Ok I was looking up prices for Vigilante TC's and I was reading the description. One place claims up 50 hp gain from a TC. Naturally this number is BS but do TC's give you horsepower is the question here? I thought they basically just adjusted where the most torque is.

 

That had to be a mistake. Not only will you not gain any HP but your gonna lose a few ponies due to less effiency then the stock converter. But I'll gladly trade the 5-10 rwhp for a .4-.6 gain in my ET

 

I have seen that add too........think they ment TQ

 

So you'll dyno much more torque but less hp in a nutshell?

 

So you'll dyno much more torque but less hp in a nutshell?

 

TC have higher torque multiplication which yeilds more rwtq. I do beleive they lower ET's b/c they allow you to rev the engine to a higher RPM before launch, which combined with Drag Radials or Slicks helps you shoot off the line faster. Also reving higher gets you futher into the HP curve. Better 60'.

Dont ever worry about Dyno #'s since 1/4 times win races not RWHP/RWTQ.

-Dustin-

 

Looser vs. a tighter TC vs. a manual tranny is a bit complicated. If what you are going by is 1/4m times. the important variables are the cars weight, torque curve and power band, and available traction. Where you have to start is that a fluid coupling like a TC will eat up power, there is no way around that. So assuming the gear ratios aren't way out of whack if you take a typical underpowered econobox a manual tranny will be faster and quicker. Often by a long way, as much as a second or more in a quarter mile. That's simply because the auto eats up hp and there is none to lose in the case of the econobox.

Now, lets take a stock 4th gen F-body with a stock converter A4 and a stock M6. It will be a close race in the 1/4m but with a skilled driver the M6 will ET quicker and it will definitely mph higher. Why? Well, the TC is eating up power, just like with the econobox. That's why the M6 will trap higher. But the ET will be close. On the one hand, the A4 will have little more torque off the line due to torque multiplication. But OTOH, if street tires are used this extra torque may not be usable due to wheelspin. And in spite of the torque multiplication with the A4, first gear in the M6 is lower and the "average gear" over the 1/4m. is lower as well (4 gears are used, not 3) and an M6 has a higher rear end gear. So, the engine will stay in its' powerband better with the M6.

If you put an optimized converter in the A4, optimize the rear end gear choice, and use sticky tires I think it would be a wash. Very close race. Skill will be a mojor factor here, especially when you take into account the ability of the M6 driver to shift as well as skill in launching the car. The M6 car will still trap higher, a reflection of the hp loss from the converter. In fact, the A4 car optimized for ET will probably trap LOWER than a stock A4 due to converter losses, but it will ET faster. Similar logic applies to mildly modded cars, where it will come down to the driver. It's not easy to get the best out of an automatic, but it's easier than with an M6, by far.

Now, let's go to a really high-po 4th gen. Of course, we can't use the A4. The automatic will need to be stronger, typically a TH400. And let's assume the converter is optimzed for the particular combo for track use as is the rear axle ratio. With the M6, also assume an optimized rear end and a clutch that's up to the job. Here, we get to the interesting situation of the TH400 car still showing a lower trap speed, but probably with a quicker ET if slicks are used. In this case, the loose converter needed will eat up a LOT of power. Maybe as much as 10%. Hence the slower trap. But with the auto and correct converter the motor will be in the power band more than with the M6, the shifts will be faster, and the launch will be harder due to the off the line torque multiplication (a race auto will have a line lock, allowing the revs to be brought up to the converter stall speed at the launch). Still, a very skilled M6 driver willing to really abuse the clutch and tranny would still have a shot. The M6 has marginal strength for a hi-po heavy car, that's really why some of us switch. Also, for bracket racers, the auto is much more consistent. A race "auto" is manually shifted, BTW.

The ultimate drag racing tranny is an "automatic with a clutch". IOW, a tranny with a planetary gearset like an automatic but without a torque converter. It can be shifted under full power without use of the clutch but does have a clutch to allow the car to stand still with the motor running. IOW, to allow it to get off the line. These have the lower power loss of a manual with lightning fast shifts and the number of gears can be oiptimzed to the powerband and weight of the car. The Lenco is the grand daddy of clutchless drag transmissions. Very strong, but heavy and bulky. The G-force is a lighter clutchless tranny. Not as sturdy but less bulky as well. There are people using these trannys on street cars, but not many. I strongly considered a 5-speed Lenco for mine. But in the end, the ~$10,000+ price tag (for the whole job) was big negative. That and the extent to which the car would need to be hacked up to get it to fit.

