Yeah, it's just too much load for the face width. The contact stresses are huge!

Yep. Looks like the reduction in contact ratio is increasing contact stresses too much. Next stop is failure. I wouldn't be supposed if the ppg sets do that too. I think it could be improved with better heat treatment.

I remember talking with jack at the shootout and seeing some gtr stuff that was all pitted like that.

I have seen similar conditions before from several gear manufacturers, including early Albins (Evo 1-3) and Frana (SRT4 stuff). The PPG stuff I have seen are much more durable than these. As well, even the PAR gears are very nice, but I have had more issues with snapping input shafts and ripping teeth off of their gears on 1st/2nd, as well as exploding 3rd/4th hub and sliders.

What's going on with the wear between the gears in the 4th picture?

I have had the thought in my mind that mathais could be breaking these gears in his car and just not telling anybody. seein these gears kinda confirms it may be true. its a shame either way.

how much tq was put on these gears and what oil was used?

He says Redline 75W90; I'm not sure about the power level but I don't think it's too crazy.

What are you asking? That wear is pitting. By reducing the pitch of gears he has reduced the bending stresses in the teeth which allows them to not break off at the root. But by doing that he has reduced the contact ratio, so now the load isn't transferred as smoothly. This is increasing the contact stresses to above the fatigue limit of the material. This starts small micro fractures in the surface, and chunks just blow out leaving pits. This is bad because not they become stress concentrations, and a crack begins there and propagates through the tooth. However these look kind of high on the tooth, and the bending stresses there might not be very high. they could last a very long time yet.

I wonder if they are not case hardened.. I asked Matthias about all this, and he had no answer. I chose not to buy them.

I am also very surprised I have not seen a stock dsm gear with pitting like this.

The gear teeth above display scuffing too. In any case, scuffing is due to lubrication conditions, not material strength. Scuffing often happens to new gears when tooth surfaces are not yet bed-in. The user claimed to have put on ~200 km or ~124 miles on the gears which consisted of 2 dyno runs and 6 track days. Definitely not the proper way to break-in trans gears. Another contributor to pitting—as well as scoring and galling—(seen in the above pics) is inadequate lubrication and heat. He ran it hard enough to break 5th gear in the long straight on a 3.0 mile circuit afterall. Improper preloads, especially on the loose side, can factor in too. But not convinced the gear oil used, temp., lack of break-in and potentially incorrect installation can explain the extent of the wear seen here.

Now we have a sample size of 2. Matthias, who continues to test the limits of this gear setup with ~1000hp and running low-9s…disassembled his trans after 10,000 miles and the gears looked great. Since then he’s dipped well into the 8’s and reports that he is still using the same gears which are holding up to even more punishing traction. He runs a 50/50 mix of 75w/140 and shockproof light and performed proper initial break-in. Matthias posted pics of disassembled trans/gears on FB @10k interval—no pitting, wear, etc., etc. and this is after something like 80 times more mileage than the above gears—not easy miles either. This does not reconcile with the other users experience considering far-less power, far-less shock loading and stress cycles yet exhibiting worn gears/ surface fatigue after only ~124 miles, as shown in the above pics. The gears appear to show initial pitting below the pitchline, in dedendum region of the tooth as opposed to destructive pitting or spalling. These gears were not put through careful break-in at reduced loads and speeds. Unsure if this may be considered normal (corrective) pitting and plateau or may become progressively worse and fail. Time would tell.

Matthias runs his car hard (as seen in his videos) and one would expect that this too would certainly result in pitting like seen above or worse due to such factors as surface overload and stress cycles building up. But this is not the case. This is what doesn’t make sense. I’m assuming that there have been no design changes between the two sets with the endurance limit/hardness of the material should be the exact same. Not sure what to make of this considering real world feedback from only 2 users with essentially opposite outcomes, respectively. Maybe this isn’t the whole story? Maybe he just got a bad batch—this particular set above could have an issue w/ material hardness? More likely a quality control issue as opposed to design or size limitation? This is disappointing nevertheless…time will tell and hopefully there will be more feedback and fine details that come out about these gears.

twicks69 said:

I have seen similar conditions before from several gear manufacturers, including early Albins (Evo 1-3) and Frana (SRT4 stuff). The PPG stuff I have seen are much more durable than these. As well, even the PAR gears are very nice, but I have had more issues with snapping input shafts and ripping teeth off of their gears on 1st/2nd, as well as exploding 3rd/4th hub and sliders.

