Broken input shaft 4L80E

[eazly]

I have recently rebuilt my engine. 18:1 marine pistons, turned up pump, shop made high flow injectors, waste gate linkage boost upgrade from diesel injection service, and K&N filter. My truck has alot more power now compared to before. I just got back from a hunting trip. I hunt in Alabama. I was hauling a 2000lb trailer with 3 four wheelers and hunting gear. Doing about 85 mph in the hills. 210 max engine temp, 20+ lbs of boost(in the hills). I have yet to install tranny temp guage and pyro guage. About 40 miles from Montgomery my truck stop pulling after running like a champ from Lafayette LA(375 mi). It would not pull at all. I was confused :confused: Had it towed to the AAMOCO in Montgomery. They hooked the computer to scan and found no codes set. They dropped the pan and could not diagnose the problem. They had to tear down the tranny to find the problem. It turned out that the input shaft to the tranny was busted in two. "MORE POWER" I got it. They rebuilt the tranny and I am back on the road again. I have checked the torque rating on the 4L80E and found that it is only rated for 440 lbs of torque. My question is? Does my motor with modifications exceed the torque of 440 lbs. I think it does. I drove my buddy Duramax the whole time my truck was in the shop and my truck pulls better than his. :D

[rjschoolcraft]

I would suggest that your input shaft had a flaw that would have caused failure eventually anyway. The 4L80E is based on the THM 400. They are tough transmissions. The torque ratings are based more on the clutches and their holding capacity than on the mechanical hardware. If you increase line pressure, you can run well over the torque limit as spec'd from the factory.

[eazly]

Do you have a 4L80E tranny? If so,how hard do you drive it?

[rjschoolcraft]

Yes, I have a 4L80E transmission. I drive it hard. See the thread Significant improvement in towing performance! (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005059) for a more descriptive answer.

[eazly]

So did you increase your line pressure? If so, how is this done? THANKS

[Kennedy]

Does it have a dual stator converter?

Conventional wisdom theorizes that with the abrupt stopping and rocking (high cylinder psi) at shutdown on a diesel engine can twist these shafts when using dual stators...

[rjschoolcraft]

On my 95, this was accomplished through the use of the Kennedy TDMax chip. However, there are other ways to do it. Check out some of the advertisers on the Page and you'll find something suitable.

[eazly]

I'm not sure what a dual stator convertor is. I can call AAMOCO to find out though?

[Russell Warren]

Seems your problem is similar to one that I had. My '93 Safari motorhome with a car in tow weighs about 18,500 lbs. I always drive it easy as is required for safe RV use. With less than 50K miles the input shaft broke and destroyed my 4L80E. My inspection made me believe that there had been an internal defect that caused the problem. I showed the pieces to several DP members who disagreed. My rebuilder said that he had seen several broken input shafts.

[eazly]

My rebuilder said that he had never seen that failure before, but I think it must be a common thing for this tranny because I've found a site that offers a beefed up input shaft designed to handle increased amount of horsepower and torque. The shaft is made of a different type of stainless(4340 I think). I just would like to know If my tranny can hold up to my stronger motor. I will not change driving habits so do I need to beef up my tranny to match my driving habits is the question?

[rjschoolcraft]

4340 is not a stainless steel. It is a high strength steel alloy that can be case hardened by nitriding.

[Kennedy]

Originally posted by eazly:
I'm not sure what a dual stator convertor is. I can call AAMOCO to find out though? The trans shop should be able to tell you this if they have it apart.

[moedog]

DONT LET THEM FOOL YOU. YOUR GM TRANNY HAS AN OIL PASSAGE THRU THAT MAIN SHAFT AND WHEN YOU BOOST UP THE HP AND TORQ.AS YOU DID, IT WILL SNAP AGAIN. YOUR REAL ONLY WAY TO BEAT IT IS TO GO TO A 5 OR 6SPD. MANUEL AS IM DOING TO QUIT BREAKING SHAFTS

[rjschoolcraft]

"Don't let them fool you?" That's what I'm all about. Fooling people into breaking their equipment. I've been exposed. :rolleyes:

[Jim P]

Like Ronniejoe stated, 4340 is a high strengh steel alloy. Also like he stated it can be case hardened by nitriding but it can also be through hardened.

