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Update on Tranny Prob and towing in OD myth

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by GRINCH, Apr 19, 2002.

  1. GRINCH

    GRINCH 1/2 ton status

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    Thanks to all who helped me get across country pulling over 6000#'s.

    I had the tranny rebuilt in Rapid City SD by Logans. Awesome shop. You could almost eat off the floor. They even dynoed it before they installed it back in the blaze. Come to find out the place that rebuilt my tranny before I left really screwed it up, they drilled the holes in seperator plate too big and one of them looked like they took a punch to it. No corvette servo nor kevlar bands (which is a good thing from what I learned at logans.)

    While it was down I installed a tranny temp gauge and a tach.

    Anyway back on the road I went still towing the trailer.

    I did some peliminary testing on the flat roads and my average temp was about 165 in OD. If I put it in Drive (3rd) it rose up to 180-190. So back in OD again. It may be the strong motor,gearing, tire size or FM. When I hit the grades and Mtns I would feather the gas enough to keep the converter locked up and in OD. As long as I did this it would never get over 190. As soon as it would unlock the converter an slip down into drive up would come the temp. I never let it get over 210-215. I would stop and let it cool down for a half hour or so.

    The blaze also cruised the best around 70-75 and I still managed to get 14-16 MPG pulling that heavey load.

    Finally settled in at Helena MT.

    Thanks again to all who helped....

    That's what K5 is all about....
     
  2. Thunder

    Thunder 3/4 ton status

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    Yeah. I tow in OD a lot with my stock 700r4 with no problems.I have found similar results as you.
    I use drive in the mountains and city. But on the flats and open road I mostly tow in OD. I drop the pan once a year before summer and it is always clean.
    I think the eariler models of the 700 are the ones that gave the 700 a bad rap. By 1988 they pretty much got the bugs out of them.
    When I tow a lot or for long distance I put on my set of 31" tires. With the 3.73 gears and the factory tow package the ol K5 makes a pretty decent puller.
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    16 MPG pulling 6000 lbs????? HMMMMMMMM............./forums/images/icons/tongue.gif

    C'mon, man!!!!! I get about 18 MPG(and that's AWESOME) with no trailer driving in OD at 55 mph.
     
  4. GRINCH

    GRINCH 1/2 ton status

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    No BS,,, I was doing between 70-75 in OD @ 1800 RPM. No wind and flat road. Fresh tranny may of helped. For some reason the truck runs the best at that speed. I'm no expert but thats what i got. The worst mileage I got was 12 .
     
  5. 90K5

    90K5 1/2 ton status

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    If you look at his profile, you see he has a 1996 Vortec in his truck. What gears? Without calculating speedometer error I get pretty good mileage.
     
  6. Thunder

    Thunder 3/4 ton status

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    I get around 15 MPG towing my 18 foot boat.
     
  7. GRINCH

    GRINCH 1/2 ton status

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    I also have Edelbrocks Multi Point fuel injection, Thorley Headers 3" exhaust, MSD, Ram Air Induction, and 4.10 gears.
    Speedometer professionaly recalled for the gears and tires.

    This post wasn't about gas mileage, but to help others who tow with the 700R4. It may be just my blaze but it was healthier on the tranny to tow in OD. It ran way cooler.

    Just trying to help others!!! Hate to see them spend the 1200 bucks like I did.
     
  8. 90K5

    90K5 1/2 ton status

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    What happened to your tranny? I had to spend the money last September cause mine went out, and I've been curious about towing in OD too. I have basically the same setup as you do, except for the Vortec. I've been thinking its ok to tow in OD as long as it doesn't keep shifting in and out of OD...since shifting is when heat builds up...
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    WOW! There is a God! 16 MPG? I need port fuel injection!
     
  10. calcide

    calcide 1/2 ton status

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    Don't bother with port injection, REAL motors have direct injection.
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I'm buying a Powerstroke next spring. I know.
     
