Mazdacomp 1.6l LSD failure

[tnord]

this past weekend i had a rear end failure due to 5 of the pinion gear teeth breaking. this is not at all an uncommon problem with this differential (currently the only legal one), just this weekend 3 of us had failures, and another had a problem that was caught before it became catostrophic.

there are other problems with the LSD unit itself, but specifically referring to the ring and pinion gear, i'm looking for a way to keep this stuff from breaking, as it's just too expensive to replace on a regular basis.

i was thinking of sending them off to be cryo treated and REM'd. cryo would hopefully harden the material, and a REM on them would hopefully reduce friction and thus oil temps, allowing the oil to work as it was intended. although i don't think oil breakdown is our problem (mine was certainly not cooked when it gave up the ghost).

i'm looking at you engineers and materials experts as to if this is a legitmate solution to a rather significant problem. i'm also not in the least concerned about legal issues regarding these treatments, so please keep that discussion for another topic.

[imported_Webmaster]

>> currently the only legal one

Can you use another manufacturer? Or is this for a Spec Miata?

[tnord]

Originally posted by Webmaster@Oct 11 2005, 03:26 PM
>> currently the only legal one

Can you use another manufacturer? Or is this for a Spec Miata?

62326


spec miata.

[ddewhurst]

Are the top dogs in Spec Miata or Pro Spec Miata having these same rearend issues ? or have they implementated solutions.

Have you looked to the Spec Miata site or information/solutions or asked these same questions ?

Who is setting up your rearend ? A shade tree job or a pro job ?

[zracre]

I only have one race in a SM and the rear end failed at the 12 hours of homestead. there were 2 other failures during that race as well. I have seen numerous failures due to the gear not being properly secured and working loose but it seems like a common failure and a weak point :bash_1_: ...

[Bildon]

Originally posted by zracre@Oct 11 2005, 07:51 PM
I only have one race in a SM and the rear end failed at the 12 hours of homestead. there were 2 other failures during that race as well. I have seen numerous failures due to the gear not being properly secured and working loose but it seems like a common failure and a weak point :bash_1_: ...

62342


Wow that sucks. I personaly would have 0 issue with you running a rear end with the spec ratio but made of non-spec super strong 'unobtanium' or whatever it took to be reliable. Cause you know Mazda loves to sell you the disposable ones :angry: :bash_1_:

[RP Performance]

Most of the failures that I have seen have been from not being assembled correctly. The LSD's have not failed but either the ring bolts have backed out or the pinion height was incorrect.

[tnord]

yes the top dogs in SM are having the same issues. one of the top 5 car/driver combos in our division has been through no less than 7 diffs in the past 2 years, from no less than 3 different supposedly "pro" builders. we lost 3 diffs this weekend, 2 from the top 5, and one from someone near the bottom.

i would say the person that setup my diff was an inbetween. he's run countless runoffs, and has been racing and prepping RX7's in EP for i don't know how long, though he's not specialized in miata's.

the common belief used to be that the diff's that failed just weren't setup correctly, but in all honesty, we've had diff's blow from everyone within a 1000 mile radius of kansas city. even if there is a way to get these things just right, it shouldn't be so damn hard and complicated that only 1 person in the country can get it right, or that if you're off .0000000001 inches on your shim, that it blows up.

we've had failures including the ring and pinion breaking (like mine), to the bolts backing out of the ring gear and vacating themselves from the housing (like many others).

quite frankly, it is clear to me that this is NOT a setup issue, but a weak and expensive part on the car.

[C. Ludwig]

I'm not familiar with the SM rules but I am assuming you're referring to the 1.6L rear diff. The smaller 1.6L diff shares the same type of setup as the larger 1.8L diff. I've never had a 1.6L diff apart but have had many of the larger 7" and 8" diffs apart from Miatas and RX-7s. Both use a similar design and though failures are not unheard of they are IMO reliable units. We've done some drag racing with a turbo Miata (~300whp) and the 7" 1.8L units and though we've broken our fair share of axles haven't broken a diff. Also, diff failures in ITS RX-7s (which share the same type of adjustment mechanism with the Miata) are fairly rare. They do happen but not with the frequency you're describing. None of that helps you, it's just astonishing to me that it can be a setup issue since all three sizes of diff share a common adjustment design. Sounds more like you're at the limit of the strength of the smaller rear end. Again, I am assuming you are running the smaller diff. If the 1.8L diffs aren't breaking would it be feasible to petition Topeka to allow the 1.6L cars to upgrade?

As far as ring gear bolts backing out...unless the SM rules strictly forbid it that can be easily remedied with some safety wire and frequent inspections. Would suck to have to drop the diff every so often to inspect but that would save a racer a ton of money in the long run.

Not sure if cooling becomes an issue here or not but I figure this would be a good time for me to address on of my IT pet peeves. Again this doesn't help, or have anything to do, with the question at hand but while we're talking about rear ends... In IT we're allowed to spend an infinite amount of cash to have whatever R&P we'd fancy custom machined from solid gold if we desire turning whatever differential we'd like to have built up from platinum if we'd like. But we're not allowed to spend another $300 on an oil pump and a small cooler to make it last. Rules creep they say. Doesn't make sense to me.

