LT1/6spd swaps, rear gear ratio's?

[Guest JAMIE T]

Hey guys! I've got a wild hair up my a$$ again and want to put the motor and trans out of my Z28 in my '73. The specs are '94 LT1, ported and polished heads, HOT cam kit, elec. H2O pump, and loads of various bolt-ons that may or may not effect the 240Z swap. It has a SPEC clutch and aluminum flywheel. The car dynoed 340 RWHP(about the same torque) with bone stock ECU tuning. This thing revs incredibly quick and smooth. The thing I'm worried about is the gear selection for R200's. Mike Kelly had a T56 in his white car(with 500hp 383). and said it was a pig in 6th with 3.70's. I know that with my cammed LT1 I like to cruise in 5th most of the time with 3.42 gears. I'm not sure what to expect with the MUCH lighter weight 240Z(compared to the Z28) and gear ratio's. We have a couple of options for ratio's like 3.54, 3.70, and 3.90's. 1st goes by pretty quick with the aluminum flywheel(and spinning tires) in the Z28, I can only imaginehow it will be in the 240Z. What are you guys running for gears? 1/4 mile times? trap speeds? horsepower/torque? Thanks.

[80LS1T]

Well my engine is basically the same as your, minus the alluminum flywheel. I am running a 93' T56 with the .62:1 6th and a 3.54 open rear end in my 80' ZX. My car was not running the best due to a wiring problem with the IAC motor but when it was running good 6th was actually useful at like 65mph. I think a 3.70 or 3.90 would be a better choise but then you lose 1st because all it will be good for is pulling houses off their foundation or pulling stumps! LOL Well maybe not that bad but 1st gear for me is still worth shifting through. You also have to take into account that my car is a "little bit" heavier than a 240Z.

 

 

Guy

[SBC_400]

I would not even wory about how the car will pull in 6th. 6th is basicaly just an over drive gear any way. it is there for good highway fuel economy. My brothers 2001 ss has 3.42 gears and he only uses 6th when his is cruising. but 1800 rpms at like 75-80 mph is how you get 25 mpg out of a 330 hp ls1.

 

just my two cents.

[Mikelly]

Couple of things to remember with my setup on the Z...

 

I have a pretty high lift cam for the T56, and my car was never optimally tuned. The carb I was using had issues with the motor and 6th was useless below 2000RPMs... Others have NOT experienced that.

 

In the Corvette I'm running 3:42s and I can pull 1200 rpms with NO PROBLEM at all in 6th gear. That is how to knock down 28mpg. I think Jamie's setup would be fine in the Z, and I'd run as steep a gear you can find Jamie!

 

Mike

[Dan Juday]

Steve C.'s Tomahawk has the 3.54 rear gears, open diff with a bone stock '95 f-body LT1/T56. 65mph requires 1400rpms in 6th. Drop the loud pedel and it walks smartly to 90. It doesn't jump, but drop it down into 5th and it will.

 

First gear is short enough with the 3.54's, go any lower and I think it would soon become useless. Good for nothing else but converting solids into gases.

 

JMHO

[Phantom]

Which T56? Do yo have the .50 overdrive 6th or the .62? I'm assuming it's the .50? The .62 would be better then you could go with 3.54 or 3.36 gears and still have a functional 6th.

I have the .50 6th in my LS1/T56 3.70:1 R200 280Z.

Observations:

In 6th 60mph=1,500 rpm, cruises great, pulls ok, 5th is just a flick of the wrist away but 4th is even better.

1st is only really needed if you are drag racing. I made a pont with a guy today and started the car, going UP a slight incline in 4th. The LS1 has gobs of torque and the 280Z weighs about 3,300 lbs WITH 2 passengers.

If you're drag racing you'll need some seriously sticky tires or they will be overwhelmed. You can do it with width (275 or better) or with soft compound. My 225/50-16 Yokohama S306's are pathetic. Best I can mange so far is a 2.0 60'.