5.12 clutch pack 2nd Gen LSD

mbuskuhl

mbuskuhl

New member
I've got the 5.12 clutch pack LSD. I have ran it 2 race weekends, after both weekends I changed the oil and notice some small metal shavings and some metal dust that had stuck to the magnetic drain plug. I have ran Mobil 1 synthetic 75/90 both times. Anything to worry about or is this normal?

Here's what I know about the diff, maybe some of you know about this one I got. I got it from an EP guy who supposedly used it about 6 races. It was a spare that he bought off Greg Sabol out of St. Pete, FL who I'm told had built this particular one.

"...its a stock type LSD with every MazdaComp part that can go in. It has extra clutch pack plates and springs(I think it goes from 4 sets in the stock LSD to 6 sets in the comp set up). These rears are so tight when it comes to the 'slip' part that when you turn in the paddock or pushing the car around you can hear the clutches slipping and catching." - definitely true about the paddock


Here's what I scraped off the drain plug this last oil change. Please tell me this is normal.

pict0114kx4.jpg
 
Sorry to be the bearer of bad news--that is not normal for any diff I ever built. Looks like possibly parts of the bearing cages or someone used some very thin shim material to get the preload. Not good either way. Needs to be looked at in the off season at the very least.
 
Thanks Steve. I will have it checked out first time I get a chance, is this something I should worry about and get looked at ASAP or will I not do much more harm if I run it another couple race weekends? I'd rather skip the next race weekend than ruin this diff, they aren't easy to come by and not cheap.

Adding to the history on this diff, it was dropped by UPS when shipped to me and one of the mounting brackets on the aluminum housing broke off. I had to get a new aluminum housing before it was installed and did not file a claim with UPS as it did not seem worth it at the time. Two people I spoke with after this happened said the diff should be fine. Could the dropping it have caused internal damage and be a cause of these shavings?
 
Not normal Mark, I'd take the diff out of the car and get a look inside to see what might be coming apart. It doesn't look like anything major if that is the only sign of trouble(no new noise besides the normal noises, like a bearing howl or gear backlash issues) Are all those pieces the same dimension if you seperate them and flatten them out? Are they sharp at the edges like they might be bearing cage that has worn or been sent through places they don't belong?

I'll see if I can get this link to Greg, Ed's at Sebring helping at a drivers school this weekend so when he gets back we'll get this picture in front of the guy that built the diff.

As for UPS damage, its hard to say what would have been hurt in a drop hard enough to break a housing. I can't think of anything.
 
NEVER saw anything like that from a rearend. The strange part is that from the picture ALL the little parts look similar width/thickness & that is NOT normal from anything wearing in the rearend. Take er apart while there should be minimal damage.
 
Does anyone have any advice on what to do? I don't know enough about these diffs. Any advice??? :(

I was told this diff had 6 weekends on it and I've only put on 2 weekends since I bought it. I've already emailed the seller. Here's the email I got today from Jason Saini and Shannon McMasters who are working on my car these days.

"We've torn down the rearend, and although the parts appear fine there appears to be too much lash in the R&P. There appears to be nearly .4mm of lash, when .09-.110mm is the spec. We believe the pieces you found in the fluid were basically strips of metal that had been machined off the pinion. Were they metallic? Were they shiny?

We can try to tighten the lash back up, but that may affect the contact pattern of the R&P. We don't feel comfortable taking the pinion bearing stack apart, which we would need to do to correct the contact pattern. I believe we can tighten the lash, but we can make no guarantees on the life left in this diff as it already looks pretty worn. There is no bad wear with heat marks, but the teeth of the gears are extra-polished and appear to be pretty high mileage. Do you know the history of this diff?

We believe the diff won't last too long adjusted the way it is now, but we want the decision to be yours on if you want it re-adjusted or if you want us to just leave it alone. Let us know!"
 
ABORT! ABORT!

my experience with miata diffs tells me this is not good at all.

you have a larger r/p than our weenie little pieces, but if i found that stuck to my drain plug, that diff is done until further notice. the good news is your $800 mazdacomp clutch pack is probably fine. i shredded both ring and pinion teeth on mine and the clutch pack survived.

imo, the smartest thing to do would be find another donor diff carrier ($250?) to transplant the clutch pack into ($300 P&L?).
 
imo, the smartest thing to do would be find another donor diff carrier ($250?) to transplant the clutch pack into ($300 P&L?). [/b]
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If only it were that simple, The 5.12 R&P for a 2nd gen is custom made, close to $1000, and nearly impossible to find used.
 
Could be some trash was in there when it was assembled, hiding in one of those front oil galleries maybe. It doean't look like diff parts or gear bustedness. I guess bearing cages is about as close as you get, but those are thicker/larger even. I think someone didn't clean it up really well when it got put together.
 
Mark, the good part from the info Saini/McMasters forwarded to you is that they said their "GUESS" is that the pieces you found were "MACHINED" off the pinion. Their responses are ALL very iffy. If I were in the business to build/repair rearends I would lay down the FACTS to you & not leave you the CUSTOMER MAKING THE DECISION & WONDERING.

What is the detailed info from the person that you bought the rearend from. What spec did he have the lash set to.

