[Binford]

Simple and stupid question. But will the new TKX hold up behind a big block thats puts out more the 600 ft lbs?
Seemingly that the tkx was designed for the 68-72 tunnel it seems Slightly weird that is not rated for more.
With today's advancements in cylinder head design and cam profiles a bbc can sneeze and make over 600 ft lbs these days....and alot of the 68-72 cars have big blocks...

Am I missing something?
Thoughts?

 

[vortec710]

Warranty claims, everything has space and design limits. Smaller gearbox, less internal space and let’s be serious, not everybody’s BBC makes over 600 ft.lbs and is street driven and needs O.D. Big hp sometimes requires compromises like stronger gears, bigger trans cases and massaged floors.

 

[GuysMonteSS]

I would bet that they rate them at a lower torque capacity to cover themselves for warranty issues.
As you say,lots of BBC powered cars are making that much easily.
IIRC,the Doug Nash 4+1 5 speed like mine were only rated at 450 lb.ft.
I'm well over that at 625 and mine is still holding up,although I did send most of the gears out for cryogenic treatment.
A lot probably depends on how they are going to be driven.A strip only car would likely disintegrate sooner than a street one.
Guy

 

[cheveslakr]

It's more the shock load. Street tires, no problem, too sticky of a track tire at peak torque and dead hooking, it's likely a countdown to explode.

 

[-SS454-]

My friend has a TKO-600 and launched off a 2 step behind his LS6 454 crate engine. Low 1.70s 60fts and he did it like 300 times. Car weighs about 3750 with driver.

The key is displacing the energy on the hit. Bias ply tires are a must. A slipper clutch or a clutch tamer device is highly recommended. Gear is also your friend.

 

[TX66SS]

I have a TKX sitting on the floor next to me waiting on a 675 horse or so BBC. The guy I talked to at Silver State Transmissions said that the 600lb torque rating was based on "continuous use". As in, it's designed to handle non-stop 600 ft lbs. This could be bullshit but their lack of concern for me exceeding the torque rating gave me enough faith to give it a shot. It's important to note that I don't intend to take it to the dragstrip or run slicks so the chances of the transmission feeling all of the torque are probably not high.

 

[69-CHVL]

Before the T56 I had a TKO, which sustained 100+ runs at 4000LBS. It also was subjected to (2) incidents were by mistake shifted from 3rd to 2nd gear at over 100 mph. I thought the rear of the car got hit with a missile because the thing jumped up in the air. I thought for sure the trans was f'd after that. But that trans still worked great up till the day I sold it.

So I would imagine that TKX should be just as good if not better than the 'ol PROVEN TKO!

 

[GoFast Beaumont]

TKX has a lot of the same architecture as a T56 Magnum. TKO was just a modified for toploader/T5 in my opinion. TKX is a superior design that has addressed a lot of the short comings of a TKO. Things like poor synchros, 3 gear weakness on powershifts, case deflection, etc. i would venture to say a TKX will handle upwards of 900ft/lbs before there is a concern. Looks around and see what others are offering in there "stage" packages. If there quoting higher numbers without replacing a gearset, well you have your answer.

 

[Sipowicz400]

I'm currently installing one behind a tired 355, but there's a 454 waiting it's turn in the corner. I suppose we should also ask what the definition of "Big Block" is. I'm sure the TKX will life happily behind any 396/427/454 that Chevrolet had to offer in stock trim, hell, let's throw the 348/409 in there too. However, most folks are building 496 and up strokers, and tall-deck monsters these days.
The 454 I intend to build will be relatively mild by modern standards, but 500hp and 600lb-ft is cheap and easy from a stock 454 short block, and that's just skimming the middle of the catalogue, so to speak. I have faith that this new Tremec will live behind what ever I'm throwing at it.

Something else, somewhat related, is that I think a lot of folks have forgotten how fun an old light-weight car with 400hp, a stick, and some gears can be on the street. You're not setting the world on fire, but you can get into a lot of trouble when every corner is sideways and every stoplight is a clutch-dump.

 

[Binford]

I'm currently installing one behind a tired 355, but there's a 454 waiting it's turn in the corner. I suppose we should also ask what the definition of "Big Block" is. I'm sure the TKX will life happily behind any 396/427/454 that Chevrolet had to offer in stock trim, hell, let's throw the 348/409 in there too. However, most folks are building 496 and up strokers, and tall-deck monsters these days.
The 454 I intend to build will be relatively mild by modern standards, but 500hp and 600lb-ft is cheap and easy from a stock 454 short block, and that's just skimming the middle of the catalogue, so to speak. I have faith that this new Tremec will live behind what ever I'm throwing at it.

Something else, somewhat related, is that I think a lot of folks have forgotten how fun an old light-weight car with 400hp, a stick, and some gears can be on the street. You're not setting the world on fire, but you can get into a lot of trouble when every corner is sideways and every stoplight is a clutch-dump.

I roughly stated that a middle of the road big block will lay down a 600/600 combo.
And plenty will make more.
I am currently building one of those middle of the road big blocks. No fancy parts. Just basic proven stuff. I my goal is 650/650 with another 125 nitrous shot on top. Even if my build is short at say 600horse /600 torque, my nitrous hit will take me over 700.

 

[sr530]

If I can put way over 800 thru a stock geared small in/out Ford Toploader, a TKX is probably good for at least 1000. Just keep in mind that it's clutch engagement rate that actually decides how much impact abuse the transmission will actually see. Install too much clutch, it will draw inertia out of the rotating assy too quickly, which will either bog the engine, spin the tires, or break something in the drivetrain. All those things make your car slower, so avoid installing more clutch than required to handle the power that you are making.

Clutch engagement rate is just as important to a stick car as proper torque converter stall is to an automatic. Too much clutch will pull the engine down out of it's optimum operating range, just like installing too much converter. Put nitrous on an automatic car, it will require a tighter converter. Run that nitrous converter without nitrous, it will take forever for the engine to get up into it's power range. Adding a 125 shot on top of 650 is going to require a clutch that can handle around 800ftlbs. A car/clutch set up to handle 800ftlb on nitrous is going to bog a 650ftlb engine without nitrous.

On an automatic car, some loosen up an otherwise too tight converter by dumping some converter charge pressure during launch. That basically causes the converter to cavitate, which in-turn temporarily reduces torque multiplication and raises it's stall speed. Bottom line is the engine gets to it's happy place quicker. On a clutch car, you can temporarily hold back some clutch clamp pressure with a clutch hit controller for much the same effect, keeps the engine from getting pulled down out of it's happy place by too much clutch.

All this is a long round about way of saying it's your clutch that will ultimately decide if a TKX lives or dies. Too much clutch will kill it, too much clutch will also make the car slower. Lots of guys go overkill on the clutch, those are the same guys bogging, spinning, and breaking stuff. Adding nitrous is going to require more clutch than optimum for NA launches, but adding an external clutch hit controller is an easy way to dial back that nitrous capable clutch to also work for NA launches.

Personally I would not hesitate to choose the TKX at your power level. High rpm synchro'd shifts, overdrive, in a package that fits? In my book that makes it ideal for a street/strip car.

Grant