The Stovebolt Site Forums The Shop Area Driveline How to increase freeway speed (216 - 1938 Chevy 1/2ton)

Before I re-assemble my 38 1/2ton I was wondering if someone could coach me as to the best way to increase my freeway speeds using the OEM 216. Between the 3speed floor shift trans and stock rearend I’m assuming top speed is probably 50mph??

I would like to keep manual trans and 216.. are there any later model “drop ins” for improving drivability?

Good morning and welcome to Stovebolt!

Our resident gurus will be along soon with some ideas for you. In the meantime, though ...

Right off the bat, let me deliver the cold, hard reality slap here ... You can do some gearing changes, transmission swaps etc, etc.... but in my opinion, the 216 just doesn't have enough power/torque/whatever to do freeway speeds. If you want to comfortably achieve/maintain freeway speeds, start thinking about an engine swap.

There will be folks who will tell you about add-on overdrives, t-5 trannies, etc, etc, etc all day long. But at the end of that day, you will still have an engine insufficient for the task. The venerable 216 can huff and puff but it simply can not blow that house down. Show me someone who sez it can and I'll show you someone who is constantly shifting and messing with an overdrive.

Been there, done that (even started this web site ...) tried to live the 216 dream .... twice! Which is why my truck has a 261 in it now.



Just sayin'


John

Help the guys out a little bit as well with a little more information.

What is your plans for this truck. Daily Driver or weekend warrior? Your tag says Phoenix AZ is your plan hwy around town for a few miles or are are your going to Interstate 10 this thing for hours to Vegas and want to get it up to 80 comfortably.
trying to keep it stock or ok with resto mod? etc

Now if your looking for getting that thing up to over 70 and staying there a while. I am with John that is not a stock build and definitely not a 216. Putting that foot to the floor and hitting the on ramp to I-10 will definitely be some be wanting for more power and better gearing.

When I got my 56 it had a 307 v8 bored over but a 350 3 speed tranny with the stock 4.10 rear end. It would get it out of the gate (first 500 feet) but trying to top it out it was screaming the RPMs and sucking gas with the 3 speed and low gear rear end.
changing out to the LS and a much better trans and rear end. it runs comfortably down the interstate and around 285 here in Atlanta where if its not gridlock it humming at 80 and doing less than 65 your creating a big hazard. Your already getting folks looking at you and taking pictures with the phone and not looking at the road at any speed

What John says above is gospel his tried and tested findings with multiple trucks.
But once we know your truck plans the guys her can give you all kinds of options.

Ditto!
Running my truck to Winchester a little while back, my “think I can 216” on the Pa. Turnpike was a little over confident. We made it to Winchester, but,……….on a flat bed trailer I replaced that engine with a 235cu in. Now I can confidently run 65 mph with a 410 rear. I do have a T5 to install, hopefully soon. That will also assist in lower highway RPM’s.

I think the term "freeway speed" may mean different things to different people.

I also live in Atlanta and drive my truck several times a week on the interstate. My stock 216 with 3spd cruises comfortably on the interstate at 60mph. Of course, that's right lane only territory. It's fast enough not to be dangerous to me or others but I'm under no illusions that I'll be cruising at 70.

The truck performs just fine at 60 mph and I have no desire to make any modifications to drive any faster than that.

About the best thing you can do for your truck to increase "high speed" driving is to install the largest diameter wheels and tires that will fit like 225/85 R16.

Only drive downhill?

You could change out your rear end to a different ratio.

The issue is not making it go faster but stoping it. If you get in a wreck at high speeds, there won’t be much left of your truck ….. or yourself…. To worry about. Love them or hate them, the modern safety systems put in cars are there for a reason.


Mike

With enough time and money that 216 can become a 258 cubic inch engine with pressure-lubricated connecting rods and a much higher top speed capability than it has now and still look "original" from the outside. However, it requires the services of a mad scientist machinist- - - -and there are very few of us left on the green side of the grass these days. If you can find a rear axle with a 3.55:1 gear ratio for a 1950-53 Chevrolet car with a Powerglide automatic transmission, it can be modified to fit the transmission on your 38 truck, and keep the original-appearing torque tube drive system. Bring money- - - -lots of it!
Jerry

Freeway speed? 80 MPH in MT for top legal speed? I'd first beef up the brakes but I still wouldn't ride in it.

Excellent points, Mike, Jerry and Wally!!!

I've changed the engine on my 38 to a GMC 270 with the matching 3 speed from 1955. I have a 3.90 rear axle. The truck will run north of 70.
I have added disc brakes and Bendix drums so it will stop.
I have 235/85/16 radial tires.
I don't like how it drives over about 55. I mostly cruise at 50.

My 50 still has its original 216. I swapped an S10 T5 in place of the 3 speed, and a 3.90 Task Force truck rear in place of the 4.11 and torque tube. It cruises 70 at a happy 2500 rpm. First gear is a little short (usualy shifting before I've cleared the intersection at a 4 way stop) but otherwise it's a great driving experience.