  12. GRINCH

    GRINCH 1/2 ton status

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    The shop who originaly rebuilt mine did a bad job of beefing it up. They drilled the holes in the seperator plate to big and never put the corvette servor nor the kevlar or heavy duty bands in it. Bottom line is check out the shop really good before you spend the money.

    My suggestion is put in a temp gauge and do some experimenting if it runs cooler in OD then use it. I also have the largest tranny cooler B&M makes installed . I have been thinking about installing another one one but I think my towing days are over with.
     
  13. Thunder

    Thunder 3/4 ton status

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    As I said in my other post I tow a lot. I like to fish and there is not a lot of water around me. Its not uncommon for me to hook up the boat fill it with camping gear ect and head for Lake mead , Lake Powell , lake tahoe, or the ocean a couple of times a year. These trips usually put over 1000 towing miles each on my K5 in the heat of the summer over tall mountains and desert.
    My k5 also has towed many travel trailers, It hauls many loads of wood out of the hills every year. It seems I always have something hooked up to it. Right now its sitting in the yard with my boat hooked up ready to go.
    The previous owner regulary towed a 22' travel trailer up and down the west coast with it also.
    When I bought it I expressed my concerns about towing with the 700. he said he had never had any problems with the trans and that he changed the fluids every 10k miles.
    Every spring I change the fluid in the Trans, Axels and x-fer case. I use an additive called in the trans. And an additive called <a target="_blank" href=http://www.tufoil.com/>Tuff -Oil in the engine, Xfer and axles.
    I will change the fluid in the trans if it even gets the slightest bit discolered. Burnt fluid looses all its lubricating and heat transfer qualitys and bad lubrication is what kills the 700r4. I like to keep my fluid fresh and clean all the time.
    My K5 has pretty much been towing stuff sence new with 10 bolts and a 700r4. And yes after 13 years it is showing a bit of wear but nothing major.
    I am not trying to say that the K5 is the best tow rig around by any means.
    I just posted this for everyones info and to show what works for me.
     
  14. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Whoops....I guess I should have checked your profile. Sorry....../forums/images/icons/crazy.gif

    HOWEVER, I really think that you should consider changing the title of your post. It is not a "myth" that 700r4s should not tow in OD, it is fact. Maybe your new super tough tranny coupled with your new motor make it doable, but I still wouldn't tow in OD (and I tow everyday at work with a new 1 ton Chev). For a newbie who just looks at the tiltle of your post and doesn't bother to read it, the title is a little misleading.

    A really reputable tranny guy explained it this way - in OD your fluid pump slows down by 40%. This means that your cooled fluid travels 40% slower through the system and can leave hot spots. It's a little more involved than that but that's the gist of it.

    Where is your gauge sender hooked up in the system? Just curious.....

    And just so you know, I have a lot of experience towing with Chev trucks. I've been towing various loads with them since I was 18. Bobcat trailers, small flatbeds and lowboys, utility trailers, pipe reel trailers all the way down to single axle GrimmerSchmidt compressors. I've seen my fair share of trannies melted down at the side of the road, and I've learned a lot about proper towing habits. I also tow my 21ft TT all over Western Canada every year. So I'm not some dude who's trying to give you a hard time just to be a dink.../forums/images/icons/wink.gif
     
  15. GRINCH

    GRINCH 1/2 ton status

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    You are right that it may be misleading if they don't bother to read it. If a newbie doesn't bother to take the time to read all opinons of a post then he will be a broke newbie.

    As I have learned not all vehicles tow or even have the same power bands. Each one is different depending on gearing, engine size, weight and size and types of coolers.

    In my blaze and most other 700R4's (as explained to me by the tranny shop) it will run hotter in Drive (3rd) because the torque converter is not locked up and the 3-4 clutches are disengauged. The tranny was designed to run in OD for optimum performance.

    I suggest people who tow install a good temp gauge and see what their rig does in each gear and where it runs the coolest.

    The best place to have the sender is in the pan. I don't have mine there yet becuase 1st I can't find a deep pan with the sender bung already there (Mag pans are to expensive) 2nd I don't want to drill out my stock pan because of the problems associted with brazing a bung in such thin metal.

