Wow awesome start and thanks for sharing.
This will provide great info for those of us who eventually need to pull our rear subframe to replace the bushings, and what to look for when we do.

 

Much appreciated.

I see your eccentric bolt brackets are nice and straight. I had to get mine bent back and reinforce welded. Driftmotion has OEM brand new eccentric bolts and washers. Definitely recommend snagging some before they go extinct.

Not all of them are that nice, I'll have to repair a few. Have also been tempted to opt for tubular suspension components like the battle version products that Driftmotion sells, curious if the eccentric bolts are still used for alignment with those. I'd assume it's a question better suited for Aaron. If so, I will definitely be picking up new eccentric bolts as one was removed as a liquid... was a little stubborn.

 

I see your eccentric bolt brackets are nice and straight. I had to get mine bent back and reinforce welded. Driftmotion has OEM brand new eccentric bolts and washers. Definitely recommend snagging some before they go extinct.

 

Have completed the rear subframe, I coated the inside with Eastwood's Internal Frame Coating as it came with a fancy straw to insert into the drain holes and was very thin as to seep into all of the seams and such. The outside got coated with POR 15 and a topcoat of grey enamel. Letting everything sit for a bit and harden before installing new poly bushings. Also have new eccentric bolts for when the new suspension arms show up.

 

Have received new rear suspension parts, went with Battle Version camber links, toe links, and traction links and all look very nice and beefy compared to the OEM parts. I also purchased some new upper control arms for the rear made by Punch-Out Performance & Machine, and I wish I didn't.

I also Installed new subframe bushings, went with SuperPro bushings but I'm confused on whether or not I am supposed to use the rubber discs that go between the subframe and chassis or not. I have sent SuperPro an email to hopefully get a definitive answer but would greatly appreciate input from you guys.

START RANT

The welds were ass, looked like they paid someone who puts the square toy in the round hole in cheerios per hour, the paint was just some rattle can stuff, and the MOOG joints that they claim are the huge benefit, having a replaceable ball joint that is, are modified versions of the off the shelf part so they have to be ordered from them and likely have a wait time like the control arms themselves.

The welds really just looked like they didn't use any filler rod, which any kind of negligence kind of omits any benefit to having something TIG welded over MIG welded which so many aftermarket manufacturers boast. However, when I removed the paint (which could have easily been done with a can of brake cleaner, but I used paint stripper anyways) it was apparent that they both skimped on adequate filler and that they had big gaps to fill which can only mean that their parts don't fit nicely in their jig. This also means that there is potential for air pockets if the gaps are not filled nicely, which I would frustratingly find out later as these air pockets would send my weld puddle hurdling towards my tungsten like Ron Jeremy's special sauce.

They even forgot to weld the insert that blocks off the end of the tube that I didn't find out until after painting as it was ground flush with the end of the tube, I assumed they sanded the welds down but when the paint leaked into the seam it was apparent that I was wrong. I was pretty fed up and in dire need of a beer so there was little consideration into the aesthetics at this point.

The joint itself is much larger than the OEM unit, however the threads look to be more barb shaped than a standard 60-degree thread angle and the smooth end is not much smaller than the major diameter of the thread (which is where the boot is supposed to stretch over to seal, but can't because the threaded boss on the control arm is too long to allow that... so no seal.) gives indication that it is supposed to "thread" into a stamped sheet metal part, which it is as the K772 ball joint is for late 50's to late 80's Chrysler vehicles that have stamped sheet metal control arms. The threads on the control arm are standard 60-degree threads with a typical minor diameter, which means you only get to replace this thing once or twice before you don't have any threads left and are left to weld it in. You also can't just buy the k772 joint at the parts store because PPM has modified the taper to fit out cars, not very well either as the original taper would have been a nice smooth finish which would have been ground with a special machine but rather is a very rough finish done on a lathe, which could have been avoided had they used better tooling for the hardened steel that the shank is made form. (grind > finish pass on lathe, better tolerances and smoother finish promotes greater contact area and smoother force transmission)

It may be minor but they also didn't include dust covers for the heim joints used instead of the rubber bushings that the OEM unit uses, so if it were to get driven in anything but perfect dustless and saltless conditions the nylon bushings withing the heim joints would not last long.

