FGY33 4.08 differential swap project: A SUCCESS!

[97Q45t]

Ladies and gentlemen!

I'd like to present you the first FGY33 with a Z32 NA 4.08 differential!



For a while back I've been searching for the answer to improve the acceleration of the "not so fast" FGY33. To make a long story short: I DID it!

I just finished the installation tonight. I haven't test drive the car yet but since I put the shift in D the car didn't go backward I figured the job was 99% done. I will have a write up sometimes next week on my FGY33 website if someone is interested. Well, gotta go take a test drive now to see how my $75 diff performs . Good night, guys!

Duy

[5zigen]

Looks great man, how long did installation take?...

Also I must add... you have to add more stuff onto your website! I frequent that website to check if theres any updates.

[jamesmost]

thee you go cant wait to hear your results

[450zxtt]

good job...-450zxtt

[Jesda]

Awesome! The Y33 seriously needs more affordable performance mods. Cant wait to see how it improves acceleration.

[squeefoo]

Very, very, very cool.

[AZhitman]

SCORE!!!

Good work man! I LOOOOOOOVE my 4.08.

Shoulda had that from the factory.

[FarFetched]

AWESOME man, you are an inspiration for me!I've been thinking of gear swap on my Old Lady!Where did you score this diff?

[Radioaktiv]

im very curious to know the results

[DominickJ30]

Does the N/A Z32 have the same size gear as the J30?

[97Q45t]

Thank you ALL for the compliments!

5zigen: The installation (including prep and clean-up) took me 7 hours. With proper prep and tools available in advance, installation time could be much less.

FarFetched: I bought the differential on eBay for $75 + $50 shipping.I sanded and repainted the diff case with highheat paint to make it looks better.

DominickJ30: I believe that J30 diff has 3.916 gearing vs 4.08 for N/A Z32 diff.

Update on the project: The car's acceleration at stop lights is now comparable to my girlfriend's '01 Acura 3.2CL. The 3.2CL's 0-60 time is 6.9s - 7.0s. Unfortunately, my G-tech meter broke a few weeks ago so I don't have the exact 0-60 and 1/4-mile numbers before and after the swap. The car DEFINITELY pulled harder, especially above 3000 RPM.

So far everything is fine. I haven't test the TCS and ABS yet to see if they're still functioning but I have no reason to believe that they won't. The speedometer is off by 10%. It doesn't bother me for now but that might be my mid-summer project.

Stay tune for more updates!

[FarFetched]

Have you inspected gears (opened diff) for possible damage?That would be sweet to find one like that. I don't care if speedo 10% off. Speedo in my Jeep was ~10% off. I lived with it for 6 years till I sold it. Not a big deal. Accel from dead stop woul be a huge improvement over stock gearing. What's N/A Z32 diff (interpretation), is it from ZX300?Thanks!

[jamesmost]

N/A Z32 is A Naturally Aspirated (non-turbo) 90 - 96 300zx

What prep work did u do ?

[97Q45t]

Yep, it's a sweet deal I got the diff for $75. Local junkyards wanted $300 for the diff when I surfed around. In the uncertainty of the fitment in this experiment, $300 was alot of money to waste if it is unsucessful so I spent some extra time to look on eBay for a better deal. Even at $300 for the Z32 diff it is still an awesome mod for the money because the G50 guys had to pay more than $1000 for the same mod. My friend had to pay $1500 for the Rod Millen Torsen diff (identical to a Supra diff) on his GS400.

The diff that I got was in good working oder. The diff I got had VLSD (yellow/orange sticker on the cover with the word "VLSD"). I believe that all Z32 300ZX differentials have VLSD but please don't quote me on this. A little trick but really important is to check if the diff has an 4.08 gear ratio by counting the number of revolutions needed by the driveshaft flange to make the side flanges to turn 1 complete revolution. I checked mine and the driveshaft flange needed a little more than 4 revolutions so I knew I got the right diff.