    I currently have my sender in 2 locations both are in the cooler lines from the tranny. I have a switch that I can switch between the temp leaving the tranny and the temp coming back in. I take my readings from the temp leaving the tranny.

    Do you have a temp gauge installed in any of your vehicles? If so try seeing what your temps are.
     
  16. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Hmmmmmmmm.........Nope, I never installed a tranny temp gauge on my K5. My engine temp never gets over halfway on the gauge(mine's in Celcius no tFarenheit) so I never worried about heat. My yearly tranny service is proof that the tranny works ok, too. The ATF is red and the filter is clean with nothing in the pan.

    I don't know if my 700 is different than yours, but I have a lockup in D. I always try to tow with the TC locked, and most of the time even when climbing I can keep it locked.

    I think this all boils down to your engine output. How many horses do you have under the hood? My little 305 doesn't have enough power to keep my tranny from hopping back and forth between D and OD......
     
  17. GRINCH

    GRINCH 1/2 ton status

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    My engine temp never got over 200 when the tranny blew. I think it's because there is such a small amount of heat transfer in the stock radiator for the tranny fluid.

    Ooops I do have lockup in D.

    I don't know how many ponies my set up has but I'm very happy with it.

    Your'e right the bottom line here is to keep the TC locked up and no cycling through the gears and locking and unlocking.

    I just came back from wheeling in the Mtns and I still got it hotter running in D than OD.
     
  18. Blue85

    Blue85 Troll Premium Member

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    Are you sure that the torque converter locks in 3rd gear? An unlocked converter is the only logical explanation for more heat in 3rd gear unless the engine is running a lot hotter in 3rd gear.

    There is less fluid flow in 4th, due to a greater restriction and a slower turning oil pump.

    Oh yeah and the 3/4 clutch is fully engaged in both 3rd and 4th gears. The only difference between them is whether or not the band is applied.
     
  19. scrappyk5

    scrappyk5 1/2 ton status

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    i just towed my s15 4x4 250 miles with a car dolly,which weighs in the neighborhood of about 4200 lbs and i got about 16 mpg.
    i also left it in drive. i was told by the whole world not to tow in OD , many years ago
     
  20. 87K54WD

    87K54WD 1/2 ton status

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    Get the SM465 and forget about it FOREVER. I hear your pain, my brother has a '96 Chevy Z71 305 and he is on his 3rd tranny. The original blew while pulling a loaded down U-Haul (double axle). He kept shifting from OD to D when a hill would come up. Started leaking tranny fluid real bad. Made it back home (400 miles) without the U-Haul but had to keep pulling over and adding tranny fluid. The 2nd tranny blew for no real reason other than maybe the fluid was too old. He let it get 75K miles on it without changing the fluid. Took off from a light and just heard a loud thump ... that was it. For his 3rd one, he had a tranny cooler added ... not sure if that will do much. GM dealer said it might help a little but said to change the fluid more often. From his experience, I would rather pull in D rather than OD. Just leave it in D and don't go back and forth. I've got a new 2001 Z71 5.3L, which has the pull / tow button on the stick. Not sure if this really works or not ... haven't towed with it yet. Maybe someone here can shed some light on that. For a tow rig, I would stick with a manual. My K5 with the SM465 has pulled some heavy stuff up mountains, etc. and never had a problem. The power band is just incredible with the SM465 and the stock 350. Just can't beat it in my opinion for a 1/2 ton stock truck. She wears her K5 badge proudly. About the worse thing with towing with my K5 is the short wheel base and the engine doing the braking on a downhill. Almost lost my K5 and my trailer once because of that. One hell of a scary ride! Ended up gunnin' it down hill to get her rear end and my load straight. Also, the loose steering we all seem to have doesn't help much either ... causes over correction etc. I've learned with the K5 that I have to just take it slower with the speed since it is not a long wheel base like most towing rigs. In summary, I would keep the fluid changed often and keep the tranny from going back and forth between lock and unlock. A tranny cooler would probably help some too.
     

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