Heard someone mention this at a recent meet...

Has anyone who has gone the boost route swapped an automatic 350Z differential for their 6M differential? I believe the thought process is that gearing of the auto rear end will grant you more range to rev the gears.

Bottomline, you sacrifice a marginal bit of gearing acceleration in favor of not having to shift as quickly. In my case, I'm also hoping it will help to cut down my excessive wheel spin.

Is this possible? And if so, anyone know where I can get an automatic differential to try it out? I don't want to swap with someone, I'd prefer to get the differential off a wrecked auto in case I decide to switch it back.

 

My only concern would probably be the driveshaft input shaft to the differential. You would have to compare the 2 to make sure they are the same. It might be different between the auto and 6mt. You might be able to swap the pinion and ring gear from the auto....there had been talk about that on other forums. This would give you the final gear ratio you are talking about.

 

Good point! I'll need to find someone with an auto to run some comparisons... driveshaft length, see if differential housing is the same, etc.

Provided it can be done, that still leaves me with where to look for an auto 350Z differential. any thoughts?

 

I would think the case would be the same but the input shaft spline size/shaft diameter might be different. They will most likely have different lengths of drive shafts too because the auto and manual trannies are different lengths. The guts are what I think you will need...pinion and ring gear. There are a few auto wreckers where you could probably get a whole rear diff assembly if needed.

 

i have done this swap already. i swapped the pumpkin from a 350 5AT into my 6MT. its plug and play between the auto and manual final drives. the swap took about 1.5hours, changing out diff fluid also.

for some reference, i now go 84mph instead of 80 @ 3K RPM in 6th.

i did the swap so i dont have to shift to fifth in the 1/4mi. combining this swap with the TS ECU flash, and I can now get to 125 at the top of 4th. (i think stock 6MT goes to 116MPH or so). theoretically, if i had enough power to overcome wind resistance, the gearing on the car would now let me go over 200MPH topping out 6th at redline (7100rpm).

when looking for a 5AT final drive, if it is from a Z, it will have the stock viscous LSD in it. if from a G35c, its harder to tell without opening the pumpkin.

i got mine from z1 auto in georgia: http://www.nissanzparts.net/index.htm

oh yeah... i have plenty of power also, so the loss of acceleration was not a huge deal to me.


hth,
michael

 

So you picked up some MPH per gear with the rear swap from a 5AT into your 6MT?

That sounds like a soultion to one of my other quandries... How to get more MPH out of the gears. I don't know alot about transmissions so I won't even guess at the gear ratio numbers or what they mean. But swapping out the rear "pumpkin" is a quick easy job that even I could do on my garage floor!

What is your MPH top out in 1st and 2nd gear, SKiDaZZLe?

 

Thanks, SKi! I'm guessing from your post that there is no noticeable change for you in acceleration.

It sounds like you are getting the very benefit I am looking for... not having to shift as quite as quickly to achieve the same speed.

Time to start looking for an Auto differential... if you don't mind me asking, how much did they charge you for yours?

 

i'm might be swapping mine with an AUTO g35. I need the extra gearing, plus right now, 1st and 2nd gear is useless.

 

FLY BY Z was trying to do this a while back in anticipation of FI. He was trying to defer possible suture FI people away from a final drive solution. I havn't seen him post on here in a while, but you might want to PM him. I think he will have the info you need.

 

I wonder how long it will be before someone makes a kit to drop a Ford 9" rearend center section into this car. Bulletproof and a WIDE selection of gears.

 

I wonder if an auto guys would like shorter gears to help with acceleration?

Any autos interested??? I'll pay for labor!

 

Man, I would like the change too, but I thought it would give more than 4 mph in 6th. Guess that is like a 300 rpm drop, which is OK I guess, but more would be better.

 

Think of it no your top gears... but 2nd and 3rd...

What did Skidazzle say in 4th?? 125????

That's a 15mph increase with both the rear-end of the rev limit increased!

 

i know JimH went the other way (swapped auto pumkin for manual pumkin). you might want to contact him to see if he still has his old one. otherwise, i think it might be a good idea to do a swap thing with someone who has an auto and wants a little more acceleration. that way, you both win.