Transmission temp gauge.

Transmissions and Rear Ends

  1. MBDale

    MBDale Well-Known Member

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    Thinking about installing a transmission temperature gauge. Probably a 2 1/16” Autometer. Use a trans line manifold fitting. Any of you guys running a trans temp gauge? Any advice or ideas?? Thanks again!!
     
  2. Aspen500

    Aspen500 Well-Known Member

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    A sensor in the pan would give a more accurate fluid temp. Not running a trans temp gauge though.
     
  3. Charrlie_S

    Charrlie_S Well-Known Member

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    In my race car. Trans temp gauge in the side of the trans pan. Just make sure you put the hole and fitting where the sensor "bulb" won't interfere with anything inside.
     
  4. Duke5A

    Duke5A Well-Known Member

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    I've got that exact gauge in my car. The sending unit is screwed into the side of a deap aluminum pan.

    Do you have an aftermarket torque converter that stalls higher than stock or do any towing? If not it probably isn't necessary. Just add a stacked plate B&M cooler to the front if you want for the peace of mind.

    20190512_103505.jpg
     
  5. M_Body_Coupe

    M_Body_Coupe Well-Known Member

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    I have been wanting to toss a nice gauge in as well, my MP deep pan has a nice little sensor mounting spot, but the gauge pod I'm using is a 2-piece only (bigger 2-5/8" faces) so I'm out of space...grrh....

    As Mark pointed out, runing my 9.5" 4K stall converter on the street sometimes makes me wonder how HOT things are getting under there...the cooler helps, but real numbers would tell the story!
     
  6. Ele115

    Ele115 Active Member

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    Use the test port or line port for the gauge. Otherwise, I wouldn't expect any issues. You have a cooler, the transmissions in these cars were very durable, it's not like you are pulling a boat behind a Hyundai or a Ford Fusion or something. Your chances of trouble are not very high like today's cars where a little heat could mean a $4500 repair
     
  7. MBDale

    MBDale Well-Known Member

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    Yes Duke5A I have a 3000 stall converter. Also running a B+M stacked plate cooler. I’d just like to know what temps are when driving and a little strip time too. 3:55’s, 8 1/4.
     
  8. Ele115

    Ele115 Active Member

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    You running slicks?
     
  9. Ele115

    Ele115 Active Member

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    Sticky street tyres you may have some heat but probably nothing to lose sleep over
     
  10. MBDale

    MBDale Well-Known Member

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    Not for the most part. Just Radial T/A’s. Slicks for track.
     
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  11. BudW

    BudW Moderator Staff Member

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    Automatic transmissions like to operate at a certain temperature – which is about 200’ F (93’ C).
    Any cooler than that, and the transmission fluid is a bit too thick for transmission to operate correctly. The transmission cooler is not named very well and is more of a transmission fluid heater than a cooler, but the radiator (cooler) does keep it around 195-200’ F mark.

    The primary item in transmission that produces heat, is the torque converter. When at a stop and you stand on both the gas and brake, the converter will swell in size (a bit) and fluid temp will skyrocket to 300-400’ F (150 to 205’ C) due to the fluid vortex inside the converter. The converter is about the only thing that will produce any major heat. The bearings, pump and clutch packs can generate some heat – but not much.
    Transmission fluid will start to break down once it gets to a certain temperature (not sure what temp that is, exactly). Also, the rubber seals inside of transmission will harden if exposed to a lot of heat. When those clutch pack seals (look like a large O-ring, but rubber is “L” shaped) turn hard, the clutches will start to slip because fluid flows past the seals. The clutch plates are primarily made of paper and glue. Yes, out of paper. When those clutch packs start to slip under a load, you now created a new heat source with a material that can actually burn (the clutch disks).

    When you hear someone say they burnt the transmission up, they are referring to the clutch disks catching fire (or worse, catching the vehicle on fire). I have seen some transmissions that are burnt to a crisp and to the point you cannot dissemble the transmission. Bearings/bushings seize onto shafts, aluminum will distort and warp and other things. It is not a pretty picture and IF you can get the transmission apart, generally, most parts are damaged beyond reuse.
    Typically, I only see this on vehicles towing something or when four-wheeling off-road for a long period of time.

    Usually the transmissions that do need an external cooler (in addition to the radiator cooler) is are those vehicles that tow, that have the gas petal pointed down for lengthy periods of time (more than a ¼ mile at a time) like police pursuit or racing, or who drive uphill for lengthy periods (life in the mountains).
    Occasional periods of those three is nothing to worry about.

