Fubar's GT Build

Most likely, improper break-in from initial owner... also found a bad bearing in one of the output shaft plates we'll need to replace

Mark, ya missed over a year of your life in a FGT..... while owning one.

Mark,
Kind of difficult to see what you mean as to "ruff edging" along the spline. Any better pictures or arrows superimposed onto the pictures?

Looks like some rough edging along the pinion teeth top edge if I interpert the picture correctly. I would "stone" the teeth top edges to insure a 0.008"- 0.012" break edge fillet. Same applies to the spline teeth. Top of tooth profile should have a broken corner.

You indicated you "hardened the half shafts". Was this a hardening operation applied to the stock half shafts? What process was used and how hard and deep did you go? Is your concern ultimate torque capability of the shaft or something else?

How was it determined one of the bearings had failed? Spalling, surface fatigue, lack of lubrication, overload...?

You are in good hands and hope to see the final product some day (like Detroit, Rally X).

Half shaft are from Johnny B. produced by DSS for them. 300m... nice parts. Supposed weak spot for higher hp cars with traction.

The pinion gear looks slightly burnt... typical of high oil temp and high loading (flogging) a new or low mile gear set prior to proper break in that would result in a work hardened surface that would prevent something like this.... I don't think Mark's GT came with the trans cooler which would also contribute to this theory... but I could be mistaken. He bought the car used with a few thousand miles on it so I'd suspect it was the first owner.

The bearing was rough like it had trash in it... flushed it out and it still felt rough as though some debris must have gone through it. However... It is the side that isn't directly oiled...

Typically a badly burnt gear will progressively get worse... becoming louder and louder. Mark nor I ever remember hearing much if any gear noise. We believe the issue occurred 35k+ miles ago and has likely plateaued. At the moment we have no reason to believe it is on a path to catastrophe. Because of this... we came to the same conclusion Indy GT did... same night Mark took images, we simply de-burred the tooth edge, smoothing it into the existing chamfer.... we'll replace the bad bearing and move on down the road. If the problem intensifies later, there will be audible cues prior to a total failure of the surface, and we'll address it then by tearing it down, and rebuilding it. At the moment, it's an expense we're looking to avoid.

We're a PPG dealer... maybe we'll put a badass PPG gear set in the box... that's an inexpensive solution! LOL....

He hardened the shafts by Viagra soaking for a week (despite manufacturer warnings regarding 4 hour limit).

There goes Frank sticking his nose into the technical jungle with medical metaphors. Check back with us in 4 hours Frank. Or check with your doctor.:rofl

MoTeC – the 300M is good material. My only thought is the weak-link theory. If you utilize larger rear tires capable of absorbing more torque and you transmit the (higher) engine torque to these the rear wheels through improved capably half shafts, if something is to fail, it will likely occur in the transaxle. Which could be expensive to fix or beef up. The lesser strength (if it is necessary) OE half shafts might provide a mechanical fuse to protect the more expensive-to-fix transaxle.

I agree with your thoughts on just cleaning up the pinion teeth edges, installing a new bearing and putting it back together. Although I had to chuckle at the statement “If the problem intensifies later, there will be audible cues prior to a total failure of the surface, and we'll address it then by tearing it down, and rebuilding it.” Maybe. But Mark’s final build engine will be so loud as to defeat this audible transaxle warning indication. :lol

And I am sure you are aware you do not need to go to Ford or Ricaro to get a replacement bearing for the transaxle. Probably no printed OE P/N available anyway as the transaxle assemblies are not “serviceable”. Just go to a bearing house with the removed bearing in hand…

Indy GT said:

My only thought is the weak-link theory. If you utilize larger rear tires capable of absorbing more torque and you transmit the (higher) engine torque to these the rear wheels through improved capably half shafts, if something is to fail, it will likely occur in the transaxle. Which could be expensive to fix or beef up. The lesser strength (if it is necessary) OE half shafts might provide a mechanical fuse to protect the more expensive-to-fix transaxle.

Click to expand...

From a practical, non-theoretical perspective, this is exactly what we experience in the off-road 4WD community, where we run 33"-35" tires replacing OEM 31"s (or much grippier tires than stock). Axles break > Put in stronger axles > Diffs break.

Perhaps the Ricardo diff is overbuilt for the OEM axles/CV-joints. And, most likely, the tires are going to break loose first.

Indy GT said:

There goes Frank sticking his nose into the technical jungle with medical metaphors. Check back with us in 4 hours Frank. Or check with your doctor.:rofl

MoTeC – the 300M is good material. My only thought is the weak-link theory. If you utilize larger rear tires capable of absorbing more torque and you transmit the (higher) engine torque to these the rear wheels through improved capably half shafts, if something is to fail, it will likely occur in the transaxle. Which could be expensive to fix or beef up. The lesser strength (if it is necessary) OE half shafts might provide a mechanical fuse to protect the more expensive-to-fix transaxle.

I agree with your thoughts on just cleaning up the pinion teeth edges, installing a new bearing and putting it back together. Although I had to chuckle at the statement “If the problem intensifies later, there will be audible cues prior to a total failure of the surface, and we'll address it then by tearing it down, and rebuilding it.” Maybe. But Mark’s final build engine will be so loud as to defeat this audible transaxle warning indication. :lol

And I am sure you are aware you do not need to go to Ford or Ricaro to get a replacement bearing for the transaxle. Probably no printed OE P/N available anyway as the transaxle assemblies are not “serviceable”. Just go to a bearing house with the removed bearing in hand…

Click to expand...

