Does anyone know the fastest a stock/untouched T56 has been? What would be considered the breaking point/limit?

 

are you talking track time, with higher rpm clutch dumps
from a dig, or roll races ?

 

Speed will not be the limitation of your trans as your cannot go fast enough to hurt it.The real limiting factor will be the torque. Torque that you actually get to the ground without slip.

 

It's kind like when someone asks the limit of the stock 10 bolt....some break at stock power, and others like myself do fine with double that lol. Really how it's driven is going to determine the outcome

 

Guess I was more wondering whats the fastest ones been, 1/4 mile.

 

Best thing to make one live is a really good slip yoke. Like a Mark Williams, or chromoly Strange unit. Also good hydraulics and good clutch.

 

I have a Mark Williams slip yoke, tick master, mcleod street twin. Just going to put fresh fluid in and keep pushing it.

 

Here is where I found the limit. I don't remember exactly, but it was around 5000-5500rpm clutch dump on Hoosier drag radials. It just went "BANG" and the engine revved up. Luckily it didn't hurt anything else inside, just sheared the mainshaft flush at the end of the slip yoke splines.

 

Mine is surviving 900 rwhp, but I don't go to the track often and mostly do highway pulls.

 

I would like to see the slip yoke splines.

 

OUCH!!

I am SO glad I don't do test and tunes/time trials (drag race) anymore.

 

In your case, it looks like radials + Spec Stage 5 clutch = broken T56. Rated to over 1000ft/lbs, an un-buffered Spec Stage 5 will pull a 496ft/lb engine down substantially on the hit. That rpm loss indicates a huge inertia energy release, enough to make a 1000ft/lb rated clutch slip for about .13 sec or until something breaks.

A clutch well matched to a combination will have just enough capacity to hold in high gear at the engine's torque peak, which allows it to initially slip more when the clutch is dumped. The "softer" engagement will result in less bog, less likely to break parts, and easier to hook the tires. This can allow you to "have it all" by choosing a lite flywheel without incurring the nasty bog that would usually come with it. There are a couple problems with this though-
...the trial and error process to find just the right balance of "clutch vs power" for your combo can be expensive
...any significant increase in power will upset your "clutch vs power" balance
If you are a nitrous user, this basically means you must compromise your NA potential in order to still have enough clutch capacity to handle the spray.

To address this issue on my nitrous street/strip car, i went a different route and came up with a simple way to easily adjust how hard my aggressive clutch initially hits.
...allows me to easily adjust the hit of the clutch to suit either NA or nitrous hits
...allows me to enjoy the benefits of a lite flywheel without fear of a bog
...allows me to choose as low of launch rpm as I want (no-prep anyone?) without fear of a bog
...allows me to choose a clutch with excess capacity, leaving room for future growth without incurring that penalty from too much clutch capacity…broken parts.

Radials + proper hitting clutch = no broken T56 + quicker pass. With a proper hitting clutch, you will be putting no more stress on your T56 when you dump the clutch than if you were roll racing. It might be hard to believe, but that "softer" launch will result in a quicker 60' as well.

 

My transmission isn't exactly stock but it's not heavily modified either.... steel 3/4 clutch fork and billet slider keys. ...car has run countless 10 second passes and 15-20 9 second passes...a lot of it is in your launch....if you just dump the clutch you will break it....you need to learn how to slip the clutch and save part's

 

5k dump on hoosier stiff wall slicks, 150 shot netted me 10.37 with a 1.38 60 and a 5500 netted me a 10.41 with a 1.39 60 ft. Changing the jets, and a few other small things for this year. Stock bottom end and stock t56. See what lets go first. Only hit the track once maybe twice a year. Rest is street rolls.

 

Upon visual inspection the splines looked fine. Also, the broken piece of mainshaft slid in and out of the yoke and bottomed out with no resistance.

I decided to do the same thing after this happened. Every time I try to race it I end up breaking something or hearing new noises (in my head).

I've always heard the same thing and agree with everything you said. With the Spec 5 and dumping the clutch, it usually either bogs or spins depending on the launch RPM.

Agreed as well.

I'll need to figure out the clutch slipping off the line deal if I decide to try racing it again. I've always been a circle track guy, so I still have a lot to learn. I'm not afraid to admit it.

 

On a Stage2 rebuilt T56 (steel 3/4 fork, billet keys/bronze fork pads) we went 9.20's@162mph launching mellow in a 3100lb setup (includes driver).

Combo was: GTS76 turbo, 376ci LS3 (stock crank/forged rods/pistons) with ported SDPC LS3 heads/stock LS3 intake in a Mazda RX-7 on IRS 8.8" Cobra. That was all that turbo had and the car was all over the damn track on a not so great prepped surface.

 

I ran 10.04 at 149mph on a 100% stock T56, 3700lbs, 60ft in and around 1.7x I think. Ran quite a few very low 10's and slower over the years, the box was always faultless.

I did change the trans shortly after that to a mildly upgraded unit, shift forks, keys, Viper Mainshaft and supposed to cryo'd.

I just keep the old box as a spare now.

No real reason for the change other than being paranoid and I had some money to spare at the time, so upgraded clutch and trans together.

Still keel the old Tex OZ700 I had been using with the original box as a spare too.

And have had to re-used both on a couple of occasions.