The Stovebolt Site Forums The Parking Lot Big Bolts Top speed

So my 1940 1.5 ton with a 216 isn’t exactly road worthy. All six tires are about 30-40 years old and cracked badly. It also doesn’t have a tachometer and the speedometer doesn’t work. I do have access to some gravel backroads and I downloaded a speedometer app today and took it for a spin. It seems to max out rpm very quickly in 1-3, but in 4th I can get it up to 50 MPH on the iPhone app and it isn’t really redlining at that point. I couldn’t go faster because I didn’t feel safe bug is seems to do 50 with ease and if I had more straight road I think it could’ve easily gone faster.

Wish I had a working tach and speedometer so I could calculate the gear ratio! Maybe I’ll just have to break down and remove the rear diff cover and start counting teeth!

Cleaner to just jack up one wheel and count revs. Whatever it is, it will be slow. What do you want to do with the truck?

Ed

Just some trips to Home Depot, tractor supply here and there. Not a lot of miles but a lot of smiles. And having a 1.5 ton would be a blessing on the farm, I could actually load
Up a ton of bricks or concrete bags, or whatever and not be overloaded.

The main issue is that between my farm (horseshoe bend Idaho) and home
Depot (eagle Idaho) is a 7% grade mountain.
It’s literally 5 miles up 4 miles down.... and I see lots of trucks overheated on the side of the road every day in the summer, mostly F250 and F350 with way too large a travel trailer.

Leave it the way it is...it sounds perfect to me! You may be slow going up the mountain, but you'll be glad to have those lower gears when going down. The factory had the gears and brakes dialed in...messing with one will have an impact on the other.

Mike B

Only issues with counting this way is that I can’t see the driveshaft, due to torque tube.

I had a 46 2-ton that I used for my business. Top speed on the interstate I was able to accomplish was about 65. It didn't like it and was a little uncomfortable. 60 was alright. 58 was good. 55 was great. I would routinely put 10,000 pounds on the back and run across town for deliveries. Largest load was 12,500. Mostly stock. refreshed 235 engine. Updated electrical system. Disc brakes on the front with a dual circuit master. Stock exhaust manifold with 2 1/4" exhaust pipe.

Keep it how it is. Get some good tires and tubes on it. 7.5 in the front. Maybe 8.25 in the rear, but 7.5 might be a better option with the 216 to give you a little bit more torque for those heavier loads.

If you really want to know, put in in high gear, take the plugs out, have a friend turn while you count, or to eliminate any work, roll it down a gentle hill, mark one fan blade, count wheel and fan revs.

Ed

For torque tube type driveshafts we use an old hand held tach/dwell meter and a variable strobe light. Run the engine rpm up to 2000rpm and measure the rpm of the jacked up rear wheel. Engine rpm divided by wheel rpm equals rear end ratio. With an open rear end you multiply by two or on a limited slip you jack up both wheels and read direct. Example: engine rpm 2000, wheel rpm 300, rear end ratio is 6.66.

Well I cleaned enough crud off the axle with a wire brush to find the numbers 37 and 6, rings and pinion tooth counts which comes out to 6.16

Anyone successfully added a 5 speed to a big bolt?

Unless the 5-speed is an OD transmission, the final gear is still the same as your 4-speed...1:1 or direct drive.

Mike B

Most 5 speeds are overdrives.

In these old rigs I'd not make that assumption, most I've seen in farm trucks of this era are direct drive in 5th.

I added a 'brownie' to my 1.5 ton GMC firetruck with 302 engine. 6.6 diff. ratio, made a very useful high gear. 5 speed direct trans.

Many 5 speed OD trans' are just converted direct trans' which they take 3rd. gear to make OD. That leaves a big gap without a 2 speed rear, so with a load, get stuck in too low gear because of big gap.

Ed

Most car 5 speeds are overdrives. Most 5 speed Clark, Fuller, Spicer, Eaton, etc. truck transmissions were not overdrive.

NP- 540 series, some Clarks, IHC(Warner gear) were some trans' that came in direct and OD versions that have a wide ratio gap to accommodate OD.

Ed

I put a Ranger overdrive in my 58. Goes between the bellhousing and SM420. I like the drop in RPM, I should have put bearings in it and the trans before I just dropped them in though! I may do that later this winter.

What size tires are you running? I'm running 7.50 20s on my 46 COE and 45 MPH is tops 8.25s or 9.0 20s you would gain 5 or maybe 8 MPH. I'm happy with the 7.50s because I know I will be able to stop easier with all the original running gear!

I am running 9r-22.5 all the way around.

That would make a lot more speed. How much over 7.50 x 20s ?

The 9.00-22.5 is only one size bigger than your 7.50-20...it will have the same diameter as a 8.25-20.

The 8.25-20 and the 9.00-22.5 are about 2" taller at about 39".

Mike B