NA6CE 1992 Form vs Function Build and History

[— kung fu jesus —]

Altering some of the configuration for my needs. Nothing too drastic, but just to my preferences.

I am changing out the differential. I currently have a 4.1 Torsen and have found a 4.3 Torsen locally from a '01 I hope to install this weekend. Additionally, I am planning to switch out my M2HDHCDD for a hardtop version for more cabin space fore and aft. I also will secure another set of wheels for the track that will be more beneficial in terms of steering geometry and performance. I think my investment for these alterations will be minimal as I can recoup a majority of the expense selling off the components I remove. I should have some pictures soon.

[MiataQuest]

Hey KFJ,
What goals are you looking for from the change from 4.10 to the 4.3 gear ratio? It could be a negative at the track and autocross but better to get you there.

[— kung fu jesus —]

I disagree. The lower gearing will help in acceleration and helping me keep the RPMs up on the 1.6, where it's modest power and torque reside. This is better at the track for corner exit and the elevations at the tracks I frequent. The ratio difference is roughly 4.8%, which is significant gains in this car and worth the work.

The 4.1 results is a lower cruising RPM than the 4.3. Perhaps you may have your logic reversed?

Picked up my 4.3 T2 this morning. It is out of an '02.

Pounding out the mounts. I will swap over my PU mounts when the 4.1 is removed.











Cleaning up the assembly:

Before


After

[MiataQuest]

You are right, somehow I was thinking in reverse. I need more coffee in the morning.

[— kung fu jesus —]

No worries! Ran out to sell the remnants of my BMW projects this morning, brought the wrong box of parts. I blame lack of coffee.

[— kung fu jesus —]

So, I invited some buddies over to help today. Mainly to laugh at me while I dropped stuff on my face.

Disassembly went well. Had the exhaust, calipers, hub/axle assemblies out in about an hour working solo. No big deal. They helped me lower the diff and then we couldn't get the PU bushings out of the carrier to transfer into the new one.

It had occurred to me that it might be an issue before, but, oh well. We stopped there, and I ordered new PU bushes that will arrive on Tuesday (Xenu bless Amazon Prime).

The weather was good, not so hot and humid, so that was a positive. We ended up getting tacos and watching some of the qualifier futbol matches at the taqueria down the street.

I did verify the unit I pulled was a Type 1 Torsen by shining a bright light into the oil filler hole while I spun the pinion by hand. I watched the spider gear cage turn and saw the gears, which was my confirmation. I left the PU bushes in the carrier, cleaned it all up, took pics and a short video, posted it up for sale. I suspect I will have it done before next weekend.

[— kung fu jesus —]

Made a little progress, the bushes arrived. I had some adulting to do first, the dryer needed to be fixed and the parts for it arrived too. Mrs. KFJ likes her laundry dry and springtime fresh. The performance value of a 4.3 Torsen does not compare.

Anyways, after I tangoed with our Korean appliance, Gangnam style, I prepped the 4.3 to be installed.



The Energy Suspension bushings come complete with grease (the little yellow containers), sleeves, and two-piece bushings for each side. Also shown are new oil seals for diff. These prevent oil from getting past the axles.



Flip the diff over like so. The new bushes go in from this side. I strongly suggest wearing nitrile gloves. The supplied grease is nasty, nasty thick-ass stuff. It will stick to anything it touches, so have your tools ready and laid out, and change the gloves if you need to do other stuff after handling the grease.





Smear some grease on the carrier, only on the surface bushing will touch. Don't be shy! Lube it like a you're prepping for a hot night out in Bangkok (I know you know what I'm talking about).



Next, guide the bushing in the hole (hurr! hurr!) and push it in with the heel of your palm. It will likely go in about 2/3 the way, that's ok.



Apply more grease to the center thru hole on the bushing and insert the sleeve as far as you can by hand.



I've used about this much grease so far.