    Vehicles with a lock-up torque converter (which most Chryslers made mid-year ’78 and newer have) is likely to produce less heat from torque converter than non-lockup converters (mid-year ’78 and older) will – but either type can produce heat, in cases described above.

    - For drag race usage (only) – if you can afford the extra weight, I recommend keeping the stock radiator/cooler in place to keep the trans fluid at the 195-200’ (F) mark, for consistent shifting, sense consistency is sometimes more important than random times are (to some). I would at least run an air cooler if you don’t want to use the radiator.

    - For real road racing or for real police pursuit (where gas petal will be pushed to floor, more than not), for full time towing or for those who live in the mountains, I do recommend adding a large external transmission cooler (much like what the factory police cars use) as well as using the radiator.

    - For normal street usage (the other 99% of us), using the radiator cooler (only) is all you need.

    Now with that said, some transmission coolers can not be cleaned out very well (typically with other brand cars) and for those cars, after a transmission failure has occurred, it is recommended to replace the trans cooler (and/or add an in-line filter) just because of possible metal contamination.
    Most of all Chrysler vehicles, even those made today, the trans cooler uses brass or aluminum tubing and are easy to clean out.
    Note: always flush the cooler lines after any transmission failure (no matter what brand vehicle)!

    In my case, I do want to take my cars road racing every year and even drive on Texas Motor Speedway – so adding an external transmission cooler is in my plans.


    Now getting back to the transmission oil temp gauge. By far, the best location for the sensor it is in the pan. The cooler lines will not give you an accurate reading (either too hot or too cold, depending on which line you tap into). The pan will give you the best result.

    I took a Mopar Performance Deep sump transmission pan and had an adaptor welded onto it for a mechanical temp gauge. I don’t recommend doing this to a normal transmission pan – for the sensor most likely will interfere with the valve body or something else inside (unless placed in an exact position). Using a deep sump pan will help with that. Even better, I have seen some aftermarket transmission that are already pre-drilled for a mechanical temp sensor – so they did the homework for you.

    On my garage wall, I have an A727 Mopar Performance deep pan, with a mechanical sensor fitting welded in, for when I build the A727/A518 for my Fifth Ave.

    It is highly recommended to use a deep sump oil pan for any vehicle that will see more than “old lady” driving. Not picking on anyone, only trying to give a “vision” as to my thinking.

    If you looking for an inexpensive deep sump pan, I recommend getting one for the 4-speed overdrive pans like this one for A727 46RH 46RE 47RH 47RE Transmission Pan A518 618 A727 Chrysler Dodge Jeep (99976) | eBay
    A518 pan.jpg
    A904/A998/A999 A500 40RH 42RH 42RE 44RE Oil Pan 1988 & Up fits Jeep Chrysler Dodge NEW | eBay
    A500 pan.jpg
    I “think” these pans are made by Dorman, but not sure. Most of these pans use extra thick metal – which is a good thing sense they sit a bit lower in the car than a stock pan.

    I like working with these painted pans for they look better, tend not to rust and cleanup is faster. The overdrive transmissions have an extra layer to the valve body – which requires a deeper pan for the extra parts. These pans can be used as is, but I do recommend using a filter extender – so filter is closer to the bottom of pan.
    3690730.jpg
    A727 kit, like the one I mentioned above.
    904 Deep Pan.jpg
    Aftermarket kit for A904/A998/A999

    Most people can get by without a need for a transmission temp gauge.
    Personally, I would prefer a mechanical sensor with a bright warning light (or buzzer) if temperature gets to a preset reading (like say at 275’ F (135’ C) - but not sure if someone makes one that way.
    I would STOP if transmission temp got to 325’ F (163’ C) and would consider a larger cooler if temps get to 300’ F (150’ C) often.

    I can’t remember where I welded my sensor fitting to, but I “believe” it to be on the rear of pan because I remember routing the cable (not sure what you call the sensor wire) along with the speedometer cable.
    BudW
     
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  12. M_Body_Coupe

    M_Body_Coupe Well-Known Member

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    BudW:
    That is a superb review of the heat aspects of transmission operation. Totally agree, if your budget allows a deep pan is a great piece of equipment and a wise investment to protect your existing hardware investments.
     
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