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Operating Temp of the 700R4 Tranny

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by opfor2, Oct 29, 2004.

  1. opfor2

    opfor2 1/2 ton status

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    Hi all,

    I just installed a temp gauge in my tranny pan and I would like to know what is the proper operating temp of my trans ? I have a 90 Blazer with both trans cooler in the rad and an external cooler.

    thanks

    Dan..
     
  2. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    somewhere around 200-220 warmed up
     
  3. Thunder

    Thunder 3/4 ton status

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    200- 220 ? /forums/images/graemlins/yikes.gif 700R4s wont last long at those temps.

    With a sender in the pan operating temp should be around 160 degrees.
    Anything 200 or more will cook the fluid(and the Tranny) fast.
     
  4. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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  5. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    [ QUOTE ]
    200- 220 ? /forums/images/graemlins/yikes.gif 700R4s wont last long at those temps.

    With a sender in the pan operating temp should be around 160 degrees.
    Anything 200 or more will cook the fluid(and the Tranny) fast.

    [/ QUOTE ]

    copied from the page that ryoken linked

    "The ideal operating temperature for automatic transmission fluid is between 175 and 225° F."
     
  6. Thunder

    Thunder 3/4 ton status

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    I dont care what the charts from someone trying to sell you a transmission say .
    But
    Notice the life of the tranny goes wayyyy up when ran at 175 degrees.
    Regular non synthetic Auto trans fluid is designed to be ran at around 175 degrees. Every 20* increase in temp over its designed operating temp doubles the oxidation rate. This cuts the life of the fluid in half. It looses lubricating qualities and its friction properties. Operating at 210 will thin out the fluid enough to cause pressure loss.Correct pressure is critical in a 700 R4! Above 220* it degrades rapidly.
    Of course, changing the fluid regularly will help keep the fluid in good shape if ran at higher temps.
    But
    The closer you can keep to the 165 to 175 normal operating range for the fluid the better it is for your trans.
    That way when you are towing or puting a heavy load on the trans you have a larger temp range to work with. IMHO 200 to 220 degrees is far too hot for a 700r4 in a truck.
     
  7. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    [ QUOTE ]
    I dont care what the charts from someone trying to sell you a transmission say .
    But
    Notice the life of the tranny goes wayyyy up when ran at 175 degrees.
    Regular non synthetic Auto trans fluid is designed to be ran at around 175 degrees. Every 20* increase in temp over its designed operating temp doubles the oxidation rate. This cuts the life of the fluid in half. It looses lubricating qualities and its friction properties. Operating at 210 will thin out the fluid enough to cause pressure loss.Correct pressure is critical in a 700 R4! Above 220* it degrades rapidly.
    Of course, changing the fluid regularly will help keep the fluid in good shape if ran at higher temps.
    But
    The closer you can keep to the 165 to 175 normal operating range for the fluid the better it is for your trans.
    That way when you are towing or puting a heavy load on the trans you have a larger temp range to work with. IMHO 200 to 220 degrees is far too hot for a 700r4 in a truck.

    [/ QUOTE ]

    I will agree that cooler is better, but 175 is the lowest I would go

    as for 200-220 being too hot, that is the temp the OE transmisions and coolers are designed for(think about it, a cooler in the rad will not drop the trans fluid temp below coolant temp)
     
  8. Thunder

    Thunder 3/4 ton status

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    [ QUOTE ]
    as for 200-220 being too hot, that is the temp the OE transmisions and coolers are designed for(think about it, a cooler in the rad will not drop the trans fluid temp below coolant temp)

    [/ QUOTE ]

    Not really. The OEM trans cooler is located on the cool side of the radiator. If the cooling ststem is in good condition the temps on the side where the trans cooler is located should be around 130+- degrees depending on engine load. That is the side that the engine picks up cool water after passing thru the radiator used to cool it.
    If the engine was picking up 200- 220 degree water it would overheat and blow in no time. It will also ruin the trans in short order if the water surrounding the trands cooler is that hot.
    The OEM cooler is also pretty small.
    Every aftermarket trans manufacture I have ever seen recomends using a Large 20,000LB GVW aftermarket trans cooler with a 700r4 in truck applications. If the OEM cooler were sufficent to cool the trans.. Why do all aftermarket trans builders they recomend better cooling?

    My K5 was ordered with a dealer recomended and GM installed towing package. It has a 22,000 GVW trans cooler instaled inline with the OEM cooler. I have a temp guage installed in my pan. I usually run around 160 down the highway. it will creap up to around 200 when towing up a long hill.
    Mt trans (700r4) is 15 years old and never been rebuilt.
    When i drop the pan to do an anual service it is always clean with very little if any clutch residue. My fluid is always nice and pink and looks like new. i use my truck hard. i know the trans would have died long ago if i just had a OEM cooler and ran it at high temps.

    I would sure like to see some info that says 700r4s shoild be run at high temps(200+ degrees). 700rs have got a bad rap because GM put too small of a cooler on them. And they wore out because they were constantly ran overheated.
     
  9. woody9

    woody9 1/2 ton status

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    i've got a huge cooler on my 91 /forums/images/graemlins/burb.gif with the 700R4, and have the temp sensors in both the OUTBOUND & RETURN lines (won't get in the debate on where the sensor should go to get the MOST ACCURATE TEMP ON EARTH), but my locations are consistant with the instructions /forums/images/graemlins/deal.gif that came with them.
    Normal days i run just at/just over 100.. /forums/images/graemlins/waytogo.gif towing it may rise to 150 and hills will take it to around 200 (lower more often than over).
    Sometimes not sure if i'm getting enough heat to remove condensation moisture, /forums/images/graemlins/dunno.gif but think i'd rather have it run COOLER than HOTTER. /forums/images/graemlins/thumb.gif
    Temps normally vary 20-40 degrees between in/out.
     
  10. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    General consensus, from what I've read over the years, is to keep it between 160 and 180. Lower than 140 and it shifts slow and more than 180 and the fluid starts to cook. I wouldn't worry about the fluid until it gets to 235 but no reason to run it above 200 all the time.

    Keep in mind that you're supposed to change the transmission filter every 20,000 miles. That's 5 quarts of fresh fluid every 20,000 miles. It helps prolong the life of your transmission greatly.

    I run the factory GM transmission cooler that they put on plow trucks from the factory. I don't use the in-radiator cooler. My early (1983 build date) 700R4 survived 61,000 miles of plowing snow with 2.73 gears. It then survived 20,000 miles of hard driving with 33s and 2.73s and some wheeling. It then has survived another 20,000 miles of 33s and 3.42s with a motor that makes twice the power of stock. And I shift it manually quite often (six grand).


    To get a 700R4 to last you need to:
    have the TV cable adjusted properly
    change the filter every 20,000 miles
    keep it cool
    don't let it seek for gears
     
  11. Jonny-K5

    Jonny-K5 1/2 ton status

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    my tranny from bowtie overdrive runs between 145-165, depending on if its locked up in OD or running around town.gets hotter when wheeling, around 180

    the installation instructions say temps should be in the 150 range. and these are people who only work on 700r4's and 200r4's.

    the old th350 and th400 would tolerate higher heat better than a 700. i believe those usually run around 200.
     

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