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4r70w questions/issues

Discussion in 'Driveline/Suspension' started by 03blkann, Jun 22, 2019.

  1. 03blkann

    03blkann Member Established Member

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    Location:
    syracuse new york
    This is more of a transmission question thread. I am not totally sure if this is the right place to post this or not. So I am running a turbo 11-14 aluminator with a 4r70w Lentech Manual valve body, freshly rebuilt using the best of the best parts.

    I am having issues on my shift. Sometimes like a flare in the RPM between shifts (this happens when it is hotter). Or even like a chatter kinda between shifts (happens when its cooler). It only happens at WOT inbetween shifts. Other than that everything works perfect. I have had a couple of people ride with me to feel the issue. The most feed back i am getting is that it feels like i am not getting enough line pressure. So one of my questions is. What size lines would some of you guys recommend?

    Also

    I've pulled the pan checked for material to my surprise some light dusting nothing major, but the fluid was slightly burned. I will be adding a trans temp gauge soon. Because clearly it is running pretty hot to be burning the fluid. What are some of the best spots for transmission coolers, and what are some of the best transmission coolers out there? I have mine mounted inside my front bumper behind the passenger side fog light. So very little air flow is able to reach it. Although it does have a fan on it.

    The car is making around 700whp. Which i know of plenty of other cars making much more power, and running the 4r70w. So i guess my question is what am i doing wrong?? and how do i fix it lol.

    Thanks for taking the time to read this. Appreciate any feedback!!
     
  2. Norm Peterson

    Norm Peterson Member Established Member

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    on a corner barstool in Boston
    Line pressure in an automatic transmission has nothing to do with the size of any lines attached to it. Line pressure is the pressure inside the valve body in whatever fluid passages are being used to apply clutches and bands.

    Low line pressure might be the transmission's pump itself, its pressure regulation, or a leak or a missing check ball somewhere in the valve body that's allowing some fluid to bypass what it's supposed to be doing (this can cause line pressure under operation from a good pump to drop).

    You need to get that cooler out where it has direct airflow both into and out of, or open up that whole fog light area and add some ducting. Maybe it needs to be bigger, particularly if you're running a torque converter with a higher stall speed than OE. More slip = more heat. Are you also running the oil to water cooler that's in the radiator?

    That's about all I can offer. Maybe you'll get some more detailed responses.


    Norm
     
    Last edited: Jun 22, 2019
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  3. 03blkann

    03blkann Member Established Member

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    3500 stall, and for the oil to water cooler thats in the radiator. I honestly have no idea..
     
  4. Norm Peterson

    Norm Peterson Member Established Member

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    Location:
    on a corner barstool in Boston
    That oil to water cooler I was talking about is for the transmission, not the engine. It's the normal OE method of cooling tranny fluid.


    Norm
     
  5. nyuk98GT

    nyuk98GT Member Premium Member Established Member

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    Location:
    Chesterfield, MO
    03blkann,

    I can only offer my experience with a 4R70W in my old '98 GT that had 1/3 the horsepower your car is producing.

    If you are not familiar with the J-mod, it consists of modifying some of the holes in the valve body plate to let select passages fill quicker and updating some of the 'pistons' (servos) located . This makes the shifts quicker but not harsher.

    Link to J-mod:
    Tech Article: A-Train's Shift Kit Install - Jerry's mod - TCCoA Forums
    This may be a bit dated for your model year transmission but it is good reading.

    A secondary trans cooler is recommended when running a stall converter (not my opinion but advice from guys who know, lol). I had an FRPP Mustang trans cooler in series (after the in-rad cooler) and it helped to keep the oil temperature from getting too warm. I do not remember the trans oil temperature in my old car but I may have some ancient datalogs (i'll look for them).

    There are a bunch of transmission control parameters in the tune. From the basis of SCT Advantage (ProRacer), I had access to tweak shift points, lock points, pressure, filling times, etc., and your tuner will have access to even more parameters to modify and perfect the behavior of the 4R70W.

    In the older model years, the OD band was a weak point and WOT shifts (into 4th/OD) were strongly discouraged. The J-mod helped to fill the OD valve quickly to apply maximum clamping force. I presume that the OD band material is much improved now.

    That's about all I can offer. I hope it is helpful info.

    Chris
     
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  6. 03blkann

    03blkann Member Established Member

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    Location:
    syracuse new york
    Thanks for the info! I have heard of the j-mod. The trans is manually shifted, not electronically so i do not believe it can be tuned for certain shift points, locks points, pressure, etc etc. The Manual valve body i have. Has a fixed line pressure. Also yes OD is strictly for highway cruising it will never see WOT.

    I recently replaced the fluid with a type f synthetic fluid recommended by a well known builder of these transmissions. Going to see if that makes any difference. I am just looking for any info i can get because i am just at a loss on what the next step i should take is. Before breaking down and buying a new trans or having this rebuilt..
     
  7. nyuk98GT

    nyuk98GT Member Premium Member Established Member

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    Location:
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    03blkann,

    Ah, OK, manual valve body - you did mention that early in your post but my brain apparently missed that fact. :oops:
    So, in a manual vb, are the shift solenoids still used or are they replaced with hydraulic valves? (Maybe I should just use "The Google".) What about locking/unlocking the converter? It's possible to get a little flare during the locking process so that is something to discuss with your transmission guru. If you tell me that you run an open converter, I am just going to shut up and stop cluttering your thread.

    What does your t-guru say about the J-mod for late model 4R70Ws? Does Lentech mention (or advertise) modifying the vb separator plate (using their own orifice sizing secrets for the 4R70W)? I was so impressed with how quick but not harsh the shifts became when I finished up the J-mod, I remain a big fan.

    If you can, datalog the trans fluid temperature (along with the shift parameters (RPM, slip, TP, etc.). Heat is baaad [/George H.W. Bush voice] for the automatic. The data will confirm whether a cooler is needed (I think it will be just because of the higher stall converter). And your trans guru will probably "see" what is going on with the WOT shifts.

    Anyway, I hope you get the chatter/flare thing sorted out. A well-behaved auto is a beautiful thing.

    Chris
     
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