Regardless I chose to repair these to the point I felt comfortable using them, I may end up welding the ball joints in anyways as the threads don't look like they do much besides turn sharp machined edges into mushroomed playdoh. I have chosen to do this because my OEM units needed to be replaced and I didn't want to find a set of used control arms in mediocre shape to get by with. If I end up having to replace the joints in these I may end up just making my own, fabricated to CNC machined as a single part, whether they're offered to the rest of the community or not I can't be certain of. I have sent PPM an email about how ass these control arms are but don't expect much from it as I have "modified" their product and is now my product. LEARN FROM MY MISTAKE, DONT BUY CRAPPY PRODUCTS. These cost me over $600 in 2022 money, but the quality is far less than what I've seen on ebay exhaust kits for early 2000's audi cars.

End Rant

 

Made some progress this last weekend, I installed the subframe, some Battle Version rear lower suspension links, and the OEM upper control arms. the UCA's will be coming back out at some point in the near future to replace the rubber bushings with some new polyurethane ones and to replace the old crusty bolts with some new stuff as well. The hubs went back in the car with new wheel bearings, axle seals, and studs. I also have a set of new parking brake shoes and hardware waiting to be installed when the time arrives.

I finished rebuilding the differential as well which will be installed as soon as I can get my hands on some FIPG. The original unit was a 4.30 ratio stock LSD carrier with the 27 spline input shaft that these came with. This was changed out for 3.58 gears, 29 spline input shaft, and a OS Giken Super Lock LSD unit. I'm tempted to place a temp sensor on the cover to see if extra cooling is necessary, and either install a mocal pump, filter, and cooler or just machine a new diff cover to better resemble that of a euro spec unit.

 

Been a little while since the last update. I haven't made TONS of progress, not tangible anyways.

After dealing with the rear upper control arms I decided to make my own which I am nearly done with - the constraints I had set for them were that they needed to fit the OEM inside bushings or any aftermarket equivalent, and that they had to use an off the shelf ball joint that was actually off the shelf and replaceable. Link to thread specifically about the arms HERE

I also found a suitable engine to put in, along with a transmission. More on this when it's in the car and running

As far as fitting the engine goes, I learned was going to be no quick 5 minute job. While the subframe is designed to surround an engine with a rear sump, the new engine is front sump. And while I would love to take the "easy" road of converting the engine to rear sump, that is in fact, not the easy road. The oil pump is located in the middle of the sump and is shaft driven from the timing set on the back of the engine, which then has a "PTO" of sorts for another shaft to drive the water pump at the front of the engine. The "easiest" way to convert this to anything other than front sump would be to go dry sump and electric water pump, which would net a benefit of ~1.5" of height clearance with the added complexities of the fluid systems.

I opted to change the subframe to accommodate a front sump engine, which requires me to relocate the steering rack to the other side of the front axle centerline as well. While I could achieve this by using a RHD A70 steering rack and flipping it upside down for use in my LHD chassis to ensure the wheels steer left when I turn the steering wheel left, they are fairly hard to find. The next suitable replacement was a steering rack from a Nissan S13 - same steering shaft diameter and spline, larger diameter housing, larger diameter threads for the inner tie rods, overall length is less than that of the MA70 - which is perfect as I can then make spacers that bring it out to the correct width and utilize the OEM A70 tie rods.

The next task within this endeavor is to make new front knuckles to relocate the mounting ear for the tie rod to the rear side of the axle centerline. Instead of modifying the existing knuckles, I will just make new ones - most likely a solid machined part. I figured while I was there I might as well add provisions for better brakes, as the stock A70 front brakes make use of a 6x mm single piston front caliper and a 305 mm rotor. I opted for 370z Nismo brakes, which use 4 44mm piston calipers and a 355 mm rotor; which is some 25mm larger than the 350z / LS400 brake upgrade. They will also be made to accept 370z wheel bearing cartridges, as it will be much cheaper and easier to machine a new knuckle with a flat face and a bolt pattern than one with a stub for the wheel bearing and hub to be assembled upon. Pictures coming soon

 

Quick update, I have been elbow deep in designing suspension parts for this,

Subframe has been designed to accommodate stock suspension mounting points with location adjustability to be able to adjust RC and camber curve, uses the stock alignment hardware, and uses a S13 steering rack.

