I'm FI with my X and will soon be upgrading the engine to handle up to 600HP. My concerns are now starting to grow for the transmission and transfer case. Honestly this hasn't been done a lot on an X so far that I know. I've called around to some shops in my area and they just don't know the answers as to the correct limits on these. Do any of you guys out there know a good safe number for the auto with valve body upgrade? How about any knowledge on the transfer case? Clearly at some point I'm going to have to upgrade components of them to handle more power I'm just not knowledgable as to where/what.

 

auto limits with VB are about 400-450hp/400wtq have never heard of anyone upgrading an X auto trans before. dunno if they even make parts to do so for the older awd G's.

 

If you're pushing 450 at the wheels that's great. That tells me you're pushing close to 600 at the crank. You may want to consider upgrading the drive axles front and rear. As far the auto tranny, upgrade the torque converter and I'd go to the GT-R forums for ideas Regarding the transfer case. Their isn't much you can do to get an automatic to handle anything over 600hp but, give it a try. Good luck.

 

Go to a MT the Auto sucks big time!

 

GTM sells an upgraded tranny for roughly $4,600 that includes valve body and torque converter. https://www.gtmotorsports.com/produc...7&cat=0&page=1

But, the catch is I have not heard anything good about this company on this forum. Stuff along the lines of folks sending money and never hearing from them ever again. Since I already have the valve body it seems my logical next step is the torque converter like this one (good for over 600HP, my goal): https://www.gtmotorsports.com/produc...cat=262&page=2

Here is the full list of components: https://www.gtmotorsports.com/home.php?cat=262

Any help picking through those to pair with my torque converter upgrade would be GREAT. Thanks.

 

I have taken GTM's 5AT to 550-580 whp (on a 2004 coupe, not X). It is not consistent at that power level. A built 5AT is great for FI around the 500 WHP mark. You will beat most drivers with a 6MT in the 600 whp range.

To clear up misinformation in this thread:

1. You do not need new axles and I do not think you will need to strengthen the front or rear diff or transmission casing.
2. You will need a transmission cooler (cheap)
3. You will need a valve body upgrade
4. You may need clutch packs (this is a full build, like what GTM offers). GTM did a good job for me years ago but I don't know anymore (as they are out of business!). IPT has failed others so I wouldn't go there either.

Going to a 6MT is about a $10k investment, just FYI. I did that too to make the jump from mid 500's to mid 800's. To the wheel...

 

The stock T case is going to be your first issue IMO, and there is no way to add an external cooler to keep it from burning up at those power levels and there is only about 1.5 qt of fluid in there. Mine started giving me hell at 125k. Burning smell, clunking at low speed acceleration (from electric clutch coupling being bad) and awful gas mileage.

http://x.infinitihelp.com/forum/loca...o#.VSGlKPnF98F

Between the transmission and T case both being questionable I would never go FI with an X. If I needed an AWD FI car, I would either look into a used GTR or leave nissan altogether.

Food for thought; the HR models have an entirely new T case, maybe they fixed or re-designed it... Hopefully some HR guys can chime in with their experiences. Not like you're going to do a HR swap...

I am currently doing a 6MT swap in my '05X for a bunch of reasons.