Iv'e been wanting to get a set of 3.7 gears installed in my 04.5 5at coupe and was wondering where i could get the gears from and how hard it would be to have them installed. Also what gears would be better for a 5at 3.7's or 3.9's?

 

3.7's would probably be as far as you should go on a 5at.

 

I got mine from Performance Nissan... West Covina Nissan has 'em too...

 

Why you say that ???

 

I'm not trying to speak for him, but AT can’t take advantage of than short of gear like the MT can... besides, the 3.692 (3.7) FD is an OEM Nissan ring & pinion so it's cheaper than the after market 3.9

 

You're going to have some trouble with that... The AT has a 3.35 FD with an open diff. If you want to switch, you have to change both the diff and the FD. I'm having my Quaife diff installed on Monday. In order to do that, I have to switch my FD to the one used by a 6mt. Since there is no 3.35, I have to go up to 3.5. I think you'll find that 3.7 is a pretty big jump.

 

cheapest option is to get a 3.5 off a 6MT with a VLSD...

you can get one at a junk yard or they pop up on the forums now and again...

next step from there if it is not enough for you, then upgrade to 3.7 gearing...

 

I have 3.7 and Quaife... it's great... btw way, check some of helldorados posts - there are alternatives to going shorter gears in order to use Quaife... I won’t go into them unless asked because I feel as long as the diff is being replaced it's a good idea to go shorter gears... the 3.7 was actually a much better bang for the buck than the diff (IMO) I wouldn't even suggest doing Quaife and keeping the 3.3 (but it can be done).

Also, I don't know if your post implies that you can't use shorter gears with open diff... but if so, I don't know why not?

 

The problem is just getting parts that will fit. The pinion on the 3.35 is thicker so the diff doesn't extend as far forward. You can't just change the 3.35 to 3.5 (or up) because the 3.5, 3.7 and 3.9 are all made for the MT and require the longer AT diff. If you are willing to switch out the diff, then anything goes.

 

Keep in mind that you may loose cruise control. Some 5ATs loose it and some don't. There doesn't seem to be much rhyme or reason to it. I think OCG35 still has use of his. At the strip, I've run 24" drag radials which technically drop the effective rear gear ratio to a 3.55 or so. On the same day, my stock sizes tires (~26") resulted in quicker ETs and faster MPHs by about .15 seconds and nearly 2mph. It turns out that the 3.55 gear ratio forced an early 4th gear shift about 150' short of the finish line. That shift into 4th killed acceleration. Now running 3.7 gear like OCG35 has may allow you to cross the finish through the heart of the powerband in 4th gear (5200rpms or so). I haven't done the calculations to see if this hold true. Maybe you can get OC to post his before and after runs with the gears. I think he goes to the track fairly often.

 

happy to report CC remained! I was a little weary of that because not many AT had done the 3.7 when I did... I do believe several have lost CC when going to 3.9... haven’t run 1/4 mile yet - will Dec 1st (and looking forward to it!)... I ran 1/8 with the 3.7 and blew past the turn out to see if I could 1/4 in 3rd (undetermined)... however my ET was substantially better than the norm!

Dec 1st will be a tell all for me... for those that care, results will be posted in So Cal Regional Under "Meetings and Events then = 1/4 Drag Racing.

BTW - Rev Limiter has been bumped so pushing in order not to shift is an option that untuned won't have... If anyone decides to do FD gear swap, it will be a kick in the pants street driven, but without rev limiter bumped you might suffer on the track - keep it in perspective.