Rich Krause

 

Stalls kill rwhp. But its well worth the incredible launch. Just be prepared to eat through tires and trannies.

 

A buddy of mine has a mustang race shop and he uses the Lencos exclusively in his race cars. Two of them are in the 8s IIRC. He had both 4-speed and 5-speed trannys lying around. They look a little weird.... long and narrow.. but with REAL thick cases. He said he paid 6 grand for the 4-speed and the 5 was a little higher. Pretty expensive, but when you consider that he bought them and put them right in the cars and haven't touched them in a couple of years that's a pretty good deal. I was considering a 400 for my car in the future, but a lenco is really starting to catch my attention.

Rich, other than the DS, bellhousing, crossmember, and shifter location, what would be involved in installing one of these in a F-body? Would tunnel modifications be extensive? Whats the price difference between the Lenco and the G-Force? Thanks

 

FC: there are two basic Lenco models. The one we would be interested in is the "street" version. It is "rated" to 1200hp, reality is that I don't think it's possible to break one with a small block (boosted, juiced. or both), so don't worry about it on that score. As you can see from looking at one, it's kind of "modular". You add another segment for each additional ratio. My thought was to use a 5-speed plus reverse and a very low rear end gear )maybe 2.73's). That way, one could use 1-4 at the strip and have on OD. The choice of ratios is very extensive, but top gear is always 1:1.

A 5-speed plus reverse is quite long. At the front, there would be no clearance issues because the Lenco is also fairly narrow. But at the rear the tunnel would probably need to be cut and rewelded. I suppose I you had one BFH is might also be possible to pound it out. It could be made to fit though - I did put a 4-speed Lenco up under there and the interference wasn't terrible. The tranny tunnel would have to be hacked pretty good to get all of those shift levers in the right place (there would be 6 levers for a 5-speed+reverse). A new torque arm mount would have to be fabricated. Obvioulsy, a new DS as well. As I mentioned, a new (conventional clutch actuation sustem would have to be devised and a conventional bell housing used. A tranny cooler would be needed. I think.

A 5-speed costs ~$6,000. I estimated ~$10,000 for the whole job. It would be awesome, I have driven one on the street and it's kind of weird. It shifts RIGHT NOW, as fast as you can pull the levers. If you use the clutch when you shift, it's fairly smooth. When you are at WOT and just yank the lever as hard as you can - WOW, now THAT'S a shift! When you coast, it freewheels. When you get back on the throttle it immediately re-engages. A bit herky-jerky but you could get used to it if the car weren't a daily driver.

A nice thing about a Lenco is that it's the last transmission you would ever have to buy. My friend has a 3-speed in his alcohol Hemi car and he has had for over 15 years! He takes it apart now and then to inspect it (easy to do) and just buttons it right back up, nothing has ever broken or worn out in it. I strongly considered one and after I got through with spending close to $5,000 for a TH400 setup and now wanting a GV OD for another $2,000 I kind of wish I had. That's one reason I haven't gotten the GV yet. I still have a Lenco in the back of my mind.

If you do this, I'd really appreciate you keeping us informed of the pearls and pitfalls.

The G-Force is about $1,00-1,500 less, small (a lot) and lighter. But you could not use one on a street car and it is not as strong as the Lenco. It cannot really be downshifted easily, unlike the Lenco which is happy going from any gear to any other gear.

Rich

 

Thanks Rich. Good info. I think Lenco even has a 6-speed version now, but that will probably be a little too extreme for what i'd use it for. After hearing this i probably will go with a Lenco when i get to building this thing. Both of my bud's mustangs were taken down cause he was switching to different combos this year, so i didn't get to drive either one. But driving an 8-second fox would've been pretty neat itself .

If push comes to shove, i'll probably fool around with different engine mount, subframe, or crossmember modifications to try to avoid beating/cutting into the body to make it fit. The switch would be pricey, but would probably pay for itself over a few seasons. Or maybe right from the start like you mentioned with the TH400+ GV setup being expensive in itself.

Not sure about the lever location, but i know from the M6 conversion i did last year that the M6's shifter is about 30 or so inches from the back of the block. So if the Lenco's levers are close then it probably won't involve too much cutting. I guess you could be the ginea pig, sell the TH400, and go Lenco first.