I'm planning on building a pro touring 1970 Dodge Challenger, and I am intending my engine to be a built 440/512 stroker, putting out somewhere around 550-650 horsepower and foot pounds of torque. How would a properly built Tremec T56 stand up to this? Can I have the shifter in the traditional spot that the 4 speed shifter was in, or would I have to get the TKO 5 speed for that? How hard is it to install in the car, match up to the 440, and get it all running and functioning perfectly? How would it compare to an A518 auto swap performance- and fuel economy-wise? Whatever I do I'm not leaving the old 727 auto or 4 speed in there.

The T56 doesn't fit easily into an older Mopar. Besides, with a 512 stroker you don't really need a 6 speed transmission. You'll have enough torque to work with a 5 speed. Best bet is probably the Passon 5 speed. Everything else is a bit of a compromise. If I was doing it all over again I'd either go with the Passon 5 speed or take a serious look at the 6 speed auto.

they put the t56 behind a 645 hp v10 and the 707 hp hellcat, so it should survive behind your stroker just fine

I have a 6 speed T56 in my 2005 GTO. Love it but never use 5th gear. I shift from 4th to 6th on the highway, because I'm already at cruising speed when I'm finished with 4th gear.

The only use for 5th is when cruising at 40-50 mph, and 4th seems just as good or better for that.

My 5th gear is 0.74:1 and 6th is 0.5:1 with a 3.73 rear end. In 6th gear at 65-70 mph, the engine is doing 1,800 rpm. I think the 0.5:1 is just right for highway, considering my rear end ratio. I'm not sure, but I don't think a 5-speed will deliver 0.5:1 in 5th gear, which might be a disadvantage.

I'd say to choose the rpm you want at highway cruising speed and pick either a 5 speed or a 6 speed that will deliver that rpm with your rear end.

I'd only put a 6 speed in if I was running 4.11s or 4.54s. It's really good for some tall gears in the back. Otherwise go for a 5 speed.

I use a Richmond ROD. It fits the tunnel but the shifter is in a different spot,(its very close to the oem, I relocated the console), but you have to cut and reinforce the crossmember. I also had to modify the bellhousing for one mounting bolt.

T56 shifts great period. The only 5 speed I'd use is the Passon but I think the wait is 9-12 months still. Don't waste your time with a TKO - they are really poorly shifting units.

My T56 Magnum ships Monday, from everything I've read and seen, it's far from a couple cuts here and there to get it in there, especially if you plan on keeping the torsion bar crossmember.

I doubt the T56 will be too concerned with how much power you plan on putting through it, I consider the T56 Magnum as my "final solution" for anything I can put in front of it.

Have a T 56 in my 59 Vette, 3:73 rear axle. Love it, wish would simply fit in our Challenger, currently Passon 4 speed equipped, 4:10 axle. Tremec shifting action in all gears is very smooth, positive with a very short throw. Not certain how well would hold up in a 512 big block engine however.

Have 2 pals that are running Passon equipped E Bodies. Both quite pleased with them. One is running a 3:73, the other a 4:10. I've not driven either to Find how well they shift compared to T 56. Am curious as Passon does still use external linkage system.

Also running a hydraulic clutch in the Vette. Kicking myself for not installing same in Challenger last time had engine out. Much easier on the old left leg.

Simply put, 0.5:1 is a really excellent overdrive ratio if you have something close to 400 hp and a 3.73 rear end. My GTO with T56 will climb every hill I've ever encountered in 6th gear, which is 0.5:1, without downshifting.

In my opinion, an overdrive of 0.74:1 or close to that just isn't enough help to reduce engine rpms at highway cruising speed with a 3.73 rear end.

Here's the engine rpms from my car with T56 trans and 3.73 rear end at 70 mph:

4th gear, 1:1, 3250 rpm.
5th gear, 0.74:1, 2700 rpm.
6th gear, 0.50:1, 1800 rpm.

These are actual speedo and tach readings that are slightly different from theoretical (for example, 1800 is 0.55 x 3250).

Bottom line: a Passon 5 speed will only give you about 0.70:1. But it's a direct bolt in with no modifications. A T56 6-speed will give you 0.50:1 but modifications are needed.

The T56 does have two places to put the shift lever. It has a hydraulic slave/throw out bearing. Highly recommended: ventilate the bell housing with openings for air in and air out to blow the clutch dust out. Otherwise the slave may fail from the abrasive clutch dust. My closed tight system failed at 20,000 miles, and I added the ventilation with a new slave. Also recommended for T56 is the tickperformance.com clutch master cylinder kit and one person clutch bleeder line.

why not bolt on a gearvendors to the 727?
you can build a bullet proof 727 and still have options on gearing with a button.The 727 will bolt in easy,gearvendors easy bolt in,cut shaft and burn the sh!t out the tires

Even in Houston, 0.5 x 3250 = 1625.

Gear ratios are not theoretical. That's one of the niceties of mechanical engineering.

On the other hand, speedometer and tachometer readings may be inaccurate, and that's where the discrepancy lies. If you knew what your tire revolutions per mile was, you could calculate everything else.

R.

An brand new external linkage transmission will feel as good as a T56 with 150,000miles on it.

Forget the calculators, savings accounts, install set backs. Spend some seat time in both transmissions before you decide. You will not be dissapointed in the T56.

I stress this over and over again but I'm very picky about shift quality. If you don't really care about quick shifts and just need the overdrive, there are cheaper options than the T56.

Shifter will not be in the stock location, so in this case, starting with the auto trans floor pan is better. You will have to cut out and restructure your torsion bar crossmember. The T56 is a fat transmission compared to your 727. And don't plan on just buying a 90's camaro T56 and dropping it in and expecting it to be the same. Those will work but require upgrades internally to handle the power. Different T56 models have differnt internals and some require more upgrades than others. I would budget minimum 3000 for a diy type swap. More if you plan on buying the premade converion hydraulic clutch goodies and a T56 magnum.

I have a Geforce built T56 behind a 1500 RWHP Viper and it stands up OK. Twin turbo Viper people do eventually break them and most then go to the newer versions but thats at 1000HP plus levels...

Something to know about a T56: it's easy to accidentally downshift to 1st gear at 60 mph when aiming for 3rd. I did that twice, and the rev limiter saved me by shutting off the ignition. And I clutched mighty fast.

If running a T56 with a computer-less engine, beware.

If it's the clutch spinning the engine up from an accidental downshift. A rev limiter will not limit the rpm.