I work at a shop that makes parts for overhead cranes. Some of these cranes hold a ladle that is full of 200 tons of molten steel with people working on the floor so these have to be extremely durable. I have made many axles for these cranes and they are always made of 4340 or 4140.

I have never had any experience making a transmission shaft from 4340 but I did make a transmission gear for my old David Brown tractor out of this material. It is still working today even after taking it to the tractor pulls.

[rjschoolcraft]

The aircraft industry, especially gas turbine engine manufactureres, make shafts out of 4340 all of the time. It is a great shaft material and I've spec'd it many times for shafts. However, in through hardened form, it has very little fracture toughness and does not perform well in bending.

It is not a good choice for gear steel because of two reasons. One, case hardness is usually only applied through the nitriding process. Nitride case depths are not very deep, on the order of .010-.015" max. Depth of case is important because when contact loads are encountered, Hertzian deflections at the surface cause subsurface shear stresses to occur deeper in the part. For the gear to live, the subsurface shear stress must occur within the case hardened zone. Furthermore, a phenomenon known as "case crushing" can occur on thin case parts. Again, this has to do with the depth of the subsurface shear stress. Fatigue cracks can form below the case causing it to fracture off the part. Nitrogen embrittlement problems are a concern. If you try to drive the case any deeper, the surface of the part becomes overly rich with nitrogen. Iron nitride networks form between the grain boundaries causing its fatigue strength to plummet. Second, as stated above, the the through hardened form cannot live up in bending fatigue.

Gears need a material with good core properties: good ductility, high fracture toughness, high tensile strength to support the tooth in bending. They also need good case properties: deep case depth with gradual case to core gradient, high surface hardness, minimmal (to zero) intergrannular imperfections to support the tooth in contact. Also, case depth is important at the root of the tooth for bending fatigue.

Most automotive and tractor gears use SAE 8620 steel. Almost universally, aircraft use SAE 9310 steel. 8620 has better contact fatigue properties than 9310, but 9310 has a huge advantage in fracture toughness and ductility. Since tooth breakage is a sudden catastrophic failure, aircraft sacrifice some surface durability to have longer bending fatigue life. There is no where to pull over and park in flight. Almost all aircraft transmission use a device to monitor debris in the oil... a magnetic chip detector. Since contact fatigue usually causes small particles of the tooth surface to break off long before catastrophic failure, the detectors can identify that failure mode early so maintenance can be done.

4340 has been used for gears in some cases, but they have all been in lightly loaded conditions in non failure critical areas. If you'll notice, the gear steels that I mentioned above are all low carbon steels. That is because carburizing is the best currently known method to apply case depth to gears. Carbon is diffused into the surface of the part in an oven with a carbon-rich atmosphere at high temperature (1700+F). Case depths up to .030" are possible on properly selected geometries.

Another method for case hardening 4340 is by induction hardening. Deeper cases are possible than with nitriding, but there is a very radical case to core interface with very high residual tensile stress. This is bad and causes case separation under load (in some cases, even when sitting on the shelf never used).

[Jim P]

Ron,

I agree totaly that 8620 is the normal material to use to make gears and then they are carburized and hardened. We don't normally make gears at work so I didn't have access to any 8620 material but we use alot of 4340 so that is what I used. I agree it is not the best but it didn't cost me anything and it is still working, so for me that's what counts.

We have blanked out some gears for cranes but had somebody else cut the teeth. They were made of 4140 if I remember right and they were flame hardened.

[Kennedy]

Originally posted by moedog:
DONT LET THEM FOOL YOU. YOUR GM TRANNY HAS AN OIL PASSAGE THRU THAT MAIN SHAFT AND WHEN YOU BOOST UP THE HP AND TORQ.AS YOU DID, IT WILL SNAP AGAIN. YOUR REAL ONLY WAY TO BEAT IT IS TO GO TO A 5 OR 6SPD. MANUEL AS IM DOING TO QUIT BREAKING SHAFTS The 4L80E was the old standby in my '96. It never gave me a lick of grief. Truth be told, I don't think that there is a 6.5 built that can twist a 4L80E input shaft with pure torque.

Again, the dual stator theory...

