AWD Speed 3 Project - Halfmilespeed3

Last update for the weekend: This is the mock up test fit using the CX7 subframe with the MS3 trailing arm, toe, arm, camber arm, and lower control arm.

- IMG_3838: We removed the complete "moving" components from my MS3 subframe and bolted them directly into the CX7 subframe. Everything lined up great and was the same spacing so no new spacers were needed for the OEM control arm and the CorkSport Toe and Camber arms.

- IMG_3839, 3840, 3841, 3842: Completed the MS3 component install without issue. Was even able to reinstall my previous spring setup and ride height appears to be in the exact same spot (can see further down).




- IMG_3843 & 3844: I forgot to capture an image of the CX7 about the trialing arm. We fought to get the leading pivot mount for the CX7 trailing arm to line up with the chassis. I don't think this was an alignment issue as much as it was jsut the stiff OEM rubber bushings and OEM spring fighting us. Anyways, the MS3 with without a spring installed lined up perfect and was easy to install. With everything bolted in, camber, toe and position look great.

 

Ok, one more post...I guess I had too many images in that last one.

- IMG_3845, 3846, & 3848: At this point I was ready to see it on the ground. With 255/50r16 on 16x8+38 wheel/tire setup installed, we set the car down and were pleasantly surprised. Fitment is on point, ride height appears unchanged, camber and toe look great (well within adjustable range). Oh...and it looks tuff AF.




- IMG_3847: here you can see the spare tire wheel tub removed and the location and access to the rear diff.



Next Steps:
- With the track width reduce to MS3 spec, the CX7 axles are a no-go. I am going to install new CX7 wheel bearing assemblies into the MS3 trailing arm assembly then test fit MS6 axle to see how those lengths work out. They are very close in track width. MS3 = 60" and MS6 = 60.6"
- The MS3 trailing arm design does not have a provision for the ABS/wheel speed sensor so I will have to fab up a bracket. I would like to mount the trigger wheel on the inboard side of the CV axle and mount the sensors off the diff...we will see.
- The CX7 diff is open from the factory but the MS6 has an LSD. I've learned they they are identical other wise. However, the clutch pack for the differential is different, the CX7 has an extra mounting bracket (and looks beefier to me but IDK for sure). I have a lead on the MS6 rear diff, so I am doing to steal the gear section to get the LSD and keep my clutch pack section.

Other updates:
- Dog Box gearset is coming from Freektune this week
- Front Diff LSD from Damond arrived
- time to get the speed 6 trans and t-case prepped.

 

Loving the updates and the very well documented steps of this build. This could be huge for the high hp guys in the future. Maybe even some CS AWD future components like S1 for Hondas.

 

I'm not going to lie...the thought has been bouncing around in my head but looking at what has been needed so far and what I expect in the future...there isn't alot that is truly one-off.
- RMM for Speed 6 trans in MS3 subframe
- Could do diff mounts for the CX7 (technically not required though)
- AWD Controller (but this is more about splicing an OEM unit into the car)
- Driveshafts and Axleshafts (I will be inquiring with DSS for those)
- Rear dampers since they need to be shorter to clear the axleshaft (Speed 3 spring setups appear to work fine)

With that said...people do love a turn-key one-stop shop option so who knows. Would most likely have to be a group buy with deposit so people are committed. AND said person would still need to source some OEM components on their own (Trans, T-Case, CX7 Subframe and Diff at a minimum)

 

Quick Update on my Rear Suspension Plans:
- I completed the assembly design for the inboard rocker arm & pushrod actuated setup.
- I am working out how much bracing I want to add to support the main tube and how I incorporate the parachute mount to anchor directly to the cage vs just the rear crashbar mounting.

 

Haven't been doing to much through the holidays, but trying to get back on the wagon here:
So I pulled the wheel bearing out of the trailing arm to test fit the CX7 wheel bearing and see how the MS6 rear axle fits...

Its doesn't on both parts.

1) The MS6 axle is jsut a bit too long so the rear will require custom axles. Not surprised but disappointed either way as its not much different.
2) The CX7 wheel bearing is NOT a direct bolt in part. The bore diameter in the trailing arm is slightly too small (74.35mm vs 78.05mm for the CX7 bearing) and the bolt pattern is different aswell as the bolts used for the CX7 are one size larger.

