Power steering MEGA thread

OK, the more I research this, the more confused I get! I decided that I don't want to choose a gear and/or pump without having a better understanding of the variables. So, let's get more in-depth than "I'm running a ZJ box w/ 35's and it turns great".

As I understand it, there are two main Saginaw boxes for us to consider. The 800 model (like the stock one) and the 808 model (like are found in Durangos and J20s). The model number refers to the "case", but also determines the piston/bore size. Either case can have a variety of different line thread sizes, ratios, speeds (lock to lock), and mounting bolt patterns. These options seem to vary by vehicle year/make/model and are not easily identified by any casting numbers on the box.

So... let's determine the stock XJ specs (correct me if I'm wrong!)...
Saginaw 800
3 Mounting Bolts
(Variable??) Ratio of 14.1:1 or higher?
3 3/8 - 3 1/2 turns lock-to-lock
2.75" Piston Bore?
Line Thread Size: M18x1.5 (return); M16x1.5 (pressure)
Type of Hose Ports:Tube O-Ring
Input Shaft Diameter: 3/4"
Output Shaft Diameter: 1.25"

Now... let's talk about the room for improvement...

A larger piston bore will result in more power, but will also require more fluid. From what I've read, the 808 box has a 3.175" bore, which seems to work just fine with the stock XJ power steering pump, but if a hydro assist ram is added and the stock XJ power steering pump is used, the system will be slow to react. Since a larger bore would no longer be needed with a hydro assist ram, it is usually recommended that the 800 box be used for hydro assist.

Now, I haven't been able to confirm whether the XJ box is a variable or fixed ratio. From what I understand, a variable ratio makes the wheel easier to turn when the steering gets closer to full lock, correct? And this could be identified by the worm gear and it's consistency from end to end? Can anybody confirm whether the XJ box is or isn't a variable ratio? Which would be preferred (for street use, rock crawling, pre-running, etc)?

So... the ratio represents the ease and speed of which the jeep would turn when the driver turns the steering wheel? A 12:1 ratio would be faster than a 16:1 ratio, but the 16:1 ratio would have more torque? And torque is going to effect road feel as well? Again, what would be more desirable (for street use, rock crawling, pre-running, etc)?

Is the ratio (above) also a direct correlation to the number of turns lock-to-lock? Some people seem to have the desire to decrease the number of turns lock-to-lock, but searching on another forum, there was a lot of concern about doing this on a vehicle with a higher-than-normal center of gravity (and especially with a short wheelbase). Can we hear some arguments on that?


OK, that's probably a good start. I'll get into replacement options and PS pumps later (likely in addition to a bunch more questions).


Billy

I can confirm that the Saginaw 800, as used in RENIX, is a constant-ratio gearbox (having had a few apart and inspected the worm shaft.) I don't know if that changed later, so I can't confirm past 1990 (the latest Saginaw 800-series box I'd had apart was from a 1990.)

Variable ratios can be done in two ways - in the manner you describe (effort gets easier as you get closer to lock) and "speed sensitive" (I'm not sure how it works, but I know I don't like it. I prefer predictability in my steering, thank you very nice.)

Generally speaking, the ratio of a steering box works in much the same manner as gearing ratios. Take the effort being put into the box (distance * force) and apply as follows:

Output Distance = Input Distance/ratio
Output Force = Input Force * ratio

So, if you put a force of 10 pounds over 1 foot into a 12:1 box, you get an output distance of one inch (12"/12 = 1") and an output force of 120# (10#*12=120#.) It's just that, instead of conventional spur gearing, you're dealing with recirculating balls on a worm shaft (which is simply another version of a geartrain.)

Oh - and subscribed. This could get interesting...

As a further point to my last reply, I run the 800 series and hydro assist, and a massaged Renix pump can't keep up at idle with quick direction changes. At 1100 rpm and up, it will.

My 800 series is out of an SJ, it got me a fourth mounting bolt.

5-90 said:

I can confirm that the Saginaw 800, as used in RENIX, is a constant-ratio gearbox (having had a few apart and inspected the worm shaft.) I don't know if that changed later, so I can't confirm past 1990 (the latest Saginaw 800-series box I'd had apart was from a 1990.)

Variable ratios can be done in two ways - in the manner you describe (effort gets easier as you get closer to lock) and "speed sensitive" (I'm not sure how it works, but I know I don't like it. I prefer predictability in my steering, thank you very nice.)

Generally speaking, the ratio of a steering box works in much the same manner as gearing ratios. Take the effort being put into the box (distance * force) and apply as follows:

Output Distance = Input Distance/ratio
Output Force = Input Force * ratio

So, if you put a force of 10 pounds over 1 foot into a 12:1 box, you get an output distance of one inch (12"/12 = 1") and an output force of 120# (10#*12=120#.) It's just that, instead of conventional spur gearing, you're dealing with recirculating balls on a worm shaft (which is simply another version of a geartrain.)

Oh - and subscribed. This could get interesting...

Click to expand...

I can open up my '95 box if nobody else knows for sure regarding the later model boxes.

