Pulled my differential out tonight, took about 2 and a half hrs by myself at a leisurely pace. Not too bad of a job so far. I had a bit of trouble because my downpipe and midpipe are welded together and they sit right in the way of my transmission brace bolts so i couldn't drop the PPF, I could have removed my downpipe and then dropped the PPF, but decided to wrestle with the differential instead. The other differential hopefully will be here tomorrow and I can start inspecting it and swapping everything over.

 

Ok I have a question.

In the FSM on page M39 the last paragraph regarding the backlash states "use adjustment shims of the same thickness for both sides" then I turn the page to M40 and step 12 says "If replacing the adjustment shim on one side with a thinner shim replace the shim on the other side with an equally thicker shim" So i'm not sure if it requires the same size shims or if it might require different sized shims. I'm guessing different sized shims otherwise the ring gear wouldn't move over. Is the steps on page M39 just to get to a starting point with the correct size shims?

 

Yeah the FSM is screwy sometimes. The correct way is the second statement "If replacing the adjustment shim on one side with a thinner shim replace the shim on the other side with an equally thicker shim" The goal is to get the correct backlash but keep the same total amount of spacer thickness.

Dan

 

Alright that's what I thought but wanted to verify first.

I have my old LSD out of the case, it was the small worm gears that were damaged, several teeth were broken and they all look kind of ground down. Everything else seems to be okay.

I also took apart the S4 differential and cleaned everything really well. The friction disks are out of spec, ranging from 1.75 mm to 1.85 mm. New is 2mm and min spec according to the FSM is 1.9mm. I'm going to mention this to the guys on the mx5 forum and see if shimming it will be good enough or if I should just buy new disks.

 

Have you tried Mazda Motorsports for the discs?

 

Isn't that the one that you need a membership for? I'm pretty sure they have the parts but how do I order from them or even see prices? EDIT: anyone have a membership to MMS wanna help me out?

 

If you are experiencing wheel hop that will kill your diff. It isn't the diff's fault so to speak. What you can do is get rid of all of those braces and actually MOUNT the diff in the rear. Mount the tranny in the fron and run without the PPF. This is what some of the LS1 guys do to eliminate the wheel hop and get the FD diff to withstand the torque of the V8, myself included...

I run this diff mount on my car and have ZERO! wheelhop. Like night and day difference over running the PPF, even with poly mounts on both the trans and diff, and all the bushings replaced. I blew up my FD diff with my rotary...bought one from Japan2LA and now run it with the below linked mount.

http://www.v8rx7forum.com/samberg-ro...prototype.html

If you really need something you should move to the cobra diff. At your power level and drag type launches, you are pushing the limit of the PPF design. I would address the issue and I think it isn't necessarily the diff as it is the wheel hop/ppf design.

 

I don't have wheel hop on a flat road. But when theres a stretch of road with bumps any setup will hop. My differential and tranny are both solid with braces. I'm still running the ppf as well but everything is very solid. I've already decided to go with the tii differential and have it in my shop torn down. Now i just need help getting the friction disks.

 

Well I know the mounting solved all of my diff issues. I had problems before and I was as solid as I could be with the PPF prior to moving to direct mounting.

 

MMS prohibits members from buying parts for others. It even prohibits buying parts for another car of your own. It's only for your "race" car.

If you autocross it's not a big deal to submit 2 past event results and you're in. If you don't have results but plan to participate, you are allowed to tell your story and get a membership beforehand so that you can finish preparing the car.

Dave

 

Yeah i read that on the site. But they require a nasa or other racing organization member card which i don't have. I would like to autox and take the car out at events but i'm not sure how or where to get started with all that

 

Join SCCA. It's 75$ and if you don't join you'll have to pay an extra $10 for the autocrosses because a weekend SCCA membership is required.

Trust me it's worth getting into this autocross stuff. You'll never look through the windscreen the same way again.