The track width has been widened to fit the new steering rack and avoid bump steer, keeping the location of the tie rod pivots in the correct location in relation to the suspension pivot points.

knuckles are roughed with stock suspension pivot point locations in relation to the hub center, they have tabs for the 370z nismo calipers and the tie rod mount relocated to the correct location.

I gathered scan data of the oil pan to ensure all of this will fit

I also compared my model's static alignment and Ackerman angle with the alignment hardware in a neutral position to that specified in the A70 TSRM, accounting for the specified tire size and ride height.

I'm working on comparing the travel rate of the stock NA A70 rack to the S13 rack and plan to change the location of the tie rod tab on the knuckle to favor a quicker steering ratio which will also result in more steering angle.

Im also gathering information about how far others lower their car from stock and with what wheel specs as I am going to lower the hub center on the knuckle to lower the ride height without affecting the suspension geometry, which will also raise the RC in relation to the CG. This will also give me some insight as to what will fit in the fender with the widened track width.

I also have to make some new LCA as the tie rod would be passing through the OEM one

Soon everything will be finished in CAD, I may tweak the static camber and caster a little bit but then I will be left with doodling some jigs and making the subframe, LCA, and knuckle.

 

Love the attention you're giving the suspension.

FYI, I provided detailed specs of my setup on FB. Super excited to see what you come up with.

Why 370z rotors and s13 rack?

 

Love the attention you're giving the suspension.

FYI, I provided detailed specs of my setup on FB. Super excited to see what you come up with.

Why 370z rotors and s13 rack?

I really appreciate it, should take some of the guess work out of what is going to fit.

The engine I'm swapping in is front sump, and because of the way that it is, it isn't an easy task to convert it to rear sump. An iteration of it came factory dry sump but even that wasn't going to clear up much room between the stock subframe/rack combo and the hood. So, I decided to swap from the hard to find, expensive to replace OEM A70 front steer rack, to the much more common and cheap rear steer S13 rack. moving it to behind the axle centerline positions the steering rack perfectly between the oil pan and bellhousing. I purchased a few different steering racks trying to find one that would work and the S13 rack is about the right width and has the same input shaft diameter and spline count.

Side note, I've thought about coming up with a solid solution to replace the hard-to-find A70 front steer rack with something more affordable for those looking to replace their old worn-out rack with something readily available and affordable. Every manufacturer that I have come across so far no longer rebuilds A70 racks and used racks are not very cheap.

With having moved the steering rack to the rear of the axle centerline, I had to design new knuckles to move the tie rod ear to the rear to match. I didn't feel like welding the ear on, so instead opted to make an entirely new knuckle. My thought was, If I'm making a completely new knuckle, why not make it suit my every need. So I ditched the press in wheel bearing from the A70 and opted for a bolt in bearing cartridge with the same bolt pattern because it will make it easier to service, and has provisions for a ABS sensor if I choose to use it (my car is non ABS). I wanted bigger brakes for sure, big brake kits for the A70 are a couple grand, with the other solution to use 350z or S500 rotors and calipers, but I had endless possibilities, a clean slate, so I chose 370z Nismo rotors and calipers. Comparison:

-Stock A70: Rotor-302mm; Piston Count - 1 ; Piston Area - 2826 Sq/mm - $CHEAP - Parts readily available
-DM BBK : Rotor-330mm; Piston Count - 6; Piston Area - IDK ; $2130 -parts readily available online
-CEIKA BBK: Rotor-330mm; Piston Count - 6; Pison Area - IDK ; $2400 - Rotors are probably the same as the Willwood kit but calipers are CEIKA proprietary
-350Z(SPORT): Rotor-322mm; Piston Count - 4; Piston Area - 4534 sq/mm - $740 - Parts readily available
-370Z Nismo: Rotor-355mm; Piston Count - 4; Piston Area - 6134 sq/mm - $618 - Parts readily available
-S500: Rotor-330mm ; Piston Count - 4(armored car option); Piston area - 6079 sq/mm - $558 - Parts available online

While they are all great option for their own reasons, the 370Z Nismo seemed like the best bang/buck for off the shelf parts.

