Question on Final Drive Gear
 

I know it is a tranny question but geared (no pun intented) toward FI applications.

I read a couple of older threads on using the final from the AT on the MT cars, which would make the gears longer and might lose some accel but would be able to be longer in boost on a given gear specially 1st and 2nd which are almost useless now.

I was wandering if any more have gone that route and what they think, I know Skidazzle did it and liked not having to shift into 5th at the drag strip but I was also wandering how it affected regular driving. I ask as I have an opportunity to swap with someone locally that would be a cost savings if it is worth doing.

a question on top of his question...under regular driving would it make gas mileage better on the highway, because of the higher speed for a given rpm?

I would think you would get better MPG . You run at a lower rpm . I expect to get lower MPG , as I went the other way . I put in a 3.5 LSD from a 6MT into my AT5

you'd get better mpg and a higher top speed assuming you'd overcome air resisitance. I don't have much need to go 180mph though so to each his own

It is not about going 180, although it would be nice, but about getting a better 1st and 2nd gear with the boost.

westpak,

I have done it and it is great. You will be surprised by the length of 1st and 2nd for sure. Plus you actually accelerate faster WITH the AT gears. My 0-60 was around 5.4 and I had to shift into 3rd. It is now 4.8 and 2nd gear is good to about 65mph.

You will lose some HP and TQ on the dyno, but the car feels and drives better, which is more important to me. I would definitely recommend the swap.

Great, that is what I was looking for. Thanks.

I'm looking to do the same thing . . . can I merely buy the AT gearing from a vendor or do I have to find someone who's willing to trade?

I'm looking forward to this since like westpak said, 1st & 2nd are virtually useless with FI . . . its not about your whp or tq numbers, its all about the time slips and streetability ;)

G

rear diff for FI
 

3.3 rear diff on 6MT is a def improvement for TT setups and less so with SCs , but still an improvement IMO.

I think it is easier to change the whole pumpkin as the call it, one option is to trade with someone or find one at a junk yard.

I am looking to have it similar to the 300ZX 5MT, 1st and second are so nice you can go to 70 on 2nd, much better than the 350Z on FI.

diff swaps
 

Basically :
- the OEM_6MT diffs benefit the FI_ATs
and
- the OEM_AT diffs benefit the FI_6MTs

maybe a dff swapping interest thread is in order?

btw my 3.5 final drive is still for sale for $350 only has 6500 miles on it

How does the swap affect our speedo? Any other benefits / trade offs?

G

No effect on speedo.

On the 6MT with the 5AT dif I would think you lose some low end accel but you have longer gears so you are able go longer and get more speed, get better use of 1st and 2nd specially.

So are the sizes like so?
5AT have 3.3
6MT have 3.5
and the EVO is 3.9

Now I have already gone with the 6MT(I have my stock 5AT final drive gear which I'm willing to sell for cheap).
Would I have any benifit going with the EVO 3.9 final drive? Or will I just have more traction issues?
The 6MT lowered my 1/4 mile speeds.Will the EVO make me able to switch into 4 earliesr to get my speeds up?

Out of curiosity, how much for the 5AT final drive gear? I was really looking for a rear end swap, but if its cheap, I may consider it ;)

G

I dont know, $100 + shipping
I had to switch to 6MT to make the KAAZ lsd fit.Are you sure the final drive will fit on yours?

Hmmm . . . I don't know. Anyone have an idea of whether his 5AT (G35C) will fit in my 350Z?

Well I am taking the plunge and swapping with someone down here this week, I sure hope I like it.

well if someone has a 3.5 they want to trade me i would be willing to do a swap....i suppose...but it might be awhile hopefully someone local or semi local would want to do this...

Ben Y