Which T-56 and which rear gear ratio?

[Raw Untamed]

Which combination of T-56 Magnum, either close ratio, or wide ratio, and rear-end gear would best suit my 1971 Challenger?

Close ratio = 2.66, 1.78, 1.30, 1:1, .80, .62
Wide ratio = 2.97, 2.10, 1.46, 1:1, .74, .50

470 stroker big block 600tq/625hp
mostly street driven but taken to road course for open track days
rear tire is 305/35/18 (26.4" tall)

Also I am looking for at least 20 mpg highway, so I was thinking about keeping the 70mph cruising rpm at 1900-2000.

[wellis77]

I've got the wide ratio and went 3.73's. I should be around 1700/1800 cruising at 75.

[chicane67]

The 2.66 box with the 3.73's would be my choice.

A 9.9 1st gear ratio with a 2.3 6th covers just about everything... very well I might add.

[JEFFTATE]

2.66 with 3.73 would be great.
The close ratio box would keep you in the power band.
No lugging .

[killer67]

close gear and 3.73 for sure

[Raw Untamed]

Now what if I told you the cam was this:

Lunati 60333
Solid roller, rough idle. Excellent cam for street/strip applications with explosive mid range and upper RPM torque and horsepower. Works well in 383-440 cubic inch engines. Needs 3000-3500 RPM stall speed converter or 4-speed transmission, 10.25:1 or better compression ratio, aftermarket performance exhaust and 4.10 rear gears.

Advertised Duration (Int/Exh): 279/285
Duration @ .050 (Int/Exh): 249/255
Gross Valve Lift (Int/Exh): .585/.600
LSA/ICL: 110/106
Valve Lash (Int/Exh): 016/016
RPM Range: 3000-7000

Heads are stock Victor
Intake = Eddy RPM
CR = 10.8:1

Car is mostly for street use. Just taken to the track about 3 times a month tops.

Do you still recommend the close ratio and 3.73?

[Payton King]

I agree with above. I have an LS1, which is going to be different, in my 69 camaro and my cam is 230/230 on a 110 lsa with .597 lift. Idles at 950. I run the close box with a 4.11 gear set, but I also run a tire that is 27 inches tall (335/30/19). I did have a 3.80 in it and it would cruise at 65 mph at 1500 rpm. If some one slowed me off of that speed it would start to buck or I would need to down shift. Went with 4.11 and my cuise at 65 is 1750, so it gives me a little room if I need to slow without having to down shift. The shorter tire will raise your RPM obviously

[Black93GT]

I have a LS1/T56 combo and wanted to keep a reasonable RPM for longer highway trips. I anticipate 80-85mph and using a few calculators online decided that a 3.89 would be what I'm looking for. I got lucky and stumbled on a nodular 9" with that gearing on Craigslist.

The calculator I liked best was THIS ONE (http://www.f-body.org/gears/).

[Z06vet]

I also have T56/LS1 with 228/232 cam and 335/35/17's. I have 3.73's but think 4.10 or even 3.90 might be a bit better. At 80mph it's about 1900rpm. Scott

[Raw Untamed]

So since I first posted the question, I've decided on a beefed up 2002 Viper spec T-56 and not the magnum. Also, the gears in the trans will be the viper set which is the combination of close and wide ratios: 2.66 1.78 1.3 1:1 .74 .50. I want these overdrives because the car will be mostly street driven and taken on long road trips. My car will weigh no more than 3500 with driver, and my engine is putting out 625hp/600tq at the flywheel. That's quite a bit more than most LS1s. I've studied many rpm/gear charts and narrowed the rear gear decision down to 3.55. Make that 3.73 as of March 7, 2012.

[Z06vet]

I just think a 3.55 with .50 OD will be almost unusable given the engine characteristcs you described above. I know it will make plenty of torq, but i don't think that motor will be happy at 1500rpm or less. I could be wrong, as I've never run that type of motor.

