Gears for a T56?

[Hart_Rod]

What would be a good gear to run with an LS1/T56 with 30" tires?

[STOCKISH]

4.10 Luckily with the 6 speed that gear works great. A buddy of mine ran that in a Camaro with no issues and a 28 inch tire.

[swb85]

Stock or modded? If it's a 1/4 mile app, need to know about what mph you're going to be at through the traps.

Otherwise, you can run a TON of gear with 30" tires and a t56. The .5:1 sixth gear makes for crazy low rpm cruising. If it were me, I'd go 4.56 at a MINIMUM. Check out how low your 70mph cruising rpm would be with:

4.56 = 1800rpm
4.88 = 1900rpm
5.13 = 2000rpm

I run 4.30's with a 28" tire in my camaro only because of the nitrous. If she wasn't bottle fed I'd have 4.88's!

[no moa]

My impala ss will use an m29 t56 with 373 rear gears running the stock 255/50/17 tires. But that is a car not a truck.
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[Hart_Rod]

Thanks for the info guys. This is in a 68 SWB that I'm going to build for my son's first truck. I've read somewhere that if you go to low (numerically high) with the gears that it makes first gear useless, but if you get to high (low numerically) that the overdrive will be useless. The motor and tranny are out of a 02 WS6. I checked the specs on it and it had a 3.23 gear with a 25.6" tall tire. I think a 3.73 with a 30" tall tire is about equivalent. Thoughts?

[GCncsuHD]

I would go 4.88 or even 5.13 with a 30" tire. That t56 could use all the help it can get under a heavy truck. They have an insanely high ratio overdrive, so you will have plenty of road gear.

A friend of mine in highschool had a H/C + Nitrous 98 Camaro with the t-56 and 27" tires. He swapped in 4.10s and it still cruised at less than 1500 rpm at 60, and would go faster than you would ever need to on the top end.

On a heavier truck you are going to want to be cruising around 2000 on the highway to be in a decent torque range to pull it along, otherwise you will NEVER even use 6th gear.

Edit: Love the look of that truck, should be fun, and yes 1st gear may become useless in most driving, but is still nice for starting up hills.

Yea, 3.73 is close to equivalent with the car it came out of with 3.23, but again you are going to want more mechanical advantage, because not only are those wheels and tires larger diameter, they are also heavier, and the truck is much heavier.

[Hart_Rod]

This site is calling the curb weight of the WS6 around 3500 lbs. Isn't that about what most SWB trucks weigh?

[GCncsuHD]

Curb weight of a SWB is right around 4,000 lbs, that stepside with a wood bed may be a little lower.

Stil would go with atleast 4.88s with those 30" tires in a truck.

[Shon]

If it were mine to just DRIVE, I would get a 4.10 or 4.33s with a 30" tire.
if it were to get every tenth out of it on the track will take a little more thought.

[GCncsuHD]

I'm still going with 4.88 or better.

That setup with 5.13s and 30" tires you will be shifting out of first gear at 20mph at 3000rpm for example, that is more road speed than 2nd gear in my sm465 and 4.10s, so 1st gear would not be useless IMO. Then at 70mph you are looking at 2011 rpm, a good cruising speed in my opinion, and much lower than the stock setup with no OD.

And assuming a 6000rpm redline, you still have a top speed in 6th gear of 209mph with 30" tires and 5.13s

[HavinSomeFun]

going to be a tire burner for sure.

[kSStamp0182]

i had a 2001 SS T56 and even with 4.10s 6th was almost useless unless your doing 80. id agree with 4.88s minimum.

[swb85]

The t56 first gear is only 2.66:1. With 4.56's, you'd redline in first gear at 45mph....4.88's and it's 42mph. You gear it much higher than that with such a tall tire and you're going to have to slip the clutch excessively to get moving and you won't be able to use 6th gear until 70+mph.

[TR65]

Rob,

I run 3.73 gears with 29" tires, T56, LS2, 390 hp out of an SSR.

I think it is a perfect gear for a daily driver. Plenty of low end, first gear very usable. I use 6th gear all the time even at lower speeds. Cruise at 70 mph is 1800 rpm. Good mileage, good accel.

By the way, the SSR weighed 4750 lbs. The C10 weighs less than 4000.

TR

[GCncsuHD]

Originally Posted by TR65

Rob,

I run 3.73 gears with 29" tires, T56, LS2, 390 hp out of an SSR.

