Pearlpower

iTrader: (2)

Several here have experienced bouncing off the rev limiter and having to lift off the throttle a tad to get the GS to shift into 2nd. Supercharged and those with lower gears and TC. For those that have run into this, I am curious what size tires/wheels you are running to ascertain if the tires were improperly sized up and causing the issue.
I have yet to run into this issue with my lower gear/TC combo and now even with the S/C kit and lower gears the car shifts into 2nd and 3rd with no problem. I believe this would be very helpful to other GS owners looking to upgrade their cars and would like to prevent this from occurring.

List your tire wheel combo with your mods and indicate if you stick to the rev limiter or not.

I am running, 265/35/18's in the rear which are sized to the stock 245/45/17's. 3.76 gears/LSD, RMM supercharger. No shift issues.

Lee

klynchgs4

rmm s/c with 2.87 pulley (waiting for proper tuning, but even before the pulley change, i'd hit the limiter briefly on the 2-3 shift, 1-2 was fine). i'm running 285/35/18's in the rear (nitto extreme drag radials) - stock gearing - trd lsd coming soon.

morris

iTrader: (2)

I'm running stock 17's 235 45. I have the RMM kit in a 400 and am using the stock 3.12 pulley. I boucne the limniter but dont ussulay get stuck there. It will evenutally shift. 2800rpm TC and stock differential.

BA_GS400

iTrader: (1)

My engine is still stock, but I've hit that limiter a few times when trying to use the e-shift buttons.

The buttons were not giving a very responsive shift,....it would take a few seconds to shift, meanwhile the RPMs kept climbing a few hundred extra RPM.

morris

iTrader: (2)

One thought I have is that if I go up to the 19" rims from the stock size of 16" that will effectively lower the final ratio. If I then raise the ratio with the lsd to 3.76 hopefully that will in effect cancel each effect out to a point where the transmission wont notice that much of a differecne.

Any thoughts?

Mr Johnson

275/35's on the back and 245/40's on the front. Will hit the limiter in 1st and not shift unless I let off. Will hit the limiter and bounce for while before it shifts in 2nd. 3rd is just a short tap on the limiter. FWIW: I've got the SRT valve-body.

morris

iTrader: (2)

Johnson should we assume those are 17's? its the diameter not the width that effects the drive ratio

Mr Johnson

DOH!

Actually it's the combination of wheel diamater, tire profile and tire width that matter in this measurement. I gave you two out of three here's the third: These are 18s.

FutureGS400

Generally speaking, there are two options for staggered 19" setup. One is the "fat tire" combo where you do end up with a slightly taller tire than stock. The other setup (using a lower aspect ratio tire, same approximate width) will be closer to stock diameter.
When you say "lower the final ratio" I assume you mean numerically lower (i.e. 3.27 to 3.15 or whatever). Your basic idea is correct, the numerically higher gears (3.76) will compensate for the change to the effective final drive ratio that taller tires will cause.
However, the 3.76 gears will MORE THAN compensate for the increase of the 19s. In other words, you will still have lower gearing than stock because the difference in gearing is greater than the change caused by the taller tires in this case.
Anyone with this setup can feel free to correct me of course, but I believe this to be accurate....

rominl

iTrader: (4)

if you get 19s and stay with 245/35 and 275/30, you are just as close to stock diameter as possible, you didn't effectively lower the ratio. now for example in my case with 20s, yes, i lower my gear ratio. same for those with 19s and fat setup

morris

iTrader: (2)

Well that shot that idea down.

But thanks for the clarification and education.


So I can go with fat staggered 19's and wear the inner edges out (Camber)
And I can go with a complete with gears LSD pay little in labor for the install but kill the shiftinng abillity, decisions decisions.

RMMGS4

iTrader: (5)

REVIEW:
These are mathematical calculations, however do note that manufacturers do vary from this slightly.

235/45-17 = 25.32 inches stock diameter.
265/35-18 = 25.30 less than stock dia.
275/35-18 = 25.57 a little over 1/4 larger in dia.
275/30-19 = 25.49 about 3/16 larger in diameter.

These differences are quite small and from those that have reported so far, I don't think there is any consistent evidence showing that the diameters have a great effect, in fact the 3.76 gear would affect the overall ratio much more than what these tires sizes could do.

For the record I have:

3.76 LSD
275/30-19
RMM TC
RMM Valvebody upgrade

No bounce in any gear.

Upshifts are crisp and solid
0 to 60 in 5.2 (G-Tech Pro)
It probably doesn't get any better than this for a NA car, without doing radical changes, like weight reduction, drag radials, etc.


Lee,
when was the last time you changed your tranny and diff fluids? You might NOT see the problem if your fluids are fresh.

For those that get "The BOUNCE" I'd strongly suggest having the tranny flushed (around 14 quarts of oil) and the diff gear oil changed. The tranny runs sluggish after even 20k miles. Don't follow the maintenance schedule, it's too long if you have a TC and LSD.

Use Synthetic oil for both. I use Redline for the differential and Amsoil has just released a Synthetic that is Type IV approved for Lexus / Toyota.

The tranny will shift quicker/ cleaner with high performance oil. With old stock oil, the shifts will be a fraction of a second slower. This translates to a few more rpm, before the tranny will engage the next gear. This time delay could mean the difference between shifting right before redline and hitting the rev. limiter and "BOUNCING".

RMMGS4

iTrader: (5)

Nope. Camber wear on the rear tires is negligible. The front tires are another story.

HUH?

Please clarify.

rominl

iTrader: (4)

huh? what are you talking about?! cna't understand

FutureGS400

Staggered 19s won't necessarily wear on the inner surface quicker, that is dependent on a number of factors including: wheel alignment, amount of drop, driving habits etc.
The 3.76 gears with Torsen LSD (Supra TT diff) shouldn't have a negative effect on your trans shifting. Install costs should run around $150-200 or so. The cost of the unit new can run around $1400 or so, sometimes you can find used ones for much less, but the condition will be unknown.