Jon, When I was searching, I found a few threads where you were talking about the possibility of using an F-body box on your wife's daily driver because of a faster ratio... is this desirable because her Jeep is fairly stock and mostly used on the street? Or would you prefer/recommend the faster ratio for a trail rig too? Any idea what the ratio is on those f-bodies (roughly)?

Thanks!
Billy

JeepFreak21 said:

OK, the more I research this, the more confused I get! I decided that I don't want to choose a gear and/or pump without having a better understanding of the variables. So, let's get more in-depth than "I'm running a ZJ box w/ 35's and it turns great".

As I understand it, there are two main Saginaw boxes for us to consider. The 800 model (like the stock one) and the 808 model (like are found in Durangos and J20s). The model number refers to the "case", but also determines the piston/bore size. Either case can have a variety of different line thread sizes, ratios, speeds (lock to lock), and mounting bolt patterns. These options seem to vary by vehicle year/make/model and are not easily identified by any casting numbers on the box.

So... let's determine the stock XJ specs (correct me if I'm wrong!)...
Saginaw 800
3 Mounting Bolts
(Variable??) Ratio of 14.1:1 or higher?
3 3/8 - 3 1/2 turns lock-to-lock
2.75" Piston Bore?
Line Thread Size: M18x1.5 (return); M16x1.5 (pressure)
Type of Hose Ports:Tube O-Ring
Input Shaft Diameter: 3/4"
Output Shaft Diameter: 1.25"

Now... let's talk about the room for improvement...

A larger piston bore will result in more power, but will also require more fluid. From what I've read, the 808 box has a 3.175" bore, which seems to work just fine with the stock XJ power steering pump, but if a hydro assist ram is added and the stock XJ power steering pump is used, the system will be slow to react. Since a larger bore would no longer be needed with a hydro assist ram, it is usually recommended that the 800 box be used for hydro assist.

Now, I haven't been able to confirm whether the XJ box is a variable or fixed ratio. From what I understand, a variable ratio makes the wheel easier to turn when the steering gets closer to full lock, correct? And this could be identified by the worm gear and it's consistency from end to end? Can anybody confirm whether the XJ box is or isn't a variable ratio? Which would be preferred (for street use, rock crawling, pre-running, etc)?

So... the ratio represents the ease and speed of which the jeep would turn when the driver turns the steering wheel? A 12:1 ratio would be faster than a 16:1 ratio, but the 16:1 ratio would have more torque? And torque is going to effect road feel as well? Again, what would be more desirable (for street use, rock crawling, pre-running, etc)?

Is the ratio (above) also a direct correlation to the number of turns lock-to-lock? Some people seem to have the desire to decrease the number of turns lock-to-lock, but searching on another forum, there was a lot of concern about doing this on a vehicle with a higher-than-normal center of gravity (and especially with a short wheelbase). Can we hear some arguments on that?


OK, that's probably a good start. I'll get into replacement options and PS pumps later (likely in addition to a bunch more questions).

Billy

Click to expand...

So if I put on a bigger steering wheel the jeep will turn quicker? I like my smaller than stock grant.

xj9140 said:

So if I put on a bigger steering wheel the jeep will turn quicker? I like my smaller than stock grant.

Click to expand...

No... actually it will make it feel slower. Did I say something misleading?
Billy

I had a 2000 F body and seem to remeber that it hada 2 1/2 turns lock to lock. Another interesting F body option is the late model p/s coolers they came with from the factory that ran in line with the upper radiator hose. Not sure if there would be room to run one of these on an XJ but might be cool.

JeepFreak21 said:

I can open up my '95 box if nobody else knows for sure regarding the later model boxes.

Jon, When I was searching, I found a few threads where you were talking about the possibility of using an F-body box on your wife's daily driver because of a faster ratio... is this desirable because her Jeep is fairly stock and mostly used on the street? Or would you prefer/recommend the faster ratio for a trail rig too? Any idea what the ratio is on those f-bodies (roughly)?

Thanks!
Billy

Click to expand...

I'm highly inclined to think that the F-body box was quicker (something like 10:1 or 12:1?) and her rig saw mainly street use, so it seemed a viable idea.

Granted, the damned City got involved, I'll have to find another rig to build for her.

But, I wanted to put a fairly low-ratio box on hers (as I said, her driving is mainly street) and a high-ratio box on mine (since I do all the off-roading, towing, hauling, &c. - I'd benefit more from a high-ratio box and the additional leverage.)

@xj9140 - A larger wheel will make the effective ratio (overall) higher, so it will turn slower. However, you'll further reduce the effort involved - why do you think the steering wheels on buses are almost two feet across? Likewise tractors (except you also find Brody knobs on tractors. Pity you can't use them on cars anymore - I wonder what yo-yo screwed up enough to give us that asinine law?)

5-90 said:

Generally speaking, the ratio of a steering box works in much the same manner as gearing ratios. Take the effort being put into the box (distance * force) and apply as follows:

Output Distance = Input Distance/ratio
Output Force = Input Force * ratio

So, if you put a force of 10 pounds over 1 foot into a 12:1 box, you get an output distance of one inch (12"/12 = 1") and an output force of 120# (10#*12=120#.) It's just that, instead of conventional spur gearing, you're dealing with recirculating balls on a worm shaft (which is simply another version of a geartrain.)