Dave

 

Ok I have some information that's probably very important for anyone rebuilding their turbo II differential. According to:

http://www.mazdamotorsports.com/pdfs...Drivetrain.pdf

The friction disks for the TII differential are part number 27-2660-P020, it then lists what the size of them are NEW. guess what size they are!?????? 1.75MM !!!! They also have an oversize disk that's 1.85mm. Both numbers are well under what the FSM claims as spec!(1.9-2mm)

Most likely because the NON TURBO LSD uses 2mm disks along with a different part number. So WTF, why didn't mazda feel this was valid enough information to put in the FSM!? Maybe an improper revision of the manual? Who knows, but my disks are all right around 1.75 mm so I should be good the way it is! I wonder how many people had their LSD rebuilt when it was completely healthy.

EDIT: New plan, put everything back together with a couple small shims to make up for the tiny amount of wear my LSD appears to actually have!

 

No it hasn't been launched that much. But I now run BFG drag radials and do plan on launching it more. I've read a lot of cases of people breaking the stock differential. To say the stock LSD is better is subjective to the use of the car. For some it may be better, for others a different option like the TII is better. Either way it's an opinion based on use of car, and driving style.

Maybe my differential didn't break because of the power, but it still broke. It broke in 3rd gear on the highway. Had fresh neo only a few months old. Maybe the mileage was getting to the differential, or maybe a new differential would've broke just the same. 450 plus hp + ripples on the highway = rear end shutters and hopping around the road at 90mph. The One thing that is certain is it broke. No one I read that switched to a TII or Kaaz had any regrets. I also picked up the TII for much less then the torsion LSD's I've found, and surprisingly based on the new information I found is in near perfect shape.

As far as wheel hop goes, I don't get wheel hop, everything has solid braces made by me, It's basically solid mounted, I just leave the PPF in to line everything up and add an additional brace.
I don't abuse the car, but i do want to be able to get on the car without worrying that an unknown road condition is going to break my differential. Obviously for my use the stock differential was not up to the task and the security of the TII is an important factor for me. I'll let everyone know how I like the TII once it's back in the car.

 

Considering you have almost 500hp I don't blame you one bit for forgoing the stock Torsen and going TII.

The streetability of the torsen becomes a bit of a sideshow on a 500hp car where other things affect streetability in a bigger way.

Dave

 

update:

Everything has been back in the car since monday. It worked out perfect with the shims I had to get the backlash right. I used royal purple 75/90 and 75/140 with the LSD additives already added to them. My drivetrain feels so much better now, the backlash was very high when I checked it on the stock torsion, this made me have a clunk when power was applied. So every time I went from a stop or shifted gears or accelerated I would have a small clunk that I could feel. I always thought it was my pillowballs needed to be replaced but it feels perfect now with the tighter backlash. I am glad I went with the swap. I'm also glad the differential was in such new condition. I notice no drawbacks compared to the stock tosion on twisty roads.

 

pics from the swap

 

get rid of the stock style torsion gears and swap it for a t2 lsd. its cheaper and if it fails it dosen't trash ur case.

 

lol, did you read his posts?

 

Lol right.. I even have pics of the tii differential taken apart. A little behind there buddy, but thanks for the advice. I do like my tii swap

 

Is there any way to tighten backlash on the torsen?

 

when going for the T2 diff, only the S4 T2 diff is clutch type...just throwing it out there. Let me know if someone needs one...The S5's are viscous LSD's.

 

Yes you can tighten the backlash with different sized shims. If yours has a lot of mileage the back lash is probably pretty loose like mine was. Depending on how your shims are arranged you might be able to switch the left and right around to make up for some of the slack in the back lash. The individual shims are expensive and it might take a few combinations to get it right.

 

kinda nice when a scam comes together dont it!

nice to see that diff is treatin you right makes me second think now that its gone cause all i here about the kaaz is LOUD but we will see.
z

 

yeah the s4 tii LSD doesn't make any noise. I think the kaaz can be adjusted to add or reduce lockup which will probably effect how loud it is, the amount of friction modifier used will also probably have an effect on the noise. But a lil noise never hurt anything anyways