Anybody know anything about the 6-speed that GM uses behind the 8.1L Vortec V8 (340hp/455ft-lb) and 6.6L Duramax diesel V8 (300hp/520ft-lb) engines in the Sierra and Silverado? It is described as a "ZF S6-650".

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Fred
94 Formula A3: 381/TH400/N2O

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11.513@115.59 on motor; 11.162@127.67, 1.643 60' on a 125-shot. Going with a 275-shot this year

 

Jimlab-
More gear you will find helps you actually. if you try to tone down first with less gear(or start in 2nd) you will find that you will have to slip the clutch more, etc.


by having more gear, you can slip the clutch less, and/or launch(of racing) at a lower RPM.

4.10s and my 401ci motor was great.. even on street tires, I woulda switched to 4.56s if it weren't for the need to trap 140+ in 4th!

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-94 Black T-Topped Z28 M6, 10s, and daily driven!
-96 CBR F3, modded of course
-92 Talon Tsi AWD, also too many mods..
-99 Tony Kart
http://www.fastblackcar.com

 

[iB]Anybody know anything about the 6-speed that GM uses behind the 8.1L Vortec V8 (340hp/455ft-lb) and 6.6L Duramax diesel V8 (300hp/520ft-lb) engines in the Sierra and Silverado?[/i]

Info found by searching the Internet:

It's a medium duty transmission. In contrast, the T-56 is a light duty transmission.

It was described as being able to easily handle the output of the high power/torque requirements of the new GM motors, and will be used in the medium duty truck line (Siverado is a light duty truck)

Gear ratios are:
5.79 3.30 2.10 1.31 1.00 0.72

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Hear LT1 cam WAVs, DIY head porting: members.***.net/gmarengo

'95, !CAGS, CAI, ForceII, Hooker Shorties, 14.2@103

 

Killer first gear..... .

It's available on the Silverado 2500HD w/ 8.1L V8 or 6.6L diesel V8. These also come standard with 4.10 gears.... hmmm 23.7:1 overall.

Oh well, back to the drawing board.

 

I'm sure it is in the upper gears, Jordon, but I've got a ~2,700 lb. skateboard with a 2.97 1st gear (to your 2.66) and 550+ lb-ft. of torque. Since it wasn't built for drag racing, 1st gear is only going to be a tire shredder with anything but the most careful use of the throttle.

The car should have more than enough torque (quite a bit more at idle than the stock engine had even at peak) to start out in 2nd gear "normally". At 8.49:1 final drive (2.07:1), second gear is actually shorter than the McLaren F1's first gear final drive (7.65:1; 3.23 first gear, 2.37 differential), and my car is a hair lighter.

 

Mind telling me how you trap 140+ in 4th with 4.10s?

 

A solid roller motor turning ~7,000rpm helps a bit. However that still leaves him a bit short so I suspect he's running a taller than stock tire. I bet a 28" ET street would get ya pretty close at 140mph@7k rpm.



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Jason
93 TA, M6

 

I'll go out on a limb and state that I think that Jordon meant to say "130+". In the two drag racing videos he used to have on his web site, his trap speeds were in the low 130s.

 

We don't have any of the big ZF trannies around work (at least not the last time that I checked), but we do have the NVG counterpart, the 5600. It's an iron case 6sp that weighs about 360 lbs (~200 more than the T56), and is about the size of a SBC block. There's no way it'd ever fit in a passenger car without huge amounts of floorpan work.

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1996 Impala SS - LT4 396, T56
1996 GMC K2500
1992 Buick Roadmaster Estate Wagon

 

I think he meant 140s. Nitrous is a nasty thing on a 130 mph NA motor.

I've also had a great experience with D&D when I blew my countershaft in my T-5 with the Mustang. Ford wanted around $300 for their countershaft. D&D wanted $179 for theirs

Mike

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1994 Sunset Orange Metallic Camaro Z28 Convertible - The Gorgeous and Sadistic Bitch Who Mistreats You and Lets You Down, Yet You Still Keep Her


1989 Red Ford Mustang LX 5.0 Convertible - The Dependable Girl Who Treats You Right, Yet Your Mind Wanders Elsewhere