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68GMCCustom · 06-23-2010, 09:01 PM

Yes the trans will shift way earlier then redline w/o modification. Your LQ4 has a 5800 redline and a 6000rpm fuel cutoff. I'd guess you'd be OK to up the cutoff to 6200 or so and when racing shift 1-2 at 6000 and 2-3 at 5800. I ran my LQ4 in my '01 Sierra C3 up to 6000 (after tune) quite a bit since the 4L60HD has such a rpm drop for the 1-2 shift.

My guess is that you might loose 3-5% power in the upper range with a dual plane vs single....but will gain 7-10% in the lower to mid range....well worth the swap.

Jim? Your thoughts?

06-23-2010, 09:01 PM	#89
68GMCCustom Truck and auto performance nut Join Date: Feb 2007 Location: McKinney,Texas Posts: 3,848	Re: 85 burb meets 6.0 lq4 Yes the trans will shift way earlier then redline w/o modification. Your LQ4 has a 5800 redline and a 6000rpm fuel cutoff. I'd guess you'd be OK to up the cutoff to 6200 or so and when racing shift 1-2 at 6000 and 2-3 at 5800. I ran my LQ4 in my '01 Sierra C3 up to 6000 (after tune) quite a bit since the 4L60HD has such a rpm drop for the 1-2 shift. My guess is that you might loose 3-5% power in the upper range with a dual plane vs single....but will gain 7-10% in the lower to mid range....well worth the swap. Jim? Your thoughts? __________________ Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken