40flash

I have just installed the ultimate semi-affordable Diff for a VQ or V8 conversion (in my opinion). It turned out to be much easier than I expected.
The gears that work for street driving with a turbo four are too low (high numerically) for a V8 or the VQ.
I am in the middle of an S14 VQ swap. My goal for the diff was two fold.
I wanted the 3.538 gear ratio that is found in the stock 350z diff. I also wanted a Helical diff. Here is how I achieved the goal.
I started with the pumpkin out of a 1996 Infiniti Q45. If you'd rather have the 3.7 ratio then start with the 97-01 Q45 which comes with the 3.7
Next step was to buy an S15 helical diff off Ebay. Be sure you get the output shafts with it. You will need them and it's usually cheaper that way.
Since the Q45 diff comes with the same 3.538 ring & pinion as the 350Z I didn't have to mess with the pinion gear at all which made the helical install very easy. Simply remove the output shafts (I used a rubber hammer) unbolt the old diff, remove the ring gear from it and bolt it onto the helical diff with the ring gear bolts from the Q45. (Use thread locker).
Bolt the helical assemby into the pumpkin being careful to put all the shims back in the same way they came out. Check the back lash to make sure it's within spec. With mine I had just a tiny bit too much slop (backlash). I made a new shim out of a beer can and put it in on the left side to get the ring gear just a few thousands closer to the pinion. That did it and it turned out perfect. Tap in the output shafts, fill with oil and put it in the car
Side benefit is that the Q45 diff comes with a speed sensor that can be useful to make your speedo work because the VQ trans doesnt have a speedo sensor like the stock trans did.
When doing an engine and trans swap you will need a new driveshaft. I would recomend Doing the rear end swap before making the driveshaft as the Q45 diff is a long nose diff which is about a half inch longer than the stock R200 diff and it uses a larger input flange.
This is a much easier swap than fabricating a 350Z into a 240sx and you end up with a helical diff instead of a Viscous diff with the same gear ratio. Hope this helps someone. John

g6civcx

I appreciate your efforts. Please don't take my comments the wrong way. I just want to clarify for the people.

This portion is a little confusing.

So you take a 96 Q45 R200 which has 3.538. This is the same as the Z33 diff. So basically we can ignore all the references to the Z33 since it's not relevant.

This statement is not accurate. The long nose diff is considerably longer than the short nose. It's more 1/2". Look at the Z31 R200 and you'll see.

The length difference in the Q45 is due to te sensor sticking out at the front. The Q45 is still considered a short nose.

There isn't any fabrication of the Z33 that you wouldn't have to do on the Q45.

40flash

No offence taken. We are all trying to get to the truth here. You have enlightened me on the length issue. I assumed it would be considered a long nose because it is longer than the S13 & S14 diff but apparently there are even longer ones.
I do disagree with your conclussions on the Q45 and Z33 being the same. The gears are the same but it is my opinion that the cases are different. I recently read an article (don't remember if it was here or on Nico) on installing a Z33 diff into an S14. It took considerable modification and welding to the subframe because the front mounting ears are in a different position whereas the Q45 housing is a bolt in with zero mods except to the driveshaft because of the length and larger input flange. If you take a minute to search for the Z33 to S14 install how to it will be clearer. If I can find it again, I will add a link to it. Thanks for your input.

40flash

The reason I originally mentioned the 350Z is because I am installing a 350Z engine in my S14 and wanted the same diff ratio that comes in the 350Z. The Q45 uses the same gears but will bolt into the S14 unlike the Z33 diff that takes a bunch of fabrication. I found the web site that explains the 350Z to S14 differential swap. This should clear things up I hope. The end result with the Q45 diff is you get the desired ratio in a housing that bolts in.
Copy and paste this into your browserand check this out.
350z Differential Install into a 240sx Dennis Mertzanis

Acreus

Im working on doing the same exact swap. Vq35hr into s14. This was very helpful. thank you

40flash

The car is now running and is my daily driver. with the low profile 17s on the car, I'm finding that the 3.54 gears are too low. The car is 500 lbs lighter than a Z and there is a bunch of torque. The end result is that 1st gear is too low. Barely get started and have to shift. Much of the time unless I'm starting on an up hill incline I start in 2nd gear, shift to 4th and them 6th. Also, at cruising speeds I'm turning a lot more RPM than I'd like. 3,000 RPM at just under 80 MPH. Much of the time using it as a 3 spd. I'm looking into alternative to raise the final ratio.
The 2 possibilities I'm looking at are the 350Z automatic diff that came with 3.35 gears, (I'd have to do the fab work to make it fit into the car since The ring & pinnion won't fit into my Q45 housing.
The 2nd option is the r200 diff from a 2005 to 2008 pathfinder which came with a 3.13 ratio.
I believe I can install my S15 helical diff in either of these options.

daily missile

this is what i was gonna say. my friend has the pinion and stuff out of a pathfinder. i sent him link to this incase you want to buy it

__________________

roadbuster

Got any pics of this setup? TIA

40flash

Update. Although my Q45 diff, the z33 and Pathfinder diffs are all R200s, the z33 and pathfinder diffs are wider than the Q45 diff which my Helical fit in perfectly. The problem then is that my S15 Helical is 3/4 of an inch narrower than the z33 diff and the bearings have nothing to support them and it can't be bolted into the Z33 diff housing without serious modification.
So, a diff that is designed for a narrow case will not bolt into a wide case. I'm thinking I will sell the Q45 diff with the Helical S15 limited slip with 3.538 gear ratio installed and ready to go. It is a bolt-in for the S14 subframe. Your stock axles will work. You just need to shorten or change the driveshaft which you need to do anyway if you are doing the VQ or V8 swap.

Black R

Sub'd for future reference.

__________________
S13 XE coupe: Aristo GTE, R154, GT37, Defsport Wilwood kit, KTS coilovers

NismoSilvia270R

for my ls1/t56 swap i used:
s14 housing and bearings/seals
s13 cover
s15 hlsd
s15 3.69 gears (same p/n for q45)

the for drifting it's an excellent ratio pairing with the 6spd trans.
i don't do much else with the car, but i imagine the 3.54 would be nicer for racing.

4.08 rear gears will make all of the t56 gears overlap power bands.
ie. shift at top of 3rd and you're in the top of 4th, as opposed to mid 4th.
3.69 do a better job at spreading this, but still overlap.

Ghostdrifter

All you have to do is use the pathfinder ring gear, not the whole diff.

__________________

jr_ss

You also need the pinion gear. Ring and pinions are mated pairs when they are manufactured. They are not mention to be mismatched.

If you want lower gearing, pull the S15 or the JDM S14 R&P, they are both 3.6xx.

__________________
My SR20VET