[Cliff R]

Cliff, When did GM start putting 480LE's behind 8.1's (except in the Suburban's)?

Not sure? I've worked on several 4L80E's that were behind the 6.5 turbo diesels from back in the mid 1990's, but none that came from behind an 8.1 to date.

The 4L80E quickly became the "workhorse" transmission for GM in HD applications. They used the Allison sparingly, probably due to the additional cost of those units.

The Allisons are nice units, but not without their share of troubles. They seem to be just about bulletproof at stock power levels, but the 5 speeds are hard pressed to hold the Duramax when folks start turning up the boost.

When I bought my 2007 Chevy with the Duramax, it had 6400 miles on it. The first thing I did was to drop the pan and install a shift kit. I went on to do a couple of minor upgrades to the engine, kicking it up to about 450hp and over 700ft lbs torque. I don't push it really hard, and the transmission works FLAWLESSLY everyplace.

It was quite a change going from my second Cummin's powered Dodge to a Chevy diesel. Like getting out of a Peterbuilt and jumping into a Cadillac Escalade. The Chevy rides 10 times better, smoother, faster, quieter, etc. It's on par with the Cummin's for towing capabilities, at 1/10 the noise level and 10 times the driver comfort.

Before I retired I was the vehicle officer for my last unit, and we had two HD Surburban's with the 8.1 and 4L80E set-up. We also had one with the 6 liter, and two older ones with the 5.7 V-8's.

To be perfectly honest, the 6.0 liter gas engine would pull as well as the 8.1's, but required a LOT more rpm's to get the job done, but it was quite comfortable doing so.

The 8.1's were really strong runners, but consumed a LOT more fuel than the other Suburban's at every level.

A good friend of mine tried the 8.1 deal to pull a two car trailer, and it did OK, but he lunched a piston due to an intake manifold leak. This happened a couple of miles outside the Warrantee, but GM stepped up and covered it (nearly as I can remember). He quickly upgraded to the Duramax and says it's ten times better at doing the same thing....FWIW.....Cliff

[Stu Norman]

Originally Posted by SRR

The Allison is a fantastic transmission. I have no idea where your getting your info.

Just do a Google search on Allison transmission problems.

[SRR]

Did you read Cliff's post? That pretty much sums it up.

[bdk1976]

Originally Posted by Held for Ransom

The only problems I've had with my '01 Chevy 8.1 so far are...
3. Likes to die on me (cut out), out of the blue, while driving.

My 8.1L did this too - I think it was around 80k. Did a few google searches and found that the crankshaft position sensor failing is a common problem on 8.1L. Replaced it and the problem went away.

The part runs about $90-100. Installing it yourself may cost you your sanity - especially if you break the old one when you are removing it.

[455Grandville]

Originally Posted by Cliff R

A good friend of mine tried the 8.1 deal to pull a two car trailer, and it did OK, but he lunched a piston due to an intake manifold leak. This happened a couple of miles outside the Warrantee, but GM stepped up and covered it (nearly as I can remember). He quickly upgraded to the Duramax and says it's ten times better at doing the same thing....FWIW.....Cliff

Uh huh; if you're pulling a heavy load these newer diesels are more then up to it. When I went to FL last time a newer Duramaxx passed me on a steep Tennessee grade hauling ass and pulling a very large 5th wheel camper.

[David Holmberg]

The Allison 1000 is a med duty truck transmission. They are built to handle a rated HP and TQ amount, the only problems start when those numbers are surpassed.

I've had two, a 5 speed in my 03 Duramax and a 6 speed in my 06 Duramax, both awesome transmissions. I research the crap out of anything I'm involved in, and the Allison is as good as they get UNTIL you tune your motor (Diesel) above 500 HP and 900+ TQ. After that, they will die at some point, normally shifting into 5th or 6th under full throttle. They just weren't built to handle that much power, to blame the Allison at that point is comical at best.

All 8.1's in the Trucks got the Allison from 01 to 06, Big blocks before 01 got the 4L80's, as did all Suburban's since 92/93. The 2500 Suburban didn't get the 2" body lift so the Allison wouldn't fit.