[moedog]

PROBABLY ALL FAILURES FROM OTHER PROBLEMS. HA HA HA .IVE NEVER MET A 6.5 OWNER YET, THAT WILL ADMIT ALL THE WEAK DESIGN FLAWS THE FACTORY DESIGNED INTO THE 6.5S FROM 94 ON!!INCLUDING MYSELF! GUESS THEIR LIKE A REAL NAUGHTY WOMAN, YOU HATE THEM DEEP DOWN BUT KEEP THEM AROUND AND FIGHT FOR THEIR HONOR THEY NEVER EARNED.

[rjschoolcraft]

Let's see... 189,000 miles... hard working, trailer towing miles at that... not the first problem... yep, it's a bad design.

Edit: I had a slip of the fingers. My original post said 289,000 miles. It should have been 189,000 miles as it now reads. Still, that's a lot of miles on the transmission with not the first hint of a problem.

[ 02-10-2004, 06:37 PM: Message edited by: ronniejoe ]

[moedog]

AND HOW MUCH MONEY DID YOU POUR INTO IT WITH ALL YOUR UPGRADES TO MAKES IT LAST THAT LONG!!!!!HA HA .
REMEMBER I SAID FACTORY DESIGN. THE DIESEL PAGE WOULD PROBABLY NOT BE HERE IF THE FACTORY HAD BUILT THE 6.5 THE WAY THE PAGE HAS FIGURED OUT TO MAKE IT THE MOTOR IT SHOULD HAVE BEEN.
I STAND ON ALL THE PROBLEMS THIS SITE HANDLES ,,,,,, BECAUSE THEY ARE SO TROUBLESOME. GET OVER IT AND ENJOY. GM SCREWED ALL OF US. HARD TO SWALLOW BUT TRUE. AT LEAST THERE ARE WAYS TO CORRECT THIS POOR FACTORY DESIGN THANKS TO ALL THE PAGE PEOPLE!!!

[G B Sisson]

Ronniejoe,you mean all those miles and same injectors,harmonic balancer,etc, etc.,or are you just talking about the tranny?

[rjschoolcraft]

Primarily the transmission.

My engine was replaced at 65,000 miles under warranty. However, the balancer is the original one... don't see any evidence of any problems with it. I have replaced the crank pully (at 131,000 miles last year). The original injectors and glow plugs were in it until the Christmas break this year. Total miles on those was 186,000.

I've had my share of overheating problems, but that all seems to be cured now with the upgrades that I've made. I run this truck hard. It has worked very well for me (aside from the overheating issues) and I really like it. The engine really feels strong now and I'm sure has more power to give.

I am disappointed that GM didn't get it right from the factory, but it has been fun to re-engineer the system to make it work.

The transmission has performed flawlessly. In fact, I must admit, that for a while I neglected its maintenance. Those complaining about its design don't understand what can happen in a modern factory regarding quality. Managers can get behind and have to push production to make the "monthly numbers" and force bad decisions on accepting inferior parts. I've fought those battles for years on aircraft engine parts. That's not making an excuse... I'm just saying that quality problems are different from design problems. Most people don't recognize the difference.

In response to Moedog:

All of the upgrades have been installed in the last 20,000 miles. So, it went 160,000+ in stock trim and would be going still, just not as fast. :D Next time I rip through Grand Junction, I'll have to stop and look you up. I went through there at more than 70 mph twice in November while towing my trailer. The second time, on the way back, I was about midway through the 1,000 miles that I drove that day. I started in Las Vegas, NV at 6:00 am PT (9:00 am ET) and didn't stop for the night until I was in Western Kansas at about 10:00 pm PT (1:00 am ET). I don't know how anyone could complain about that.

[ 02-10-2004, 06:31 PM: Message edited by: ronniejoe ]

[G B Sisson]

Thanks,Ron... A newcomer such as myself could be lead to believe that these engines are a nightmare of cracked heads,cracked blocks,broken crankshafts,major overheating,pump and pmd problems etc. I joined the page last October after researching my fsd failure,and was given great advice which saved me 1500.00 right off the bat.My 94 suburban has about 147,000 miles which I believe are easy miles.Bought in Oct 2002 was trade in at caddy dealer,looked absolutely like brand new,no evidence of ever having a brake controller and I dont tow except a 7000# flatbed load once a year.I am hoping to get some more trouble free miles out of her so what is reccomended for transmission maintanance?.At 50 yrs old ,somehow this is my first ever vehicle with an automatic!