So the plan is to machine the MS3 trailing arm bore larger and create the new bolt pattern needed.

 

Hey Barret, when you go to order the custom axles give me a buzz. Currently doing the same build so maybe we can get a discount. I was gonna go the other way to use the cx7 parts with modifications but I like your method better. Shoot me an email when you do and hopefully we can get a group deal thanks!! bekimcukovic@gmail.com

 

No progress on the car last weekend, but parts are arriving! SendCutSend is pretty cool for this smaller one-off projects.
Steel mounting brackets arrived for the rocker arm rear suspension.

Everything fits togethor as planned and looks great. The coped bracket and bends on the big triangle even line up on the 1.75" tube as intended! Super happy the CAD model and final product are so close.

The billet rockers arms will be arriving late January and I have all the hardware now. Once I have all the pieces we can start fab in the car.

 

1 of 2 progress updates:
The billet rocker arms arrived! They look amazing. I've pressed bearings into one of them to do a bench test assembly. Everything fit togethor as expected but the shoulder bolts are a tad too long. Not a big deal though.
The attached images are "half" of the suspension system.

 

2 of 2 progress update:
Images 4261, 4260, 4263: Here is an external comparison of the CX7 and MS6 rear differential. There are two major systems in the rear differential. The Gear housing and the Clutch housing. They bolt to each other in the middle and share the same gear oil.
From what I can tell, the gear housing is the same but the clutch housings are different. The CX7 has mounting brackets on both side of the clutch housing vs the single mount on the passenger side for the MS6. To me this seems much stronger and better balances the forces on the mounts.

Images 4257 & 4256: This is the MS6 gear housing with the rear cover removed. You can see the LSD (which I'm not sure what style it is right now).

Image 4264: This is the gear housing (right) and clutch housing (left) split apart. Its really nice that these can pull apart so easy. There is a splined shaft that they interface via and then the bolts...Thats it.

So the reason for this was to swap the MS6 gearing housing and LSD to the CX7 clutch housing so I retain my dual front diff mounts and get the LSD.

 

Is there any difference in pinion flange thickness? The CX7 looks like it could be slightly larger however it could just be the pictures.

 

Same flange thickness 0.227+/-0.005

 

Progress Updates...1 of 3 of them!
Firstly, I got my rear trailing arms back from the machine shop. Look pretty good and fit great with the CX7 bearing hubs.

They welded the original holes then post machined the new holes for the CX7 bearing hub.

On the back side you see that the "cutout" for the steel stamping fits the original and the new CX7 bearing hub bolt pattern inside the cutout. This makes me thing the stamping is a more universal part but the steel plate welded to the stamping that has the bolt pattern is unique to use different brakes and hub for the mazda 3. Seems silly but I bet it saved Mazda money.

Lastly, the machine shop pocket machined the back side so the hardware has a flat consistent surface to clamp against.

 

Progress Update...2 of 3
With the rear arms done, I could reinstall the arms and bearings to get my rear axle lengths.
In doing this I had to make sure I was using proper surfaces to base my lengths from.
Differential Side:
Measuring off the face of the seal that is more of a face vs the flared cone part of the seal that you can see. I'll be sending this image to DSS with my order.

Suspension Side:
Measuring off the large inner face of the bearing. Again I will be sending this image to DSS.

I wanted to also verify that CX7 and MS6 interchange so I measured the OEM shafts for each and installed the CX7 bearing hub onto the MS6 axles.

MS6:


CX7:


I would say they are the same and when installed they feel/act the same. So this is good news as I know DSS has all the data for the MS6 fitment.

 

Progress Update...3 of 3

I did some CAD modeling aswell.

Made an edit to my CX7 Differential Mount Fronts: Working on a 2-piece design so that the parts are simpler and can flip to work on both sides. Will be 3d printing and checking this week.


Also designed a crashbar with integrated parachute mount and jack point that will poke through the diffuser slightly.

The design gets the parachute mount as high as possible to help reduce the chance of the chute picking up the rear of the car when deployed. I've seen this happen with car and high speed...its a very unsettling and scary situation for the car and driver.

 

Lastly!
I will be rebuilding the speed6 trans this coming week and getting ready to install it into the car.

I attempted to rebuild the t-case I sourced but found it had questionable gears. Probably fine for a moderate street car but for a high power racecar its won't cut it.
If anyone has a spare MS6 t-case to sell let me know!