[chicane67]

Yup... you might, just might... be able to use sixth gear at about 100 mph...Lol

I would put your target cruze rpm right in at about 1800-2200... and NOT less. If you are making that kind of power... your camshaft selection wont like anything less either. That's just the way it goes.

[BonzoHansen]

I have a 0.50 6th 4th gen T56 in my car and a generally mild 355. I have 3.73s and 26.5" tall tires and really need to be doing 60-65+ to be useful. 3.55 is way too low. When I re-do the rear I'm going 4.10, which will jive better with shorter tires and the new engine on the board that will like the rpm more.

[rrstroker71]

Just finished a 70 Challenger with a 6.1 [550hp]and a t-56. Customer insisted on 3.55s. He drove it a week and we put 3.91s in it. Now he can run 6th gear. I tried to talk him into 4.10s, but he didn't want them. We did another Challenger with a 6.1[stock] and it had a 5 speed, the 3.55s worked ok for him.

[thedodgeboys]

I'm running 4.10's in my 6.1 hemi (480 hp) 70 challenger, 27 inch tall tires .5 6th gear. Love it 22 mpg at 80 mph. Did the power tour last month with it and she had great road manners. Pulled the hills at highway speed with no issues. used 5th on the slower roads less than 60mph with great results.

[Raw Untamed]

Sweet. Thanks for all the info and ideas. I really appreciate them.

Okay now I'm thinking the 3.55 is way too low. lol The 295/35/18s and 305/35/18s are only 26.1 and 26.4 inches tall. If I go bigger, I'll have even less rpm at speed. Hmm, either 3.73 or 3.91 sounds good to me now.

[thedodgeboys]

do the 3.91's and dont look back :)

[chicane67]

:headbang:

[Vegas69]

I agree, 3.73 or 3.90 and your minimum crusing rpm will be around 1800 rpm before it wants to chug with any load.

[fatelvis]

So since I first posted the question, I've decided on a beefed up 2002 Viper spec T-56 and not the magnum. Also, the gears in the trans will be the viper set which is the combination of close and wide ratios: 2.66 1.78 1.3 1:1 .74 .50. I want these overdrives because the car will be mostly street driven and taken on long road trips. My car will weigh no more than 3500 with driver, and my engine is putting out 625hp/600tq at the flywheel. That's quite a bit more than most LS1s. I've studied many rpm/gear charts and narrowed the rear gear decision down to 3.55.

If I may, I have a 69 camaro with a similar combo as yours, ls3 t-56 3.55. Please reassess your choice, 3.55 cruises at 1500 rpm w/ a 26.5 tire.
This renders my 6th gear useless under 70. I am trying to decide between 4.10 and 4.56
My opinion for what its worth..

[Raw Untamed]

Some things changed since I last posted here. I'm going to use a 295/35/18 tire which is 26.1 inches tall, and almost decided to go with 3.91s, but now I'm thinking about changing 5th and 6th to the .80 and .62 ratios and run 3.55s. I'm still trying to figure this out. My big block is putting out a ton of torque down low so I don't need tall gears.

With the 3.91s, it throws everything way off. 1st gear would be really short, and probably just spin the tires under the lightest throttle, which makes it unusable. Then the .5 6th gear at 70 is 1750rpm, and 75 is 1875 and that's too low.

With the 3.55s and .62 6th gear, 70 is 1975rpm, and 75 is 2125. This gear is also better suited for 1st through 4th. It's basically perfect! That's going to be much better for my stroker I believe.

One other thing I must mention is, all the responses I got were from guys running small blocks. I think my situation is a bit different because small blocks usually need to rev higher, and they make peak hp at around 6000rpm or above. They need the gears to keep their engines in the power band.

Also, everyone just commented on the 6th gear and not the other 5 gears. Well, when you change the rear gear ratio, it changes ALL of the trans gear ratios. That's important to remember. 6th is really only used for cruising on the highway, never racing or top speed runs.