Do you know which T5 variant you installed? There are a few different gearing options.

I had the same issue with "first gear is a little short" with my T-5 with 4.64 rear gears. At that time I had 28" tires. I swapped out for 30.5" radial tires and that dialed everything in. First gear is now very usable for a reasonable distance before shifting into second.

What is it that you don't like about it over 50?

It's a 1 ton, so the springs are very stiff, unless it's got a load on it I also am not in a hurry when I'm behind the wheel of this 86 year old truck.
I stick to the right lane and let them go around me on the interstate.

It's an S10 box, Muncie bolt pattern, electronic speedometer that has had the mechanical speedometer tail housing swapped on. I don't remember what tag number it is- I will pop the floor panel off and look one of these days, and write it down in my truck notebook this time. I have it in my head that it's 0.76 overdrive. I'm pretty sure I found that number on one of the T5 info sites, and the math works out on the Spicer gear ratio calculator site with a known RPM (I have a tach), speed (GPS on phone), and tire size (to two decimal places from the product page on the Discount Tire website). However, I have seen folks say S10s only came in 0.72 and 0.86 overdrive. The math just doesn't work with 0.72 or 0.86.

There was a .76 fifth but it isn't as common, some people don't know about it and some may even say you're wrong. But you aren't. It was used in S10 trucks with a V6 in 84 & 85 and the gear chain began with a 4.03 first. As I recall, 3 id numbers had that 5th gear ratio. Let me know if you need them...I have a list somewhere here.

Back to the idea of driving a 1938 pickup at freeway speed, others have mentioned this but a friend of mine is dead and has been for over 60 years because he thought he was smarter than GM engineers. Please understand you own a truck for which the suspension and steering was designed 85+ years ago. This is not a bad design but never in any way did GM consider anyone would be driving at 70 or 70+ mph for extended periods of time. They realized somebody might get the truck up to 70 but they did not expect it to be anything but an infrequent occurrence. I should add my first car was a 1936 Ford. It only had 30,000 miles on it when I got it. At any speed over 60 it would wander, veer and shimmy so much you needed to carry extra underwear with you. Like your 1938 truck, you could only make a couple of adjustments to that front end and new parts only did so much. The deficiencies of handling were built in to it. It also had mechanical brakes which were just a bit better than dragging your feet to stop.

The 1938 Chevy truck he put a V8 and different transmission and rear end into would easily drive at freeway speed but it couldn't steer safely, couldn't stop safely and here is the really important point: not one thing inside that cab or about that cab was designed with the idea of protecting the occupant in a high speed crash. Not the steering column, the steering wheel, the glass panels in the 3 gauges, the bracing, the swing-out windshield apparatus, the way the doors attach and lock, the way the seat mounts...nothing contemplated a high speed crash. In his crash everything flew apart instantly and either became a weapon or left parts of him exposed for severe injury.

They thought my friend was probably going 70 to 73 when he lost control. Measurements suggested that. It was on a 2 lane flat and very straight section. At that time of day the sun was at his back. The truck rolled over so violently it looked like somebody had pushed it out of an airplane and onto the side of a rocky mountain. They said parts of him and the truck were scattered 30 yards. The ambulance driver told me he figured it took less than 5 seconds from the time he lost control until it stopped rolling. At 70 you're covering over 100 feet per second, by the way.

Years ago...it is gone now...there was an internal memo on the GM Heritage Pages that advised dealers to instruct people the AD pickups (which were designed years after 1938) had been engineered for a safe and prudent highway speed of 55mph. My honest suggestion: if you want a truck you can drive at freeway speed, go buy something built after about 1963. Stay safe...you have one life and it is better if you hang around a long time.

DIDITO DITTO and MORE WAYS TO SPELL DITTTTTOOO on the steering.

When we were all new drive train and stock straight axle with 1.5 caster max and old steering parts. High speed was a pucker. One guy cutting you off and I feared to snatch the wheel. It helped a bunch getting all new kingpins, tie rod ends, drag link. even after upgrading to power steering it was still wandering. Now its up to a much higher caster and much stiffer arms and life is much better. but you can resto mod that 1938 up to something that looks 38 but drives more like late 70s and beyond.


And I always say

"It is still your truck, your drive and your life" Build it, drive it and live it the way you want. Just take into what all the guys here say form you own opinion (let us know your plans so we wont bug you so much) and start your builds. We will be glad to assist in helping in the directions you choose.

Find a stretch of road with no other traffic, and drive whatever speed you want. That way when you kill yourself, you won't take any innocent bystanders with you. That soccer mom with a minivan full of rugrats doesn't deserve to become the victim of your lack of judgement, and the kids certainly don't need to be put in that kind of danger.
Jerry

Jon, that's funny that you mentioned a 1936 Ford. When I was in high school I wanted to buy a 1936 Ford but my dad told me no. He said it has skinny tires and mechanical brakes. You'll kill yourself. Look for something newer.

