Project R35 GT-R, What is inside our 1200 lb/ft Capable GR-6 Transmission!

 

 

Nissan is pretty lame and doesn’t even sell the transmission filters as service parts!  This is the internal second filter and we replaced it with Dodsons cleanable and reuseable stainless mesh part. Dodson’s in-pan OEM spec filter is used down in the pan.

The GR-6 has perhaps the biggest oil pump we have seen on transmission.  The stock oil pump shaft is known to sometimes break.  Our shaft is replaced with this heavy-duty Dodson unit.

These Dodson Piston Selector Shims were added to the pistons that move the shift rods. The pistons can sometimes rotate and thus will not allow their magnetic strip to register with the transmissions sensors.  This causes the transmission to go into limp mode and your transmission will not shift into 1st, 3rd, and 5th gear or 2nd, 4th or 6th gear.  This is a common GR-6 transmission problem and these shims stop the pistons from rotating.

As a note, every o-ring and seal in the entire transmission was replaced with Dodson’s heavy-duty, high-temperature parts. This is comforting as Nissan does not support this transmission for parts at all!  Before if the smallest part broke your only recourse was to order an entire $16,000 brand new transmission from Nissan!

Back in the day, our cars were plagued with shift problems in the lower gears.  We could not figure it out. The car would stick in gear ignoring the paddle shifter input or even the transmissions automatic controller. The car would overrev, slam into the rev limiter, then the transmission would do a slow slipping shift.  Not good for ETs and for sure not good for the transmission or engine.  Since then it was learned that high G launches and cornering would force the transmission oil pickup to suck air.  Dodson came out with a high-capacity billet oil pan for the GR-6.  The pan gives 2 quarts more oil capacity.  Since the GR-6 can tend to run hot, this capacity is useful.

The Dodson pan has cooling fins to help the transmission run cooler. The beefy billet construction also helps reinforce and stiffen the transmission case.  When you get to 4-digit power levels case flex issues are real!

6 comments

  1. Are you sure you want to add “super-strong ARP bolts” in the blind holes machined in to the cast aluminum differential cover? Higher strength bolts means more clamp load to achieve the same stretch which in turns leads to shearing the threads in the non-serviceable transaxle. Those holes don’t look to deep so it would be a good idea to triple check the thread engagement calculations.

  2. Is there some reason that they don’t go with straight cut gears? Seems like noise and vibration wouldn’t be a serious consideration in this application.

    Personally, I kind of enjoy a bit of gear whine in a race car.

    1. The helix of the gears is changed for more strength. Helix gears can be stronger although they do waste more power.

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