It's kind of apples to oranges. I wish somebody with a big block and a T56 would've chimed in.

[Raw Untamed]

Does anybody run a big block and a T56?

[go-fish]

Joe, I will be talking a lot more about this when you get everything sorted. You need to get this thing driving before you OR I move out of town, LOL. I know I don't have a lot of time right now with everything going on in my life but I don't think I am going to go to school over the summer so I can hang out more. We have get our ladies together, they have the same taste too (i.e. shoes, hand bags, ....)

I am really excited about your build. I met guy in one of my classes that has a bitchin 71 Charger with RMS suspension, Hydroboost, Wilwoods, you know, the "package".

[cubicylndr16]

I run a big block and a tko-600 2.87/1.89/1.28/1.00/.82 with a 315/35/17 tire and 3.08 gears.

600hp/620ft flywheel

I cruise at 75mph in 5th @ about 2100rpm iirc. Im most likely changing to 3.23 or 3.42.

[72BBSwinger]

I run a BB and Viper t56 in my Dart with 3.91s. First is short but its an animal out of the hole with 335s. Interstate at 2000 rpm is nice but it does lug it pretty good and I get some timing rattle on pump 91. Going to hook up a timing retard switch and pull a couple degrees out for those conditions. I'm happy with it for what I've accomplished on my budget but the closer 5&6 gears would be better for 1 mile shootout stuff.

[gsxrken]

I'm curious to hear if there is a way to tell a timing retard device that the T56 is in 5th or 6th gear.

You might also look into this method of detonation control. A lot of Porsche guys use these:
http://www.jandssafeguard.com/tech.html



I run a BB and Viper t56 in my Dart with 3.91s. First is short but its an animal out of the hole with 335s. Interstate at 2000 rpm is nice but it does lug it pretty good and I get some timing rattle on pump 91. Going to hook up a timing retard switch and pull a couple degrees out for those conditions. I'm happy with it for what I've accomplished on my budget but the closer 5&6 gears would be better for 1 mile shootout stuff.

[Raw Untamed]

I run a BB and Viper t56 in my Dart with 3.91s. First is short but its an animal out of the hole with 335s. Interstate at 2000 rpm is nice but it does lug it pretty good and I get some timing rattle on pump 91. Going to hook up a timing retard switch and pull a couple degrees out for those conditions. I'm happy with it for what I've accomplished on my budget but the closer 5&6 gears would be better for 1 mile shootout stuff.

72BBSwinger, what BB do you run? What are your cam specs and compression ratio? Do you know what rpm it likes to cruise? Did you say 2000 rpm still lugs?

[72BBSwinger]

I have mild 400/451 with a xe284 hyd cam and about 10.2.1 compression. Viper t56 and 3.91s with a 26" rear tire and I am at 2000 rpm at 80 mph. There is a lot of load for that low of rpm and I've had to slow down the curve in the msd dizzy and take 2 degrees out of total timing to get the engine happy on pump gas. The load at 70 is a lot less, pushing a lot less air. If you could shoot for 2-2300 at 70 I think you would be happy. BTW 3.91 and the 2.66 first is not to low at all, some guys that have driven it think its tall. I think its perfect. You can do the math until you're blue in the face, with my setup its badass, if I had a Magnum with a .62 6th I'd run 3.73s. And getting 20 mpg out of that 470 ain't gonna happen unless you can idle at 60 lol!

[Raw Untamed]

That's good info. It's greatly appreciated.

[TheJDMan]

I read somewhere that Bret Vogel is running a 3.50 gear in the 48 Hour Camaro but I don't know if he is running the wide ratio or the close ratio T56.

[72BBSwinger]

I thought that car have a Muncie and a gear vendors?

[andrewb70]

I thought that car have a Muncie and a gear vendors?

It was replaced with a Magnun T56. Bret had a long post about it around here somewhere...LOL

Andrew