Use mallet or dead blow hammer (a piece of wood and a hammer if you have neither), and pound the sleeve into the bushing flush. Continue pounding until the bushing is fully seated in the hole. The underside, you can see how far the sleeve comes through, that's what you want.

Wipe off the excess grease and transfer it to the other bushing hole for the next bushing.









The result should be as above. The last pic shows why the sleeve protrudes, as it will center and capture the other half of the bushing set.









On an NA, you need to cut the rubber off the OE diff bushing cap (I don't know the technical term, but it's the metal piece that captures the ends of the carrier and is held on by 2 12mm nuts and the single 17mm nut). I had already done this back in '11 when I installed these in my 4.1 Torsen diff. IIRC, I used a hacksaw.





Next, new oil seals! Skipping this is pretty silly. The seals were $8/ea at NAPA and are made by SKF (nicccce! SKF is a trusted brand in BMW circles).

I use a long, flat screwdriver and feel for the edge of the seal against the diff and pry them out. They can take a *little* leverage and force if they are old. They might also shoot off when they release, you have been warned.

Wipe the hole with a clean cloth.









I used a light coating of grease on the outside of the seals, square them up in the holes, and use a dead blow and a block of wood to land them flush. Be careful not to punch them all the way through the hole, that would suck. once they are flush, I like to apply more grease to the inside of the seal and the shroud. This helps axles go in smooth and lubes the contact area the axles touch on the seal.





That is how you prep a diff for installation. Don't be deferential to your differential, spend a few more dollars and replace those seals!

***forgot to add: save the remaining grease. You will want to apply some to the face of the bushings before installing the diff in the car.***

[Pyr0monk3y]

Any thoughts on some quick tig welding to reinforce the diff carrier? You're making good power and spending a lot of time on track, probably not a bad idea for reliability. On the other hand, Mazda did put that relief there for a reason.

[— kung fu jesus —]

Not really a big issue if the PPF, mounts, and fasteners are correct. I've seen endurance Miatas run stock carriers without issues. These tend to break when stuff becomes misaligned or tweaked (rear end minor collisions often affect the diff alignment more than people realize). At that point, I might consider an RX7 carrier.

[HarryB]

Nice welds, albeit I would be skeptical when welding cast parts.

[— kung fu jesus —]

Most definitely.

[Pyr0monk3y]

Above are not my welds, I found that on google.

Just a thought. I guess if you are not smashing curbs or bump drafting, it's not under an abnormal load.

[— kung fu jesus —]

The surprising failure a lot of people don't consider is the PPF. I saw a few that cracked from repetitive stress of racing and developed some fairly large cracks.

[— kung fu jesus —]

Wrapped up the installation today between client phone calls. Did it solo, easy peasy.









Just using a floor jack and a piece of 4x4 lumber, I guided the carrier home.



Zipped in the nuts, released the jack.





Wiggled in the PPF, aligned the spacer, put the captive nuts on top of the PPF, drove in the long bolts through the diff. Aligned the front of the PPF on the transmission. Used the jack to raise the tail, and secured the PPF to the tranny.







Slid the axles in the diff, attached the uprights to the control arms and pounded the axles in with a mallet.

I rehung the exhaust, then filled the diff before reinstalling the rear subframe brace. The driveshaft went in after that.

I rehung the rear calipers, pads, and wheels. Torqued it all down. After giving everything the once-over, I lowered the car off the jackstands.





Awwww yeah! 4.3 Torsen! Bling blong, mothertruckers! Let's test it out!



Pouring rain. *sad trombone*

At least it worked well enough to back it out and in the garage to get the wife's car in.

[NCGreasemonkey]

Nice! (Oh here it comes)

But the captive nuts on the PPF. If they are removed aren't you supposed to replace the PPF?

If have done them both ways. But doesn't Mazda say to replace?

Just for clarification as I know you have torn them apart more than myself.

And I have the bolt set to pull down the spacer. A few of them.

Peace Guru of all that is Miata!