Gear ratios... suggestions?

[Steve1968LS2]

Rebuilding my LS1 T56.. was going to go with this:

2.97, 2.07, 1.43, 1.00, .80, .62

But I'm not sure if it's the best I don't want my sweet spot to end up between two gears.

Ideas?

I have 3.70 gears and a 26" tall rear tire. Redline is 6,700 rpm.

Here are the other ones they offer:

[hotrdblder]

up rear gears to 3.89 or 4.11, other then that your split looks good

[Steve1968LS2]

up rear gears to 3.89 or 4.11, other then that your split looks good

They are 3.90 now.. and they were expensive (lightened/polished) so I would rather stay with them

So you like the first set of ratios? (2.97--.62)

[hotrdblder]

They are 3.90 now.. and they were expensive (lightened/polished) so I would rather stay with them

So you like the first set of ratios? (2.97--.62)

above you said they were 3.70 gears?

[Vegas69]

I was thinking more along the lines of peak torque but it sounds like some experience has chimed in.

[Steve1968LS2]

above you said they were 3.70 gears?

Did I? hmmm.. well I am old.. maybe I forgot I just put in that alum unit with the lightened 3.90 gears. ;)

[Vegas69]

I am no expert but waiting for your dyno graph seems to make sense on your new setup. Then you can match your power output and your favorite autocross or road course exit speeds to your gear ratios.

[Mkelcy]

A little hard to read. I'd go with the 2.71 or the 2.62 box with your current gears (I ignored the 2.98 tranny); but you're going to be spinning on the freeway at 70:

• Gear Ratio 0.75 0.89 1.00 1.30 1.79 2.71
• Overall 2.78 3.29 3.70 4.81 6.62 10.03
• Gear Spread 0.84 0.89 0.77 0.73 0.66
• Redline 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0
• Max MPH/Gear 168.1 141.7 126.1 97.0 70.4 46.5
• Speed @ 2000 RPM 50.2 42.3 37.6 29.0 21.0 13.9
• RPM @ 60 MPH 2391

• Gear Ratio 0.76 0.85 1.00 1.21 1.60 2.62
• Overall 2.81 3.15 3.70 4.48 5.92 9.69
• Gear Spread 0.89 0.85 0.83 0.76 0.61
• Redline 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0
• Max MPH/Gear 165.9 148.3 126.1 104.2 78.8 48.1
• Speed @ 2000 RPM 49.5 44.3 37.6 31.1 23.5 14.4
• RPM @ 60 MPH 2423

• Gear Ratio 0.76 0.85 1.00 1.21 1.60 2.29
• Overall 2.81 3.15 3.70 4.48 5.92 8.47
• Gear Spread 0.89 0.85 0.83 0.76 0.70
• Redline 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0
• Max MPH/Gear 165.9 148.3 126.1 104.2 78.8 55.1
• Speed @ 2000 RPM 49.5 44.3 37.6 31.1 23.5 16.4
• RPM @ 60 MPH 2423

[Steve1968LS2]

A little hard to read. I'd go with the 2.71 or the 2.62 box with your current gears (I ignored the 2.98 tranny); but you're going to be spinning on the freeway at 70:

• Gear Ratio 0.75 0.89 1.00 1.30 1.79 2.71
• Overall 2.78 3.29 3.70 4.81 6.62 10.03
• Gear Spread 0.84 0.89 0.77 0.73 0.66
• Redline 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0
• Max MPH/Gear 168.1 141.7 126.1 97.0 70.4 46.5
• Speed @ 2000 RPM 50.2 42.3 37.6 29.0 21.0 13.9
• RPM @ 60 MPH 2391

• Gear Ratio 0.76 0.85 1.00 1.21 1.60 2.62
• Overall 2.81 3.15 3.70 4.48 5.92 9.69
• Gear Spread 0.89 0.85 0.83 0.76 0.61
• Redline 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0
• Max MPH/Gear 165.9 148.3 126.1 104.2 78.8 48.1
• Speed @ 2000 RPM 49.5 44.3 37.6 31.1 23.5 14.4
• RPM @ 60 MPH 2423

• Gear Ratio 0.76 0.85 1.00 1.21 1.60 2.29
• Overall 2.81 3.15 3.70 4.48 5.92 8.47
• Gear Spread 0.89 0.85 0.83 0.76 0.70
• Redline 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0 6,700.0
• Max MPH/Gear 165.9 148.3 126.1 104.2 78.8 55.1
• Speed @ 2000 RPM 49.5 44.3 37.6 31.1 23.5 16.4
• RPM @ 60 MPH 2423

Can you calculate that with the 2.97 gear-set I posted? (.62 6th)

Thanks

Good info

[Steve1968LS2]

My guess on power output is 600hp and 560tq with max power being around 6,200rpm. (engine dyno, no accessories)

Right now I'm at 448hp and 396tq at the wheels. Hoping to see 475rwhp and 440 rwtq. (mustang chassis dyno)

Time doesn't allow me to build the engine and then the trans so I have to go with a best guess.

