm still on the 700R4 with I believe either 3:83 or 4:10 gears on 33x12.50's. My truck happily rolls down the highway at whatever speed I please, however, my driveshaft u-joints are in need of replacement so the vibration disappears above 80 mph! It spins around 23-2,400 rpm at 80.
However you see it, if your truck is in good mechanical order there is NOTHING to worry about.
Although vehicles these days are quiet, more efficient, and more comfortable the basics are the same as they always have been.

 

[Keith Seymore]

Bury the needle at 85...no problem. The truck will outrun what the speedo reads. Gm topped out the speedo at 85 to slow the public down. Earlier speedos read up to 100mph

Agree. My '87 was a daily driver for almost 30 years - it will go as fast as you want for as long as you want.

4.3L TBI, overdrive trans, 3.73 axle.

K