I'm looking into buying a pumpkin that has central 20 3.917's installed in it. I really want 4.08's but I've found the 3.917's already installed in a pumpkin and that makes it so much easier for I don't have to get the gears installed etc... I've searched around and most say go with the 4.08's and I want too but then I found a pumpkin with a 3.917 already installed in it.

With that said, are the 3.917's pretty close to the 4.08's? Or would I be wishing I had tried to find a 4.08 pumpkin instead?

I know on paper they are only like what 4% different or what not but I also had a 3.3 rear end in the manual 6 speed 350Z (HR model) for a bit and when I put the 3.538's back in I noticed a pretty big difference for a 6% change. I know the 3.90's will be a pretty good jump from the 3.538's but just don't know. I really want the 4.08's for I wanted 2nd gear to be stronger for autox'ing.

If anybody has any experience they can chime in with that would be great!

Thanks!

Ted

 

save your money or spend it on a proper LSD if you don't already have one.

 

I know what you are saying, had a Cusco RS before but this time around planning on going with a Quaife and 3.9's or 4.08's.

 

is it a DD or weekend play car? then go from there.

 

I have two differentials pumpkin and everything both are loaded with Quaife LSD. One has 4.083 final drive gears and the other has the 3.53 final drive. I took off my 4.08 diff and put on my 3.53 diff. Reason for that is that I am changing my final drive from 4.08 to 3.916 final drive. Just so people get an idea of the difference, with the 4.08s at the track I hit a 13.03 at 105 mph and with the 3.53s I hit a 13.056 at 94.6 mph. <--- WTH

 

^gimme 60ft, reaction time, tire pressure, tires, mods, temp etc. could be alot of factors factoring in to that 10mph difference

 

On the 13.03 at 105 I was running 4.08s, 27x10.5x15 M/T ET Street semi slicks @ 15psi 60ft 1.78 passed in 4th gear. The 13.056 was with 3.53s, 26x11.5x15 M/T ET Streets Drag Radials @ 14psi 60ft 1.908 passed at the top of 3rd.

 

Kind of both... not the main DD but my brother and I do take it to work 'sometimes' but not that often. But mostly a weekend play car.

 

Why are you switching to 3.9's from that of 4.08? Cause you want to reduce the amount of times you shift in the 1/4 by chance? (just guessing, maybe way off)

 

There is a guy on here that ran a 12.5 @ 110 natually aspirated, and he's running 3.9 final drive. So maybe that's all I need. I have to beat that time.

 

Is he below sea level? j/k

 

I think he's from NY/NJ.

 

Andre did set the bar pretty high huh. Keep in mind, he didn't fully mod his car either. I think he only had TP, clutch, and maybe an exhaust with tune? But, he was also running full slicks and skinnies up front with the 3.9 gears to get that time.

I think with 4.08 and more mods, plus slicks/skinnies you should be able to do it.

 

I have some 3.917's in a complete pumpkin on the way so soon will find out what I think of them! :-)

 

DA does make a difference so that is a valid question.

 

Was your HR Boosted? If not why the hell would you put a 3.3FD in an NA car lol! Only cars with 500+whp will benefit from taller gearing you are looking at it the wrong way.

The 3.9 on an HR IMO would be perfect. You dont need any more or less gear for a well rounded NA car. 3.9 IMO is too short for DE's with only 6600rpms but on an HR spinning to 7500rpms its where its at.

 

Nope, not boosted, all stock. The reason, when I bought the Cusco RS pumpkin I was told it was a 3.538 rear but when it showed up it was a 3.357. I was pissed but mistakes happen and wanted to see what the Cusco RS was like still so tried it out. It's now in a boosted 350Z so it has a nice new home.


I have read some talk about the 4.08's being really good for the HR but I found a good deal on a used carrier with 3.917's in it that are suppose to be quiet so I went with that. Figured it's close enough to the 4.08's and should make the car more fun.

Thanks for all the responses guys!

 

His DA was around -1300 when he ran that time. TX will never see DA's that low.

MM what was your DA when you ran those times?

 

I believe it was -626. It was a pretty cold night. car ran like a champ.

 

- Numbers are always nice. Tracks in CA are all well above that figure lol.