Max Road Speed

[Peter Lahmann]

I have looked and found discussion about governors and getting 60 out of your 715. My truck is a 1967 and doesn't appear to me to have a governor, but it's top speed is 45 MPH. On the dash it has a painted warning of Max. speed 45 MPH. And they mean it. So what is causing the speed limitation on this truck? thank you. PL

[MarknessMonster]

The first thing to check is the free spin on the wheels. Raise each wheel off the ground and check the resistance. If the brakes have not been adjusted, this would add a little to a lot of resistance. A review of the manuals will show that an easy adjustment is made through a small slot in the lower inside area of the drums. There is also an e-brake adjustment in another section. Just these two items may hinder the top speed performance.

[MarknessMonster]

I should add that, while in my possession, the stock truck has never been driven at speeds exceeding 40 mph. I'm sure the government boys had it moving faster, but I don't have any reason to drive a 40 years old military truck at excessive speeds.

[kwai]

Properly tuned the trucks will do 55-60 easily. My truck on it's way to Pa now cruises nicely at highway speed. Just noisy. The main factor limiting top speed is gearing with transfer case heat buildup a close second.

[brute4c]

If the truck does not have a governor, there is no built in limiter anywhere that restricts top speed from the factory.

It could be as simple as an ignition that needs to be tuned up well or drag in the wheel/bearing/hub area...dragging brakes...or as complicated as a bit of drag at all 4 corners and a motor out of time that needs an ignition and carb tuneup along with other items.

I guess one thing to look at up front is...

When you press the gas pedal, can you insure that the linkage on the carb is fully opening? If not, that would limit you real quick.

[rboltz]

Good point on the linkage as I discovered some time ago. Unknown to me, my carb was only opening 3/4 of the way due to slack and other hoses obstructing free movement. Have not driven it on the road since repairs so will get to see the difference. 45 was top speed with 50 down hill! Warm weather will also help as all the stiff lube I had when it was 20 degrees did not help.

[pistolnut]

Good point on the linkage as I discovered some time ago. Unknown to me, my carb was only opening 3/4 of the way due to slack and other hoses obstructing free movement. Have not driven it on the road since repairs so will get to see the difference. 45 was top speed with 50 down hill! Warm weather will also help as all the stiff lube I had when it was 20 degrees did not help.

These engines run great when they are waaay out of tune as well. You can have the timing way off or the carb way out of adjustment or jetting and it will apparently run fine. That may be what is going on that's holding you back. Check those things as best you can to make sure as you won't just "know" like on many other vehicles.

[brute4c]

The ignition is probably the one thing that affects top speed when its off by a little...let alone when its off by alot....

[agengr]

When I first got my truck, I got it up to 53. After I put on the XLs, the best I could do was 44 (indicated on the stock speedo). After adjusting the timing with Barrman, I was able to get to 65 mph indicated on a handheld GPS (indicated as 58 on the speedo). Note, I was just trying to see what it could do and once I hit 65, I backed off immediately and now keep it between 50 and 55 when driving.

[Peter Lahmann]

Thanks you guys for the tips. I have been through the brakes and bearings and I know these are not race horses.

but I have always wondered why some people tell me that they can do 55 or 60 with their trucks. I too drive this truck with a usual speed of 40 to 45.

The carb and linkage issues seem to be a reasonable place to take a look at this issue next.