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Can a 4L80E tow in OD?

Discussion in 'The Garage' started by tom_at_ktp, Jul 12, 2004.

  1. tom_at_ktp

    tom_at_ktp Newbie

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    Howdy folks!

    I am in the hunt for a new tow vehicle for a boat that weighs about 6500 lbs that still has room for the wife and kiddos. Been looking at Tahoes and Suburbans, and recently started gravitating towards the 'Burbs for the extra room. I have looked at a few of the 1500 series 'Burbs (need the 3.73 to tow this much weight), but am starting to worry because I will be right at the max tow rating for these. Yesterday I checked out a '96 'Burb 2500 4X4 LT with the 7.4L, 4L80E and 4.10 gears. It was pretty clean except for the bullet holes in the back door. /forums/images/graemlins/eek.gif Probably why it was so cheap. Following are some questions that I'm hoping that some of the experts around here can answer:

    1. What kind of mileage (hwy and city) should I expect for this rig? Seller claimed 16 hwy, but I think he was trying to blow smoke where the sun don't shine. Would a taller tire help with this?

    2. Is 120K too much for a 7.4L? It seemed to run fine, held 20 PSI at idle in gear and went to 40-45 lb at 2500 RPM (hot - cold ran about 60). Temp held at 210* at idle - seemed kind of warm to me. Do these numbers sound OK? My big worry - on cold startup, it took about a second for oil PSI to get there, and I heard a rattle right as it fired off. I never heard it again, but should I worry?

    3. Can I pull 6000 lbs with this tranny in OD, or will I burn it up? Not real steep terrain, but some gentle rolls.

    Thanks for any info you can provide. He is asking $8K, and like I said, it looked real clean other than the fact that it needs tires. Oh yeah, and the bullet holes in the door - hopefully that wasn't someone's DNA that was on the back carpet! /forums/images/graemlins/yikes.gif

    Thanks for any viewpoints you can provide!

    Tom
     
  2. Pookster

    Pookster 1/2 ton status

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    Depending on the price, I'd say your ok

    I think 97+ got the vortec big block- so that would mean more power and more fuel economy. Since you got the 96, I think you get the older motor. Still a great motor though.

    120k is nothing, if well maintained, and everything if it wasnt.

    In regards to towing in OD- If your high enough in the RPM band, it is ok- your not stressing the OD too much- but if your lugging the truck in OD and it cant keep up RPM, you'll increase chances of frying it.

    at 60mph, I think your crusing RPM would be around 2000ish in OD. if your using the stock 245 tires on there, you should have some good RPM's spinning anyways in OD.

    Just do yourself a favor and get the biggest baddest tranny cooler you can fit, (I think the 2500's came with an oil and tranny, but not sure). Replace the stock one with a big stacked plate cooler. Then do a good tranny fluid flush- Synthetic isnt a bad idea! It costs a little bit more, but the fluid gives you like a 200 degree extra protection.
     
  3. uao85

    uao85 1/2 ton status

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    Yeah I am positive that the 4l80e tranny can tow that and pb more in overdrive. They are very stout transmissions. But I would definitely steer clear of that sub your talking about. High miles, rattle on startup, a 454, and a ridiculously low price are all IMO signs of a lemon. I think you would be way better off finding a 2500 sub with the 6.5 td engine, because they all came with a 4l80e. Plus you get way better gas mileage and good low end torque. Plus if you need more power, just get a banks power pack, or a propane kit. /forums/images/graemlins/woot.gif

    Remington
     
  4. dremu

    dremu Officious Thread Derailer Premium Member

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    1991 3/4's came with the 4L80E too, just as an fyi.

    -- A
     
  5. afroman006

    afroman006 1/2 ton status

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    *Some 91 3/4 tons came with the 4L80E, not all. Depends on their GVRW. GM started using the vortec in 96. My 91 burb has the 4L80E, it kicks ass, nuff said.
     
  6. Okiemuddog

    Okiemuddog 1/2 ton status

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    [ QUOTE ]
    What kind of mileage (hwy and city) should I expect for this rig? Seller claimed 16 hwy, but I think he was trying to blow smoke where the sun don't shine. Would a taller tire help with this?


    [/ QUOTE ]

    Really bad, my '98 CC dually with the same drivetrain averages about 10MPG on the highway unloaded.


    [ QUOTE ]
    Can I pull 6000 lbs with this tranny in OD, or will I burn it up? Not real steep terrain, but some gentle rolls.


    [/ QUOTE ]

    According to the owners manual, as long as the engine is not lugging then it should tow in OD with no problem.


    I would personally do a complete look over on the truck and run a carfax report on it before buying it.
     
  7. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    The rattle on cold startup could be caused by a dirty oil filter, especially if it's a Fram. How did the oil look? How did the rest of the fluids check out?
     
  8. tom_at_ktp

    tom_at_ktp Newbie

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    Oil looked clean - probably changed recently. Trans fluid was a little tired, but didn't stink and no worse than most of the other vehicles I have been looking at.

    Rattle only occurred at cold startup. I immediately shut it down and waited about 15 minutes while I inspected the rest of the vehicle. It never did it again. Sounds like an oil pump issue to me.

