SC430 3.76 /LSD differential installation
09-01-06, 08:59 PM
#1
SC430 3.76 /LSD differential installation
It took a while to aquire one but this is one of my favorite Lexus mods and does make a noticeable performance difference. 
I picked this one up from another member with 5k miles on it. I opened it up and inspected the gears which appeared to be in very good like new condition. Backlash was very good. Put in some Royal Purple synthetic and installed it.
Installation is more involved vs. the GS series due to the additional bracing under the car making things a little tighter to maneuver around. One rear bolt in particular is a little challenge requiring me to grind down the length of my T-60 to fit in there with my breaker bar.
There are two versions of the Supra TT Auto differential. One is the worm gear units from 1993-1996. 1997 and up went to the helical LSD units.
Worm gear units are supposed to be able to handle more power (not an issue here). The Helical units are supposed to have quicker response times. The helical unit seems to engage the traction control system more easily vs the older worm gear design.
This is a direct bolt in install and should take no more than 3 hours for a good mechanic. 4-5 for others. First thing to come out is the exhaust from the rear cat on back.
Performance wise the car is snappier off the line and on the get-go as it kicks down to a higher RPM well into your powerband. The LSD works great when launching as there is no need to turn off the overly sensitive VSC system that steals power at the wrong moments (sometimes dangerous moments when you pull out into traffic). Top speed is down to 133 which is no big deal. Have not done that in a long time (well, ok, since the SC430 meet). Changing gears is an old hot rod trick for good reason. RPM's do go up 500rpm at the same speed or around 3000rpms at 80mph.
Just to note, increasing the gears from 3.26 to 3.76 is similar to adding 15.4% of RW torque to the car or similar to having over 390lbs of torque taking into my other mods such as headers.
Expect a decrease of about 2-3 mpg.
Downside other than mileage is lost of control if both wheels spin through a corner such as in the rain as the car will spin QUICK. Been there, done that with the GS and do not expect the VSC to kick in to save the day as it does not sense a problem as both wheels are spinning.
I highly recommend this mod if you feel the SC could be snappier or like to launch your car. I bought my first 3.76 years back before they were in demand for $400.00. This one cost me over $1300.00 total as it is a low mileage example. New is over $1600.00!
Real world performance numbers are unknown for the SC but I expect the same as the GS400. 0-60 is the same as there is now extra shift before 60 but expect .2-.3 off the quarter mile time. Put another way, I once raced a 350Z in my GS400 when it was NA (no supercharger) with exhaust/SRT intake and the 3.76. I pulled on him from the line. I then barely lost to one after I removed it.
It does make a difference. Car is more pleasurable to drive around town as more power is on tap and it reduces that waiting for the power to come on feeling.
Install tips:
T-60 with break bar required
Wrenches from 10mm-19mm
Move sway bar center links so that it can move around. This way you can access the rear pumpkin bolts
Purchase 2 quarts of high quality gear lube 75w/90 like Royal Purple, Redline, Mobile 1,etc..
Remove exhaust first. Then cv shafts on both sides. Then the front 3 driveshaft bolts. Use a nice floor jack to lower the differential. It is 100lbs.
Put new gear oil in unit while out of car as it is easier than using a pump
LSD unit exposed
Old picture of the worm gear LSD from my first GS400 LSD 3.76 install and OEM diff(left pic) next to it. Note the 2 different LSD designs? Helical above (97+) and the worm gear lower right (93-96). OEM is lower left.
Some links:
LINK 1
LINK 2
I picked this one up from another member with 5k miles on it. I opened it up and inspected the gears which appeared to be in very good like new condition. Backlash was very good. Put in some Royal Purple synthetic and installed it.
Installation is more involved vs. the GS series due to the additional bracing under the car making things a little tighter to maneuver around. One rear bolt in particular is a little challenge requiring me to grind down the length of my T-60 to fit in there with my breaker bar.
There are two versions of the Supra TT Auto differential. One is the worm gear units from 1993-1996. 1997 and up went to the helical LSD units.
Worm gear units are supposed to be able to handle more power (not an issue here). The Helical units are supposed to have quicker response times. The helical unit seems to engage the traction control system more easily vs the older worm gear design.
This is a direct bolt in install and should take no more than 3 hours for a good mechanic. 4-5 for others. First thing to come out is the exhaust from the rear cat on back.
Performance wise the car is snappier off the line and on the get-go as it kicks down to a higher RPM well into your powerband. The LSD works great when launching as there is no need to turn off the overly sensitive VSC system that steals power at the wrong moments (sometimes dangerous moments when you pull out into traffic). Top speed is down to 133 which is no big deal. Have not done that in a long time (well, ok, since the SC430 meet). Changing gears is an old hot rod trick for good reason. RPM's do go up 500rpm at the same speed or around 3000rpms at 80mph.
Just to note, increasing the gears from 3.26 to 3.76 is similar to adding 15.4% of RW torque to the car or similar to having over 390lbs of torque taking into my other mods such as headers.
Expect a decrease of about 2-3 mpg.
Downside other than mileage is lost of control if both wheels spin through a corner such as in the rain as the car will spin QUICK. Been there, done that with the GS and do not expect the VSC to kick in to save the day as it does not sense a problem as both wheels are spinning.
I highly recommend this mod if you feel the SC could be snappier or like to launch your car. I bought my first 3.76 years back before they were in demand for $400.00. This one cost me over $1300.00 total as it is a low mileage example. New is over $1600.00!
Real world performance numbers are unknown for the SC but I expect the same as the GS400. 0-60 is the same as there is now extra shift before 60 but expect .2-.3 off the quarter mile time. Put another way, I once raced a 350Z in my GS400 when it was NA (no supercharger) with exhaust/SRT intake and the 3.76. I pulled on him from the line. I then barely lost to one after I removed it.
It does make a difference. Car is more pleasurable to drive around town as more power is on tap and it reduces that waiting for the power to come on feeling. Install tips:
T-60 with break bar required
Wrenches from 10mm-19mm
Move sway bar center links so that it can move around. This way you can access the rear pumpkin bolts
Purchase 2 quarts of high quality gear lube 75w/90 like Royal Purple, Redline, Mobile 1,etc..
Remove exhaust first. Then cv shafts on both sides. Then the front 3 driveshaft bolts. Use a nice floor jack to lower the differential. It is 100lbs.
Put new gear oil in unit while out of car as it is easier than using a pump
LSD unit exposed
Old picture of the worm gear LSD from my first GS400 LSD 3.76 install and OEM diff(left pic) next to it. Note the 2 different LSD designs? Helical above (97+) and the worm gear lower right (93-96). OEM is lower left.
Some links:
LINK 1
LINK 2
Last edited by Pearlpower; 10-19-07 at 10:46 PM.
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bigdaddygr (07-04-21)
09-05-06, 05:37 AM
#3
Great write up Lee! As usual.
I am seriously considering my next project. This mod is certainly a contender.
Though I could not easily locate the right LSD for the right price last time I checked around.
Thanks again for your continued enlightenment.
I am seriously considering my next project. This mod is certainly a contender.
Though I could not easily locate the right LSD for the right price last time I checked around.
Thanks again for your continued enlightenment.