[RP Performance]

[quote]
yes the top dogs in SM are having the same issues. one of the top 5 car/driver combos in our division has been through no less than 7 diffs in the past 2 years, from no less than 3 different supposedly "pro" builders. we lost 3 diffs this weekend, 2 from the top 5, and one from someone near the bottom.


i would say the person that setup my diff was an inbetween. he's run countless runoffs, and has been racing and prepping RX7's in EP for i don't know how long, though he's not specialized in miata's.

the common belief used to be that the diff's that failed just weren't setup correctly, but in all honesty, we've had diff's blow from everyone within a 1000 mile radius of kansas city. even if there is a way to get these things just right, it shouldn't be so damn hard and complicated that only 1 person in the country can get it right, or that if you're off .0000000001 inches on your shim, that it blows up.

we've had failures including the ring and pinion breaking (like mine), to the bolts backing out of the ring gear and vacating themselves from the housing (like many others).

quite frankly, it is clear to me that this is NOT a setup issue, but a weak and expensive part on the car.

62374




The problem still sounds like a set up issue to me. If the actual diff from Mazda Comp is not failing but the pinion and ring are the problem then the diffs are fine. There are some things that really need to be done on the set up and I know that we have had some problmes at first. Now that we know what to do we have not had any problems this year. Let me know if you need anymore info on these. Once again is the Mazda comp LSD is still intact and the ring and pinion are breaking then it is int he set up. Also what kind of oil is being used and how oftten is it changed?

[tnord]

well, if it is a setup issue, than NOBODY has figured out how to do it right then. like i mentioned before, the ring and pinion breaking is not the only problem, as the bolts are backing out of the LSD unit itself and fleeing the scene through the case.


diffs have failed with every kind of oil in them. redline lightweight shockproof, mobil 1 75-90, mine was amsoil 90-140, some sort of castrol, and others. i changed my gear oil after every weekend, but i only did it once, because it failed on the 3rd race.

i'd love to hear ideas on what you think is being done wrong on these, because if that's the case, you can make a TON of money.

[tnord]

Originally posted by C. Ludwig@Oct 12 2005, 02:09 AM
I'm not familiar with the SM rules but I am assuming you're referring to the 1.6L rear diff. The smaller 1.6L diff shares the same type of setup as the larger 1.8L diff. I've never had a 1.6L diff apart but have had many of the larger 7" and 8" diffs apart from Miatas and RX-7s. Both use a similar design and though failures are not unheard of they are IMO reliable units. We've done some drag racing with a turbo Miata (~300whp) and the 7" 1.8L units and though we've broken our fair share of axles haven't broken a diff. Also, diff failures in ITS RX-7s (which share the same type of adjustment mechanism with the Miata) are fairly rare. They do happen but not with the frequency you're describing. None of that helps you, it's just astonishing to me that it can be a setup issue since all three sizes of diff share a common adjustment design. Sounds more like you're at the limit of the strength of the smaller rear end. Again, I am assuming you are running the smaller diff. If the 1.8L diffs aren't breaking would it be feasible to petition Topeka to allow the 1.6L cars to upgrade?

As far as ring gear bolts backing out...unless the SM rules strictly forbid it that can be easily remedied with some safety wire and frequent inspections. Would suck to have to drop the diff every so often to inspect but that would save a racer a ton of money in the long run.

Not sure if cooling becomes an issue here or not but I figure this would be a good time for me to address on of my IT pet peeves. Again this doesn't help, or have anything to do, with the question at hand but while we're talking about rear ends... In IT we're allowed to spend an infinite amount of cash to have whatever R&P we'd fancy custom machined from solid gold if we desire turning whatever differential we'd like to have built up from platinum if we'd like. But we're not allowed to spend another $300 on an oil pump and a small cooler to make it last. Rules creep they say. Doesn't make sense to me.

62375


yes i am using the smaller 1.6 diff, every single failure i've ever heard of in SM has come from a 1.6l miata with the smaller diff. i've written letters to topeka before requesting the 1.8l torsen diff, and it's even been addressed in fastrack. topeka says they won't change the rule because "it isn't a problem."

on the ring gear bolt issue, my plan is to look into some ARP bolts that are pre-drilled for safety wire, and won't loose their strength when they get hot. the ring and pinion i have no idea what to do about, which is why i asked about the cryo/rem treatments.

i think cooling does become an issue, as we've opened up many diffs that stink like the dickens. many of our exhausts run right by the casing, which probably doesn't help.

[JIgou]

Originally posted by RP Performance@Oct 12 2005, 05:28 AM
There are some things that really need to be done on the set up and I know that we have had some problmes at first. Now that we know what to do we have not had any problems this year. Let me know if you need anymore info on these. Once again is the Mazda comp LSD is still intact and the ring and pinion are breaking then it is int he set up. Also what kind of oil is being used and how oftten is it changed?

62379


Brett, I'm interested in any details you might be able to share with regard to the setup of these diffs.

I can say that one of the guys drained his fluid after about 2.5 hours of track time this weekend and he nearly drove everone in that end of the paddock away with the stink. He was running Redline Shockproof lightweight.

