Drivetrain strength

[Ryan Selcer]

Ok so in the spirit of not muddying up other threads ill start a new one to ask my other questions. I did a search and don't see any driveline threads.

After talking with another member yesterday (I think it was @bpd1151) it sounds like ford engineers told him our tranny tends to have issues around the 750 crank hp number and they apparently told him as long as you stay away from that you should be ok. Now thats an impressive number to me and im not sure how much I believe it but it was exciting to hear. Now I have to ask about other parts of the drive train. So my next guess at a weak link is the PTU. As long as you keep it serviced can it handle around 550hp pretty well? Then my next guess is going to be the diff? Then the driveline? And the axles? You guys with numbers around or north of 500 what have your experiences been? @Jordan_R im guessing you've gotta be up there if your about to get bigger turbos.

 

[SM105K]

PTU! Understanding why it fails and ways to prevent failure.

Yes that thing. Here is a very good explanation by a member on here named Mr.HighCaliber.


"PTU's don't fail at least not from a power handling perspective. These only fail from lack of maintenance. Spun bearings and galling of the gears from lack of lubrication.

High Heat dries up the lighter oil molecules in the ****, which causes more heat due to lack of lubrication (thermal runaway) which leads to the remaining gear oil turning to thick black paste which clogs up the vent tube in the ptu which cause pressure buildup in the ptu which forces the remaining, non-congealed fluid out past the shaft seals. Now the only left is a thick paste thats easily flung off of the gears, sticking only to the case. After this chain of events, the bearings run dry and begin to fail, next are the gears. Tolerances widen or things begin to sieze. Bearing and gear noise are usually the first signs of mechanical failure.

But the PTU internals are stout. The weakest part of our powertrain is the RDU Atc coupler. (The electronic coupler in the rear differential). At least in terms of tq capacity and power handling."

The being said, you will need to change your PTU fluid.

 

[Ryan Selcer]

PTU! Understanding why it fails and ways to prevent failure.

Yes that thing. Here is a very good explanation by a member on here named Mr.HighCaliber.


"PTU's don't fail at least not from a power handling perspective. These only fail from lack of maintenance. Spun bearings and galling of the gears from lack of lubrication.

High Heat dries up the lighter oil molecules in the ****, which causes more heat due to lack of lubrication (thermal runaway) which leads to the remaining gear oil turning to thick black paste which clogs up the vent tube in the ptu which cause pressure buildup in the ptu which forces the remaining, non-congealed fluid out past the shaft seals. Now the only left is a thick paste thats easily flung off of the gears, sticking only to the case. After this chain of events, the bearings run dry and begin to fail, next are the gears. Tolerances widen or things begin to sieze. Bearing and gear noise are usually the first signs of mechanical failure.

But the PTU internals are stout. The weakest part of our powertrain is the RDU Atc coupler. (The electronic coupler in the rear differential). At least in terms of tq capacity and power handling."

The being said, you will need to change your PTU fluid.

Ok that was the plan, I was going to retrofit a cooled PTU onto it as well, but the original owner supposedly changed PTU every 10k so if I pull it down and it looks good maybe ill just keep doing that? But the driveshaft and axles are good? Is there an aftermarket diff that fits?

 

[SM105K]

From a transmission stand point, I agree with @bpd1151 . If you are pushing more power for peace of mind I would do the 5 out and 5 in trans fluid change every other oil change. The 6F55 like clean trans fluid. I would also upgrade your trans cooler as well. Use Mercon LV.

If I have really beat on my SHO I will change the trans fluid every oil change. I never go more then 3K on an oil change either.

The PTU fluid is super important. Under normal driving conditions I would change it every 20K. I am extreme and change it every 10K miles. I have a PP so it is easier. I personally use Redline Light Weight Shock Proof Fluid.

The RDU should be changed every 25K honestly. The RDU only has the capacity to transfer only 150 hp IIRC to the rear tires. So unless you are thrashing it consistently, 25k is good. I personally use Redline Light Weight Shock Proof Fluid as for the RDU.

Axles are stout, I personally have not seen one fail on the SHO what I have remember.

I have only seen one drive shaft failure. That was a failure from a member that lived in Germany and he was one the autobahn. Remember the driveshaft is always spinning, but it isn't always applying power. When it does apply power IIRC is only 150hp max.

 

[Ryan Selcer]

From a transmission stand point, I agree with @bpd1151 . If you are pushing more power for peace of mind I would do the 5 out and 5 in trans fluid change every other oil change. The 6F55 like clean trans fluid. I would also upgrade your trans cooler as well. Use Mercon LV.

If I have really beat on my SHO I will change the trans fluid every oil change. I never go more then 3K on an oil change either.

The PTU fluid is super important. Under normal driving conditions I would change it every 20K. I am extreme and change it every 10K miles. I have a PP so it is easier. I personally use Redline Light Weight Shock Proof Fluid.

The RDU should be changed every 25K honestly. The RDU only has the capacity to transfer only 150 hp to the rear tires. So unless your are thrashing it consistently, 25k is good. I personally use Redline Light Weight Shock Proof Fluid as for the RDU.