The 8.1 will tow just about everything the Duramax (stock) will tow, but will use MUCH more fuel doing it.

YMMV.

[KS circutguy]

Real diesels are in-line variety
Just buy a Dodge with a Cummins and enjoy!

[David Holmberg]

Originally Posted by KS circutguy

Real diesels are in-line variety
Just buy a Dodge with a Cummins and enjoy!

I'd agree with you if it came in a GMC or Ford Chassis.

[mike nixon]

Originally Posted by KS circutguy

Real diesels are in-line variety
Just buy a Dodge with a Cummins and enjoy!

The problem with the cummins isn't the engine so much as it is the **** drivetrain behind it.

[mike nixon]

Originally Posted by Jerry H.

Cliff, When did GM start putting 480LE's behind 8.1's (except in the Suburban's)? I can't remember the last year of the 8.1, but 2003 was the last year I was in sales at a GMC store and the 8.1 required an Allison in the 2500 and 3500 trucks IIRC.

4l80's came out in late 93 for the 94 production yr with the exception of a few "test mules" that were released for data gathering. 4l80 is a good trans but is heavy for it's class.

[mike nixon]

Originally Posted by JLHarper

Ive owned two, both 01s and although worried about piston slapas the main issue, I have not had any major problems.

Had dual 8.1s in my boat too.

Mike....whats it cost to rebuld these 496s? Ballpark....? I see some high prices...wonder why?

Any good time to start thinking about its time to tear one down even if "appears" to be running well?

Mine is starting to sound like a diesel. Piston slap is worse. Bought for towing and hunting/fishing, has over 150K now.


Jeff

I've no clue on the re build cost on these. I know they're not cheap like any medium duty truck engine they cost when you get into them. My Customer's either drive them knocking or trade them when the engine's warm and the noise is subdued.

I do have a customer who's got one on LP in a 7000 series [i think] and it's got a barrel of miles on it, over 300k, still runs good and is relatively quiet.

Mike

[Jerry H.]

All 8.1's in the Trucks got the Allison from 01 to 06, Big blocks before 01 got the 4L80's, as did all Suburban's since 92/93. The 2500 Suburban didn't get the 2" body lift so the Allison wouldn't fit.

Having been heavily involved into training when these trucks came out, that is what I remembered. But from what was posted I didn't know if somewhere after 03 they had put some 480LE's behind the 8.1's in the trucks. I couldn't imagine them doing that, but you never know what GM might have done. A friend of mine went to buy a new 2500HD in 08 and wanted an 8.1 and was surprised to find out they weren't available anymore.

[Held for Ransom]

Originally Posted by bdk1976

My 8.1L did this too - I think it was around 80k. Did a few google searches and found that the crankshaft position sensor failing is a common problem on 8.1L. Replaced it and the problem went away.

The part runs about $90-100. Installing it yourself may cost you your sanity - especially if you break the old one when you are removing it.

Good to know, thank you.

[Held for Ransom]

From what I remember about my friends Avalanche 8.1L, it was a 4-speed auto.

[David Holmberg]

Yes, the Avalanche got the 4L80E for the same reason as the Suburban.

Another oddity is the Duramax equipped van, it came with the 4L80E as well. Making it the only Duramax vehicle without the Allison in the light duty line.

[JLHarper]

Was there any "real" failure in the field due to piston slap issues? I mean on a larger than average failure rate whereby GM would have to deal with the problem.

I know there were some settlements on a case by case basis but that was due to NOISE only, iirc.

Ive owned four and other than the noise, never had any real problems.

I wonder if this was buyers actions trying to get some protection going in case they did start failing? Trying to get GM to step up and cover them, which they never did, correct?

GM tightened the tolerance up after this came out in 2001 I recall.

I was told when I investigated this before buying my boat, that the 496s would "tighten up as they broken in and these were made loose"

Jeff

[David Holmberg]

It was very common with the 97-99 LS1's in the Vettes and F bodies as well, annoying but no real problem.

