I've been seeing a lot more successful T56 swaps in NBS trucks lately and I'm just exploring my tranny oportunities. I'm currently trying to locate a 4L70E, but I'm still very open to other ideas.

My question is about manual trannys and building boost off the line. I know that with my 60e and a crappy *** TCI stall I could make almost 2psi on the line. That's due to the fact that I was loading the engine.

With a manual, are you able to build boost off the line? I don't see how, since you have your foot on the clutch when you launch. So there would be no load on the engine, and turbo wouldn't spool right? Correct me if I'm wrong.

Could this be why 1000rwhp Supras run 10's at 145mph?

 

no, its because their suspension sucks *** and they are dyno queens.

to answer your question, I launch my GTO like an Automatic car. its hard as **** on the clutch, but a good 60ft times make or break the whole run. hint: use the parking brake. really, if you do it right it only slips about 1/4 second before ya launch.

 

Well if I have to use the parking brake, I'd need a third leg, because my left foot would be on the clutch. My parking brake is on the floor in my truck. Even so, I don't think a 1/4 sec is enough to build boost and load the engine, especially if the clutch is slipping.

 

Line loc maybe have the button mounted on the back side of the steering wheel so you could hit it easily.

 

The fastest turbo cars in the country are running manual trannys and launching under high boost. Most just use a two step rev limiter to build boost on the line. Most turbo vehicles will build boost in nuetral if you rev them hard.

 

The only thing I have ever run on the dragstrip for years is a manual. You wind it up to at least 6k and when you come off the clutch you won't need much boost. The turbo will already be spun up it just needs a reason to build more boost. The only problems I have ever had out of NA vehicles and a manual is traction. The turbo lag (if there is any) may help the traction problem. The one's I have seen though either don't rev until 1 second or less before they launch due to building boost when they rev or they use a 2 step like stated above. I have never run a turbo'd manual but I won't be able to say that for too long.

 

My 4.7 Dakota has a very low 1st gear and it barely makes any boost in 1st before you shift it to 2nd. If I launch it (at the track with slicks at about 4,000 rpms) in 2nd gear it makes boost hard and fast but either slips the clutch or blows the tires off. I have made several successful launches in 2nd and even managed to pull a 1.58 60' time out of it once, but it cost me a clutch. Now I just suffer with 1.70-1.75 60's and leave in 1st.

 

Very intesting gentlemen......

I've never reved my engine in neutral (automatic) high enough to see if it builds boost on its own. But that makes sense that's it'll build boost fast, with all the exhaust gas being produced.

so what kind of clutches do you guys use? 6000rpm clutch drops under boost in a 5000lb truck has me worried. It also has me thinking.....

 

The funny thing is I have not even tryed to launch the truck yet. I still have a one leger in it. I have the posi sitting in my garage and just ordered the MT Drag radio's yesterday. I am trying to get it ready for the track. I will let you know the results. I am really interested in this topic. I thought that boost off the line would be instant tire smoke, do to the fact that the truck is so light in the back. Very interesting.

 

I have never launced my truck more than 3k. I ran a centerforce dual friction on my old Nova and had over 100 6k + launches and 20k miles until the disc started to seperate. I was pushing around 500whp and 3400lbs. I then went to a Mcleod soft-loc fully adjustable unit that I had $1400 in. You will most likely have to go to a full metalic disc to handle that kind of abuse. They can be a little jerky on the road though.