700r4 getting hot.

Discussion in 'Transmission & Transfer Case' started by Dutch Rutter, Feb 10, 2018.

  1. yevgenievich

    yevgenievich Full Access Member

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    Check for other blown fuses and the brake switch
     
  2. Dutch Rutter

    Dutch Rutter Full Access Member

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    Better shot of the vacuum module, sorry about the fingers, had to move a mess of wires out of the way.


    NVM guess I sent the same one. Damn it is not my night.

    20180212_180403.jpg
     
  3. Honky Kong jr

    Honky Kong jr Super Sarcastic Man

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    Yeah because fingers gross us out lol
     
  4. Dutch Rutter

    Dutch Rutter Full Access Member

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    Fingers are SOOOOOOOOOOOO gross. Alright I'll go roll around looking at fuses.
     
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  5. Dutch Rutter

    Dutch Rutter Full Access Member

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    Found the brake switch with some janky wiring added (pictured). Checked that in line fuse, it was good. checked all of the clear fuses under the dash all looked good. turned key on, checked all of the wires coming from and going to the brake switch and nothing no power at any of them.

    Is one of the big metal relay/fuse on the fuse panel something that feeds the power to this switch? or is it another in line?

    I think were getting closer to this being solved.

    20180212_191552.jpg
     
  6. bucket

    bucket Super Moderator Staff Member

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    I'm not arguing with your trans building experience, but this statement here tells me you don't have much experience actually running a 700r4 in a heavy 4x4 truck with gearing that's a bit on the economical side. The fact is, running in overdrive unlocked at speeds of 60 mph or better will cause excessive, transmission damaging heat. But running in 3rd unlocked at those same speeds will not. Even with a freshly built trans with a matching quality torque converter.

    Why? I don't know, I'm not a trans builder. Hopefully you can fill us in? I'd imagine it's a high load vs low rpm thing. Similar to why you shouldn't full throttle foot brake any auto trans for too long, it builds excessive heat.
     
  7. 4WDKC

    4WDKC Full Access Member

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    The big meal cylinders you mentioned should be your flashers, are you physically testing the fuses or just looking at them?
     
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  8. Dutch Rutter

    Dutch Rutter Full Access Member

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    Just looking at the moment since I only have this cheapie tester. I don't mind replacing them all just to be on the safe side, honestly there are only maybe 8 or so. I believe I have brand new ones in the glove box as well.

    I was thinking about that add on wire with the inline fuse this morning, Could it be that is something for my trailer brake controller? It also has not worked since I purchased the truck. I'll be tracing more wires after work today. So might as well replace all of the fuses while I am at it. Part of me says to just put power from an Ign. wire to one of the reds on the brake switch but the other part keeps saying to do it right, fight with the hard AC duct, trace the wires and find why its not working properly. I'll be doing the right way. At least until I start pulling my hair out.

    I can vouch for this. I started running it in 3rd since you mentioned it would hold off the heat, and it in fact works. The trans doesn't get as hot as it would if I had it in D. Yes the motor runs at a higher RPM but it can cool itself very well. I was thinking maybe the higher RPM would be turning the fan more which would be passing more air as well?
     
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  9. 74 Shortbed

    74 Shortbed Full Access Member

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    I've mentioned this several times, it will NOT heat up from running unlocked, but it WILL heat up if you run under the stall speed, a converter is a fluid coupling and there's a lot of slippage under the stall speed which creates heat big time, stock stall speeds are anywhere from 1500-1800rpm depending on torque, at 65-70mph in OD(unless you have a real steep gear or heavy ass load)you'll be right at or under the stall speed and there's where the heat comes in, if you run 2100+ you won't heat up, mine was never hooked up in the c10 and I ran thousands of miles at 75-80 at 2200 in 110* weather and never got hot. With a TH400 and TH350 you're always gonna be running 2500+ on the highway so you're always way above the stall speed so there's no worries about heating up..
     
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  10. Dutch Rutter

    Dutch Rutter Full Access Member

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    This is probably why I have been able to drive it for as long without getting any ill effects or problems until now. I can 100% say that the Torque converter has not been locking up since I have purchased it, almost a year and a half ago, I never noticed, always thought 4th was my OD. It has always ran about 2200-2500 RPM at 65-70 mph which I thought was low coming from my TH400 which would run 2800-3K all day at 65.

    When I do get this torque converter to lock will it be dropping my rpm too low? Maybe the PO cut the power to the switch for a reason?
     
  11. yevgenievich

    yevgenievich Full Access Member

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    it is possible the the power was cut because tcc clutch is bad and was causing shuddering issue. Just need to meter out the wires on the brake switch and see if one of them goes to the trans. Check why it does not have 12v on it and then test the lock up. Maybe you will find that PO did not like it and cut it off, it broke, or tcc clutch disk is bad and was causing issues. There are two switches on the brakes, one for the brake lights and other for the tcc. Brake switch for tcc is normally closed, so there should be 12 volts coming to it, and 12 volts coming out when brakes not applied. If it does that, then need to move to checking the wire between the brake switch and the transmission. Somewhere there is a break causing no power to the transmission.
     
  12. 4WDKC

    4WDKC Full Access Member

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    multiply those rpm numbers by .70 and that should be close to your rpm
     
  13. 74 Shortbed

    74 Shortbed Full Access Member

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    4th is OD, lock the converter and it will drop another 200-300 rpm's..
     
  14. Dutch Rutter

    Dutch Rutter Full Access Member

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    Ok, so by those numbers, theoretically when I get it locking up I should be able to do 70 at roughly 1900-2000 RPM which would still be above the stall rpm or course unless the torque converter was changed out or something entirely else is going on or burned up.

    Now, I have heard about torque converter shuddering before. If that were a problem I would feel that as the converter tries to lock but it cant therefore giving a shudder while at speed? There have been times I get a kind of shudder but its near a shift point at a lower gear and only does it occasionally. I chalked it up to fuel delivery or carb tuning. Could that be something to worry about with the transmission?
     
  15. Dutch Rutter

    Dutch Rutter Full Access Member

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    All this auto transmission troubleshooting and worry really is making me wish I had a 4 or 5 speed in it.
     

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