Click to expand...

Alrighty, I had time to read and comprehend that. Thanks for the explaination.

So, clearly the ratio does directly relate to the number of turns from lock to lock, since all the boxes are going to have the same distance between the stops, right? Which would be determined by the length of the worm gear?

Does this ratio also effect "road feel"? I saw that mentioned in a search as well. Less required input force, so less "feedback"?

Thanks again,
Billy

To help clarify the variable ratio thing...think "speed sensative" like 5-90 said.

With variable ratio (usuall) a small ratio is used when wheel is near center so that small steering wheel movements result with small changes in tire angle. This is so that when on the highway (high speed), small inputs to the steering wheel result with small changes in direction...prevents inadvertent over-correction.

Now, when turning the wheel closer to lock, the ratio changes to magnify the movement of tire angle with respect to steering wheel rotation. This is so that you can reduce the number of turns (lock-to-lock), and easier to make large direction changes when driving slow (parking, turning corners in town, etc.)

Hope that helps.

Flyfisher said:

To help clarify the variable ratio thing...think "speed sensative" like 5-90 said.

With variable ratio (usuall) a small ratio is used when wheel is near center so that small steering wheel movements result with small changes in tire angle. This is so that when on the highway (high speed), small inputs to the steering wheel result with small changes in direction...prevents inadvertent over-correction.

Now, when turning the wheel closer to lock, the ratio changes to magnify the movement of tire angle with respect to steering wheel rotation. This is so that you can reduce the number of turns (lock-to-lock), and easier to make large direction changes when driving slow (parking, turning corners in town, etc.)

Hope that helps.

Click to expand...

That does help! Thank you. The problem I see with that though, is that the system does not know if you're going fast or not, so driving slowly, in a near straight line would require large changes of the steering wheel to affect the direction of travel, right?
Billy

Not to get off the Predictive steering at current topic on the MEGA thread, but has any one experimented on a filter system on the return line? I have seen some systems use a Transmission filter (a style similar to an oil filter) but our system does not use ATF which those systems do use.

Magus2727 said:

Not to get off the Predictive steering at current topic on the MEGA thread, but has any one experimented on a filter system on the return line? I have seen some systems use a Transmission filter (a style similar to an oil filter) but our system does not use ATF which those systems do use.

Click to expand...

The fluid is similar to ATF (just not as detergent, mainly,) and uses the same viscosity of base oil. So, that's no trouble.

Putting the filter in the return line makes sense - not only is it much lower pressure, but it keeps any trash from the steering gear (bits of seal and what-have-you) out of the pump.

I tend to replace PSF with ATF after a refit anyhow - haven't had any ill effects as a result (been doing it for a number of years,) and the fluid seems to hold up better. The higher detergents and slightly higher percentage of anti-foam additives seem to help out a lot as well.

I use a cooler (OEM ZJ trans cooler), and an inline power steering filter (OEM Ford, but available at any NAPA if you ask for a universal PS or trans inline filter) in the return line.

Still on the box I put in 4 years ago, with no leaks, and the hydro-assist cylinder stays warm to the touch.

Would the filter have a replace life of every 5 years or so? (the recommended PSF flush/change is every 5 to 7 years right?)

will standard transmission rubber line work on the return line? Or is there special PS rubber line that should be used? And can standard brass barb fittings work on the rubber lines (talking on the return line)?

I use the push-lock hoses for the return line. Good ones are rated at 250 psi, and use push lock fittings. All available at NAPA.

squidd said:

I had a 2000 F body and seem to remeber that it hada 2 1/2 turns lock to lock. Another interesting F body option is the late model p/s coolers they came with from the factory that ran in line with the upper radiator hose. Not sure if there would be room to run one of these on an XJ but might be cool.

Click to expand...

Does anyone which f-body specifically the "better" box is found in? Is it just in the 1LE's?

A 2000 F-body uses a rack I believe.The 82-92 use a regular steering box. I have a fast ratio box on my camaro.They can be found on any IROC or WS6 trans am as well as Monte carlo SS and others. They can be identified by a Z cast on the top near the mounting bolts. They will most times be installed with a framerail support "wonderbar" under the swaybar brackets.So if the car has the bar it will usually have the fast box.The ratio is 12.7-1 i believe

Milford Cubicle II said:

Does anyone which f-body specifically the "better" box is found in? Is it just in the 1LE's?

Click to expand...

So, is it your opinion that a faster ratio box would be an upgrade? What do you use your rig for? Is your rig lifted? And if so, are you concerned about the sensitivity of the steering at speed with a higher center of gravity?

Let's discuss what variables could be improved upon from the stock setup, the compromises involved with those changes, and then we'll figure out what box is the best fit for us and what application it came in.

If you just want to cut to the chase and find out what F bodies the box came in, just search.

Billy

I would think the faster ratio box would be even harderer on the framerail than the stock box is. F-bodys all got extra bracing to support the faster ratio. I personally didn't care for how fast my stock box turned and swapped it for a yj box. I am pleased with the turning now.