NB power steering swap into NA.

[JamieH]

I've seen and read just about all the info I can find on doing this swap before doing it myself. But none of the threads and info I found were all that exact. So, I figured there should be a write-up discussing what's required and the differences in parts. This will include installing a power steering cooler line for '96-'97 cars as it was omitted during those 2 years.

Being that this is a complete plug and play type of deal, if you can remove all the original NA parts, you can just as (nearly) easily installed the NB parts. It is very obvious where everything goes.

I will point out the differences and why each part is needed. Pics will be for showing differences and to identify parts. I intend to add in OEM part numbers later.

Install tips are at the end.

Parts needed:

• NB front subframe - Mazda part# NC72-34-800A

• NB steering rack - Mazda part# NC10-32-110R-0K

• NB rack to column U-joint - Mazda part# NC10-32-850

• NB rack bolts

• NB or NA outer tie rods (I recommend 93LE/R-package)

• NB pump - Mazda part# NC10-32-600

• NB pump tensioner/bracket - Mazda part# NC11-32-609A

• NB rack the pressure line hardline/cooler (this usually stays attached to the rack when sold used) - Mazda part# NC10-32-460

• NB pressure line - Mazda part# NC10-32-490J or N066-32-490 or N115-32-490

• NB pressure line subframe bracket & line to line brace

• NA return line (reservoir to pump) - Mazda part# NA02-32-684B

• NA cooler hard line ('90-'95)

• NA cooler line hoses ('90-'95) - Mazda part# NA02-32-682

• NA reservoir ('90-'95)

The cooler line/hoses will already be installed from the factory on '90-'95 cars. The OBD-II cars didn't have the cooler hard line, but the mounting points are there. Yet, a minor change was done to the reservoir on the '96-'97 cars (more on that later). But depending on the mileage of your car, you should probably replace all the soft hoses. Maybe irregardless of the mileage as NAs are all 20+ years old now.

The break down of why each part is required to do the swap.

The NB subframe is needed as the mounting points of the NA and NB steering racks are different in 3 ways.

1. Distance between the mounting points.
2. Left side NB mount is incorporated into the rack itself.
3. NB rack bolts are larger

The bonus of using the NB subframe is slightly better suspension geometry. If I have understood what I have read and found elsewhere, better chamber gain under compression.

Bare NA subframe installed ('97 shown):



Bare NB subframe installed (same '97 as above):



The NB rack is self explanatory, it's the reason to do the swap. Even though all sources I have found say the ratios are the same 15:1 for the NA and NB power racks, the lock to lock is different, 2.8 NA and 2.6 NB. Which means the NB rack has a slightly larger turning radius or the ratio info is incorrect or some other explanation I have yet to find. But, according to Keith of FM, the NB rack has less assist for a given pressure/volume.

The NB rack to column U-joint is needed because the NB rack has a larger input shaft than the NA rack. But, the column shaft size itself is the same between NAs and NBs.

NA & NB racks side by side (NA top, NB bottom):



NB rack to column U-joint installed in '97 NA:



The NB rack bolts are larger than the NA bolts, in two ways.

1. Larger diameter.
2. Left side bolts are also longer.

NA rack bolts:



NB rack bolts:



The NB or NA outer tie rods can be used. They thread on the same and will fit the steering knuckle the same. But I recommend the 93LE/R-package tie rods if you happen to be lowered a bit. They'll help with bumpsteer a bit.

The NB pump uses a banjo like fitting rather than the NA's flare fitting for the pressure line. No banjo/crush washers are used. Instead, two O-rings seal the fitting.

The NB pump tensioner/bracket uses a different bracket extension to brace/direct the pressure line towards the front of the car.The bracket itself has a stud as part of the assembly, whereas the NA bracket has a welded nut. The bracket extensions are also at different angles.

The NB pressure line, as explained above, uses a banjo style fitting at the pump. But, it also uses a double flare fitting at the rack. The NA pressure line uses a single flare fitting at the rack. There is also a small bracket that secures the pressure line to the subframe as well as a small, two-piece line to line brace.

NB pump, bracket, and pressure line assembled:



NA pressure line fitting on pump:



NB pressure line fitting on pump:



NA tensioner/bracket assembled:



NB tensioner/bracket assembled:



NA & NB brackets side by side (NA left, NB right):



From below:



From above (NB left, NA right):



Engine to tensioner bracket, NA on top of NB:



Bolt holes are the same distance from one another.

Engine to tensioner bracket, NA in front of NB:



But the NB bracket is thicker than the NA bracket.

Pressure line to pump brace/bracket:



NB tensioner/bracket fully assembled:



NA pressure line:



NA pressure line pump side fitting:



NA pressure line rack side fitting:



NB subframe pressure line bracket:





NB rack/pressure line, line to line brace/bracket:



NB rack/pressure line, line to line brace/bracket installed:





NB pressure line fitting installed on pump:



Note that NO crush/banjo washers are used.

NB pump, tensioner/bracket, pressureline installed in '97 NA:



The NA return line is used as the pump and reservoir are in the exact same places, so the NA line is the correct length.

NA return line: