RT66ProTouring

iTrader: (2)

There are a limited number of choices in manual transmissions.

I don't read many people listing two overdrive gears as a large factor in their decision making. Price, size, weight, Tq rating and smooth shifting tend to all come up in these discussions, but rarely the gap between 4th and OD.

Any thoughts? There might also be a "cool" factor to a 6-speed vs a 5 speed, right?

I'm currently in the middle of this thought process. My application is a 3200#car with +/- 340 rwtq, 3.73 rear, 25.6" tall tires and .59 or .64 OD.

A transmission that can handle the torque and any future possible plans is a given in the decision.

QwkTrip

iTrader: (22)

You are correct, overdrive gears below 1:1 are for cruising, not for performance driving. When thinking about performance you want to consider gears 1 thru 4.

If I had to choose a single OD gear then it would be a number in between the 5th and 6th gear ratio of my LS1 T56, or a number around 0.62:1. Seems like I never us my 6th gear that is 0.5:1.

RT66ProTouring

iTrader: (2)

I think along the same lines, that I won't utilize both OD gears. But then the TKO's don't shift well and are pretty loud in 1 -4. The TKO's are lighter though which is nice.

BUT, to solve the shifting issue, the option is a *GASP* upgraded T-5 from G-Force or Astro. (Yes, I said the G and the A words ).

//<86TA>\\

iTrader: (14)

The t56 6th gear is .5 which in absurd and almost useless. Buuuuut you can use low gear like 4.10-4.56 and still be able to drive on the highway.

I agree the TKO is a bit clunky to shift sometimes but id rather have the very "positive" feel of the shifter over the t56 slushbox. And reverse in a t56 is in the worst place imaginable.

RT66ProTouring

iTrader: (2)

Yes, you can use a shorter rear gear with the 0.5 OD, BUT 1st gear (in the 0.5OD T-56's) is 2.97.

The close ratio T-56 with 2.66 1st and .63 OD might work well with a 4.10

QwkTrip

iTrader: (22)

Also keep in mind the F-body T56 does not have triple synchros and is limited to about 6500 - 7000 rpm shifts. The F-body got the lowest options of all T56 transmissions.

RT66ProTouring

iTrader: (2)

IF I did a T-56 it would be a performance rebuild from Liberty or Tick to get a +/- 600 Ft-lb rating so I don't limit myself later.

So that's really the debate in my head, transmissions at or near a 600 ft-lb rating. Weight and size VS shift quality and two OD gears.

Will a Magnum T-56 fit without major surgery? That would be about the same price as an upgraded T-56 or a shift-improved TKO.

QwkTrip

iTrader: (22)

No, you don't understand.... you don't get triple synchros with an F-body spec T56. All those "built" transmissions just improve shifting, and the increased torque rating is advertising BS.

My fancy dancy, high end T56 with Viper output shaft from RPM Transmissions shifts nicely and was put together with great attention to detail. That's about it. You could do it at home if you had the gumption to do it.

RT66ProTouring

iTrader: (2)

Hmmmm

Well in that case the choices seem to be:

Used T-56 (heavy, cheaper and figure out plan B if I ever upgrade engines)
VS
Magnum T-56 (heavy and from what I can find on the webs, longer and potential drive shaft issues)
VS
TKO ("positive" shifts)
VS
Astro T-5 (hate from the entire GM driving world)
VS
G-Force T-5 (bad customer service, questionable quality, questionable torque rating AND hate from the entire GM driving world)

QwkTrip

iTrader: (22)

Oh, there isn't anything wrong with the way my T56 shifts. That's what those shops sort out when they build it. And getting a GOOD shifter is part of the solution, such as the MGW shifter I use.

Also, don't let me scare you about torque ratings. I'm not familiar with the standards used to rate transmissions but I wouldn't be surprised if that was a continuous torque rating for life of product or some high duty cycle. There is a large margin of design and you can apply a lot more torque for short time without breaking it.

Most times what kills a transmission is the idiot in the driver seat. Bad shifting habits, watching youtube videos about speed shifting, hitting the wrong gear, short clutch stroke, choosing an undersized master cylinder.... yada yada. The other thing that can kill is impulse from a clutch dump + good traction, such as 5000 rpm launches on slicks at the drag strip. That impulse is much harder on the materials than the torque of the engine.

RT66ProTouring

iTrader: (2)

Totally agree.

and "yada, yada" includes Stage 3 1,000 hp clutches on a N/A small block.

Abubaca

iTrader: (3)

I've got a TKO600 and it's not much clunkier than my t5. I had a Pro5.0 shifter in the T5, and it was awesome to shift. The TKO is clunkier I suppose, kinda hard to describe, but the entire shift feels more precise, not just the engagement of when the shifter hits the stop/bolt. It sounds like a negative, but when you're actually in the car doing it, man it's awesome.

Bullydawg

iTrader: (7)

I've driven a faceplated TKO-600 in a fox body. That was pretty clunky. I would assume abnormal TKO wouldn't be that bad at all.

Abubaca

iTrader: (3)

..and just a quick pat on the back for the T5.... I bought my T5 in need of rebuild, and did it myself after buying a few tools. Drove it for 5 years relatively hard, behind a cammed L98 350. ...and I fell into a deal from a good friend on the TKO or I would still have the T5. Doing your own rebuilds makes the money a HUGE consideration, and if you're not gonna beat the crap out of it....just a thought.

Abubaca

iTrader: (3)

Just saw Bullydawg's post about the 600. The best way I can describe the difference, IMHO, and the learning curve needed to really grab gears at speed is that I felt the T5 would move in diagonals. The 2-3 for example, just jam it up diagonal right and it'll find third. The TKO is more notchy. Gotta go up, right, up. Not diagonal. ...now it's easy, but I hit the dead space and found neutral a few times the first few times I got on it.

Twin_Turbo

iTrader: (25)

I have used quite a few options, ZF6 (S6-40), T56, TR6060, TKO 5 speed, ROD,, T5, T10, ...etc. By far the best shifting transmission is the S6-40. It's like butter comparead to all others but it's a large cumbersome pig to isntall and you either need to modify the floor for the clutch slave or get a rare aluminium bellhousing, cut it and weld a T5 pad to it (most are magnesium, it says magnesium on them) and the shifter is further backwards (check out the SLP firehawks) For ease of installation, shifter feel and available support the T56 is pretty hard to beat.

jmd

iTrader: (4)

careful now

The T56 Magnum can be had with 2.97 / 0.50 ratios. It is in fact, a TR6060 with a marketing name. It can be switched to the 0.80 5th, and 0.63 6th.

The TR6060 is also made for 2.97 / 0.57 OEM applications, which was used in the T56 too.

The 92-07 T56 cannot have 2.97 / 0.50 ratios. One could be built custom with 2.66 / 0.63 ratios for a GM application.

Your question is broad. The lighter the car, the more sense the 2.66 ratios make. Higher power engines that need less ratio assistance also work well with it.

As far as shift smoothness, the CTS-V introduced different detent design ( internal linkage click mechanisms) that trickled down to the C6, and the entire TR6060 line. You can fine tune the horizontal and vertical detents of a T56, or go custom and make an old T56 shift like a TR6060 if you know the internals.