Tremec T-56 Magnum... guidance please.

[69_Mustang 26]

Ok, so I think my next move is going to be a good, strong transmission.

 

I'm looking at the T-56 6 speed. This is will be street driven, but the idea is to have good gears for the track/autox aka turns and whatnot.

 

I'm not sure which gears to get, I'm sure some of you know more than me with these cars and their gears. Right now I think I have a 3.25 final gear. I'm unsure since when I use the gear ratio cal, the RPMs are either too high, or too low; 3.2 final gear is the closest I can get... any input there? That will be changed later and compensate for the trans gears I get.

 

Engine goals for the 351w is to just add aluminum heads and some nice solid cams that can help me rev around 7k to 7500 rpms, if possible. Probably shooting for the 450 WHP range, if that's attainable without touching internals.

 

There's the "wide ratio"

2.97

2.10

1.46

1.00

.74

.50

 

The wide ratio is appealing because of the first 3 gears. Probably nice off the line and very fun around town, and very useful on the track. Only thing that worries me is the the first gear is shorter, so I'm not sure if I'll have traction issues if I hit my power goal.

 

And there's the "close ratio"

2.66

1.78

1.30

1.00

.80

.63

 

These are appealing because it's not too bad in first 3 gears, and the last 2 seem nice to have some nice top end pull.

 

I suppose, i could always change the 5th and 6th gear to something else, on either one. basically swapping them out for the other.

 

I'm using this site to look at the gear ratios and what speeds they'll be at: BMW E46 Gear Ratio / Cruising RPM calculator

 

What kind of gears would you all prefer for a road course/autox car that's still being driven on the street and hwy?

Edited November 30, 2012 by 69_Mustang

[FrozenMonkey 12]

I used to own a '99 Trans Am with a T56. The gearing in that car was 2.66 1.78 1.30 1.00 0.74 0.50 with a 3.42 final gearing. Car dyno'd at 328 hp and 346 tq to the wheels. The car would plain get up and move until you had to touch 5th where it would start falling on its face. With more power it would have pulled to the moon. I found the gearing to be excellent for freeway driving. Could set cruise at 80 mph and clip along at 2k rpm and never have to downshift to pass or climb hills and got over 28 mpg on long trips.

 

Where are you getting your T56 from? A custom built one or grabbing one from an F-Body/Corvette? Standard one straight out of an F-Body will hold your power goals all day long and if you pair it up with at least 3.50 rear gear I think you'd be happy with how the gears match up. Most F-body guys like to bump up to 3.90 - 4.10 gear and don't complain about the bit of raise of rpm at freeway speed. I think thats a bit too high though for a car that is going to stretch its legs and not just drive down the 1320. Just my opinion though.

 

Good luck doing the swap. I'm totally jealous. Thing I miss most about the Trans Am was rowing those gears. And A/C in this desert heat. :lol:

[69_Mustang 26]

Thanks for the input. I think I might go for the 2.97, 2.10, 1.46 gearing. Then add in the .80 5th gear, but keep the .50 6th for fwy driving.... decisions, decisions.

 

I was looking at the new 2013 Shelby gearing. They kind of dumbed down the gearing to control the power. If they can run a 2.66 1st grear with 600+ BHP and 285 rear tires, then I'm sure I can run a 2.97 first gear with way less power and tq with similar sized tires. Actually, end goal for the tires is 305 rears!

 

Then again... Idk. I can always change the final gear to help compensate for the trans gearing... man, this is a pain. ha

 

I take that back... idk what I'm going to do. This appeals more for gaining ground... 2.66, 1.78, 1.30, 1.00, .80 and change the 6th gear to a .50 ratio to give me that better fwy driving RPM. But the other one appeals for getting there faster! just using more gears.

Edited November 30, 2012 by 69_Mustang

[cphsonic 11]

I'd go for the close ratio no matter what, it'll be just fine with that 3.25 rear. The large 4>5 jump on the wide ratio will kill you, but then again will you ever need more than 4th on track with 3.25 rear and "just" 450hp? Assuming a realistic 5.750 rpm (stock internals) rev limit you'll be going 126 mph (depending on rear tire). Plenty for most tracks.

The 0.63 6th will rev 1.654 rpm @ 60 mph and the 0.50 will rev 1.313 rpm @ 60 mph.

 

I have a different variation of the the wide ratio and 3.25 rear, but once the boost is cranked up I'll have ~800 ft.lb. of torque to help out. :innocent:

 

You probably know it already, but the T-56 will need quite a bit of trans tunnel mods to fit.

Edited December 1, 2012 by cphsonic

[buening 63]

I have the close ratio (actually the Cobra T56) and plan on going with 3.73s. With a 25" tall tire, this puts me at 2000rpms in 6th gear going 63mph. Going with 3.55 bumps the speed up to 67mph.

 

I personally prefer the wide ratio, but my car is just a cruiser. I found a deal on the close ratio Cobra unit, so I snatched it up. If I went with the wide ratio, I'd be using 4.11 or 4.27s. Might make the first gear a bit short, but you'd still be going 70mph @ 2k rpms with the 0.5 6th gear with the 4.27 gears.

 

FWIW the Vipers run the wide ratio T56 and they typically stick around the 3.55 gear range from the factory. To me that makes 6th a bit useless. With the 3.55, you'd be turning 1700rpms at 71mph. I'd be pretty doggish on the interstate IMO unless you have the HP to support the gearing, which I personally don't at the moment (but the Vipers do!).