Hey TowPro I just used a trans temp gauge, I then welded a 1/8 pipe weld bung on the pto cover. I have done several and it seems to work fine. I must say I have never seen any temps to be worried about and I pull a 15 k 5th wheel.
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1996 4x4 3500 4. 10 5spd, Diesel Dynamics stage 3 injectors, #5 TST plate, Govoner spring kit, Ported Head, ATS manifold Jet-Hot coated, 16cm2 housing Jet-hot coated with 4" Jardine exhaust, Cummins exhaust brake, US Gear overdrive, Grover air horns and Mag-Hytec rearend cover. Special thanks to Piers and BD Performance.