How to make GT-R35 at RWD mode?

I have a no linked axle hub dyno, it just can 2WD or 50:50AWD car.

Does anyone know how to dyno a GT-R35?

The only R35 GTRs I've run have been i 4WD mode so I can't comment from personal experience. I found a thread on the GTR Life forum that mentions removing a front driveshaft - https://www.gtrlife.com/forums/topic/36038-running-the-r35-in-rwd/

Not sure if there's an easier way without reflashing the TCM or something of that nature.

This reminds me of there being a rumor how you could run a 997TT in RWD and that just doesn't seems to be possible without bunch of issues and is exactly that, a rumor. But I'd be interested to know if R35 can do it easily.

I've looked into it loads and spoke to a fair few people and they've all said pull the shaft is the simplest surefire way to run in RWD, you need to run the car up lightly until the 4WD system goes into fault before trying to load up the system.

I have never tried it so I really don't know for sure if it does any damage to the clutch packs or not but I don't see how it can as there will be no load to the front wheels

I am trying to do the same thing here but after disconnecting the drive shaft, the AWD light would come on shortly once the wheels are spinning even at the lightest load.

Tried letting it roll on 4th or 5th gear with the dyno holding the car steady at 2000 or 2500 for like a minute but the AWD light simply just stays on and the car continues to be in limp mode as it thinks the AWD is overheating based on the "slip" it measured.

That's normal. You'll have warnings while the front shaft is out but it's not going to break the AWD system, in fact it's easier on it than dyno-ing it while AWD.

Yes, but the problem is, when the AWD temp warning is on, it goes into limp mode and limits power. Based on the slip measured, it thinks the AWD clutches are overheating (although it is not) and limits the power output to protect it.

Anyway since my last post, I have continued to roll it on dyno the at light load for a few more minutes and the dash finally lit up like a Christmas tree and according to the 4th post on the GTR Life forum thread that Andre have linked above, it would stop the limp mode and I should be able to make full power.

We then tried to do a pull while all light are lit and it seems to work BUT the dyno started acting up and we had to lift off the throttle so I cannot 100% whether it is working now until we fix the dyno.

We actually have a 4WD dynapack and have dynoed a few R35 in AWD just fine on it. Ocassionally it would stutter as the dyno and car fights to sync up the speed on all four wheels on some runs but most of the time it works fine. Somehow with this particular R35 we just couldn't get a single run in. We could not even hold it at steady state other than at extremely low loads and that is why we had to try running it in 2WD. But even in 2WD, it seems like the dyno couldn't keep the two rear wheels in sync as soon as I floor it so it does look like there are some issues with the dyno itself.

With the tranny in R mode, traction in OFF, drive for a few seconds til the systems all fail out and then you have full power.

It sounds like the first time you stopped before you found that out, but you're all set now, which is great.

While prior vehicles may not have shown a warning light to indicate damage, operating an R35 as AWD on a Dynapak wears the center diff very quickly and I really suggest avoiding it. Shops that rebuild them are inundated with worn active diff units from dyno use.

Because pulling the front shaft is a quick job and common practice on R35 for a variety of dynos, most customers already know this and expect to be charged time to remove and reinstall it for tuning. Generally this makes it an easy conversation.

I'm sorry to say, but it's important for operators to keep in mind that Dynapak does not speed balance between hubs well. Any differential that doesn't lock aggressively can be quickly worn or damaged because the vehicle is put into an extreme situation not encountered on the road. Open diffs, viscous LSDs, weak active diffs, and some weaker clutch or mechanical locking diffs, in front, center, or rear locations tend to get beat up on Dynapaks. It's vital to watch pod speeds very carefully during operation and back off throttle soon as speeds separate significantly, or you feel the drivetrain start struggling, and check temperatures as viscous units can overheat quickly because the dyno isn't handling the balancing and there's no tire to roller or road interface to help the diffs out. Some shops with Dynapak swap the diff to a welded or spooled unit for dyno testing, then swap back after to avoid this, so that is an option if you ever want to take an extra step to protect the customer vehicles.

Thank you for the detailed information Mike.

Somehow I need to drive for over a minute for the system to all fail and have full power rather than just a few seconds but if it works then it's fine I guess?

So far our Dynapack had worked well for us on 2WD vehicles but for AWD it is indeed frustrating at times. If the front rear split is more or less constant it works fine but once the split starts to vary, then the dyno would sometimes really struggle. Yes, it does feels like things are going to break when the wheel speed falls out of sync and I too, do prefer not to run in AWD when conversion to 2WD is possible.

After having issues with the R35 we tried another RWD car with open diff on the dyno just to check whether there is something wrong with the dybo but the two hub pod speeds matched up just fine as always. Why this particular R35 would refuse to run even in RWD really baffles me and I guess the next move would be to investigate whether there is something wrong with the car itself.

Jerry,

Keep in mind when the dyno obviously struggles that's because the dyno has put the differential into an extreme state, caused persistant large speed differential across the axle, which overheats the differential and quickly damages it. It likely drives on the road, but acts more open than it used to now, and can probably still dyno on a roller dyno, but not Dynapak. You could put a new Wavetrack rear LSD in and then likely be able to dyno it on the Dynapak again.

As a general suggestion, viscous LSDs and weak clutch type LSDs seem most likely to get damaged on Dynapak because overheating them severely once ruins them and it can happen really fast on a Dynapak. Open diffs may be troublesome to speed balance, but seem less likely to get seriously damaged on Dynapak, and then spooled or really aggressive locking diffs do alright because they don't rely on the dyno for speed balancing.

Hello Mike,

The car finally dynoed properly after having a new LSD installed.

While taking the car off the dyno in the previous session, we kept the rear jacked up after installing wheels and started to car to them spin up while suspended. The left wheels would accelerate smoothly while the right would spin at a comparatively slower speed and slowing down at times. Looks like the rear diff was weak/damaged to start with any maybe have sustained more damage while on the dyno. But we have always watched the hub rpms closely and backed off as soon as the hub starts to spin at different speeds. As as you mentioned, the diffs could get damaged VERY quickly.

So we replaced rear differential with a new LSD and dynoed it again in RWD mode and everything went smoothly.

A small tip for others wanting to run the R35 in RWD mode. At first, we had to run the car for minutes on the before it would enter "all fail" and give me full power again. This was because we tried to cruise and up shift as smoothly as possible while on the dyno. Subsequently we noted by pulsing the throttle a little in between shifts while we gradually accelerate and shift up in gears, it would usually go into "all fail" by the time we shift to 5th or 6th gear. Previously, I would be rolling in 6th gear for minutes at a time before I could get into the "all fail".

Sounds like great progress Jerry!