"The Highway Hauler"

[Old-beat-up-77]

Welp,

Here I am and here is my 1977... K10?

That's really all I can call it at this point because it has taken the role of many other owners rigs.

Anywho, on to the thread...

I plan on making this rig into a smooth running highway coaster for transporting up and down the main arteries of New England. I KNOW I KNOW... "Its a square body it don't do that"... maybe 20 years ago but a lot has changed.

350 with a Muncie SM465 and NP205 will be the drive line for now so a new ring and pinion will be paramount for this application. I also need it to remain 4WD.

Top speed will be 75 MPH but I want those RPM's low but not so low that I cant get myself out of a situation where I need low gears.

Budget is... a budget so lets keep things financial friendly.

Areas to be addressed:
Shocks and springs all around (no lift)
Gearing (rings and pinions)
Wheels and tires (Highway rollers

That's what I got for now. Any suggestions on brands, ratios, specific materials, etc. let me know. Ill post a few pics when I get the chance.

 

[Dmack]

A 4x4 with a 4 speed sm465 at 75 will be screaming without an overdrive if running any gear\tire combo that would be usable in general 4x4 use, from what I am familiar wjth. Not saying it can't be done, but will be challenging. I'm looking forward to your progress and solutions.

 

[bucket]

I used to daily drive my '77 K5, with a alot of highway travel. Mild 350 (probably around 300hp) with TH350, 3.08 gears and 33" tires. It didn't just idle down the interstate by any means, but it was reasonably economical and wasn't screaming at high speeds. It was a little sluggish off the line, but otherwise not too bad at lower speeds. I'm not sure I really recommend it, but if low rpm is the goal, it works. If the gearing were any taller, low speed power would really suffer and there would be minimal (if any) gains in economy.

 

[Wumbo]

You know whats changed in the last 20 years?

Everything has overdrive.

I have an SM465 in my truck. It doesn't care for modern highway speeds. Get a trans with overdrive, NV4500 or 700R4. Keep your gear ratios and tire sizes if they are moderate.

 

[Old-beat-up-77]

UPDATE:

I now have a TH350 transmission at my disposal... probably have to be rebuilt... yeahhh...

Anything I should know about them?

 

[TubeTruck]

Yup, 20 years ago I had a '78 Stepside with a 350/TH350/203 and 33" tires with 3.08's. It works but highway speeds were 55 and gas was around $1 a gallon, lol. I'm currently running 33's with 3.42's in my Suburban but I'm doing 60 in a 70 in the right lane

Get OD if you can. The TH350 will serve you well if it's built by someone who knows that they are doing.

And where in NE? I'm originally from Central MA and I know we have a few others here from the NE area. Pop over to the Introduction thread and introduce yourself

https://www.gmsquarebody.com/forums/introduction.20/

 

[Wumbo]

UPDATE:

I now have a TH350 transmission at my disposal... probably have to be rebuilt... yeahhh...

Anything I should know about them?

It has the same 3rd gear ratio as the SM465, so you aren't changing anything in that sense.

 

[bucket]

Imho, if it worked well 20-30-40 years ago, there's no reason it can't be sufficient now. People now are just so used to being coddled by modern conveniences that they are no longer used to driving down the interstate and hearing their engine too.

Most big heavy vehicles that are shaped like bricks don't really gain much MPG from overdrive anyway.

 

[Itali83]

I’ll second the overdrive is nice but not needed. If you have a budget to stick to, use what you’ve got to work with now. If you go right out and get an overdrive trans, you really need to think about rear end gearing so that you can take advantage of the new gear set. Then, you need to make sure your motor has enough power to push that brick at the speeds you want at the right rpm so you can get the best mileage you can.

I guess what I’m saying is unless you want to completely go through the drivetrain is stick with what you’ve got, tune it to the best it can be and enjoy a taste of the old days. If you really want highway speeds you need to look at a new age power train. LS motor, or the ultimate would be a diesel swap. But again, how far do you want to go?

Ben

 

[80BrownK10]

UPDATE:

I now have a TH350 transmission at my disposal... probably have to be rebuilt... yeahhh...

Anything I should know about them?

I just learned this week that there is two versions. The th350c is an electronic lockup converter version. You will have an plug spot on the driver side of it behind bell housing but above pan flange.

 

[80BrownK10]

Oh and I was going to say. Fix up your square like you like and buy a more modern truck to cruise the highway, even if it's just the next generation truck. 88-98 or whatever.

 

[bucket]

Oh and I was going to say. Fix up your square like you like and buy a more modern truck to cruise the highway, even if it's just the next generation truck. 88-98 or whatever.

I happily cruise my '78 down the interstate...

 

[Catbox]

My truck has the SM-465 and it makes the engine sing its song loud and clear at 65 mph.
It has a 3.73 rear gear back there.

If I were to want to drive it more than I do, I would end up with a 4L80 transmission backing the 454 that is under the hood currently.

Perhaps looking into a fuel injection set up for the engine might prove to be more beneficial than changing out the transmission at this point.
Make that as tuneable as possible now and if that doesn't get what you want, then change to a different transmission....

 

[80BrownK10]

I happily cruise my '78 down the interstate...

I do the same with my 80. But not daily or even pulling ng trailers all over. I make a decent living but would put a substantial amount into my square if I drove it daily on just my 50 mile round trip commute!

 

[78C10BigTen]

I happily cruise my '78 down the interstate...

I do also! Tachin about 3k with that th350 at near 75-80mph