Power steering turn rate.

[BrandonDindorf]

I need member help. I have a 73 351 C with factory power steering. My gear box was leaking so I decided to take it out and send it in to be replaced. At the same time I decided to upgrade to a quick steer 10:1 ratio. Before it was shipped it took a little over 3 steering revolutions to make the arm go from one stop to another. Now that I have it back it still take the same amount. I want to verify I didn't already have a quick steer and what your guys normal turn rate is.

-Brandon

 

[BrandonDindorf]

Any help guys? I was planing on calling them up tomorrow. Any evidence would be helpful.

 

[Don C]

From the Ford 1971 repair manual, the Ford power steering is 17:1 and 4 turns lock to lock. The Saginaw variable ratio box is 3 1/8 turns lock to lock and varies from 16:1 at center to 13:1 at lock, the Saginaw fixed rate box is 17.5:1 and 4 turns lock to lock.

 

[jbojo]

For the 1973:

Variable Ratio

Saginaw

Ratio 16:1 on center to 13:1 at lock

Turns, lock to lock 3-1/8

Constant Ratio

Saginaw

Ratio 17.5:1

Turns, lock to lock 4

Manual Box

Ratio 24:1

Turns, lock to lock 6-1/2

-jbojo

 

[sdstang]

My steering is 3 1/8 turns. How can you tell if it's constant or variable?

What is the difference between them, and can I convert if I would like to?

Thanks for any input!

Jim

 

[Don C]

Based on the number of turns lock to lock you already have the variable ratio box. The fixed ratio boxes all had more turns.

The variable ratio boxes are the most desirable. The ratio is high enough at center, when you're driving straight down the road, so the car isn't twitchy and over responding. When turning, the further you turn, the faster the turn ratio, so you don't have to turn the steering wheel so far when driving around a corner or when parking.

 

[sdstang]

Based on the number of turns lock to lock you already have the variable ratio box. The fixed ratio boxes all had more turns.

The variable ratio boxes are the most desirable. The ratio is high enough at center, when you're driving straight down the road, so the car isn't twitchy and over responding. When turning, the further you turn, the faster the turn ratio, so you don't have to turn the steering wheel so far when driving around a corner or when parking.

Thanks Don!

-Jim

Based on the number of turns lock to lock you already have the variable ratio box. The fixed ratio boxes all had more turns.

The variable ratio boxes are the most desirable. The ratio is high enough at center, when you're driving straight down the road, so the car isn't twitchy and over responding. When turning, the further you turn, the faster the turn ratio, so you don't have to turn the steering wheel so far when driving around a corner or when parking.

Thanks Don!

-Jim

 

[jbojo]

A disadvantage of a fixed-ratio system is that towards the lock positions, more effort is needed by the driver.

This is because the angle of the steering arms reduces their effective length, and that reduces the leverage on the wheels.

To overcome this, many rack-and-pinion systems use variable ratio steering. The ratio is made variable by changing the shape of the teeth on the rack, between the centre and the outer edges of the rack.

Then, as the steering moves away from the straight-ahead position, the ratio, and therefore, the mechanical advantage, increases progressively.

As the pinion turns, and moves on the rack, the gear contact point between the pinion, and the teeth on the rack, changes. This change in tooth contact changes the effective diameter of the pinion.

Then, for the same amount of steering wheel rotation, the rack moves a shorter distance near the ends of the rack than near the centre. Effort needed to turn the wheels stays approximately the same through the whole range of movement

-jbojo

 

[BrandonDindorf]

Great information guys! I appreciate all the community effort here.