AMDguy

ok, I have read just about every diff thread that Google will give me with every diff related search. I still fail to understand the situation below, and also how our LSD works, and what is capable of (especially because I live in an area where we get lots of snow, and knowing what the car is going to do when it is very slippery is helpful .

As I was trying to pull out of my driveway the other day, the passenger wheel was in about 6-8 inches of mud (yes, there really is that much mud in my driveway), while the driver's side wheels were on dry ground. Upon trying to go forward, most of the torque was applied to the passenger wheel, which, being sunk in mud, did not provide the best traction. After turning off traction control, and some very excessive revving, I was able to get out, but I cannot help but wonder, why did the LSD (I have an '06 6sp manual) not apply more torque to the wheel that was on dry ground. I thought that it might be because something was wrong with the diff internally (I still totally don't understand how our LSD works), but I changed the fluid (the car has 100k miles on it, and I am sure it is the original fluid) last week, nothing bad came out (no chunks of stuff, aside from the fluid being dark black), and the only thing I noticed was a layer maybe 1/16" thick of metal shavings on the magnetic drain plug; almost too fine to be seen with the naked eye. very, very fine shavings.

So, my question is in this circumstance, why did the LSD act the way it did, even when I applied more and more torque (the way I understand it, the more input torque is applied to the diff, the more effective the limited slip unit is, but maybe I am misunderstanding that). in fact, when I applied more torque, the speed difference between the wheels increased and the wheel in the mud (the one with less grip) spun more). Is it possible for Our diff to fail somewhat silently, with no noises (at least not for me) and just lose its limited slip effect? or am I simply expecting it to do more then it is capable of?

TeamRX8

iTrader: (25)

It’s ok for what it is, but they do wear out or start breaking apart internally to then begin losing their proper function over time. I posted some pictures of one that broke up on somebody on here who lives local. His went out entirely and I gave him my low mileage OE LSD that I had swapped out with an OS Giken LSD. The first thing to check is to see if any metal pieces come put in the oil. However, they could be bigger pieces that might not come out or be seen without pulling the cover.


here it is:

https://www.rx8club.com/new-member-f...y-diff-270191/

.

AMDguy

Yea, that is kind of what I expected... I shined a light into the case, and looked in through the drain plug hole, and it looked nice, but that is pretty meaningless. at least it is not making any nasty noises. I feel like it is still working a little, but not really all that much... I just finished a rebuild, and the car is slowly rusting out (further accelerated by the insane amounts of salt put on the roads in my area). I will keep the car until it dies, and just drive it into the ground. I really do love everything about this car, and also might sell it at some point for a nicer example with a blown engine (which I would of course rebuild...), so the diff is the last of my concerns. If it makes the car go, then I will not touch it (for now).

I have to ask though, how is the OS Giken LSD? I was reading of their website, and they say it is capable of 100% lock. Do you find this to be true? if so, that is pretty impressive... Expensive, but it if it is true, it might be worth it (down the road), especially in my area where there is a ton of snow and other slippery conditions...

TeamRX8

iTrader: (25)

Well it’s expensive so you don’t really want to go there, but I personally like it a lot for competition purposes. For Pro Solo events; which has a drag race type start, dropping the clutch launching at 8000 rpm is a real hoot. It locks straight, but the design provides differential action when turning and then transitions between the two.

The OE diff works quite well, but it does eventually wear and weaken. You’d be better off trying to find a used OE diff with lower mileage to swap in.

NotAPreppie

What Team said.

The OE diff is based around a cone clutch. Same basic premise (albeit on a slightly larger scale) as design of a synchronizer in a manual transmission.

Wear that cone clutch enough and you have an open diff.

AMDguy

kinda figured that... probably what has happened...

wouldn't dropping the clutch at 8k be absolute murder for your transmission? even for a S2 trans?

TeamRX8

iTrader: (25)

No, it’s a hard shift into second that usually breaks it. I have four broken in the corner, only because number 5 was just rebuilt. These are all S1 transmissions. The USDM S2 trans has a big gearing gap from 2nd into 3rd that isn’t going to work for me and 1st gear is way low too with the lower rear gear, like granny gear on a truck. The S1 trans with S2 diff gear makes a good combination though.

AMDguy

really, that is interesting... ya learn new things every day I suppose. I have read about problems with 3rd gear too, is that a common failure?

TeamRX8

iTrader: (25)

well the track racers have different problems than the autocross racers because they spend more time using different gears, and the street people have different issues as well. A lot of it comes down to how you drive, but it could stand to be stronger. Dropping it in first was never any issue for me or for the OE clutch either. Of course I am dropping it and not sliding it and then modulating the throttle to control wheel spin in a very deliberate manner. If you just drop it and immediately slam the throttle down it will just spin the tires like crazy and that’s not the fast way out of the hole.

AMDguy

that makes much more sense... when someone says "drop the clutch" I assume that just means rev up, take foot off clutch, and floor it.

TeamRX8

iTrader: (25)

well it all depends how much MOI is in the clutch/flywheel assembly, but you pretty much understand more than most people

AMDguy

I am resurrecting this thread with a slightly different question then I had before. Like I mentioned previously, my LSD has lost most of its function, and it would be really, really nice to have the LSD, especially the snow in winter and mud the rest of the year.

is it possible to rebuild the LSD? I know Mazda does not officially sell the parts, but there must be some way to obtain them... It is not worth the $1000+ for a new diff, but used ones seem relatively cheap. Roughly how many miles should I look for on a used one (I found a few that have between 50-60k on them, but that seems like a lot given that mine only has 100k and is totally 100% nonfunctional (as an LSD)).

TeamRX8

iTrader: (25)

Well, they only sell it as an assembly, not as parts. Thought I had already mentioned it, but maybe it was in a different thread. Because you’d have to replace all the major parts anyway due to how it’s made. You just need to either buy a used, preferably low mileage, differential or find a factory LSD that somebody swapped out with an aftermarket one. However, it will cost around $300 labor plus parts to swap it in and rebuild yours and then you still have some high mileage parts in there. So you’re likely better off getting a low mileage used one from a recycle yard etc.

AMDguy

I suppose I thought if mazda does not sell the parts, then someone must... I found a few genuine worm gear style Torsen diffs on eBay. does anyone have any experience with those for the 8? They are especially appealing because there are no clutches/cones to wear out and lose function, and I doubt I would have any problems at stock power levels.

https://www.ebay.com/itm/Mazda-RX-7-....c100005.m1851


there are a few others that are a little cheaper... but all the same diff.

TeamRX8

iTrader: (25)

you can lead a newbs to knowledge, but you can’t make them drink