Im Davo i got some trouble whit my Roolback Tow truck 1992 ford f 600 6.6 new holland whit a At545 allison they Run around 62 to 65 mp

[Davo]

1992 ford f600 6.6 new holland whit a At545 allison they Run around 62 to 65 mp i need run 70 mph but.. Whit the engine on calm for safe monney on diesel

 

[Will L.]

Not great on Fords, but have some experience, including having wrenched on rollbacks. But I really don’t understand what you are asking.

Are you saying your top speed is currently at 65 mph but you want to run at 70mph?

If so-
If 65 top speed with an unloaded rollback tow truck, does it have a much lower top speed when loaded? Not that I promote driving that fast with a car on back, but knowing if you are running out of rpm, gear, or power is important to know.

 

[Davo]

Engine rpm go to 2.5 to 3.0 on the speed. I just whant go more fast to 70mph. On turnpike

 

[red]

Different gears for the rear axle will change the top speed, but will take longer to get up to speed.

 

[Will L.]

Really need to clean up the communication here. Be VERY EXACT AND VERY DETAILED.
If you are running an AT 545 at 3,000 rpm, it is not going to last. They are designed for top cruise rpm of 2,400 rpm.

You are trying to turn an army tank into a heavy haul race car. You are already exceeding the design specifications now.

The at545 is also only built for approximately 450 ft lbs torque. To gear up the drive axle to handle that speed and have the power to get up to speed when you have a heavy vehicle on the rollback, you meed more torque than the transmission can handle.

With current gearing if you are doing 65 mph at 3,000 rpm, you need 8% more rpm to go 70mph or 3240 rpm. That is something like 135% of it’s design spec if I am counting right.
If you can raise the governor on the engine, that will get you there. Maybe blow the engine before the input bearing on the transmission?

10% taller tires?

 

[Davo]

Really need to clean up the communication here. Be VERY EXACT AND VERY DETAILED.
If you are running an AT 545 at 3,000 rpm, it is not going to last. They are designed for top cruise rpm of 2,400 rpm.

You are trying to turn an army tank into a heavy haul race car. You are already exceeding the design specifications now.

The at545 is also only built for approximately 450 ft lbs torque. To gear up the drive axle to handle that speed and have the power to get up to speed when you have a heavy vehicle on the rollback, you meed more torque than the transmission can handle.

With current gearing if you are doing 65 mph at 3,000 rpm, you need 8% more rpm to go 70mph or 3240 rpm. That is something like 135% of it’s design spec if I am counting right.
If you can raise the governor on the engine, that will get you there. Maybe blow the engine before the input bearing on the transmission?

10% taller tires?

Tnks

 

[MrMarty51]

Hi Davo.
I know not one thingk about Fords, just saying welcome to thetruckstop.
Thaz all.