VCCA Home Forums TECHNICAL - GENERAL Trucks and Vans 37 1-1/2 ton speeds

I was curious if anyone could give me an idea of what kind of highway speeds I could expect from my firetruck given all stock running gear and tire sizes...

It's understood there are 2 different rearends for these big trucks and I've not determined which one I have yet.

With the 5.43 axle ratio and 6.50X20 tires the engine will be turning over at 2600 RPM at 40 MPH. So 40 to 45 MPH should be a safe speed. In the cab it will sound as if the engine is going at 4000 RPM.

Good to know.. Wonder if there is anything that could be done to increase this a bit to possibly 55-60. Not that we will be driving this all the time but freeway speed might be nice once in a while.

On a side note, friends have asked how fast it will go and knowing it would be slow our response has always been, "Well, not real fast. So if you are planning to have an emergency of some sort let us know a day in advance so we can plan ahead and make sure we arrive on time! LOL" The fiancee also jokes how we will be installing a scanner so we can be 'first responders,' to which I reply with 'third responders.'

One small thing you can do is increase the tire height, which would give you more miles-down-the-road for the same wheel rotation.

Of course, your speedometer would be registering slower than you would be actually going.

Don't get any speeding tickets!

Cheers, Dean

It will never go 60 MPH. With the largest 7.50 tires 60 MPH would be 3600 RPM and the power peak would have be exceeded.
With the 6.50 tires it would be 3900 RPM at 60 MPH.
Even with the resatrictor plate used on truck engines removed I doubt if there would be enough power to get up to 60 mph on the level.

If you want to put higher gears in your 37 Ton & half truck, read this web page first:
< http://home.znet.com/c1937/RPM.htm> .
Use the largest tire you can fit on the rear wheels. 7.50 X 20”, 8.25, 9.00 X 20.
10.00 X 20 or larger will strain your drive line and give uneasy handling.
There are higher rear end gears available for your Passenger and half ton.
But not the Ton & half.
Newer ton & half trucks are called 3500HD.
The only ratios available from 1933 … 2002 were 5.43 and 6.17. (6.67 in military vehicles.)
(If your 37 Chevy had a Flxible bus body they might have ordered a 4.75 ratio.
Only 164 Chev/Flxibles were produced so you will have a hard search.)
The 1964 and newer rear ends are weaker than the 37 … 62.
The ideal engine speed at 60 MPH is 2000 to 2500 RPM.
Use the chart to see what will get you there.


Advanced Adapters sells an overdrive that mounts between the bell housing and transmission.
http://www.advanceadapters.com/prod...overdrive-27-with-a-4686-retainer-index/
It would move your gear shift lever back near the seat.
Your middle torque tube would have to be shortened.
You may have interference with the brake pedal.
Advanced Adapters, 1645 Commerce Way, Paso Robles, Ca. 93477, (805)238-7000


Ask Gear Vendors if they would insert their overdrive into your middle torque tube.
https://www.gearvendors.com/contact.html
Gear Vendor, 1035 Pioneer Way, El Cajon, Ca. 92020, (800) 999-9555
Modern Under/over with Electronic controls for any vehicle.
< info@gearvendors.com >


An NVG 4500 5 speed OD trans will fit into your 37 clutch housing but the 4 bolts are in a different location.
It comes with a long, short and transfer case tail housing.
A machinist would have to adapt it for torque tube.
The gear shift will be closer to the seat.
If you purchase a used one, be sure that the correct oil was used in it.
If 90Wt oil is used, the transmission is ruined.
Sniffing the gears inside the case is the quickest way to tell.
The NVG 4500 ratios are listed on web page:
< http://home.znet.com/c1937/RPM.htm>

Though the Clark 5th over is a bolt up, it’s not much of an overdrive.
I’ve never see one with a torque tube output.

I have seen a Brownie with torque tube in a 37 Chevy.
They have large spur gears and make a lot of noise.
Be sure to rubber isolate the mounting so your fillings
don’t fall out.





The photo’s that I’ve tried to insert are not coming thru.

Thank you all for the wealth of information!