I think it is a perfect gear for a daily driver. Plenty of low end, first gear very usable. I use 6th gear all the time even at lower speeds. Cruise at 70 mph is 1800 rpm. Good mileage, good accel.

By the way, the SSR weighed 4750 lbs. The C10 weighs less than 4000.

TR

The SSR T56 is different than the car t56. It's 1st gear is much lower than the car ratio, it would become useless faster than the car 1st gear, and it's 6th gear is also a lower ratio as well, it is better suited to a higher gear ratio than the car transmission.

Vette/Camaro ratios
1st 2.66
2nd 1.78
3rd 1.30
4th 1.0
5th .74
6th .50

SSR ratios
3.01
2.07
1.43
1.0
.84
.57

GTO/CTS-V
2.97
2.07
1.43
1.0
.84
.57

[usmcchevy]

I'd want 4.10s unless the truck already has 3.73, then I would wait to see how it drives.

[Custom 68]

he neat thing about it is that 5th is teh same as overdrive in a 4l60 so u can use it alot. I have a t56 i am gonna swap and have 3.73 again with 5th being what it is I think it will be very usable then the highway u can use the 6th.

[skoffice]

Check this thingy out:
http://www.grimmjeeper.com/gears.html

[GCncsuHD]

Originally Posted by Custom 68

he neat thing about it is that 5th is teh same as overdrive in a 4l60 so u can use it alot. I have a t56 i am gonna swap and have 3.73 again with 5th being what it is I think it will be very usable then the highway u can use the 6th.

Unless you are using really tiny tires, you won't be using 6th much at all on the highway unless you move to Germany and run the Autobahn. 70mph would only be 1450 rpm with 30" tires and 3.73. That is barely chugging along, and I doubt you will overcome the force of the wind and the weight of the truck much at those rpms, especially when you climb any bit of a hill.

Originally Posted by skoffice

Check this thingy out:
http://www.grimmjeeper.com/gears.html

What I use for all my calculations

[TR65]

Man, I use 6th gear all the time at 45-50 mph (1100-1300 RPM). (235/75-15tires and the 0.57 ratio 6th, 3.73 rear). I guess the engine has a lot of torque.

TR

[GCncsuHD]

Originally Posted by TR65

Man, I use 6th gear all the time at 45-50 mph (1100-1300 RPM). (235/75-15tires and the 0.57 ratio 6th, 3.73 rear). I guess the engine has a lot of torque.

TR

Your 6.0 has considerably more low down torque than the ls1 and you have the benefit of the lower 6th and 28.5" tires.

[Jonboy]

I don't know what the height of the tires was on my CTS-V (245/45ZR18), But it was about 4200 lbs and had 3.73's in it. 6th gear at highway speeds was around 1800 (80 MPH). I don't think you would want to gear it too low so he might be able to get a little mileage out of it.

[GCncsuHD]

Originally Posted by Jonboy

I don't know what the height of the tires was on my CTS-V (245/45ZR18), But it was about 4200 lbs and had 3.73's in it. 6th gear at highway speeds was around 1800 (80 MPH). I don't think you would want to gear it too low so he might be able to get a little mileage out of it.

26.7 tires and the lower .57 6th gear....

Even with 5.13s and that 30" tire he will be looking at only 2000 rpm at 70 in 6th gear, that is pretty ideal for fuel mileage, also consider that your V was not a flying brick, and did not need to overcome the drag nearly as much as one of these trucks would.

Considering a stock 3speed would be looking at 3100rpm at 70mph with the stock 3.73s and a 30" tire, I think the 5.13s with the t56 would be great at 2000rpm at 70.

[kSStamp0182]

Originally Posted by GCncsuHD

26.7 tires and the lower .57 6th gear....

Even with 5.13s and that 30" tire he will be looking at only 2000 rpm at 70 in 6th gear, that is pretty ideal for fuel mileage, also consider that your V was not a flying brick, and did not need to overcome the drag nearly as much as one of these trucks would.

Considering a stock 3speed would be looking at 3100rpm at 70mph with the stock 3.73s and a 30" tire, I think the 5.13s with the t56 would be great at 2000rpm at 70.

agreed. and again the CTS-V is a higher torque LS6 vs the LS1

[GCncsuHD]

Originally Posted by kSStamp0182

agreed. and again the CTS-V is a higher torque LS6 vs the LS1

Yep, unless it was the even more powerful LS2