My T-56 is shot, and I really wanted to put in a TH400. Im sure that with my poor shifting that this could get me close to a second in the 1/4. Example, best time with 478rwhp/455rwtq was 11.47 @ 120mph.

I still want to drive the car on the street though, im not really a serious drag racer -- but I really want the times and I dont think Ill get them with another T56. I do not have a truck or trailer, the car often drives to the track over 2 hours and I change the tires at the track.

My thoughts were to downgrade my rear gears from 4.11 to 3.23, get a 2.75 or greater first gear in the TH400, and possible a slightly longer 3rd gear. My goal is to be able to drive 65mph at less than 3k rpm. Any insight on how to do this calculation (say using stock size 275 17 45 tires), or any of you doing something similar? I tried getting feedback in auto tranny section, but there is no traffic there.

Any insight appreciated!

 

You racing on 26's or 28's?

I have 3.50 gear (9"), 28's and T400.

 

current rear tires are 26"

 

I would think that the 2.75 first/3.23 rear gear combo would keep the car around the rpms you were specifying. I would go no bigger than a 3.42 or 3.55 to keep the r's down rolling around on 26's.

 

Do you have a 9 inch or a 12 bolt? Go with a 27 inch tire with the 3.08 if you are a 12bolt. 3.0 first gear and alum drum. you'll be 80mph at 3000rpm. With the right stall you should still sixty well

Wouldn't be too bad on the highway but you'll notice the lack of gear on the top end of the track.

You would be doing 75mph at 3000rpm with a 26 inch tall tire

 

sucks ***, don't do it.

i went TH400 last year and hated it, was fun at the track but with no truck or trailer it was such a pain driving the car to the track it took all the fun out of it. I didn't like it on the street either..just wasn't for me always being at high rpm cruising around.

I went back to a built T56 setup and have never looked back

 

how much did your track times vary between the t56 and th400?

 

12 bolt, curent rear is 4.11s
street tires are 275x45x17 drag radials
Track tires are 26x11.5x15 ET streets.

 

my car has gone significantly faster with the M6 than it ever did with the 400.

unfortunately not a great apples to apples comparison as I was running 5.7 heads and a smaller cam with the 400 setup and my converter was a spray convter that was a bit too tight for motor.

still. off the transbrake on a 28" et drag best sixty foot was 1.59. My M6 setup will low 1.5 every time on a 26" et street.

 

It is going to be different for everyone.

I went from a 6 speed to a TH-400

The car is no fun to drive on the street. I just do not drive it anymore that much.

 

I agree, the fun factor will be somewhat lacking with the TH400. But knowing the tranny won't be an issue in breakage factor (provided you find a good one) will be an advantage. My nova has a 3-speed TH350 in it, and I don't own a trailer and have never trailered the car. Granted driving on the highway at 3500 rpms at 70 mph can get old at times, but knowing the car will make lap after lap without fear of breakage b/c I've put in good parts is the deciding factor! Personally, if it's not a bracket car, try and get a built T-56 or some other 6 speed. Your mph is not far off for the et, so there's not much left there unless your 60 foots are worse than a 1.70 or you can't shift. I'd say 120 mph in all efficiency would make an 11.2 or 11.1 E.T.

Just my $.02

Derek

 

a M6 can handle some serious **** if you do it right.

I run:

D&D Performance T56 trans
Spec Stage 3I with billet flywheel
Denny's N20 Driveshaft

goes into a moser 9" with full suspension and spool.

I launch my car at 7,000 rpm dumping the clutch all day long..drive it there and back and the car never skips a beat. and i am BRUTAL on that trans and clutch when I shift.

it can be done, my car is proof.

 

what about a built 4L80? Other than being a kinda of pricey conversion, it seems like it might be a good option.

 

i'd go built 200-4r. you can have it so its manually shifted(i.e-no computer harness swap), a lock up switch, and a transbrake on it.

kinda the best of everything.

 

I have done the swap myself went from a Spec. Stage 3 clutch with Aluminum flywheel, built T-56, alum. driveshaft, 12bolt, to A Big stall T400 with Brake

And after 1000miles with my TH400 in, Ive learned this it takes SOME of the driveability away, was it more the cam or the T400 im not sure. But when i do drive it on the street I LOVE it, so much more "fun" than the M6...you can lay it to the wood whenever you want and just go..no miss-shifting no worries nothing, what about the once in a while stoplight battle, no stick car is gonna hang with my 28" Quick time pro big converter setup (trust me i know)

At the track its a love hate relationship for me and the T400, it took some of the fun of racing out of it, i was (and still am) a very talented M6 shifter....missed a handful of shifts in my 4 years of drag racing the M6. But the 60's and the consistancy REALLY MAKE ME HAPPY, and most of all NO WORRIES, i know it can go pass after pass after pass and never skip a beat. Whereas my buddy is loading up his Richmond 5sp car cause its hitting the tires to hard, cant hook up and didnt make a clean pass in 4 passes.

its your call if having a cool number to tell people is what you want get the T400, if you want a car thats fun to go here or go there keep the six speed.
Andy

 

appreciate the input.

the 200r4 -- in theory it looks great, but its so damn pricey and Ive heard that they arent as strong as they are touted to be. Plus I havent seen one LS1 or LT1 or even ever heard of one running this trans and doing any kind of consistantly good times. I combed most of the boards looking for info on it too.

I see a lot of people and I know a lot of people that are having problems with built T56s. They just dont seem to hold up (or at best its really hit or miss). This is now the third time Im having a problem with mine, and I never really push it, Im so afraid of breaking it that I pretty much granny shift all the time, which is taking the enjoyment out of driving with it and absololutely killing my times at the strip.

MPH is not a good indicator of how much power your car makes when people comment at the track that they think they counted 3 seconds between your 2-3 shift.

 

1--Care to test that theory of no M6 hanging with you sometime?

2--Sorry but I don't agree. I will drive my car ANYWHERE, road trip it you name it..get over 20 mpg and still e.t and mph your Th400 car on 26" dot tires with a stock displacement motor.

Sometimes this gets on my nerves. Switch to TH400..that is fine, but don't say you are a great M6 driver and then say you blew shifts alot so you went to TH400.

Not trying to be a jerk, but your post is a bit imflamatory and you are making innacurate claims. My car is far from the only one on this board that would prove you wrong.

 

I find the 4L80E interesting. I myself would not mess with a 200R4 conversion I think that their reputation for durability is overstated. GN guys go to T400 when they get really fast.

4L80E has been done a few times. I think honestly you could probably get a 4L80E to work with the stock trans harness.

IMO if you are going for low 10's and faster, the T400 is the least expensive and most consistent way to go. I like mine.

 

See if Lenntech will make a ford conversion with a GM bellhousing...
That'll handle anything u throw at it...

 

Your situation is kinda like mine. I have a FLP level IV 4l60E and I LOVE IT..... but I don't want to break it and then have to spend another 2K for another one when I could sell the 4l60 and buy a t400 with a break and converter. This is one hella delima for me b/c I would LOVE to have a transbrake..... but then again I love the damned over drive.... but I also know that for the setup I want to build the 4l60 will never live.

Josh S.