 

The suspension mounting points on the subframe and knuckle along with control arm lengths currently match the OEM design, and with the ride height set at 201.5mm and tire size at 225/50r16 (as specified by the A70 TSRM) the RC is at 39mm - without COG data, I'm just comparing the roll center location with the bottom of the car as a comparison with drop knuckles.
So the stock ride height and tire size combo RC to bottom delta is 162.5mm

stock knuckle, lowered 40mm via spring w/ 225/50r16
161.5mm to bottom
4mm to RC
157.5mm delta

40mm drop knuckle w/ 225/50r16 -10mm squish (just a guess)
161.5mm to bottom
31m to RC
130.5mm delta

40mm drop knuckle w/ 255/35/r18 -5mm squish (just a guess at desired tire size and squish, may go with a different size but hoping to be able to get away with 18" wheels with the 370z Nismo brakes)
161.5mm to bottom
25mm to RC
136.5mm delta

making the roll center closer to the center of gravity would reduce body roll and place more of the lateral force form cornering on the tire rather than the shock, it is my assumption (since I don't have track data) that this would be beneficial over lowering with lowering springs.


With the suspension geometry close to figured out, next is figuring out what I want to do with the difference in rack ratios between the A70 rack and the S13 rack.

Here is some data
A70 -travel = 146mm ; turns = 2.9 ; ratio = 7.15 deg/mm
stock knuckle dimensions
=2.4 degrees steering angle @ 45 degrees wheel turn
=4.8 degrees steering angle @ 90 degrees wheel turn
=max of 28.7 degrees of steering angle @ 1.45 wheel turns

S13 -travel = 138mm ; turns = 3.1 ; ratio = 8.09 deg/mm

So the S13 rack has less travel and a slower ratio
stock knuckle dimensions
=max of 27 degrees of steering angle @1.55 wheel turns

Modified knuckle A - supposed to make S13 rack ratio match the stock knuckle a70 rack combo more closely
=2.5 degrees steering angle @ 45 degrees wheel turn
=5 degrees steering angle @ 90 degrees wheel turn
=28.7 degrees steering angle @ 1.45 turns
=max of 30.8 degrees steering angle @ 1.55 wheel turns

Modified knuckle B - supposed to give the car a more sporty feel, but with the loss of fine control at higher speeds
=3.2 degrees steering angle @ 45 degrees wheel turn
=6.4 degrees steering angle @ 90 degrees wheel turn
=28.7 degrees steering angle @ 1.125 wheel turns
=max 40 degrees steering angle @ 1.55 wheel turns

Not entirely sure what I want to do, but the mount for the tie rod on the knuckle and the steering rack mounts on the subframe will all be bolt on parts so it could be changed later. Ackermann angle for the modified knuckles match OEM geometry. All of the RC data was gathered from vsusp

 

I vote keep it close to A70 (knuckle A). Simple because I never had the thought in parking lot "I wish steering angle was better".

The other part of me wishes I could convince you to swap in S2000 rack to pave the way for others. Works well and be great to dump power steering pump. But part availability/price is meh sadly.

 

I vote keep it close to A70 (knuckle A). Simple because I never had the thought in parking lot "I wish steering angle was better".

The other part of me wishes I could convince you to swap in S2000 rack to pave the way for others. Works well and be great to dump power steering pump. But part availability/price is meh sadly.

Yes, it seems that they aren't very cheap. As far as ditching the power steering pump, many have great results using the MR2 or VOLVO electric pump, or using a prius electric assist motor which goes on the steering shaft under the dash.

As far as replacing the steering rack with something more readily available, the deeper I have looked into a solution for other owners the more I find that supports keeping the OEM rack.

