PTU Failure types

L

lamrith

New member
Posts in another thread got me thinking, that is usually foreign and dangerous terrotory so bear with me..

We all know the PTU's on our beloved behemoths are a significant weak link.  People in the past have thrown out the idea of banding together to develop a replacement unit, but those dreams always seem to fade away into the sunset as no shop are interested.

Something that might help make a run at replacement development would be to firmly identify the failures.  I have a feeling that without information on what is failing, most places will be less than interested in undertaking such a project.  The can of worms is just far to large to even entertain the project.

SO, that is my question, beside the base known issue of excessive heat )which can cause a wide range of issues), What exactly is failing on the PTU's most commonly? 
I have seen:
  • shattered cases
  • blown bearings(case flex or heat?)
  • disintigrated frictions(heat or sheer workload?)
Is there any one issue that is more common type of failure?  My thinking is that if one issue is more common, maybe it will link to other failures and give a shop a target to address?

So lets say case integrity is the primary failure, some explode externally, others flex enough to cause bearing failure.
A fix for that is to tweak the case design, maybe even as simple as a billet steel case with the same internal component layout.  Take the flex out of the housing by using a stiffer and more durable material.  I for one would not bat an eye if the weight of the PTU jumped by 1/2, if it meant that it was much more durable.  Then once you custom make a case, you open up all sorts of possibilities for filtration, cooling etc.

Thoughts?
 
I am sure the bearings being upgraded along with the case would help immensely along with better cooling and more fluid capacity.
 
I am not an engineer but, the easiest fix and one I intend to implement is, heat shielding. I am going to try and wrap the down pipes and keep some of the heat off the oil so it doesn't breakdown,  turn to sludge. That will make the oil lubricate better and also,  cut down on the heat the bearings and gears generate them selves. This is very cheap to do,  plus change the oil every 30k as previously discussed in other forums. I  can do it myself and do it now.  I won't have to wait and spend thousand on a final product, when ever it finally makes Mass production and can be bought. Not saying this is a bad discussion. In fact I'm glad to have a place to talk about it and bounce it off others to get feed back.

Sent from my VS995 using Tapatalk

 
I fully agree preventative measures will probably help with most issues.  I still hope to spend some time under the car this summer and see if I can devise a way to tap into the sensor and drain ports to make a filter.cooling setup.  Just tough to do since it is my DD and I cannot take it off the road for any amount of time to experiment.

Just seems to me that beyond the oil issue, the case may be weak and not able to take power beyond a certain point routinely and reliably.
 
im running into a problem right now car goes into a safe mode front wheel drive must be due to heat I posted up thinking it was tire pressure which that might have made it heat up faster. Ive got Royal purple fluid in it may have to look into AmsOil gear lube.
 
The Quantum Blue gear fluids are pricey but perform well IMHO.

Derrick, it sounds like you have a mechanical issue that probably won't be fixed with fluid.

Sniff around the PTU and see if it smells like propane or natural gas. That's the first clue your fluid is cooked.

How is your tread from front to rear? If the difference gets large enough that can cause PTU unhappiness.


 
I would agree likely has nothing to do with the  RP fluid.

I've used RP religiously throughout my SHO simce the 1st changes YEARS AGO (only exception being the trans fluid) and I haven't had one failure yet to date.

Don't be so quick in dispelling its' (continued) use Derrick.
 
Not a quick in dispelling by no means ive followed people's builds on these cars and have been around car all my life so I give things a chance plus I turn my own wrenches on my cars. I know we are not allowed that much difference between the back and front. Car only seems to do it once it heats up. I read A post about doing the ATF in the PTU with some gear oil to get the sludge out because mine is bad.
I want to drill and tap for a drain plug as well.
 
DerricksSho said:
Not a quick in dispelling by no means ive followed people's builds on these cars and have been around car all my life so I give things a chance plus I turn my own wrenches on my cars. I know we are not allowed that much difference between the back and front. Car only seems to do it once it heats up. I read A post about doing the ATF in the PTU with some gear oil to get the sludge out because mine is bad.
I want to drill and tap for a drain plug as well.
Click to expand...

Where would the drain plug go?  has anyone actually done it?
 
i think 1 person over on shoforum has done it LOL.  IME, Amsoil Severe Gear is heads and shoulders above Mobil1, Valvoline, and other similarly priced brands.  It makes the AWD operation effortless.  I like it a LOT.
 
Whether its 2007 or not. ^^^^^^^

Amsoil is still prolly the top gear lube mfgr as well as other products.


SHOdded said:
i think 1 person over on shoforum has done it LOL.  IME, Amsoil Severe Gear is heads and shoulders above Mobil1, Valvoline, and other similarly priced brands.  It makes the AWD operation effortless.  I like it a LOT.
Click to expand...

 
Silverback said:
DerricksSho said:
Not a quick in dispelling by no means ive followed people's builds on these cars and have been around car all my life so I give things a chance plus I turn my own wrenches on my cars. I know we are not allowed that much difference between the back and front. Car only seems to do it once it heats up. I read A post about doing the ATF in the PTU with some gear oil to get the sludge out because mine is bad.
I want to drill and tap for a drain plug as well.
Click to expand...

Where would the drain plug go?  has anyone actually done it?
Click to expand...
I’m still trying to find time to do this , I’ll
start a thread once it happens.
Not my pic or measurements, found on edge forum I believe.
I do have my old ptu to practice on first lol.
ca709e7a2d379ee018b230cad59d6598.jpg
 
HA:

I Found a place to post, So got my car back from the dealer
(after Three Months) motor out to fix the oil leak, and well i will not go into the total detail now
(it will be a book), on and off for 2 weeks BACK to the DEALER...? after a couple of 100 plus mile an hour runs, put it in the garage, and then the next day into reverse, it locked the car up, Cracked the PTU, yea now i have broken everything except the Drive shaft and rear end.....HA

wait there is still time.... :blowup:
 
irondoor19 said:
HA:

I Found a place to post, So got my car back from the dealer
(after Thee Months) motor out to fix the oil leak, and well i will not go into the total detail now
(it will be a book), on and off for 2 weeks BACK to the DEALER...? Cracked the PTU,
yea now i have broken everything except the Drive shaft and rear end.....HA

wait there is still time.... :blowup:
Click to expand...

DUDE!? Are you sure your not driving my car?  :D
 
All the failures I've seen in the fleet seem to point to cooked out thick fluid. Once the unit starts to fail it's toast. Most likely starts with gear failure and once there's metal in the system and poor lubrication it takes everything with it. Once the bearing integrity is gone-Bang!
 
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