Building a 48re

Discussion in 'General Discussion' started by Srt10650, Mar 21, 2023.

Car Parts
  1. Srt10650

    Srt10650 Full Access Member

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    Sep 30, 2016
    Hello, I’m rebuilding my 48re and wanted some input from the 48re gurus. I’ve been looking a the diesel guys forums for a while and they know what works for the diesel application. I’d say they have us covered about 75%, basically what I’ve read the difference between the diesels and the srt10 48re is the valve body calibrations and the pump.

    Little info on my truck, 05 quad cab currently has bolt ons. Truck will be getting a Roe Whipple, I’d say maybe about 600whp. Truck will not be daily driven, weekends mostly with some track use. Just want to see what works for us, thanks.

    For this application what would the recommendations be?

    Sonnax input?
    Sonnax output?
    Sonnax billet servos?
    Sonnax intermediate shaft?
    2800 or 3200 convertor?
    Triple disc or single disc converter?
    Billet flex plate?
    727 front band?
    Transgo shift kit or built valve body?
    DNJ GM solenoid or Borg Warner solenoid?
    Rostra HD transducer or Gold transducer from the 47RE?
    5 or 7 clutches?
    What ratio lever?
    What fluid to use after rebuild?

    What I know for sure is
    Deep transmission pan
    Sonnax strut
    Billet anchor
    727 filter
    Last edited: Mar 22, 2023
  2. rottenronnie

    rottenronnie Well-Known Member Supporting Member

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    Jul 4, 2006
    Calgary, Alberta
    I have a "1500 Horsepower Diesel Build" with no special treatment just because it is behind the 8.3L. They are the same transmission.

    The Valve Body & Front Pump are identical between the diesel and SRT-10 48RE.
    RPM Shift control & O/D lockup is through ECU programming.
    I upgraded to a Billet Input Shaft.
    The Output Shafts are tough and it doesn't need to be changed.
    The Intermediate Shaft doesn't need to be changed either.
    A 2800 stall convertor (good quality) is a great choice.
    727 Front Band is a good choice as they are meaty.
    GM Solenoid is a required mod in my opinion. (Have the Mechanic watch the attachment surface, it may need a bit of filing to fit/seal properly to the Valve Body).

    I went with the 47RE Gold transducer.
    Don't use race clutches as they are for full-throttle application only.
    You can use 5 or 7 clutches (your choice), it depends on how loose/tight they are installed.
    Stock ratio activiation lever is fine.

    I use Dex 6 (GM Fluid) that doesn't use friction modifiers the mopar fluid uses (primarily for their Mini-Vans). And it doesn't stink like Mopar Fluid!

    Shift kit (your choice); My Valve-Body was modifed by the Builder so I don't have an aftermarket shift kit.
    As an additional safety measure, my planetaries were pinned. Not necessary, but I did it anyway.
    I'm using a stock flex plate.

    Have the valve body modifed to prevent drainback when sitting for a while. It MAY be part of the shift-kit. Your tranny guy should know.

    I'd also change out the cooler hose that has a check valve in it as they have been known to fall apart inside. I had a hose made without a check-valve, instead of installing another OEM hose that could cause an issue down the road. It is the hose behind and below the washer bottle. Again, check with your tranny guy.

    It might sound counter-intuitive but a deep pan WITHOUT the filter extension is the way to go. That will keep any particulates away from the Solenoids and help keep them at the bottom of the pan where they belong and further away from the Filter Inlet.

    Plugging up the TINY screens on the O.E.M. Solenoids with particulates prevents the Valve Body from producing full line-pressure for Bands/Clutch application and is the 48REs main weakness. So...the larger screens on the GM Solenoids can help the 48RE live considerably longer.

    Make sure the initial Band Adjustments are per the 48RE shop manual as they differ slightly between the SRT-10 and Diesel. Tighten to 72 inch pounds, back the screw off 1-1/2 turns then tighten the locknut.

    Your ECU will look after shift-point rpm. By the way, have your Tuner extend the 3-4 (Overdrive) shift-point. I have mine set for 120 mph. It makes a LARGE difference and prevents the tranny from short-shifting and potential engine detonation when you are up there in vehicle speed and pushing a lot of air.

    As simple as the 48RE appears to be, there seems to be a real shortage of guys that know how to build them properly, (at least around here).

    I'd also suggest having a good look at your warranty.

    Good Luck.
    Last edited: Mar 25, 2023
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  3. Adam Craig

    Adam Craig New Member

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    Apr 20, 2015
    Thank you for this useful information!
  4. rottenronnie

    rottenronnie Well-Known Member Supporting Member

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    Jul 4, 2006
    Calgary, Alberta
    You are welcome.
    That's what Forums are for (I think).
    Srt10650 likes this.