[rjschoolcraft]

Just make sure you change the fluid and filter on a regular basis. Start witht the recommendatons in the owners manual and adjust to suite your driving habits and vehicle use. What usually takes out an automatic is insufficient fluid pressure to the clutch apply pistons. They slip and burn up. Insufficient pressure usually comes from a plugged filter or inadequate oil level... pump sucks air instead of fluid. If you overheat the transmission, the fluid can break down causing similar problems.

I haven't done it yet, but it is a good idea to add an external filter. More filtering capacity with finer filtration prolongs fluid life and reduces likelihood of clogging. I keep saying I'm gonna do that, but just havn't gotten "a round tuit" smile.gif ... if you know what I mean. ;)

Keep in mind, too, that by the very nature of this board, we hear most about the problems... we don't hear a lot about the successes. For instance, my uncle has a 96 that he ordered new that has never given him the first problem at all. He towed some, but not as much as me. He has somewhere around 70,000 - 80,000 miles on the truck now. He's never heard of the stuff talked about here. His truck is completely bone stock with the 5 speed transmission and 3.73 gear. His success was a large part of why I bought mine used in 2000. When he bought his in 96, the power was comparable to, if not better than, the competition. He loves it.

[Marty Lau]

GB;

I just turned 160,000 miles on my truck I bought it new and it has been a good truck. Most things have been routine other than the DAMN PMD/FSD problem. I did the cooling upgrades but most everything else was routine or "want too improvements". And I like Ronnie Joe use my truck hard I tow a 5,000 lb trailer about 3-4 days a week.

[eazly]

Does anybody think that this input shaft will break again, if so should I change the shaft now or wait unitl it breaks. Or do I now need a manual tranny.

[Kennedy]

Originally posted by eazly:
Does anybody think that this input shaft will break again, if so should I change the shaft now or wait unitl it breaks. Or do I now need a manual tranny. If it made it 193k it could have been fatigue, but again, I'd suggest looking into the dual stator theory...

[eazly]

The shop manager at the AAMOCO Transmission shop does not know what a dual stator convertor is. He told me is that it was the OE GM replacement part.

[eazly]

By the way the tranny made 315K before giving any problems. This was before the rebuild though. I only saw 6-7lbs of boost when pulling. Now I 20+ lbs of boost when pulling!

[rjschoolcraft]

I would just replace the shaft, inspect all surrounding hardware to ensure that wear or failure of another component was not the actual root cause, and move on. FWIW, the project truck has put over 100,000 miles on a 4L80E... all with a high output 6.5.

Also, pulling a 2000 pound trailer is not gonna matter much to the transmission. The torque you put through your transmission in that case will be limited by traction. :D

[moedog]

FEEL FREE TO LOOK ME UP ANYTIME. HOPEFULLY BY THIS TIME NEXT YEAR MY CHEVY WILL HAVE A 300HP 97 CUMMINS AND A 5SD WITH OVER UNDER/OVERDRIVE SPLITTER AND NNNNNNNNNNNNOOOOOOOOOOOOOO MORE CHEVY ENGINE PROBLEMS TO CUSS ABOUT. ILL LET THE PAGE PEOPLE KNOW HOW IT PERFORMS. ANY OF YOU WITH OVER 50,000 MILES AND PULL OVER 5000LBS, HAVE NEVER DONE MODS AND STILL DIDNT BURN IT UP OR BLOW IT UP SHOULD THANK THE LORD!!!! YOUR A BLESSED FEW! I,M TALKING ENGINE, NOT TRANNY. AND I AGREE THE STOCK 4SD. AUTO IS OK WITH STOCK POWER AND NO HEAVY LOADS. OVER 500LBS OF TORQ. BREAKS THE MAIN SHAFT NO KIDDIN!!!
TAKE CARE

[Bill Voitel]

Guy's JK is on the right track with the dual stator deal. Checked with buliders in our regional rebuild center this type of failuer is pretty rare but I should have more input in a coupel weeks. our new axiline trans dyno was delivered two weeks ago techs are still training on it and breaking C-6's & 350'S on it. Software not in yet for the electronic units yet but there are a coupel of 80's ready for it to see just how good our buliders are HE HE... Will post results on the 80's when software is installed and we see what it takes to break one. I have been told it will give a print out of load & torque ratings so we will know exactly what it takes to make one fail.

Bill