    It is low on AC refrigerant, which is part of the reason he is only asking 8K. ABS light is on too, but I didn't hear the pump running. Engine was very clean and quiet once up and running, but the detailers can make anything look good.

    I'm not going to buy this one unless I can get it THOUROUGHLY checked out. Still, even if I have to spend 3K on a long block, price isn't bad.

    Thanks for the replies. I'll probably stick with a 1500 with the 3.73. Should be sufficient for my needs, and they are a dime-a-dozen.
     
  9. sjvcon

    sjvcon Registered Member

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    My Dad has the same Burb, but a '94 version. His is at 165K and still running like a tank. We went through about 50 gallons on a 500 mile trip, maybe a little more, and we were towing 7500lbs. I would agree with some of the previous posts on the Tranny. It is really stout, but you need to be careful on towing in OD. Keep an eye on those RPM's. As far as the truck you are looking at, I'd be a little leary about anything with bullet holes and a startup rattle. There's a ton of them out there. Don't get sweet on the first one, cause a better one might come out in the paper tomorrow.
     
  10. 70~K5

    70~K5 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    What kind of mileage (hwy and city) should I expect for this rig? Seller claimed 16 hwy, but I think he was trying to blow smoke where the sun don't shine. Would a taller tire help with this?


    [/ QUOTE ]

    Really bad, my '98 CC dually with the same drivetrain averages about 10MPG on the highway unloaded.


    [ QUOTE ]
    Can I pull 6000 lbs with this tranny in OD, or will I burn it up? Not real steep terrain, but some gentle rolls.


    [/ QUOTE ]

    According to the owners manual, as long as the engine is not lugging then it should tow in OD with no problem.


    I would personally do a complete look over on the truck and run a carfax report on it before buying it.

    [/ QUOTE ]

    My PU is a '95 C3500 454/ 4L80HD/ 14BFF 3.73/ 215/85RX16 tires.
    I get 8-9 mpg around town. 11-12 freeway. Best ever was 14 mpg empty driving 55 mph.

    There is a sticker on the drivers door on mine that says not to tow in OD.
     
  11. Okiemuddog

    Okiemuddog 1/2 ton status

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    [ QUOTE ]
    There is a sticker on the drivers door on mine that says not to tow in OD

    [/ QUOTE ]


    Humm, might have to check the door on mine in the morning /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif
     
  12. 6.2Blazer

    6.2Blazer 1/2 ton status

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    For towing on OD, it's best to reference the factory owner's manual and see what it says. The biggest issue with towing in OD is getting into a condition where the trans starts to frequently shift between 3rd and OD (shift-hunting), this in turn causes a lot of heat build-up and wear on the 3-4 clutch packs.

    My '03 2500HD has the 4L80e and the manual says it's not a problem to use OD as long as the engine can pull it. Of course mine also has the "tow-haul" feature which changes the shift characteristics and does a really good job of avoiding shift-hunting.

    In any case, get a large trans cooler and a trans temp gauge.
     
  13. Okiemuddog

    Okiemuddog 1/2 ton status

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    Quoted directly from the 1998 C/K pickup owners manual

    " If you have an automatic transmission, you can tow in overdrive. You may want to shift the transmission to third or, if necessary, a lower gear if the transmission shifts too often (e.g., under heavy loads and/or hilly conditions)."

    /forums/images/graemlins/thumb.gif

    Krennen
     
  14. 70~K5

    70~K5 1/2 ton status

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    From the sticker on the drivers door.

    "The transmission overdrive range "OD" Should not be used for towing a trailer, carrying a heavy load, driving on steep hills or off road.

    See Owner's manua; for more information.

    pt no 15972584"

    This is on a '95 C3500. Maybe Chevy changed their mind on latter models. They may have been "gun shy" after the problems the 700R had.
     
  15. jarheadk5

    jarheadk5 1/2 ton status

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    [ QUOTE ]
    I'll probably stick with a 1500 with the 3.73. Should be sufficient for my needs, and they are a dime-a-dozen

    [/ QUOTE ]


    If I'm not mistaken, that's gonna get you a 350/4L60E combo. I'm assuming used...
    Now this is in a truck that'll probably be pushing 7000lbs by itself, maybe more. Add to this your wife & kids, food & beverages, and a 6500lb boat. When all is said and done, you're looking at a gross combo weight of over 14,000lbs. Towing in OD with a 700R4 (or 4L60, or 4L60E - they're all basically the same) is a no-no, especially that kind of weight.

    <font color="red"> My personal opinion here: </font> If you go with a 1500-series 'Burb, and you're looking to tow a 6500lb boat regularly, you're setting yourself up for mechanical failure sometime down the road. Probably sooner rather than later. ESPECIALLY if there's any hills or mountains along your tow route. I won't even get into the smaller brakes and weaker axles of a 1/2-ton Burb (1500) compared to a 3/4-ton (2500).
    I personally would do it once or twice a year (with LOTS of mechanical prep beforehand and plenty of time allotted for the trip) with this setup AND the wife &amp; kids, but the way I'm reading your original post, you're looking to do this often.
    <font color="red"> Again, my opinion: </font> Find a 2500-series with the 454/4L80E, or better yet the 6.5L turbodiesel and 4L80E.
     

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