[chicane67]

Leave in the 3.9's... and get the 2.29 close ratio box with the .76 OD... close ratio boxes for what you intend to do with this car... RULE. The whole entire box becomes a sweet spot with close ratio's.

...Or maybe the 2.62 if your gonna go with a lighter clutch package in the future.

Any OD greater than .75 drops the efficiency beyond what you would want to go with... especially if your actually going to use the box for what it is.

[Steve1968LS2]

Leave in the 3.9's... and get the 2.29 close ratio box with the .76 OD... close ratio boxes for what you intend to do with this car... RULE. The whole entire box becomes a sweet spot with close ratio's.

...Or maybe the 2.62 if your gonna go with a lighter clutch package in the future.

Any OD greater than .75 drops the efficiency beyond what you would want to go with... especially if your actually going to use the box for what it is.

Does 6th really matter? Would it ever be used on a track? I just hate the .50

I stick with normal clutches (lightweight flywheel though). So either the 2.29 or the 2.62?

Which would be better for a street car? (that is where I spend most of my time).. I guess Im asking what's the best of both worlds. I don't want it to dog off the line or have a first gear good for seven feet. lol

[chicane67]

Does 6th really matter? Would it ever be used on a track? I just hate the .50

I stick with normal clutches (lightweight flywheel though). So either the 2.29 or the 2.62?

Which would be better for a street car? (that is where I spend most of my time).. I guess Im asking what's the best of both worlds. I don't want it to dog off the line or have a first gear good for seven feet. lol

Does 6th really matter ?? Yeah... I think so.

Will it ever be used on a track ?? It depends on the track... but yes, it may just be a player on longer circuits. The more power you make... the closer you get to using it on longer circuits.

Knowing what you do with the chassis and that it is steering itself in a certain direction... along with the "lightened flywheel"... I would venture to say that you would be good to go with the 2.62 box.

Check your @SBC email. I sent you a little toy for this kind of thinking. Dont forget to READ the "READ ME" file before you go screwing around too much...



BTW with the 3.9's, 26" tire and the 2.62 box... you get a 10.19 first gear ratio with a 2.95 sixth. That is a really easy first gear even with an aggressive clutch and its not too short... it will be like a factory six speed and 3.73's. The 2.95 final will feel like a four speed with 3.00 gears in it... which is great for hittin the freeway... and you'll actually have a useable sixth gear, so it's NOT a dog. That combination is still good for 175+ MPH...

[Steve1968LS2]

Thanks...

I will see if it's available with the LS1 T56.. I don't want to mess with new yokes and stuff.

[Mkelcy]

26" tire, 3.90 gears, 6,700 redline

Gear Ratio 0.73 0.86 1.00 1.35 1.99 2.98
Overall 2.85 3.35 3.90 5.27 7.76 11.62
Gear Spread 0.85 0.86 0.74 0.68 0.67
MPH @ 1,000 RPM 25.8 21.9 18.8 13.9 9.5 6.3
Max MPH/Gear 172.7 146.6 126.1 93.4 63.4 42.3
Speed @ 2000 RPM 51.6 43.8 37.6 27.9 18.9 12.6
RPM @ 60 MPH 2327

Gear Ratio 0.75 0.89 1.00 1.30 1.79 2.71
Overall 2.93 3.47 3.90 5.07 6.98 10.57
Gear Spread 0.84 0.89 0.77 0.73 0.66
MPH @ 1,000 RPM 25.1 21.1 18.8 14.5 10.5 6.9
Max MPH/Gear 168.1 141.7 126.1 97.0 70.4 46.5
Speed @ 2000 RPM 50.2 42.3 37.6 29.0 21.0 13.9
RPM @ 60 MPH 2391

