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700R4 and towing

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BettyBurb, Jan 20, 2003.

  1. BettyBurb

    BettyBurb Registered Member

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    Location:
    NorthEast Colorado
    I have a popup camper with uvw of 1880 which I towed last year with my 88 Suburban, 1/2 ton 4x4 with 700r4. Towed it real easily and did not seem to bother the transmission at all.

    I asked around and got differing answers on whether to use OD or not. Some said no problem, others said don't do it, others said use OD as long as it is not shifting back and forth between 3rd and OD. I went ahead and used OD when not in the hills and mountains.

    What do you guys think, should I use OD or not ???

    Also after reading on the posts here about the problems with overheating the 700r4, I am going to get a trans cooler. Also I installed a motormite drain plug kit in the pan, but it leaks. I read on another post that the B&M or Moroso kits dont leak. But now I am wondering if maybe an aluminum pan would be a better idea. I am thinking it would be best to use a stock depth, as it looks like the exhaust crossover and drive shaft could be kind of close on a deep pan.

    Any input appreciated. Thanks
     
  2. heavy4x4

    heavy4x4 1/2 ton status

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    Sounds like you did all the right things when towing. You've really got to just go by feel. If you're driving and your tranny keeps surging in and out of o.d., that's an indication to run in drive. Otherwise, if you're crusing good in o.d. just keep on going. Mountain/hill driving, and anything under 45-50 mph, I would keep it in regular drive.
    I've got an auxillary cooler and temp gauge on mine. Stock pan. In about a week, I should have pics in my Webshots of where I plumbed the sensor into the pan, so check that. It's an autometer gauge. With the cooler, I'm able to maintain about 150 degrees, and sometimes in a strong headwind on the freeway....it'll bump 180 and then go back down. So, especially for someone who tows like you, I highly recommend those two mods.
     
  3. Thunder

    Thunder 3/4 ton status

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    I have a 89 K5 and tow quite a bit. My boat/trailer is around 2500 lbs. I tow in OD when on the flats at freeway speeds and switch to D when in the hills. Been doing this for many years with no problems. Still have the orginal 700.
    I have a 18000 gvw cooler and change the fluid at least once a year usually just befor summer. I also have an engine oil cooler and keep the cooling system in top shape with regular flushes and coolant changes. I have towed many miles in hot weather with no problems
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    I agree with the others. You want to keep the 700R4 cooled well, you don't want it hunting between OD and 3rd, and you don't want to be lugging the engine down in OD.

    It's easy on the tranny and vehicle in general to keep a constant speed on flat ground with the right tranny gear, axle gearing and tire sizes, its terrain and speed changes that make it tough on components when towing.
     
  5. AZ_Overdrive

    AZ_Overdrive 1/2 ton status

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    I have talked with quite a few tranny shops and they all say the same thing... do NOT run OD when you are towing anything, ever! The 700 has a 30% OD, pulling a load is doing nothing but burning up you tranny. The tranny shops tell me that that is why the 700s got the reputation of being crap...

    Just my opinion but in my 89' Burb I don't use OD while towing (just had the tranny rebuilt in October). I can run 65 - 70 without too much complaining from the Burb.

    /forums/images/graemlins/burb.gif
     
  6. Thunder

    Thunder 3/4 ton status

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    I should add to my post that I dont advocate everyone tow in OD. Espically if you are running larger than stock tires. Or driving a eariler model (pre 88) 700R4
    I simply posted what works for me.
    My K5 came stock with 31" tires and the factory tow package 3.73 gears. It has been towing trailers on and off since it was new.
    When I tow long distance I put the 31" tires back on. It runs best with the 31" when towing
    When I tow with my 33" tires I usually keep it in D and dont use OD. The tranny feels like it is straining with the 33s and OD.
    I have kept a close eye on my tranny I pull the pan at every change. It is always clean with very little deposits. I always keep the fluid new. If it gets even a little discolored I change it.
    I also like to stop and rest my rig every couple of hours when its pulling hard in the hot weather.
    When towing in OD i try to keep the RPMs over 1800. usually at speeds lower than 60 I'll drop it back into drive.
     
  7. SickboySS

    SickboySS 1/2 ton status

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    heat is a trannys worst enemy...get a cooler for it, mabey even one with a fan depending on the distances you drive, and just keep it from shifting alot and use good judgement on hills and it should be fine
     
  8. wrathORC

    wrathORC 1/2 ton status

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    Slap a cooler on there and that'll help. As long as the filter is clean and the fluid isn't full of contaminants she should be good to go. If you can't remember the last time the filter was changed or if it hasn't ever been changed now is a good time. You'll get to see what kind of sparklies are stuck to the magnet too. I usually find two teaspoon's worth stuck to the magnet every 60,000 miles.

    As far as towing in overdrive, you can do it. You must keep the torque converter locked up though. If it comes out more than once every five miles or so drop it to third gear. If it shifts out of overdrive definitely leave it in third gear. You don't want to be one of the many casualties of either a smoked band or cripsy-crittered clutchpack.

    Of course, if you're lugging the motor then that isn't good either. It'll just generate more heat and is hard on a motor in general.

    In the wintertime I run 235s and I'm *blessed* with 2.73s. Even with those tires I still often run in 3rd instead of overdrive on the expressway to keep the transmission happy. Barn door aerodynamics don't play nice.

    You never mentioned what gears or size of tires you run either.
     

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