Take the info you have including the pieces you have & talk with a KNOWN Mazda 5:12 rearend/racer guy. If no one responds with a positive solution on this site with the known info/plus picture you have place a post on the Production site. With the info you have & if I knew that the pieces you found were not worn parts from using the rearend (but some stuff not carefully cleaned off after remachening the pinion) my concern would be the lash at 4 times the max specified ammount. But I don't know anything about excess lash............I could make some guesses.

Go to the Production site & get Tom Thrash's pm or e-mail address & mail him. He is one great guy & WILL help you down the straight path. Keep in mind that all these guys Thrash/Saini/McMasters know each other.
 
Thanks for all the responses. The guy I bought it from got back with me right away and got me in touch with the original builder of this diff Greg Sabol last night. I don't know Greg but some of you long time racers may, he retired a few years ago and used to race in FL. I also talked with another guy who is on this site and has built several and runs these 5.12's as well. Both these guys were very helpful and willing to talk to the shop today, I definitely owe them. Both agreed things should not be as bad as what Saini wrote and that the diff probably needs to be cleaned and setup again. Saini and McMasters know their stuff, no doubt about it, but I think since these 5.12's are so rare and custom some specific tips on them should solve the issue. Lash needs to be more than spec but not at .4mm, closer to .25mm with the 5.12. There is probably a bearing issue. Hopefully I'll find out something later today. I hadn't thought about Thrash, I don't know him but know of him, that's another possibility. Thanks again to everyone.
 
Looks like the diff has been saved, I guess time will tell for sure.

"I broke down the entire diff assy.did not see any outstanding thing wrong,the bearings seem to have a lot of wear which may have been the cause of the excessive back lash,when I went to press the bearings of the pinion base cage fell apart in my hands.Showing the problem,the main pinion bearing had been shaving the back of its cage off(thats the parts you pulled out).I even took the posi apart and measured all the plates."
 
So that means I get a "Bozo Button" for picking the bearing cage! :026: Glad to hear it might be saved. Good luck.
 
Sounds positive for you Mark. :D

***So that means I get a "Bozo Button" for picking the bearing cage!***

No question Steve, you get the "Bozo Button" as soon as you provide the root cause for the, what allowed/forced the cage to moved far enough to be shaved. ;) As I read Mark's quote from Saini/McMasters the shavings were part of the cage. Were the bearing races worn out allowing the cage to move & be shaved ? I always need to/like to learn the root causes of issues. ;)
 
Sounds positive for you Mark. :D

***So that means I get a "Bozo Button" for picking the bearing cage!***

No question Steve, you get the "Bozo Button" as soon as you provide the root cause for the, what allowed/forced the cage to moved far enough to be shaved. ;) As I read Mark's quote from Saini/McMasters the shavings were part of the cage. Were the bearing races worn out allowing the cage to move & be shaved ? I always need to/like to learn the root causes of issues. ;)
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I have inside information. UPS dropped it hard enough in shipping to break the rear aluminum cover . Might have taken the same hit on the front flange. Just a guess.
 
Good call Steve!

I also wonder why this happened. As Steve mentioned, yes it was dropped by UPS. It showed up to me with one of the aluminum mounts on the housing busted off and I had to replace the housing. The diff had been wrapped in cardboard was all when shipped.

I don't know if this could have caused it but let me add... remember, this diff only had 6 weekends (no reason not to believe) on it when I got it and I did 2 weekends with it (no Enduros). This diff came from a very high RPM EP car. Here's a snip from my emails with the seller when I bought it a few months ago...

"We found that we are turning RPM's a lot higher than the ITS cars and the driveshaft does not like it at all. Our tires are smaller diameter and we have higher top speeds so we are running up around 9500 in 5th at Daytona(truck 5th gear .85 ratio)"

Could it have been something to do with the high RPM? I believe these guys blew a driveshaft at 10,000 RPM with this diff in the car (hence the reason they went back to the 4.10 and re-geared the tranny instead). RX7club.com is still down but I think the story is on there.
 
***Could it have been something to do with the high RPM? I believe these guys blew a driveshaft at 10,000 RPM with this diff***

You bet it had a lot to do with the driveshaft going south. One piece driveshafts don't like 10,000 rpm's in RX-7's. MANY E Production RX-7's 10,000 rpm's cars use two piece driveshafts. With one piece driveshafts keeping the tran & diff angles minimum & equal is of MOST important to keep vibrations down & to keep from wearing out the trans tailshaft bushing & tearing up the splined u-joint fork.
 
The car ran one weekend at Daytona with the 5.12, the rest were Sebring short course. There might have been one Sebring long course in there as well. The driveshaft didn't 'blow' it had a harmonic that showed up with an aftermarket driveshaft at about 8000rpm in 5th then went away. We went back to stock drive shafts and had no problem after that, but we never went back to Daytona with that diff.

The Daytona weekend was the first of six weekends over about 7 months and it was fine the whole time. I'm glad it turned out to be simple and was caught by good car prep/maintenance. I'm thinking any drop hard enough to break a mounting arm off could cause some problems if the front flange took any of the hit. It makes sense because the hit could have hurt the cages and added some lash to the gear and front to back play in the pinion.
 
Don't forget that all important crush sleeve that keeps it all in place. Sure did not help if it got compressed.
 
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