Anyone familiar with the 2006 and earlier 2500 with the 8.1 liter?

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by ltrmc02, Apr 15, 2017.

  1. ltrmc02

    ltrmc02 New Member

    I'm interested in a Suburban or Yukon XL with the 8.1 and 4.10 gears for a tow vehicle. I'll occasionally tow it's max rating of 12K pounds but only local and very few miles per year moving a tractor or mini excavator between a couple of properties for clean up work. I'll use it mostly for towing much lighter loads like maybe pulling four ATVs and camping gear up in the NC, VA and WV mountains.

    1. Is there an axle code on a label somewhere that I could get a potential seller to give me relatively easy? I'm sure I'll have to travel to find one of these rare unicorns so I'd like to know the gearing before making a far trip to check one out.

    2. Did all the 8.1 Suburbans come with the 4L85E tranny and what's the difference between the 4L85E and 4L80E?

    3. I think I read that the 6.0 equipped models had a 14 bolt semi floating axle and the 8.1 came with a 14 bolt full floating axle, is this correct?

    4. Can you share the good and bad about the 8.1 powertrain or at least what to look out for and expected failure areas.

    Thanks for any information you can share.
    secundinus likes this.
  2. Beachbourbon

    Beachbourbon Active Member 100 Posts

    1. Yes, in the glove box door are the RPO codes, and you can cross reference them. I have code GT4 for 3.73, and G80 for positraction
    2. I believe so (but again reference RPO codes. Stronger tranny. 4=four speed, L =longitudinal for RWD(and/or4x4), 85=strength of gears, E=electronic
    3. Idk
    4. Great! Lower MPG when not towing, but about the same as the 6.0 when towing, and lots more power. I highly recommend them, but I'm a 2500/big block kind of guy.
    secundinus likes this.
  3. secundinus

    secundinus New Member

    I have a '05 8.1L w/ a 4L80E & "tow package." I'll try to take a look underneath to see any markings as I'm curious if I have the 4.10 gears. I have a transmission temp indicator in the dash and a trailer break. I bought the truck as a former cop car w/ ~130k, had the engine rebuilt, & it's been running strong w/ 270k. I towed a travel trailer and it was as if nothing was behind the truck. Unfortunately, the trailer was sold during my last military move but I got to keep my truck.

    Items to check.

    Transfer case. If you do a search, you'll find the factory transfer case will fail and start to leak. There are various theories out there to why but I would double-check that the transfer case has been updated -- or expect to do that at some point.

    Read A/C. If A/C is important to you, check about the maintenance on the rear part of the system as there are separate lines/compressor for the back. I had to have my rear system fixed up & since it's connected to the front, was not a cheap repair.

    Other than the above two items, my truck is a well running towing machine.

    I average about 11-12 mpg towing and 13 without. Filling up 37 gallons at a time seems to surprise people. I've been "yelled at" by some small car drivers in the Costco gas line & have to explain to them I've got almost 2x the gas to fill as them. Or I've discovered some gas stations limit how much gas will dispense either by total price or gallons pumped fur a single fill -- a discovery not many people get to enjoy.

    Let me know if you have any questions. I love my old cop car. When I got her, she still had some 22 shells and some stakeout paperwork in the glovebox.
    thegawd and Beachbourbon like this.
  4. Beachbourbon

    Beachbourbon Active Member 100 Posts

    Last edited: Apr 15, 2017
  5. squatchy

    squatchy Rockstar 3 Years 1000 Posts

    There's nothing actually on the axle giving you gear ratios. You'll have to explain to most dealers what you mean when you ask for axle rpo codes most are ignorant to their existence. Never heard a bad word about the 8.1.
  6. Beachbourbon

    Beachbourbon Active Member 100 Posts

    GT5 is 4.10 gears
  7. Cowboytrukr

    Cowboytrukr Active Member 100 Posts

    Only had an instance to change a front hub assembly on one once for a friend. Also, MAF can be problematic. Keep yours clean.
  8. BigRedUmpire&Graphics

    BigRedUmpire&Graphics New Member GMTC Chick

    I've expertise tyne shut off. Previously had a suburban worn tyne cross country package, and thus a 42 gallon tank. Here many pumps shut off at $100, but they'll let you run a card a serving time.
    The one Rumsey floored me aND in just couldn't leave alone was the gas attendant who told me with gas prices line they are, had come down so ib could fill it for just under 100, versus 120, that I should Newberry let it go below 3/4 of a tank, just because of the cost. I said and when's the last time you filled type car, and the tone before that, and before that and let's go one more. So she refills her car 2-3 tines week. I refill mine 3 times every 2 months. So in 8 weeks, you've stopped we'll abate them one month all 2,the other 3, 20 tones for gas at the tune of $20-25 each time, it's a 15 min minimum app each time, Rought an hour a week. Okay in 8 weeks that's 8 hours a full work day spent getting gas. Boss wold love that. I however, in those 8 weeks, spend maybe 20 min 3 times, an hour ower 8 weeks, 15 minutes every two weeks. I have 7 free hours. And I spend 90-100 each tow, so well say total of 300. Again let's average and say 22.50..4 weeks @2 times a week, 4 weeks at 3. Which we squids was 20 full ups at 22.50. The looks like nasty half those 10 fI'll up a yields $225 versus my 300. 20, gives $450. She's spnding an 150 a month. Checking milage ran about the same difference her ltitle economy 21st car got 15mpg hwy, my 99 suburban 15-18 in town depending how much traffic and 21 on the hwy. She was lucky to get 17 on the highway.
    I'll take my 42 gal tank, and know when I start creeping around 500 miles it's time to think about gas.
    The attitudes of some people are unbelievable.
    Yeah it's a bigger tank, but doesn't mean it's always a big deal. Little car with great mileage can't tow the trailer that's connected 75% of the time.
    RayVoy likes this.
  9. squatchy

    squatchy Rockstar 3 Years 1000 Posts

    My head hurts now
    xPosTech and Beachbourbon like this.
  10. Beachbourbon

    Beachbourbon Active Member 100 Posts

    Was that a big red drunken rant?

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