That led to a lengthy discussion about gear oils with folks from a couple of other classes, which led to him putting in some whiz-bang stuff one of the FA guys happened to be using. Then he broke on lap 1 the next day (not rear diff related), so it's hard to say whether that fluid would help or not.

Do you have a recommendation for fluid brand/type and change interval? Do you have a regular maintenance window for teardown and partial/complete rebuild? (One of the pinion failures this past weekend was a nearly two-season-old diff. If the pinion height/specs should be checked regularly, we're interested.....but....)

Interestingly, a multi-time national champ in a Production class who happened to be at the same track this weekend and who happens to support a couple of 1.6 cars (including one belonging to his son) wondered aloud if the amount of fluid in the diff (specifically, the lack of) may be contributing to the issues, and if a remote reservoir may help.

If it all comes down to "you have to hold your jaw just like this when you tighten the bearing cap on the non-ring-gear side during a quarter moon", so be it....as long as it's widely shared and everyone with a modicum of mechanical ability and the right tools can replicate it. (Having seen diffs from known "pros" self-destruct, I wonder if this is even possible...)

I honestly do think that, regardless of setup, the 1.6 diff is marginal for the use it's seeing in racing conditions, and whatever special motions or lotions are required to keep the diff reliable are merely band-aids over the symptoms of the real issue - that the diff is undersized for the application it's being used in.

Jarrod

[RP Performance]

I had my fair share or failures in the beginning of build these rears. The main failure was the ring bolts backing out even when torque to spec. What we found is that Mazda must use some sort of tread locker at the factory. We started to use a tap to clean the treads in the ring gear before assembly. You also need to use a wire wheel on or replace the bolts and I use tread lock on assembly to make sure they are good. Since starting this we have had no failures. As for the fluid I have been using MTL 75-90 and try to change it every couple of weekends. If it is set up right you will not have a problem. I think that after two seasons we take it apart and set it up again. I also do not remove the pinion unless the bearings feel bad and need replacing.

[tnord]

Originally posted by RP Performance@Oct 12 2005, 11:49 AM
I had my fair share or failures in the beginning of build these rears. The main failure was the ring bolts backing out even when torque to spec. What we found is that Mazda must use some sort of tread locker at the factory. We started to use a tap to clean the treads in the ring gear before assembly. You also need to use a wire wheel on or replace the bolts and I use tread lock on assembly to make sure they are good. Since starting this we have had no failures. As for the fluid I have been using MTL 75-90 and try to change it every couple of weekends. If it is set up right you will not have a problem. I think that after two seasons we take it apart and set it up again. I also do not remove the pinion unless the bearings feel bad and need replacing.

62417


well, i can only speak with 100% certainty for my own diff, but having the ring gear bolts swimming in thread lock is nothing new. it was done on mine, and i would expect was done somewhere on the order of 75% of the other 1.6 diffs. my diff also used all new bearings, new axle seals, and a new pinion nut.

are you using the 1.6L diff from mazda?

[VW16VRacer]

Call Stu at BSI. He builds so many SM cars he should have some sort of opnion on what is happening.

http://www.eng-tips.com/threadminder.cfm?pid=78

You might have some luck with your question from this site but these guys are way over my head..... :119:



Jon

[cmstrilchuk]

I don't want to dilute or hijack this thread, but I need to rebuild an RX-7 clutch pack diff, wondering if anyone here could give me advice (offline) or point me to some resources.................

Thanks all,
Curtis

cmstrilchuk <at> hotmail.com

[RP Performance]

I still want to know if anyone has had the LSD fail or is it just the ring and pinion that is breaking?

[tnord]

Originally posted by RP Performance@Oct 13 2005, 11:03 AM
I still want to know if anyone has had the LSD fail or is it just the ring and pinion that is breaking?

62546


as far as i know, either the ring and pinion break, or the ring gear bolts back out.

[C. Ludwig]

My question to Brett, since he&#39;s set up both with success, is what is the difference between the small 1.6L diff and the rest of the larger Mazda diffs as far as setup procedure? Like I said, I haven&#39;t setup a 1.6L but from the way the microfiche looks it the same basic design as the rest. What I&#39;m getting at is if the "pro builders" tnord is talking about can setup the larger diffs to last why aren&#39;t they able to make the small diff last? Assuming they have experience with 1.8L Miatas or RX-7s and their larger diffs.

[RP Performance]

Originally posted by tnord@Oct 13 2005, 04:31 PM
as far as i know, either the ring and pinion break, or the ring gear bolts back out.

62553



If that is the case the Mazda LSD is not the problem. The large and small diffs have the same set up procedures. The major differance is that larger diffs have three pinion bearings.

[2 fast 4 u]

I have been running sm for three years and build my own rearend. to this date no
broken gears but one lsd failer. the clutches wore out. disasemble clean and locktight, change fluid every 2nd weekend. I also over fill the rear end. insteed of one half quart i allmost get a full one in.

paul

[2 fast 4 u]

i have hade a couple units come into my garage with broken gears. these were broken from off track action and side stepping the cluth on a down shift.