Axles are stout, I personally have not seen one fail on the SHO what I have remember.

Ok so no matter how much power you push at the crank the rear diff will only put 150hp out to the wheels? So if you overload it it just doesn't transfer the power or? It sounds like going over a certain HP you just go 2wd? But I haven't noticed that on any of the fastest SHOs

 

[High on Ethanol]

I definitely noticed if you trick the SHO by slowly accelerating and then let off and stomp it, you get front wheel spin. Also I noticed on launches the fronts spin more than the back. Paint a line on both tires and video it launching. OK I have too much free time

 

[SM105K]

Ok so no matter how much power you push at the crank the rear diff will only put 150hp out to the wheels? So if you overload it it just doesn't transfer the power or? It sounds like going over a certain HP you just go 2wd? But I haven't noticed that on any of the fastest SHOs

Correct. The clutch packs can only handle so much power and so much heat. The computer will literally deactivate the RDU to save itself. I can watch my "Intelligent AWD Gauge" on my dash. While I am on the freeway if I floor it, it will send power to the rear for split second, then it will stop sending power back, and stay front wheel drive until I let off.

 

[Ryan Selcer]

Correct. The clutch packs can only handle so much power and so much heat. The computer will literally deactivate the RDU to save itself. I can watch my "Intelligent AWD Gauge" on my dash. While I am on the freeway if I floor it, it will send power to the rear for split second, then it will stop sending power back, and stay front wheel drive until I let off.

Ok so it appears our drivline is good for about 600 CHP as long as your **** about fluid changes.

 

[SM105K]

I definitely noticed if you trick the SHO by slowly accelerating and then let off and stomp it, you get front wheel spin. Also I noticed on launches the fronts spin more than the back. Paint a line on both tires and video it launching. OK I have too much free time

Correct. The Intelligent AWD is re-active. It will only send power to the rear if asked it too, or if there is tire spin or slip. If you drive like a grandpa, there is a good chance you are staying in FWD the majority of the time.

 

[Ecoboost_xsport]

Correct. The Intelligent AWD is re-active. It will only send power to the rear if asked it too, or if there is tire spin or slip. If you drive like a grandpa, there is a good chance you are staying in FWD the majority of the time.

Man, I gotta believe that there is some way for the tuners to access this part of the programming and make some tweaks. Is this not happening by any of the well known tuners? Brad tuned mine but I don't think I ever asked him about this particular aspect...

 

[SM105K]

Ok so it appears our drivline is good for about 600 CHP as long as your **** about fluid changes.

I would say 500-550 would be a more accurate number.

 

[SM105K]

Man, I gotta believe that there is some way for the tuners to access this part of the programming and make some tweaks. Is this not happening by any of the well known tuners? Brad tuned mine but I don't think I ever asked him about this particular aspect...

What exactly would you be looking for?

 

[Ecoboost_xsport]

oh, was just wondering if there was anyway to get that RDU to apply, not necessarily more power, but have it apply that power more...frequently/longer periods...or even full time?

 

[SM105K]

oh, was just wondering if there was anyway to get that RDU to apply, not necessarily more power, but have it apply that power more...frequently/longer periods...or even full time?

I am sure there is, however full time AWD would create more rear and tear on the RDU. Also at some point/speed it will actually hurt performance also. Turning off or reducing the power to the RDU reduces drivetrain drag. If you aren't spinning and accelerating at a high rate of speed, there is no reason to keep sending power back.

The GTR does the same thing but in the opposite way. They are rear wheel drive, with the ability to turn the power off to the front wheels. They launch AWD, then they turn the power off the front tires as they speed up going down the track.

 

[Ryan Selcer]

Anyone looked into any possible replacement/upgrade for RDU?

 

[SM105K]

Anyone looked into any possible replacement/upgrade for RDU?

Not that I know of. They really dont have major problems breaking or not performing. These boats are seeing 1.70's to the sixty foot stock suspension on street tires. I think Jordan has gone high 1.60's to the sixty IIRC on drag radials. The system works.

 

[Ryan Selcer]

Not that I know of. They really dont have major problems breaking or not performing. These boats are seeing 1.70's to the sixty foot stock suspension on street tires. I think Jordan has gone high 1.60's to the sixty IIRC on drag radials. The system works.

That is great to hear, but you can always go faster maybe when i get mine going that quick ill look into it haha

 

[High on Ethanol]

That is great to hear, but you can always go faster maybe when i get mine going that quick ill look into it haha

You must have a tacklebox sized wallet

 

[bpd1151]

Ok so in the spirit of not muddying up other threads ill start a new one to ask my other questions. I did a search and don't see any driveline threads.

After talking with another member yesterday (I think it was @bpd1151) it sounds like ford engineers told him our tranny tends to have issues around the 750 crank hp number and they apparently told him as long as you stay away from that you should be ok

720 my friend. 720

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[bpd1151]

Anyone looked into any possible replacement/upgrade for RDU?

None that I am aware of.

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