Gear Ratio 0.76 0.85 1.00 1.21 1.60 2.62
Overall 2.96 3.32 3.90 4.72 6.24 10.22
Gear Spread 0.89 0.85 0.83 0.76 0.61
MPH @ 1,000 RPM 24.8 22.1 18.8 15.6 11.8 7.2
Max MPH/Gear 165.9 148.3 126.1 104.2 78.8 48.1
Speed @ 2000 RPM 49.5 44.3 37.6 31.1 23.5 14.4
RPM @ 60 MPH 2423

Gear Ratio 0.76 0.85 1.00 1.21 1.60 2.29
Overall 2.96 3.32 3.90 4.72 6.24 8.93
Gear Spread 0.89 0.85 0.83 0.76 0.70
MPH @ 1,000 RPM 24.8 22.1 18.8 15.6 11.8 8.2
Max MPH/Gear 165.9 148.3 126.1 104.2 78.8 55.1
Speed @ 2000 RPM 49.5 44.3 37.6 31.1 23.5 16.4
RPM @ 60 MPH 2423

By way of comparison for first gear, your present overall first gear ratio is 10.37:1. The 2.98 box with 3.90's is the equivalent of having 4.37's with your current 2.66 first gear.

[TurboLark]

26" tire, 3.90 gears, 6,700 redline
By way of comparison for first gear, your present overall first gear ratio is 10.37:1. The 2.98 box with 3.90's is the equivalent of having 4.37's with your current 2.66 first gear.

When I did calcs for a t56 into my Skylark I decided on stock ratios and 4.30's. Seemed to me to be the easiest, most cost effective solution. Nice ofline acceleration and a useable 6th with more top speed than i'll ever see.

[Steve1968LS2]

Well then.. here are my two choices...

2.66, 1.78, 1.30, 1.00, .74, .50

or

2.97, 2.07, 1.43, 1.00, .80, .62

The only way to get the close ratio stuff is with the TRANZILLA.. and that's a $7,500 nut. Even the Son-of-Tranzilla only has the two above options.

So, between those two.. which to choose.

Thoughts?

[Mkelcy]

Well then.. here are my two choices...

2.66, 1.78, 1.30, 1.00, .74, .50

or

2.97, 2.07, 1.43, 1.00, .80, .62

The only way to get the close ratio stuff is with the TRANZILLA.. and that's a $7,500 nut. Even the Son-of-Tranzilla only has the two above options.

So, between those two.. which to choose.

Thoughts?

The LS1 ratios give you a 0.73 RPM drop 2-3 , a 0.77 RPM drop 3-4, a 0.74 RPM drop 4-5 and a 0.68 RPM drop 5-6.

The 2.97 box gives you 0.69 RPM drop 2-3 , a 0.70 RPM drop 3-4, a 0.80 RPM drop 4-5 and a 0.78 RPM drop 5-6.

Of the two, the splits in the four gears you'd use most are more even in the LS1 box, with less of an RPM drop gear-to-gear for 2-3 and 3-4. The 4-5 and 5-6 shifts in the 2.97 box are closer than in the 2.66 box.

I guess the question is are you doing open road racing at 180 mph, closed courses at 50-150, or autocrossing? For my money I'd still go the 2.66 box; I think the lower gears with your 3.90 rear are going to be harder to control with the 2.97 box and your 2-5 splits just aren't as nice.

By the way, so far as I can tell from web searches, the ZO6 uses the 2.66 box, the Z51 Corvette uses the 2.97 box.

[sik68]

I dont have 1st hand experience, but it has been explained to me that if you plan on using an aluminum flywheel, you should aim for at least an 11.0 overall ratio for first gear. When you go too far below that, it may be difficult to get the car moving from a stop @ light throttle.

Also, a 3.90 rear gear and a 0.50 6th will give you 1650rpm at 65mph, which seems rather lumbering. You'll probably grow fond of 5th...but with all that torque, maybe not

[z65mm6]

Well then.. here are my two choices...

2.66, 1.78, 1.30, 1.00, .74, .50

or

2.97, 2.07, 1.43, 1.00, .80, .62

The only way to get the close ratio stuff is with the TRANZILLA.. and that's a $7,500 nut. Even the Son-of-Tranzilla only has the two above options.

So, between those two.. which to choose.

Thoughts?

How similar is a tr6060 to a T56?
The cts-v and I think some of the Aston Martins have the 2.66, 1.78, 1.30, 1.00, .80, .62 gearset. If your rebuilding your existing T56 could 5th and 6th from the CTS-V be swapped in?