Dead Allison?

[Mark Rinker]

Well, it doesn't sound good this morning. Last night at 3AM, a trusted and careful snowplow operator called me, to report a ''serious transmission problem" with the 2006 K3500 flatbed (~115K miles).

This truck was ordered out as a cab/chassis by the original owner and upfitted with a hauler work body. He hauled gooseneck loads of hay. We have rolled up ~80K hauling gooseneck loads of everything, cross-country transportation of oversize boats, snowplowing while toting around a v-box sander...its lead a life of heavy duty, daily use - but always received good periodic fluid maintenance as well.

Heres what I know so far:

Normal operation, normal trans temp, light snow conditions
SES light had been illuminated since previous day, but not yet diagnosed
Truck stopped reversing, then stopped movement altogether.
Transmission temp rose to 280F and dash indicator came on indicating TRANS HOT - IDLE, which the operator did.
Hot smell apparent outside vehicle, trans appears to be full of fluid, which was recently drained/filled and new spin-on filter.
After cooling down, driver reported sluggish forward performance, which he used to get back home, tranny makes 'terrible noises' if requested to Reverse.
Transfer case function appears normal. At this point we are assuming transmission based on loss of gears, hot trans temp, etc. but need to rule out xfer case problem as well.:(


Making some repair estimate calls...its clearly out of warranty. Need to get this done for the cheapest method that gets it right the first time.

I am thinking either

Buy a used Allison 1000 (and possibly transfer case combo) out of a lower mile, daily driver wreck and replace both, selling my broken transmission as a core and the working transfer case to defray repair costs;
Turn the truck over to the local GM dealer$ship, get a reman unit in$talled, with warrantyAm hesitant to have anyone rebuild the transmission, other than a certified Allison transmission repair facility. In their own words, local GM shop 'never sees' broken Allisions and has limited repair experience...

Thoughts?

[More Power]

The standard rule of thumb when dealing with out of warranty repairs is to take whatever apart to discover what happened. Once you know the extent of the problem, you can make a decision about what to do. In many cases, the repair is reasonably easy and inexpensive.

I agree about taking the trans to an Allison dealer. The local GM dealers here take any Allison work to the local Allison shop. ;)

A rebuild will likely cost as much as a good low mileage take-out. Knowing which way to go depends on how much you trust the shop doing the rebuild and whether there's a rebuild warranty.

Jim

[Mark Rinker]

Tranny - or at least torque converter - is clearly toast. I had noticed a smell the other day in the cab, that I didn't recognize. Turns out that smell x10 was lingering around the truck this morning.

Tranny fluid is <3000 miles from a drain/full interval and its already clearish/brownish - and stinks to high heaven. No forward movement, but was able to get a small amount of reverse by shifting the xfer case to 4LO and flooring it. (Not a good feeling to do this to a truck you respect...but I doubt there is any more damage to be done.)

Purchased a used 65K mile Allison 1000 (with used torque converter) this afternoon from a reputable recycler. Planning to reuse xfer case as all function there appears normal. Spent lots of time on the phone with GM and three other independents before selecting a shop willing to do the swap, but was knowledgable about rebuilding as well. They plan to pull the pan, check the filters, and do their level best to make this a good swap with no return issues.

I was hoping to possibly 'get by' with just a torque converter replacement, but the shop/tech I selected indicated with the amount of fluid damage present, it wouldn't be wise to risk doing just a converter, even if that was the culprit. Too much downstream contamination, according to him, and since I have seen burned fluid in this transmission before, I am going to follow their advice and swap out the whole transmission and converter. Its also a much cheaper approach to the problem - a full teardown and rebuild or GM warrantied remanufactured transmission would be over $5000, installed. I'll get through this for around $2800, based on today's estimates.

We'll also address the weeping transmission cooler lines during the swap...

Another day. :o

[Kennedy]

Mark,

Don't forget the case pump wear plate.

If the used deal falls thru I did come across a listing for good used low miles w/tcase.

[madmatt]

make sure they flush the cooler!

[Mark Rinker]

Mark,

Don't forget the case pump wear plate.

If the used deal falls thru I did come across a listing for good used low miles w/tcase.

Is the wear plate still a necessary upgrade in a 2006 model year truck? I thought that design defect had been corrrected some time ago? Thanks for the reminder!

[Mark Rinker]

make sure they flush the cooler!

Quote from repair shop includes flushing cooling system, and repairing any cooler line leaks. Thanks for the reminder!

[Kennedy]

Is the wear plate still a necessary upgrade in a 2006 model year truck? I thought that design defect had been corrrected some time ago? Thanks for the reminder!

It was quite recent that GM released their "fix" which is nothing more than a heavier clip.

I'd say about 30 minutes tops to split the Tcase add the plate and reseal/assemble. It's already out and as a matter of principle I won't R&R one without doing this.

[Mark Rinker]

I'll make sure it happens - thanks for bringing this up.