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Tim,

Just curious on the configuration of the PAR gearset you ran…did it have the larger Evo VIII input shaft? Were the hub/sliders their design or the OEM Mitsu HD? Did PAR cover the gear breakage, etc. under their 12 mo. warranty?

Mike

I agree these gears could easily have been run too hard to soon with not enough breakin. I would have them shot blasted and run them again but with nice long breakin period. they look like they might still give a worthwhile life span before letting go. but really depends on how deep the hardening was to begin with.

I have a customer that brought me a fwd trans that was run low on oil. I told him it was a waste to build it. all the gears looked worse than this. we couldnt find another trans so he said put it together. the trans has been in the car for two years now. 20k miles on billet 20g 380whp. and he admits to beating on it relentlessly.

94awdcoupe said:

I have had the thought in my mind that mathais could be breaking these gears in his car and just not telling anybody. seein these gears kinda confirms it may be true. its a shame either way.

how much tq was put on these gears and what oil was used?

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The car that these gears were pulled from produces “almost 600nm” or less than 442 ft. lbs. Really not much tq. Especially in comparison to what Matthias puts through his.

While this user runs 75w90, I know circuit applications necessitate specialized gear oil e.g., Motul Gear Competition oil—that are full-synthetic GL5 or GL6 and that detail is unknown. Due to the nature of circuit racing and this power level…I think 75w90 may be too thin, for starters. Gear manufactures often require the user to run a small handful of approved oils for circuit racing in particular to avoid accelerated gear wear and for warranty purposes.

Yeah I understand this guy is unhappy. It’s a shame these gears were run so hard without careful break-in first as this most likely skewed the results here. While he is convinced the gears were “faulty” I believe his outcome deserves an asterisk, short of a failure-analysis being done. Sometimes failure modes that begin with scuffing (welding and tearing of tooth surface) give rise to pitting caused by the deformation, rough surfaces on the scuffed tooth and removal of protective oxide layer. So, scuffing would be the primary failure mode leading to pitting (micro & macro) and those would be secondary failure modes. The local stresses, initiated by surface roughness are considerable. The mating surfaces of gear teeth are not perfectly smooth but especially when scuffed—when the oil film thickness is less than the composite roughness of the gear, metal-to-metal contact occurs and then accelerated surface distress happens progressively i.e., pitting, destruction.

This example is just not a good usable data point, I wish it were. I want to see findings from individuals who bed-in these gears properly and use thicker gear oil: 75w140. There are a few on 4gtuner that posted they purchased these gears…I am curious to see what they report.

I have missed a few posts here! I will be getting back on my project real soon I think I have grieved enough .

OK i resumed the Trans build this week. A local tech machine shop machined my hub to accept the 4 spider gears, the gears and shaft and hub will now be sent to be wpc treated. Shooting for a may completion of the total project.

Great man its been a while glad your back get a hold of me when you can so I can update you on my build. We last talked to you were busy with things

Same local shop that machined my center differential also machined my 1990 3/4 gear slider today another obstacle out of the way

keltalon said:

OK i resumed the Trans build this week. A local tech machine shop machined my hub to accept the 4 spider gears, the gears and shaft and hub will now be sent to be wpc treated. Shooting for a may completion of the total project.

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sent the center diff to 300 below for all components to be treated and shipper lost all my gears, cross shaft. So I had to go to satan(mitsu dealer) and shed out cost of 185 dollars for the gears in the center diff fortunately I had two gears here in the shop. Once center diff is complete and treated I will move forward with assembly.

Whats remains of the center diff came in from being cryo treated today and my 4 spider gears and shaft came in also, these will be sent in and treated, slow coming but making progress. I pulled the engine from the fwd a few days ago and its now sitting on the engine stand. I purchased a moroso 6.25 oil pan and it should be hear today to replace the factory unit to help with the extra rpm that the car will be seeing from running the 3.909 rear end and the 64 tooth crown wheel from the evo 1 transmission. I will also be switching to the a 245-40-18 tire from the 245-35-18 tire to ease a little of the lower ratio diff. I am getting excited as progress is being made.

Ready for implant.

Glad you're back at it man hope you get it done by July I'll be in Norwalk in august of you come up.

I introduced the old engine to the 800whp transplant today I am back on the car in full swing!

There's some mad scientist stuff going on for sure in the keltalon lab!

can wait to here your comments on AWD

i don't think i would ever launch your car on that center diff...

bastarddsm said:

i don't think i would ever launch your car on that center diff...

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Enlighten me thanks!

Well, it will be center diff soup very quickly. That's a machined down cross shaft, and its probably loose hell in the case. It'll be galled up in a hurry.