kyle3481

hey guys i am just wondering what is the difference between RMM LSD and TRD LSD? does the TRD LSD lower the top speed by setting the gearing to 3.25? pros and cons?? and also any slight difference in acceleration in TRD LSD and RMM LSD?? help guys!


andrew

///MDex

I'm pretty certain the TRD LSD does not replace the ring gear in your differential, its uses the existing set, so it has no effect on top speed.

Do a search on LSD and you'll find some great info.

Mean Gene has the RMM LSD and is another valuable source of info.

mumbles

It's too early for this, but I'll give it a try. First off, the main reason we install a LSD is for the 'limited slip' benefit, and the gear ratio will be either a plus or minus depending on your perspective. So, on to your question.
Assume you are in drive, which takes the function of the transmission out of the picture, since drive provides a 1:1 ratio, and you have the TRD LSD. The drive shaft will rotate 3.25 turns for every turn of the rear wheel/axle. So the higher the ratio, the faster the engine has to turn to move the car one revolution of the wheel. This gives you more low end grunt, but less top end speed. Obviously the reverse is true, the lower the ratio will give you less low end grunt but more top end speed.
Is there a real difference between the two? Probably some. With the TRD, your cars RPM's will be lower while cruising on the freeway, and will be a little slower off the line. With the RMM, your RPM's will be higher cruising on the freeway and you'll have a little more ooompf coming off the line.

Johnny Mo

I'm not sure what the stock rear ratio is, bu the way it works is the higher the rear end ratio 3.76 vs 3.25 to 1 the quicker the car off the line and the lower the top speed. So the RMM will be quicker off the line than the TRD, but lower top speed. Once you determine what the stock rear ratio is you'll have a better idea of what it gets you.

As an example when I changed my rear on my '86 Mustang GT from 2.73 stock to 3.55 auburn locker I knocked almost a second off my 0-60 time (about 7 tenths). AS another example the automatic Mustang GTs used to come with a 3.27 rear to compensate for the auto tranny power loss.

mooretorque

Assuming top speed is rpm limited. If drag limited or governor limited, the higher rear end ratio may NOT affect top speed since redline may not be reached anyway.

LS4fun

Anyone know what the Supra TT LSD ratio is?

tinygs

From above post:

I'm not sure what the stock rear ratio is, bu the way it works is the higher the rear end ratio 3.76 vs 3.25 to 1 the quicker the car off the line and the lower the top speed. So the RMM will be quicker off the line than the TRD, but lower top speed. Once you determine what the stock rear ratio is you'll have a better idea of what it gets you.

As an example when I changed my rear on my '86 Mustang GT from 2.73 stock to 3.55 auburn locker I knocked almost a second off my 0-60 time (about 7 tenths). AS another example the automatic Mustang GTs used to come with a 3.27 rear to compensate for the auto tranny power loss.

LS4fun

Is the Supra TT the same as the TRD one?

RacingAristo

nope

itsallgood

The stock gearing in the GS400 is 3.23 and I believe the GS300 is 3.31
As for the difference between the RMM and the TRD LSD's is that the TRD is supposed to be a lot stronger, meaning it can handle more horsepower and torque.

The Supra TT has 2 different gear ratio's, 3.76 I think was for the 6 speed. I'm not sure about the Auto.

biggie27

but your saying that you will lose top speed on the RMM LSD, my question here is that the GS's are limited at 150mph ( 149mph to be technical ) but if there was no limiter they will hit anywhere from 160-170mph so with the RMM LSD Im guessing since its not such a big diffrence than stock we will retain the 149mph top speed and just get there faster off the line

tinygs

Can someone verify this???? Mean Gene? Anyone?
The RMM IS the SupraTT rear end(made by Toyota, for Toyota), for those who didnt know. They advertise theres as a 3.76 for our GS A/T as well. Does this mean that the SupraTT 6sp and A/T utilize the same rear end?? TIA, Tiny

Mean Gene

Tiny - Steve Ganz told myself & Craig Werlin that the differential RMM sells is the Supra TT piece. Since I've never had the pleasure of owning a Supra, I honestly can't tell ya if Toyota offered 2 different gear ratios depending on the transmission. It would seem probable since Chevy offers different gearing on some of their cars & back when I had my 'Vette, if U chose the manual tranny, U could only get 2.73 gears ( but the deeper first gear ratio of the transmission made up for it ) while the A/T came with the "performance" 3.07 cogs!! It's the same situation/solution that Johnny was describing with his Mustang. As far as the GEARING changing the top speed of the GS, it's not true. The top speed governor ( set at 149 mph as Biggie said ) is still the limiting factor as my tachometer was reading somewhere in the mid 5k rpm range after I installed the rear end & took a shakedown run up to the magic 149 mph mark. In other words, the engine still had another 500 rpms left to go when the governor kicked in &, as we all know from the various dyno sheets which have been posted, the Lexus V-8 makes it's peak horsepower right at 6k. I don't think it's a linear curve but I'd estimate the top speed of MY 3.76 geared GS4 to be right in Biggie's estimated range of 160-170 if we could get by the governor ( best guess is 162-164 mph ). Too many variables such as drag, wind resistance, vehicle weight, etc to be much more precise with my "educated guess". Suppose we'll have to wait for Mo to finish with the tranny ECU to see, huh!! :eek:

quocman555

iTrader: (2)

So which would you guys choose, TRD or RMM? For those of us that wanted to get the LSD but couldn't decide.

Mean Gene

Q - IMHO, it depends on how U drive your GS. If ya do alot of highway driving or like to autocross, then the TRD differential ( utilizing the 3.23 gears ) probably would be better for ya. The engine will turn lower cruising rpms & give the same economy as the stock ( open ) diff. For myself ( former drag racer ), I willingly gave up some mpg ( about 1 mpg when cruising at 80 mph or so ) for the deeper holeshot & subsequent lower 0-60 & quartermile times ( it knocked of .2-.3 depending on traction ) offered by the steeper 3.76 gearing. In fact, I installed the Dragon T/C first & could easily smoke the 18's so I expected to have an even worse traction problem once the diff was changed. However, the LSD evened out the torque equally ( well, almost because it's not a true positive traction locker ) enough that wheelspin wasn't that much more evident. They kinda canceled each other out in a way. Your call but the LSD feature alone is worth the money.