E36 Undercarriage DIY Part I: Z3 Steering Rack Retrofit

[joon]

Parts needed for this project:
1. Z3 Steering Rack P/N 32131095577 - $980 from Eng Soon
2. Power steering reservoir - P/N 32411097164 - $35 from Eng Soon
3. Used lower steering assembly - $40 from Propel
4. Custom aluminum bushing - $30 from any machine shop
5. Grade 12.9 steel cap bolts M8 x 1.25 - $6 from Yong Seng Screws
6. Indemitsu full synthetic ATF 1L - $25

Time needed: about 4hours.. if you wake up early on Sat morning you'll be done before lunchtime.. if you have a mechanic friend with a hoist it can be done in 2hrs

Abit of background info on this mod.. our standard E36's have rather slow steering and I find it rather tiring to keep twirling the steering in our urban world.. after a little research I found that the Z3 steering rack is a direct bolt-on fit for our cars. The standard way ZF quotes on-centre (straight ahead) ratio is in mm/rev, which is the travel in mm of the rack bar per revolution of the steering wheel. The higher the mm/rev the faster the rack.

M3 3.2 and standard E36 - 45.5 mm/rev - the M3 3.2 rack has restricted lock.
Z3 rack - 53.5 mm/rev - by far the quickest rack you can fit.
E46 compact rack - 50 mm/rev - apparently this also fits the E36

It appears that there was no advantage in using the M3 3.2 rack that I had, it's the same ratio as my stock E36 with 3.2 turns lock-to-lock, only that it has end locks to prevent you from overextending and damaging the rack.. the only solution was to go for the Z3 rack.. installation is DIRECT BOLT-ON.. you can do this at home using simple tools.. use a hammer to whack out the tie-rod ball joints.. the rack itself is held by 2 bolts only.. here you can see the old E36 rack.. note the cast aluminum rack body:


I was soo excited I forgot to take pics of the Z3 rack.. basically it has a galvanised steel body.. here it is installed.. you can clearly see the 2 bolts that hold the rack to the front crossmember



One thing to note.. you'll be using back all your power steering hoses.. and the cooler line bolt is off by 30mm.. I fabricated a small aluminum bracket from a piece of IKEA leftover bracket.. can't remember which furniture it came from LOL..



After you're done.. replace the power steering reservoir (see below).. the reason for this is that the PS fluid filter is built into this reservoir and it can get clogged.. swapping out the steering rack is the best time to do the replacement


While doing this rack.. I was thinking of fixing the wobbly steering.. frankly I was sick of the sloppy steering on my car and decided to change out the entire rack + lower steering assembly..On our RHD E36's.. the steering bushing or "guibo" doesn't last very long, it comes within 1" of the exhaust manifold and the intense heat just roasts the poor rubber guibo.. even if you replace it with a brand new one, the stiffness goes away within 6 months and sloppiness sets in.. I absolutely hate this vagueness in the steering..

Here you can see the lower steering assembly, for RHD E36's it's a 1-piece special-order assembly that costs over $280 new from Eng Soon.. I bought this old used piece from Propel for $40 to experiment with..


I took it apart to see how it was put together.. the assembly consists of 4 pieces (1) a long serrated cast aluminum upper U-joint with a lower flange welded on (2) a stiff rubber guibo (3) a heatshield for the guibo and (4) a short lower U-joint.. the whole thing is held together with 4 steel pins at the guibo which I had to grind off to separate the assembly


This leads me to believe that during a bad collision, the lower assembly is more likely to fracture at the flimsy aluminum serrated upper U-joint body than at the 4 steel pins which secure the guibo.. those serrations are horrible stress risers and tho' they can take torsional loads but if you subject it to a sudden compressive load it would probably collapse

I made a quick Solidworks drawing of the guibo I made.. it shouldn't take more than 10mins on a lathe to machine it out of aluminum round stock


This is what it looks like installed (look at how close the exhaust is to the steering shaft).. I tapped the 6.8mm holes for M8x1.25 threads and used 12.9 grade cap screws with some locktite to secure the bushing to the U-joints.. the steering is much much improved and I'm very happy with it so far..

After this mod ALONE.. the car is incredible.. the steering totally transforms this car into something special.. the Z3 rack is so fast it's only 2.7 turns lock-to-lock and the sloppiness is gone.. the closest car I have driven with this sort of sharpness and response is the Honda S2000.. not bad for a 16-year old piece of german junk..

[Mockngbrd]

DIY king!
great work!

[lennon Tan]

Always exciting reading Joon's write up. Another potential mod in my file !!

[iScoupe]

Originally Posted by lennon Tan

Always exciting reading Joon's write up. Another potential mod in my file !!

ya bro yet to see ur E36 CAB ! when tow to Singapore haha..
ya our E36 DIY king is Joon !

[jin teck]

kudo to Joon, everything DIY. Now we know, if our steering rack got problem, upgrade to a Z3 one.

[marklee]

Good writeup...Always wondered why my steering was so flimsy...now I know

[sszone]

joon power sia!!!! i think U King of DIY mod virus liaozzz....hehe
keep it spreading bro!!!!

[Mockngbrd]

Originally Posted by marklee

Good writeup...Always wondered why my steering was so flimsy...now I know

flimsy steering could be other factors too. (worn ball joints, coupling, etc etc)
a slow rack shud not make ur steering flimsy.

u shud try the bus-rack E30s.... turn n turn n turn... i find the E36 nice enuff for me...

[joon]

Originally Posted by jin teck

kudo to Joon, everything DIY. Now we know, if our steering rack got problem, upgrade to a Z3 one.

when I called up Jason at Eng Soon and gave him the part# for the Z3 rack.. he asked me 'How many pieces do you need?'

Apparently they have 31 Z3 steering racks in stock.. I bought one.. so now balance 30 haha.. the normal E36 steering rack they only have 2 pieces if I remember correctly..

And Louis is right.. if your steering is sloppy, there could be other factors too.. I would replace them all at one shot, this would include (1) front lower control arm bushing, (2) front lower arms, (3) steering rack tie rods, and (4) strut tower bearings (if running stock suspension)

[PsychoBoy]

great work joon. I wished that you had posted this earlier as I had my steering rack replaced about 4 months ago.