Top Speed for 1949 B1B

[Dodgebawl]

I have a 49 B1B with a 4-speed transmission and a 4:11 rear end.  On level ground it tops out around 45 to 50 mph.  For those of you in the know,  is this max speed about right?  The truck is restored and well tuned.  Thanks for your input.

[Los_Control]

The 4 speed was a option for these 1/2 tons, seems the 3 speed was common. I wonder if they both have same final drive?

Also I wonder what tire height you have, seems a 29" or 30" tire .... I bet you could get 55 mph from it. In a short burst.

 

Your goal here is to keep the rpm under 3600 rpm. There is much discussion about using 3:73 or 3:55 as the better gear ratio.

You can swap in a older jeep cherokee or ford explorer to get this ... the mods will be to grind off the existing spring perches and weld on new ones.

Now you can cruise 70 mph while running 2k-2500 rpm.

You get modern brakes, you get a newer style E-brake setup, I really do not see this mod as a terrible way to go.

 

Stock you get to drive 50 mph and sucky brakes, but it is only original once ... what are you after?

 

Here, the two lane to the next town the speed limit is 75, everyone drives 80.

Does not matter if I do a rear end upgrade or not, still going to have to pull over to the shoulder and let others pass.

 

Mark me as un-decided in Texas.

[Los_Control]

Just to add to it, back then we had terrible roads, was dangerous to drive over 50 mph anyway.

The cars did have 3:73 gears and they could, just does not mean they should.

And we did rebuild our roads and add free ways etc ... since then. But at the time, 50 mph was plenty fast for a farm truck.

 

Today driving the same truck at 70 mph, will be a challenge if not everything is in tippy top shape.

King pins, tie rods, steering gear box, brakes ... it just was not designed to drive at that speed.

So upgrading the rear end, leads to upgrading the front brakes leads to ....

It is a rabbit hole you can climb in and not find your way out again .... although pretty basic.

Why you need to decide what exactly you want, before you start modifying.

[Merle Coggins]

What size tires are on the rear? Measure from the center of the rear axle to the ground to find the loaded tire radius, then double it for effective diameter. Then use that with a gear ratio/speed calculator such as this one on Tod Fitch’s web site. https://www.ply33.com/Misc/speed

 

It doesn’t matter if it’s a 3 speed or 4 speed. Top gear is always direct drive, 1:1, unless it’s a more modern OD 4 speed like an A833. 

[Dodgebawl]

The tires are LT215/85R16.  I have not measured the diameter but Tire Rack shows the diameter to be 30.7 inches.  All suspension and drive components have either been replaced or rebuilt including front wheel disc brakes.  Not having driven any other truck of this vintage, I was just curious as to what is the normal top speed that  these wonderful old trucks can reach. I never put it on the highway.  I drive it around 35-40 mph on the streets and asphalt rural roads.

[59bisquik]

I swapped to 3.73's from a 54 Plymouth and run 225/60/17's at 27.5" tall. I drive it to Vegas as back yearly. I can hold 70mph at 3200 rpms all day. A quick sprint up to 3400 would get me to 75 for passing. This was with my 218 flathead.

[1949 Wraith]

This gear ratio calculator shows your tire at 30.4" diameter. With rear end 4.11 gears,direct drive  and those tires at  2500 RPM the calculation comes out to 55 mph.

 

You can check out speed at other rpms.

 

http://www.tremec.com/calculadora.php

[jmooner3]

 

230 flattie in 1949 B1B mated to 3speed tranny. 

 

Yep the stock set up is about 45 top end for me too.  I don’t need to pass everyone on the road but it’d be nice to be able to keep up. I just plan ahead to be on time, stay on the secondary roads, and enjoy the ride!

cheers,

jay

[Merle Coggins]

"Specified" diameter is often times considerably different than actual rolling diameter. To be most accurate you'll need to measure your loaded radius, from the center of the axle to the ground.

Even if I plug in 29.7", allowing for a 1/2" squat of the tire, I get 65 MPH at 3000 RPM. If your engine is in good condition this isn't an unreasonable RPM. I run mine down the highway at 3000-3500 RPM all the time without any issues.  It'll sound louder than you are used to on any modern vehicle, but it won't harm your engine. Keep in mind your fixed fan makes most of the noise you hear. No clutch fan, or electric fan, to reduce fan noise as in your daily driver. 

[ggdad1951]

also note your speedo might be off as well.  FEF reads a bit high compared to GPS/trailing cars....

 

[kencombs]

Easy way to check speedometer for those with a smart phone.  Install one of several speedometer apps available.  Very accurate.

[Jeff Balazs]

As you already know the 4.11 rear axle is the culprit. You would need to do something about that to speed things up.

 

When I decided to put one of these trucks together as a daily driver there were a lot of naysayers. Especially in light of the traffic conditions here in Southern California. And I had a lot of concerns about what the ride quality would be like and how safe it would be in these conditions. I ended up putting a 3.55 Grand Cherokee rear axle with discs in and adding the RH disc kit on the front. Other than that it is relatively stock. I have used it on a daily basis for the past 4 years and it is perfectly functional as a commuter. Definitely not the fastest thing on the road but I manage to keep up.

 

In my opinion these trucks in their stock form are happiest between 40 and 55mph. I have had mine up to around 75 but the aerodynamics and wind noise make a slower cruising speed much more pleasant.

 

Hth, Jeff

[Dodgebawl]

Thanks to all for your helpful comments.  The top speed I am getting appears correct for the 4:11 gearing. So, it is what is is  and that is OK.  When I restored the truck I kept it original except for front disc brakes, seat belts and turn signals.