GSC center diff - TESTED w/ VIDEO
Apr 9, 2007, 07:58 PM
#106
Regarding the "spool", I still haven't heard exactly what it is. Is it a true spool (locks the front and rear together like a welded center diff), or is it a VCU-eliminator that allows the front and rear to spin independantly??
From the description of the effects of using it, it sounds like it is the latter. . .
Greg- keep me on the list if it works out well with the ACD!
EVOlutionary
From the description of the effects of using it, it sounds like it is the latter. . .
Greg- keep me on the list if it works out well with the ACD!
EVOlutionary
With the spool in place the front and rear wheels are forced to travel (mechanically) at the same speed all the time. With the VCU and ACD the front and rear are allowed to travel at different speeds when needed, without this the car becomes unstable. The "spool" is just a large chunk of billet steel.
i'd just like to hear more detail about this kit.
i use to be a tech at shelton mitsu, n worked somewhere else before that, now i'm in the process of going back to a mitsu dealership or a lexus dealership.
Eddie Rosado
Eddie Rosado
Apr 9, 2007, 08:06 PM
#107
hey man maybe you can make some sense of this then. i'm guessing its the VCU on this car. check it out n see what you think. heres the link to that thread.
Eddie Rosadohttps://www.evolutionm.net/forums/sh...d.php?t=262775
Eddie Rosadohttps://www.evolutionm.net/forums/sh...d.php?t=262775
Apr 10, 2007, 02:12 PM
#108
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From the two piece pictures at the GSC site, it looks to be a planetary diff. The front and rear output shafts are geared to rotate at different speeds and when forced to rotate at the same speed by the tires, result in the 40:60 torque split. It's hard to tell if there's any hidden clutch packs or helicals that would make it an lsd rather than an open planetary.
Apr 10, 2007, 02:21 PM
#109
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learn to drive AWD. whats wrong with a lil understree on corner exit? It can be a good tool to have if u know how to use it (longnitudnal weight transfer with throttle without ever power-on overstree), LOL
Hint: Do all ur rotation some where else...
Hint: Do all ur rotation some where else...
Last edited by cityhugo; Apr 10, 2007 at 02:27 PM.
Apr 10, 2007, 04:36 PM
#112
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Apr 13, 2007, 07:15 AM
#114
From the two piece pictures at the GSC site, it looks to be a planetary diff. The front and rear output shafts are geared to rotate at different speeds and when forced to rotate at the same speed by the tires, result in the 40:60 torque split. It's hard to tell if there's any hidden clutch packs or helicals that would make it an lsd rather than an open planetary.
reason i ask is because i recent replaced my t-case with a t-case with evo 7 ring/pinion gear which has a gear ratio of 3.3125 vs. the evo 8 gear ratio of 3.30769.
this means that my rear wheels will travel that a slightly faster speed than the front (.288 mph at 60mph according to my math). i've already confirm this with Shepherd when I sent my old t-case to get rebuilt. so, changing the ring/pinion ratio in the t-case will change torque split between front and rear and it will be independent from what type of center LSD you use (ACD or viscous). am I correct on this?
Apr 13, 2007, 11:33 AM
#115
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if the GSC planetary diff mechanically force the front and rear wheels to travel at different speed to achieve the 40:60 torque split, than couldn't you use a different t-case ring/pinion gear ratio to achieve the same thing.
reason i ask is because i recent replaced my t-case with a t-case with evo 7 ring/pinion gear which has a gear ratio of 3.3125 vs. the evo 8 gear ratio of 3.30769.
this means that my rear wheels will travel that a slightly faster speed than the front (.288 mph at 60mph according to my math). i've already confirm this with Shepherd when I sent my old t-case to get rebuilt. so, changing the ring/pinion ratio in the t-case will change torque split between front and rear and it will be independent from what type of center LSD you use (ACD or viscous). am I correct on this?
reason i ask is because i recent replaced my t-case with a t-case with evo 7 ring/pinion gear which has a gear ratio of 3.3125 vs. the evo 8 gear ratio of 3.30769.
this means that my rear wheels will travel that a slightly faster speed than the front (.288 mph at 60mph according to my math). i've already confirm this with Shepherd when I sent my old t-case to get rebuilt. so, changing the ring/pinion ratio in the t-case will change torque split between front and rear and it will be independent from what type of center LSD you use (ACD or viscous). am I correct on this?
The nice thing about the planetary diff is that all the torque forces are occurring within the gears and not relying on friction within viscous fluid or clutch packs.
Apr 13, 2007, 03:19 PM
#116
I don't think it's easily done by the way you describe since it's still dependent on the LSD re-apportioning the torque by the amount of lock up. If you take the LSD out of such a setup I believe you would end back up with an open center diff with 50:50 split and the open diff absorbing the speed differential between the front and rear. If you leave the LSD in, it will try to distribute the torque based on the gearing differential but it will heat up and possible burn up the LSD in the process. An ACD might handle such a setup better than viscous but it will experience wear anytime it's not either fully locked or fully open. In either case you'll only get the full torque differential when the LSD is fully locked.
The nice thing about the planetary diff is that all the torque forces are occurring within the gears and not relying on friction within viscous fluid or clutch packs.
The nice thing about the planetary diff is that all the torque forces are occurring within the gears and not relying on friction within viscous fluid or clutch packs.
Apr 13, 2007, 04:50 PM
#117
if the GSC planetary diff is still connected to the viscous coupling or ACD, then wouldn't the viscous/ACD absorb the speed difference (NO) just like the way you mentioned above? can anyone confirm that the GSC center diff unit still uses the viscous coupling? (YES!) if that's the case, then i don't see any difference between using a different ring/pinion gear vs. the planetary diff to make rear wheel spin faster than front wheels, both are going to cause stress to the viscous or ACD.
The best way to think about it is - the grip of the tires turning on the ground forces the gears of the 40:60 diff to spin at the same speed, which in turn causes there to be more torque on the rear wheels. Now when things get complicated is when this torque to the rear wheels exceeds the grip available. With this diff, when power is applied and starts exceeding grip, usually the rear wheels will start to break loose first. They will attempt to spin faster than the fronts, which causes the car to feel more like a RWD and have oversteer tendancies. . .
BUT - as the rear starts spinning faster than the front it puts torque on the VCU which moves more of the excess torque to the front wheels. The VCU can never fully 100% lock like the ACD though, so when the power applied to the ground exceeds grip the rear will always spin a little faster than the front. This should give smooth, controlled, rear wheel power biased handling.
The center differential planetary gear set is extremely strong. The ring and pinion in the transfer case is not. You don't want all the stress and force of this interaction happening on the tiny contact patch of 2-3 teeth of the ring and pinion gear.
It will be interesting to see how this works with the ACD, since the torque capacity is supposed to be 10x that of the VCU. What is going to happen when the rear wheels try to spin faster when you hammer it coming out of a turn and the ACD grabs???
EVOlutionary