Xcentric said:

From a practical, non-theoretical perspective, this is exactly what we experience in the off-road 4WD community, where we run 33"-35" tires replacing OEM 31"s (or much grippier tires than stock). Axles break > Put in stronger axles > Diffs break.

Perhaps the Ricardo diff is overbuilt for the OEM axles/CV-joints. And, most likely, the tires are going to break loose first.

Click to expand...

I have a set of the hardened axles from Mr Florida in my car since 2010 and have beat the crap out of that car since then with no issues at all with my transmission. Mark H ran a stock tranny with the stronger axles at the mile all those times including the 278mph run. Don't over think the stronger axles thing and something else is gonna break theory. Real life experiences trumps engineering bench racing in this matter. That tranny is WAY overbuilt.

Mullet said:

I have a set of the hardened axles from Mr Florida in my car since 2010 and have beat the crap out of that car since then with no issues at all with my transmission. Mark H ran a stock tranny with the stronger axles at the mile all those times including the 278mph run. Don't over think the stronger axles thing and something else is gonna break theory. Real life experiences trumps engineering bench racing in this matter. That tranny is WAY overbuilt.

Click to expand...

It all comes down to traction and tires. If you run the mile with from a roll you will see less stress on rear axles or the tranny than if you run sticky tires and do hard launches from a start like at a drag strip. I can say over the years of racing everytime I made more power or used sticky tires I found the weak link. I have been running the new MTs drs Et 2s with only upgrading my half shaft bolts. I like the idea of having a cheaper weak link before the tranny like a fuse like Indy said. I needed heavy duty parts on my drag car and Always found the weak part but parts were way cheaper then these gt parts. So make power and if you spin your tires you will only be replace tires. If you get sticky tires you will break half shaft bolts, if your bolts are better you will break axles. So on and so on. What I have learned is guys like Mullet have proved even running well into the 9s on a prepped track with a stock trans and did not break drivetrain parts. Did the engineers over built these parts? until people start breaking parts we do not know the limit yet on hp or torque or tires that will start breaking stock drivetrain parts. We do have an idea on the limits of engine parts but I think the fuel system will cause more issues at this point if you want to make big power. I do not use Hp because a blower cars needs more fuel to run the same hp numbers a turbo shows. Thanks to Mullet and other like you that take the gt to the limit so others down the road can learn from our triumphs and failures. now break some parts for us. :thumbsup

I just spent 2 hours reading the whole build . Wow. I think most of us after this will have little to add and more to learn. You will need those MT tires trust me they hook. Good luck . I liked the lower throttle body idea with the blow offs. Mad skills.

Indy GT said:

MoTeC – the 300M is good material. My only thought is the weak-link theory. If you utilize larger rear tires capable of absorbing more torque and you transmit the (higher) engine torque to these the rear wheels through improved capably half shafts, if something is to fail, it will likely occur in the transaxle. Which could be expensive to fix or beef up. The lesser strength (if it is necessary) OE half shafts might provide a mechanical fuse to protect the more expensive-to-fix transaxle.

Click to expand...

A valid concern no doubt... at the moment we don't plan to start on drag radials or anything similar so I expect and agree with Jason's opinion and experience. Ultimately the upgraded half-shafts we have, upgraded stub shafts we are talking about, further coupled with a Wavetrac diff and PPG gear set would be the ultimate...

Indy GT said:

I agree with your thoughts on just cleaning up the pinion teeth edges, installing a new bearing and putting it back together. Although I had to chuckle at the statement “If the problem intensifies later, there will be audible cues prior to a total failure of the surface, and we'll address it then by tearing it down, and rebuilding it.” Maybe. But Mark’s final build engine will be so loud as to defeat this audible transaxle warning indication. :lol

Click to expand...

Lol... possibly for sure! Our headers and rear exhaust on Mark's GT is fairly loud outside but windows up it's not that bad in the cabin... can talk easily with passengers and phone conversations are not difficult to hear. With the addition of solid mounts... I don't think drivetrain or powertrain feedback will be an issue! We just did another GT with solid mounts, it isn't overbearing but you definitely get more feedback and are more "in tune" or "connected" to what is going on with the car with the solid mounts! I recommend them....

Indy GT said:

And I am sure you are aware you do not need to go to Ford or Ricaro to get a replacement bearing for the transaxle. Probably no printed OE P/N available anyway as the transaxle assemblies are not “serviceable”. Just go to a bearing house with the removed bearing in hand…

Click to expand...

Agreed... I'll be looking for a ceramic replacement or other high quality bearing....

Cheers!

MoTeC Magic said:

Our headers and rear exhaust on Mark's GT is fairly loud outside but windows up it's not that bad in the cabin..

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LOL! Mark, suggest you use another car when you are working. You will be heard miles away.:biggrin

SMOKDU- I agree with you. Mullet is “lead-the-fleet” for modifications to our GT although the MoTeC Magic being performed on Mark’s car is up there as well. You absolutely do learn from failures! But do not wish those on either of these envelope pushers. Just great to have them in our ownership community.

And one other minor detail. The half-shaft bolts we had to replace on our cars are not in the “torque-path” and actually have very little service loads. That low-load fact was the confounding issue to those trying to understand the root cause of the failure. It was not load induced, just a bad plating material microstructure interaction. No need to have “high strength” fasteners at this station.

Can't wait for it to be done and see how it performs? I'm sure you are even more anxious than us. Keep the pictures coming, they are great. I also love the discussions your car generates. Very educational.

Wow - what a thread!

Ed