So I found a 1942 Packard. My dad rolled his eyes and said,"when I said find something newer, I meant something like a 65 Mustang."

Well, Father knows best.

Ever since then I've owned nothing but antique cars and trucks. I'm used to driving them and unlike most people, I'm not used to driving modern vehicles. I am very well aware of all of my vehicles capabilities and limitations and I never drive them beyond what they were designed to do.

In fact, I have virtually no desire to "upgrade" or"improve" on the original design. I drive Old Roy on the freeway at 55 or 60 and never make any attempts to go any faster. I've made it up to the high 60s going downhill before..

If you can get your 1938 truck to drive comfortably between 50 and 60, that is all the faster that you would want to drive, anyway.

You're preaching to the Choir Otto!

I could tell you more about the 1936 Ford but not here...suffice to say it required so much complete concentration/effort to drive that you couldn't fall asleep doing it.

Otto, my 54 is set up to run at modern speeds with safety in mind. But I still drive at modest speeds. It is more enjoyable that way.

I have a 216 in my 1939 Chevy JD stake truck. It originally had 411 rear end gears. I had 353 ring and pinion gears made for it. Top speed with the 411 gears was 40-50 mph with the engine screaming. With the new gears it'll cruise 50-60 mph. The 216 was used from the 30's to the 50's. They were used in thousands of vehicles. They did the job back then and are still capable of doing it today. Know and respect its limitations. I use flashing red magnetic lights on the back when I drive it on the expressways. By using expressways it gives other drivers a lane to pass you. I've had semi-truck drivers and big motor home rigs drop in behind me and keep people off my rear end. As long as this 216 is still willing to motivate on down the road, it'll be the heartbeat of my truck.

Rick G.

I got my '65 Chevrolet C60 up to 88mph once. The flux capacitor wasn't charged however, so the anticipated time jump never happened :-D At least I don't think it did.. but I don't know, things are pretty nuts nowadays, bigger picture. Kidding, sort of.. but anyway.. I had new tires at the time and it did drive pretty nice and straight, I never felt like I was going to have a problem keeping it in line. Got it out of my system, safely :-)

I had a 1947 GMC stubby bus that I took on the freeway once. Once. It was fine up to about 50, then there was a wicked shimmy and that was just the beginning! Actually had some RPM left, but the rest of the rig just really wanted to go 48mph tops. So I backed off and took it slow til the next exit.

The differences between that old crashbox shifted AD, versus even the '65s that Dad and I both had, were stark. Either C60 will do a comfortable 68mph and stop competently from that speed. I say comfortable in terms of the chassis, steering, yes I've even had to swerve to miss something and even had a pretty sudden flat tire, tho I think I was a bit under 60 when I got the flat. Pulled to the left pretty hard but it was very manageable and I got off the road quickly and safely. Even though the kingpin bushings are the same from 1947 onward, something obviously changed. Wider frame? More caster angle? Better leverage of steering gear to linkage? I don't know, but even the 1960 debut frame just drives a whole lot better at somewhat modern speeds versus its predecessors.

I sure don't plan on making a habit of going over 80, even with the new gears in the rear end where 4800RPM computes to 98mph and I know that big Cadillac will do it especially with new, safe radial tires. But 65-70 will be great versus the 54mph at the same RPM in front of original gears. 3200RPM at 65 will make the 500 Cad very happy versus 3850RPM at that speed.

I'm greatly looking forward to that.

Coming back from Tennesee in June we cruised at 75 mph or you got run over. Not fun at night and in the rain.

Ouch, I hope you had electric wipers at least!

I’ve just installed a 3:55 gear set in my 46 1/2 ton. It has a 235 in it. I still have to replace the okie bushing but I’ll let you know how it works when I’m done. I am also wanting a bit higher highway speed.

Just for reference, my 1-ton came from the factory with a 216. By the time I got it, that had been replaced with a low pressure 235. That truck was originally geared for 3300RPM @60 MPH. The horsepower peak was also at 3300 RPM. I don't know it it would pull 60 MPH with the 216 but it would with the 235.

It now has a 261, whose stock rating was 150 HP @ 4000 RPM. I suppose the marketing department leaned on engineering to come up with that number because both engines are rated for peak torque at 2,000 RPM. I've re-geared mine with a 4.57:1 axle so at 60 I'm turning 2500 RPM in overdrive (17%). Crower cam has a peak torque at about 2800. I'll turn it 3600 to make the next gear but I don't run it that fast for long. What I've noticed it that the oil temperature starts to creep up at over about 2700. The engine is working hard all this time at about 10" vacuum on the flats and pulling a 3700 lb. camper.

A stock 235 has a torque peak at 2,000 RPM. Specific fuel consumption (gal/hp/hr) goes up pretty fast above the torque peak. So if you're running 3,000 RPM @55MPH down the highway, gas mileage won't be very good compared to say 2200 RPM @40MPH. I gained almost 20% in mileage with just a cam change that raised the torque peak.