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Superior/Fairbanks Billet Over-Drive Servo on stock box ?

J

Jay,

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Hi guys im new her i brought a vt s2 about 2 mouths ago it has 168xxxkms , ultra lows , ss rims, ss spoiler, 2 1/2 cat back with hotdog at rear and lsd and runs beautiful but im wanting to firm up the shifts alittle i have a Corvette 1-2 servo and a .490 boost valve i am going to install but before i do i noticed when my misses is driving the car at 90-100kmh on a slight rise around a corner it will jump from OD (4th) to 3rd then to OD for no reason its quite anoying as when it kicks back it takes off then instant change up again it has never done it for me i would say its her extreamly light/lazy foot and not building momentum but my question is i was doing some searching and i found the superior/fairbanks Billet Over-Drive servo and it states it helps it hold overdrive longer and firms up 3-4 shifts has anyone els installed this in a commodore i found alot of link of people installing them in other GM 4l60e autos but nothing on commodore and just wanted to know is it safe to do on the standerd box any feedback on this product would be greatly appreciated my major worrys are damage and will it still kick back with out having to put your foot throught the firewall

Also thinking that maybe the upgraded boost valve may help it hold 4th longer but unshoure?
 
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SS-Z LS1

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The speed at which the shift occurs is controlled by the setting in the memcal and the feedback from various sensors (Speed, Throttle Position etc.) not by the servo's or boost valve. The Servo's will increase the grip on the band in 2nd and 4th, but will not change the speed/load at which it shifts up or down a gear. The larger boost valve will increase line pressure only slightly over stock at lighter throttle positions and a bit more at higher throttle positions and slightly increase the shift firmness and grip of all frictions, it also will not affect when the shift occurs.

Suggestion, have the misses drive in PWR mode, this will spread the up and downshifts apart a little and probably avoid the hunting (It will shift to 3rd a little earlier and back up a little later) or use cruise control if safe to do so as it's shift points are midway between PWR and Economy modes. (or if already being driven in PWR mode then turn it off & it will probably hold 4th gear).


If this is the original box or of unknown history (i.e. not known to be rebuilt with upgraded Sunshell) then some risk exists with firmer 1-2 and 3-4 shifts causing eventual/earlier failure of the splines in the Sunshell, the 2-3 shift does not use the Sunshell so a bit firmer 2-3 should be OK (the 3-2 downshift does though). The OEM VT Sunshell is a known weakness particularly behind the increased power of LS1's - later LS1 trans had a hardened Sunshell and stand up better to firmer shifts, not sure about the V6 but I doubt it will be stronger than the LS1 Sunshell of same vintage. Failed Sunshell = no 2nd, 4th or Reverse and a trans rebuild required.

Note firmer shifts (within reason) will reduce the wear rate on the 3/4 clutch and 2/4 band friction surfaces but as they get firmer it will be at the expense of increased shock load on all other rotating parts such as the Sunshell.

Also the factory memcal will likely relearn and soften the shifts (it aims to keep shift time constant as trans wears, if it sees quicker shifts it will try and slow them back down), it certainly does in the factory LS1 tune, I expect it does in the V6 as well. You may need to have the memcal settings altered to reduce the desired shift time. You could also seek to spread the shift points in the memcal on the 3-4 and 4-3 a little more apart than stock in economy mode (perhaps closer to what the cruise setting is) or alternatively if you like to hold the higher gear longer just lower the 4-3 downshift speed a little below the stock setting in economy mode.

Cheers
Jamie
 
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