[Mark Rinker]

I spoke with the tech today, we spent quite a bit of time on the phone, here is his analysis, based on the downloads from the stored codes/data, and physical examination of the transmission:

There have been a few logged 'events' where the transmission temperature spiked in an unusually short timeframe, setting codes in the system. Because of the short time duration of these events - he questions if they could even be real, or are faulty sender/electrical in nature. If real, they would most likely indicate torque converter failure - as only that failure could shear and heat the volume of fluid in the Allision system that quickly. The plow driver did report that "...one minute everything was normal, and the next he had 280 degree fluid and no movement..." My guess is the torque converter failed.
The condition and contamination of the fluid throughout the system, combined with the fact that it was recently refreshed (<3000mile) and had a previous history from last summer of scorched fluid, prompts him to recommend the approach of swapping in the used transmission and torque converter I purchased. (i.e. if we had the same drivability symptoms, but the system fluid was still clean and bright, we might simply swap the torque converter and see if we could get by without rebuilding or replacing the entire transmission...) There is simply too much system contamination and history to risk doing this labor intensive and expensive componant swap, twice. Downtime and lost business use is also factored into this decision.
We acknowledged that the truck's previous owner had towed heavy loads and had offered to sell us the programmer he had used with the truck. I have no way of quantifying what level the programmer was set on, or how the truck was used, but it did need u-joints shortly after we bought the truck at 35,000 - which could indicate heavy towing/high power use.
The truck was used to tow heavy, tall (buku wind drag) boats last summer in hot conditions. There was one event in Montana mountains where the operator reported a transmission overheat event. The truck was running a moderate tow tune at that time - after the truck was back home, I tested it with gooseneck loads and experienced a 'shudder' through the floorboards that I now believe was torque converter slippage. The truck was returned to stock settings, fluid refreshed (drain and fill method) and fluid quality appeared to stabilize, driveability normal with gooseneck loads of ~12K daily.
One of the topics we talked about at length was the apparant slippage this transmission had endured - but the fact that the truck had NEVER limped. The tech reported that he has seen this happen in some 'later model year' trucks - where the torque converter or C2 clutch has been destroyed from heat and slip, but the owner had never been 'warned', or transmission protected by a limp. My concern for other 2006 LBZ owners: Is this a factory defect of ECM/TCM programming, transmission sensor/hardware, - or could factory protection have been overwritten by a bad aftermarket tune?
We will never conclusively know the root cause of this failure. It could be a production defect in the torque converter or clutches of the Allison, that slowly played out over time. It could be the life that this truck led - a cab/chassis outfitted to tow, and used in that manner every day of its existance. (i.e. probably has double or triple of the wear-miles on the odometer's 115K when you consider the loads and multiple drivers this transmission endured...)In summary and with the benefit of hindsite and retrospect, I would arrive at the conclusion that this transmission would still be together today if the truck had been left at left at stock power levels. The previous owner's programmer and usage and/or our second quest last summer to find fuel $$$ savings and more towing power - may well have cost us plenty with this particular truck.

I'll post the codes that were pulled when I pick up the truck later today from the repair shop...

[More Power]

or could factory protection have been overwritten by a bad aftermarket tune?

The TCM monitors the transmission, and will request that the ECM set a DTC code and MIL illumination if slip is detected. Unless the ECM was programmed to ignore TCM MIL requests (why would anyone do that?), it should still set slip codes and overtemp codes. ;)

Jim

[Mark Rinker]

We got the overtemp MIL and message. Twice in ~80K miles. Once in the mountains towing an oversized boat in the summer, the other as the transmission failed.

The only slip indicator was the burnt fluid, and a definate short-duration buzzing vibration up through the floorboards upon heavy, loaded acceleration that (in retrospect) was torque converter or clutch slippage under heavy load conditions. Never a MIL. No limp - ever - was experienced on the 2006 K3500 dually.

Why would anyone do that? I would like to think that what we are chasing here is a factory programming or even electrical problem - TCM to ECM communications related - or a factory communications change that the aftermarket tuners didn't pick up on, and is only present in certain model years, makes, or applications. This truck was an odd bird - early 2006 LLY code truck, with LBZ engine, and ordered as a cab/chassis...I certainly think its possible that it came out of the factory with a TCM that wasn't talking correctly to the ECM. Turn it up too far, and with no limp and/or MIL (codes) you have no feedback loop to let you know that its time to stop the abuse...!

For example, I am fairly sure the TCM and ECM slip threshold parameters and MIL communications is unique to my C4500, say if compared to my K2500 or K3500. The reason I say this is I have tested the same handheld programmer on both an LB7 K2500 and the LB7 C4500, and suprisingly - the C4500 wouldn't hang on to one tune with just a gooseneck trailer and a pontoon boat - without limping and illuminated the MIL. The same tune on a the K2500? It would pull it all day...so there must be unique programming across models, some that may even be over protective, as in the case with the C4500...

