Duramax with Hydra-Matic a good combo?

[The_LeRoys]

i am used to the duramax and Allison combo in my 2005 Silverado and love it. I need more passenger room. I'm looking at a 2008 express with the duramax hydramatic combo. I know it's not as good as the Allison. But is it still good and reliable? What do I lose?

[mr61impala]

blt2ski wrote:
Sounds like a similar cooling issue the 6.5td had with the pcm. Mounted where it was getting to hot. Someone will come out with an aftermarket fix or a way to keep it cooler at some point in time by GM will be implemented.

Generally speaking, I believe the 6l90 should be a better trans for towing etc, as the first gear is a lot lower, so starting should be easier in the long run. The 4l80 derivatives have the tallest first gear of any tranny I know of. Which is why I was frying them so often. Trying to get loads up 15-25% local driveway and road grades. They overheated, away they went.

So far I have one 4l80 that has 80K on a 2000 pickup with a 350 V8, so far no issues. So hopefully it goes for awhile.

Marty

I just realized that every 6L90E failure I have had were 2009 year models, all of my 2010 are still OEM.

Perhaps the issue has already been addressed.

[MPond]

I wonder how the new 8L90E 8-speed will compare? I've got one in my 2015 Yukon XL, and the extra ratios drive really nicely, with and without the trailer.

But it's too soon to tell how it's going to hold up.

[blt2ski]

Sounds like a similar cooling issue the 6.5td had with the pcm. Mounted where it was getting to hot. Someone will come out with an aftermarket fix or a way to keep it cooler at some point in time by GM will be implemented.

Generally speaking, I believe the 6l90 should be a better trans for towing etc, as the first gear is a lot lower, so starting should be easier in the long run. The 4l80 derivatives have the tallest first gear of any tranny I know of. Which is why I was frying them so often. Trying to get loads up 15-25% local driveway and road grades. They overheated, away they went.

So far I have one 4l80 that has 80K on a 2000 pickup with a 350 V8, so far no issues. So hopefully it goes for awhile.

Marty

[mr61impala]

I maintain a large fleet of delivery trucks, 29 of which are equipped with LS engines and 6L90E transmissions.
The basic design flaw with the 6L90E is the control unit is part of the valve body.

Think about it, every computer or controller you have has passive or active cooling, whether it's the fan in your PC or the fuel lines running through the ECM on a Detroit Series 60.

The TCM in every 6L90 lives (or dies) in an environment that is 160F at best and can go much higher under load with the converter unlocked.

I have replaced 8 of my 29 transmissions so far, 1 for a broken park pawl (driver abuse). and 7 catastrophically failed when the TCM shorted and engaged an additional solenoid. Visualize a trans brake applied at 60 mph, you get a pan full of large broken pieces. And a tow bill.

I have about 35 older trucks with LS power and 4L80E transmissions, they will give you a slip code when they are worn out, and in our application that's usually around 200k miles. And they just need an overhaul kit, not a lot of hard parts.

Here are the miles at which my 6l90E's failed.

68,574, pan full of metal
72,873, pan full of metal
79,874, happened at idle, had to be towed, conflict between 2 gears but no pan full of metal.
89,533, park pawl driver abuse
129,747, pan full of metal
134,558, pan full of metal
153,484, pan full of metal
186,264, pan full of metal.

To be perfectly fair I still have 21 running with OEM transmission with some approaching 200k miles, I am just alarmed at the high percentage which have failed in such a spectacular and expensive manner.

I also have numerous Allisons behind both Cummins B series diesel and LS gas power, this is by far the best transmission we use, typically going 300-400k miles without issue.

[blt2ski]

mr61impala wrote:

BurbMan wrote:
I believe that an 08 will have the newer 6L90E six speed transmission behind the DMax. Yes the DMax is detuned vs the truck versions with the Allison transmission.

Pretty sure the 6L90E wasn't available in the Express until the 2010 model year.

I would prefer the 4L85E anyway, TCM not cooking inside the oil pan.

If the 6l90e is as bad as the th400/4l80/80e versions that I had to replace, rebuild at 30K intervals......not sure I would want that trans vs the others. That included 5K drop the pan and replace filter, and 10K pull trans oil from a jug into the TC while the motor tranny was running on a stand!

The only auto trans I have had behind a BB or TD that lasted over 30K miles is an allison in GM's any how. The 6l90 looks to be a better trans than the th400 derivatives. This is pulling day in and out mind you at 3-4K a month doing my landscape work. I also have had one 700r4 go over 150K also. but it did not get towing duty, just moving an astro van around.......

marty

[mr61impala]

BurbMan wrote:
I believe that an 08 will have the newer 6L90E six speed transmission behind the DMax. Yes the DMax is detuned vs the truck versions with the Allison transmission.

Pretty sure the 6L90E wasn't available in the Express until the 2010 model year.

I would prefer the 4L85E anyway, TCM not cooking inside the oil pan.

[roman_traveler]

Looks like I shot my mouth off before I thought. Yes, mine was 3500 dually pickup. Just testing to see if you were paying attention LOL.

Have a great Easter everyone.

RT

[BurbMan]

I believe that an 08 will have the newer 6L90E six speed transmission behind the DMax. Yes the DMax is detuned vs the truck versions with the Allison transmission.

[mr61impala]

The Hydramatic behind the diesel and 8.1L in the vans and Suburban/Avalanche is probably a 4L85E, a stronger transmission than a 4L80E.

That is an excellent family of transmission, an evolutionary descendant of the Turbo 400, which is a virtual clone of the Torqueflite 727.

The 727 architecture debuted in 1956, showing that good engineering can last for generations.

[Grit_dog]

If you're going to tow anything real with it, I'd pass only because a truck with an Alli is so much better and you get 1-2 more gears which diesels need. Otherwise, the 4l80e is as good of an "older" auto trans as they make.

[MPond]

fireman41 wrote:

GoPackGo wrote:

roman traveler wrote:
The tranny behind the 8.1 is an Allison. I owned one.

RT

Did you have a van/Suburban or a pickup ?

I'm under the impression that the Allison could only fit under the pickups. That there is not enough clearance for an Allison to fit under the others.

Don't forget that the 2500 avalanche also used the 4l80e behind the 8.1

So did the Suburban 8.1's. No Allison because it wouldn't fit in the trans tunnel.

[fireman41]

GoPackGo wrote:

roman traveler wrote:
The tranny behind the 8.1 is an Allison. I owned one.

RT

Did you have a van/Suburban or a pickup ?

I'm under the impression that the Allison could only fit under the pickups. That there is not enough clearance for an Allison to fit under the others.

Don't forget that the 2500 avalanche also used the 4l80e behind the 8.1

[nevadanick]

I have a small class a motorhome with 8.1 and hydramatic thats why i referenced it.

[GoPackGo]

roman traveler wrote:
The tranny behind the 8.1 is an Allison. I owned one.

RT

Did you have a van/Suburban or a pickup ?

I'm under the impression that the Allison could only fit under the pickups. That there is not enough clearance for an Allison to fit under the others.