Best final drive for 280zxt

[neousmcswim]

My 79' 280zx is getting restored and having l28et installed. I am building the car for Highway driving and sometimes drag/ circuit racing. My question is what is the best final drive ratio to get for what I am building the car for?R200 3.5/ R200 3.7/ R200 3.9. I will later get a quaife LSD installed.

[Zmanco]

I'd suggest you try out http://webspace.webring.com/people/cz/z_design_studio/transmission.html You will be able to see what your max speed is in each gear. Compare that to what you have now.

 

Also, what cam will you be using? If it's stock, probably should go with 3.54. If you upgrade so you can make useful power to 7k, then I'd vote for 3.9.

 

But in the end, it's a personal choice based on how you like to drive and shift. I run a 4.11 and love it, but if you think 5k rpm is a lot of revs, then go with the lower (3.54) diff.

[BRAAP]

There is no right answer to this question. Being a street car and strip car, god only knows where the power band is and how broad it is, vehicle weight, then throw in how much importance fuel mileage is to the driver, drivability around town and on the freeway, (is the driver OK with the engine screaming 3500+ RPM at freeway speed and only 14 MPG?). Will the car run dedicated drag tires at the strip, if so, how tall, etc. Too many variables to determine ideal strip ratio, then throw in personal preferences for drivability and MPG tolerances and there is no realistic answer that someone other than the driver himself could deem "best with the least compromise".

 

My suggestion is, once the car is built, drive it around with the diff it currently has for a few months. Get familiar with the car and its demeanor. Then run it at the strip. Depending on how well the car launches and the what RPM the engine is at in relation to its power band and what gear your in through the traps will help point you in a direction of a more desirable final drive ratio for running at the strip. Keeping in mind how that change may also affect the cars demeanor around town and on the freeway as well.

 

This is a good example of why we have rule #4, which everyone read before they clicked the "I Agree” button, right?!

 

4. There is no Best! No best tires. No best engine. No best diff ratio. No best shock. No best big chrome foot gas pedal. Every car builder and driver is in a different situation. What's good for one might suck for another. The decision on what is "best" for you and your car is completely up to you. As with any decision time' date=' effort, and research is needed by the decision maker - you! Instead of asking what is "best", do some research, explain your situation in excruciating detail, and describe what alternatives you're considering in your decision. Posting a thread with "What's the best..." in the title it is a sure way to get that post tossed into the Tool Shed.

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[neousmcswim]

thanks for the help, I think you guys said it best. Wait and feel the car out as I build it. Put what feels best for me. I am going to start off with 3.54 R200.

[frank280zx]

Eurospec ZX's came with a diff cooled 3.3 this due to the higher speeds than the '55' they had in the states.

So to be hounest id would go with a 3.3 not the 3.54, from my experiance it still is to rev happy at 70 mph orso .

[BleachZee]

If you're upping the power a bit and you want good rpms cruising on the highway I think you'll be happy with the 3.54

 

Even my stock turbo 280ZX feels pretty good with that gearing.

[randy 77zt]

3.54 or 3.7-turbo engines work better with a load to pull against.82-83 na zxt trans had best 5th gear ratio for freeway.i use 1 behind a turbo engine.i like the way the na trans shifts better than a t5.i dont think the turbo t5 trans is that big of a deal.

[neousmcswim]

I have heard the T5 is alittle notchy. I have read around that the 81-83' NA have the best gearing for my setup. I am going to stick with the 3.54 and I am going to keep with the stock L28ET with JWT ecu until I get bored.

[BleachZee]

The T5 is notchy. Its an ok transmission and I use it because its already in my car. A shortened Mustang shifter is my preference and I bought a 2008 Mustang shift knob.

 

http://www.bleachgarage.com/images/z/silverz57.jpg

 

The non-turbo transmission you mentioned has the tallest 5th gear. Only slightly taller than the T5. It'll be some nice low rpm cruising but not too low.

[Ineptitude01]

I don't wanna turn this into another T-5 versus Nissan 5sp thread, but I ended up putting my T-5 in my NA 280ZX, and with the 3.7 diff, the spread felt just perfect. It put me right in the powerband for pulling up my local twisties hard.

 

In my Turbo, the T-5 and the 3.54 feels a little too high for my tastes. I end up lugging up hills in second that the NA would happily climb.

 

All things considered, I'd base the differential off the way you intend to drive the car. The 3.54 in my Turbo works for me, but I feel like I would have been happier if it was a 3.7, just for climbing up and down twisty mountain roads.