[Mark Rinker]

Well, the truck was done last Friday afternoon - we had the used ~65K mile Allison and matching torque converter out of a salvage truck installed.

Our temps dropped sub-zero Sunday night with snow, so the first use was plowing and sanding in terrible, frigid temps - trans seems to shift fine and no leaks, so I'll be keeping my fingers crossed. I am glad this was a used trans vs. new or rebuilt, as its already broken in and not brand new parts/clutches being subjected to such a harsh break-in experience, with thick cold fluid.

$2600 total for the used trans/converter + diagnostics/labor/cooler flush + two new tranny cooler lines, installed. Not too bad, all considered...I paid more for a remanufactured 4L80E behind a 6.5L about three winters ago, these are the only two transmission failures in nearly 700K miles total GM diesels.

If the average is going to be every ~350K in service miles for the fleet - I guess we can live with that.

[JohnC]

... This truck was an odd bird - early 2006 LLY code truck, with LBZ engine...


Mark:

Not sure what you meant by this, but the 2006 "LLY" trucks are LBZ's in every respect except they are program limited to LLY power levels.

[Mark Rinker]

This mystery makes even more sense - after John's last posting. If the early LBZ (LLY code) trucks were program limited to 2005 LLY power levels, then adding an aftermarket program (designed and tested on true 2006 LBZs - with late 2006 ECM/TCM programming) could easily exceed power levels assumed by the factory engineers for the early Allison 1000/TCMs installed on those trucks, during the production cutover... If they limited the power on those early LBZs to 2005 LLY power levels, wouldn't that indicate they were using the same TCM settings?

Lesson: In the future, if I ever smell stinky fluid in an Duramax/Allison that has not yet failed, and is not limping due to transmission slippage, I'll certainly replace the torque converter as a precautionary measure...

[DmaxMaverick]

Makes sense to me that ECM/TCM programming would have to be updated to reflect this, when the 'true LBZs' hit the production line. From my software background, sometimes all affected departments don't get their programming changes tested or in on time, manufacturing is still using up whatever they have in stock, and things don't happen in a coordinated fashion...

What if an early LBZ (LLY code) got an Allison 1000 behind it - with 2005 LLY TCM programming? Then...what happens if you add ~70hp over stock to that?

My real world experience says the torque converter slips (without setting and SES or a limp) the fluid eventually fries, and you eventually spend $3000 for the lesson...!!!

In the future, if I ever smell stinky fluid in an Duramax/Allison that has not yet failed, and is not limping due to transmission slippage, I'll certainly replace the torque converter as a precautionary measure...

Not at all likely. The 2005 Allison is a 5 speed, and the 06 (LLY or LBZ) is a 6 speed. The trannies are virtually identical, mechanically, but are not directly interchangeable due to valve body and electrical/electronics differences. If a 2006 powertrain had 2005 TCM/PCM programming, 6th gear wouldn't work.

[Mark Rinker]

Hmmm...damn...so much for that idea. :cool:

So, riddle me this.

If we knew that +40-50hp was the tow-safe max for the 300hp stock LB7, how is the aftermarket still adding that, and more, to the 360hp LBZ? i.e. What happened to the Allison 1000 to help it stand up to a total of 100+ hp, when it couldn't in 2001-2004?

[DmaxMaverick]

Good question. In stock form on the LBZ, the additional power is only available in gears 2-4. Outside of that, the aftermarket depends on GM's updates to the tranny to keep it together. Higher power levels will meet the same results, though. The off-the-shelf power adders are somewhat less aggressive than for the LB7 and LLY, too. The maximum outputs are about the same, regardless of the engine. Of course, there are exceptions with some aftermarkets. Thats where the additional disclaimers and fine print comes in.

[cabletech]

Good question. In stock form on the LBZ, the additional power is only available in gears 2-4. Outside of that, the aftermarket depends on GM's updates to the tranny to keep it together. Higher power levels will meet the same results, though. The off-the-shelf power adders are somewhat less aggressive than for the LB7 and LLY, too. The maximum outputs are about the same, regardless of the engine. Of course, there are exceptions with some aftermarkets. Thats where the additional disclaimers and fine print comes in.


I don't think this is true of the LBZ/LMM 6 speed. There were hardware changes made to handle the extra power of the LBZ/LMM. I have had my truck on a dyno and there is no less power in 5th or 6th gear with the stock tune (except for speed limiter) compared to 4th gear.


Jay

[DmaxMaverick]

I don't think this is true of the LBZ/LMM 6 speed. There were hardware changes made to handle the extra power of the LBZ/LMM. I have had my truck on a dyno and there is no less power in 5th or 6th gear with the stock tune (except for speed limiter) compared to 4th gear.


Jay

You may be right. I'm quoting the GM engineer release. What were your power outputs in 4, 5 and 6?

[cabletech]

They were all about 300hp at the rear wheels. I have seen some GM docs about reduced power and they were for the LLY. There were no hardware upgrades for the 5 speed when the LLY was relased.

Jay