SupraStore has a rebuild kit for both non-pps and pps
$582.14 p/n: oemtomk3sust

SupraStore has a rebuilt A70 steering rack however its currently listed as being on backorder
$495 p/n: 4425014110

Advantage Steering has a rebuilt 86-88 rack
$945 w/ $345 core charge & 3 year warranty p/n: 91086

Pheonix rack and axle has both a 86-88 and 88-93 rebuilt racks, does not specify PPS or not. They also have them for the MK.2 and MK.4
86-88 $349.95 P/N: 642 Link
88-93 $199.95 P/N: 728 Link

 

Short update -

I came across a listing for remanufactured A70 steering racks from Toyota, not that it matters for me but im sure others will be delighted to know that. It seems they have also started to sell all of the individual components to rebuild the racks as well. I believe this is the p/n for PFL and non PPS = 44250-14110-84 Link

As for my A70, I finished doodling the subframe and have begun building it. I still have a few hours of work left to design the new LCA's and the knuckles, mostly for ease of MFGR and some final checks. I completed the passenger sub assembly and plan to test fit it prior to finishing the subframe. Unsure what color to paint it, likely something boring as you won't be able to see it anyways - something that will keep it rust free for quite some time.

 

It's been a while. but what's the engine you've decided on?

 

Not quite ready to spill the beans, not until I have the swap done anyways.

Don't need to be hearing all of the "why didn't you do this or that" or "this makes more power for less $ or headache"

I started with a LY6 but it didn't seem right and I got bored with the swap before I could even buy a transmission.

 

Some more progress - I have managed to massage the trans tunnel enough to fit the new transmission with it lined up to the rear differential. I had just enough space under the car (I don't have a lift at the moment) to get a decent 3d scan of the area and get a transmission mount doodled up. As much as I wanted to use a readily available OEM bushing, I ended up using a universal application polyurethane bushing from energy suspension. Parts should be here soon enough, with that finished I can do the engine mounts next.

I have also put some thought into how to adapt the 370z nismo brakes to the rear. The Nissan rotors are shorter, which should give me a little more space to make an adapter. The rotors are much bigger, 350mm vs 291mm so I will either have to do away with the dust guard or make a new one. And the parking brake shoes are smaller, by ~20mm, and have slightly different hardware. I have a OEM 370z nismo upright on the way to reverse engineer and see how im going to get the nissan parking brake to work on the toyota upright.

After some tinkering I have also found that I will have to modify the steering shaft to allow enough room for the headers. The current solution is to use add a set of joints to allow the shaft to hug the frame rail a little better as well as splitting up the angle between the joints to reduce binding. By doing this, I will need to add a hanger bearing of sorts to the middle shaft to keep it in place.

 

Last update for a little while, have parts piling up and lots to do.

I managed to put the hood back on. Good news, after making a custom front subframe to utilize a steering rack that sits behind the axle centerline to clear the oil pan, and lowering the cross bar and subframe 45mm to allow the engine to sit lower, the hood just barely fits.

I have engine mounts figured out, utilizing some universal application bushings from energy suspension

Front LCA's are doodled up and parts are on the way to clear the tie rods

The rough design for the rear brakes are doodled up. They make use of the 350z nismo 350mm rotors, two piston calipers, and the parking brake shoes. The parking brake linkages are custom, and it requires a hub ring for the rotor but they're not a consumable item so I'm happy with it. I'm still using the stock A70 rear knuckles, wheel bearings, hubs, and parking brake cables as well, which I managed to score a new set on rockauto. This brake setup is complete with a dust guard and everything, I would be willing to make these as a product once I get the little kinks worked out after making the first set.




Next on my list will be to finish some final touches on my front knuckles, and I may doodle up some parts to make use of the 370Z nismo brakes on the stock A70 front knuckles if there is interest.

I will have to do some more massaging to the trans tunnel to fit my shift linkages, and while the engine and trans is back out i'll be working on the steering shaft, and moving a few components under the hood to alternative locations.

I have yet to figure out a driveshaft, the transmission makes use of a CV joint and it would be wise to make the diff match to omit driveline vibrations. interesting thing about u joints is they have to match angles and be "in time" so that the input speed matches the output speed otherwise you will see a mismatch in speed to something comparable to a sine wave. I have yet to decide if I want a 1 piece or 2 piece driveshaft. I have the space for either, the 2 piece is supposed to be smoother as its much easier to balance short shafts and they offer far less variables in terms of balance and concentricity, however it is much more expensive to go this route.