The main issue I've heard with the 8.1 is oil disappearing. They don't leak and they don't smoke, but the oil leaves the pan.

[drailed]

Originally Posted by David Holmberg

It was very common with the 97-99 LS1's in the Vettes and F bodies as well, annoying but no real problem.

The main issue I've heard with the 8.1 is oil disappearing. They don't leak and they don't smoke, but the oil leaves the pan.

Seems from what Ive read in other forums is that a lot of people claim that running a 180 degree T stat helps this tremendously. Some say 5w30 synthetic also. A lot of people were claiming they would use about a quart every 1500 miles and went down to just one every oil change which seems about normal to me. Would be nice if a $10 part could solve the whole issue.

[Cliff R]

"I've had two, a 5 speed in my 03 Duramax and a 6 speed in my 06 Duramax, both awesome transmissions. I research the crap out of anything I'm involved in, and the Allison is as good as they get UNTIL you tune your motor (Diesel) above 500 HP and 900+ TQ. After that, they will die at some point, normally shifting into 5th or 6th under full throttle. They just weren't built to handle that much power, to blame the Allison at that point is comical at best."


Driving like you have some sense will increase the life of the Allison behind a "suped up" Duramax about 8000 percent. Pretty easy to kill any auto trans with up near 1000ft lbs torque if you are stupid enough to let it upshift at FULL throttle on a regular basis, IMHO.

I installed a shift kit BEFORE upgrading the engine, to increase holding power to the clutch packs before trying to throw an additional 200 ft lbs torque at them. I ALWAYS let it find the next gear BEFORE throwing a bunch of torque at it.

Actually, I've never once found the need to put the pedal on the floor, or subject the transmission to the full power of the engine for any reason. I can tow clear across the country fully loaded and never go past 1/2 throttle for any reason, and maintain whatever towing speed I want to on any grade.

Same deal with either of the Dodge trucks I had. The first one had the auto transmission, which has poor gear spread and a whimpy OD set-up. The factory converter wouldn't hold the engine either once it was turned up. I could "push" right thru it. My second Dodge was a manual transmission 2001, with 4.10 gears. The only time you liked the 4.10's was heavy towing, otherwise 3.55's would have worked just fine everywhere else.

I loved the 2001 Dodge truck, even if you couldn't carry on a conversation in the cab towning at 75 MPH. It was a rough and grumbly truck, raspy and loud, just like they should be. Didn't ride all that well, but I liked everything about it.

When I moved on to the Duramax, it was a hasty decision as the Dodge needed about $4000 in repair work at that time, and good friend of mine tipped me off to a 2007 Duramax coming in to our local dealer with 6400 miles on it. The old Dodge was in need of a few repairs, injection pump was going out, complete front end rebuild, brakes all the way around, doors rusted out, A/C had a leak, etc.

At first the quiet 2007 Duramax powered Chevy seemed "whimpy" to me. It had a factory high speed fuel shut off which came it quickly, and was so smooth and quiet one wouldn't have thought it had the power for heavy towing.

I bought a programmer for it, shift kit, EGR block off, and 4" stainless exhaust. Thru in an 85hp program, and haven't touched it since. We've made several tows fully loaded over 2000 miles, and haven't found a grade yet I can't pull at any speed one would want to climb it. I can get out in the left lane on I-77 running thru West Virginia on the steepest grades, and it woln't come out of 6th gear unless you force it. The most remarkable part is how quiet the engine is under a lot of boost. The Dodge would howl so loud you couldn't talk over the turbo above about 20psi. I can't even here the turbo on the Duramax at any boost level......Cliff

[David Holmberg]

Cliff, those were just my findings after 5 years of researching the Duramax/Allison combo.

The six speed is stronger, and harder to shift into high gear under power. But the 5 speed, with normal gearing and tire size, you'd hit it below 80, and believe me from 65 to 100+ my 03 Duramax would pull VERY strong. You had to make a conscious effort to lift before the shift.