The preps that I discussed was basicly sanding and painting the old and rusted differential case, driving the rear of the car up the ramps, setting up additional safety. It is a good idea to drain the old diff oil, open the cover and spray the internal with WD-40 to clean, and to refill the oil if you don't have access to a pump. I didn't do all that because my major concern was the fitment so I was trying to hurry up and put the diff on.

[Q45tech]

10% more gear multiplied engine torque [3.69>4.083] ~~ 20-22 Rear Tire lb/ft. Should reduce quarter by 0.2-0.3 seconds [2 car lengths]. Again the ugly non optimized [for quarter] transmission gear ratio spread ------- rears its head.

You might find some more with a loud exhaust.Use some synthetic fluid to overcome the low speed differential stickson [at low speeds under 10 mph diffs have greatest friction loss......to get the fluid moving from a stop]

[rsiwicki]

very nice mod indeed....but I was under the impression that the Z32 output flanges/half shafts were of a different bolt pattern and that is why the mod would not on a G50 4.08 conversion. Is the Y33 differential different than the G50? Yours looks exactly the same as mine with the traction control sensors and all. Do you know what year the Z32 diff came from? I heard that after 92? they switched the output flanges to s 3-2 type of bolt pattern. The 2 different Z32 4.08 diffs that I have seen pics of had a different output half shaft bolt pattern and also a different input shaft bolt pattern. Any information is definitely appreciated as now I don't understand why the Z32 looks exactly my my G50 differential.

[97Q45t]

Dennis, thanks for the recommendation! I originally filled the diff with 85W-140, feared that summer temp in Texas might reach above 100 degF. Would synthetic 80W-90 go beyond the 104 degF protection provided by conventional 80W-90? I will drain the diff and fill it up with synthetic 80W-90, hope to see the car gets off the line a little faster.

According to my rough calculations, D3->D4 shift now occurs at 103-108 MPH (about 10 MPH above the 1/4-mile-speed I think). It is still not optimized for 1/4-mile but way better than stock speed at 114-120 MPH. Again, D2->D3 shift now is at 65-72 MPH compare to stock speed at 72-80 MPH.

An 4.36 gear ratio would perfect the FGY33 for 0-60 and 1/4 times since D2->D3 shift will be at 61-65 MPH and D3->D4 shift will be at 94-99 MPH (94 MPH is a little low but hopefully the shift occurs close to 99 MPH).

Rob, the half shafts patterns are the same on the Y33 and Z32 N/A. The drive shaft (propeller shaft) flange on the Y33 is larger the than Z32's, so I swapped them. The differential cases are identical on both with the same numbers on top: 38311-43M00; I didn't check the number on the bottom of the Y33 diff but the bottom of the Z32 diff has: 275, KN5, 71. The Z32 diff I got is from an 1991 2 seater t-tops 5 speed. I never seen a G50 differential so I can't comment on their similarities. If you have some pictures of the G50 diff I will try to see if they're the same.

I don't know about the haft shafts difference among Z32 4.08 but I've seen them with different types of cover plates (some had fins and some were just plain like the Y33 diff). If the G50 differential case is identical to the Z32 4.08 then there's a really big fat chance that they are interchangeable no matter if the output flanges patterns are different; all you need to do is swapping the flanges.

[sijoko]

This is great news for the Y33 guys, but this mod won't work with the G50 because of the difference in stub axles and internals. The G50 has a 6 bolt flange.

I bought a J30 diff from a junkyard a long time ago. It looks identical to the one on my 94 Q except for the flanges (5 bolt vs. 6 bolt).

I thought to myself, " Man, this is great. All I have to do is swap out the stub axles."

Well, to make a long story short: The stub axles are not interchangeable. Why? Because the the differential in the G50 (90-96) has thicker axles.

Nissan gave the R200v diff in the G50 stronger internals. I guess in the Y33 they didn't go the same route because it is a lighter car with less torque output.

-sijoko

[rsiwicki]

ahh...thanks for the info. I now remember why the Z32 will not just bolt into the G50. We have 6 bolt half shafts and it looks like you have a 5 bolt half shaft pattern. I did not know that the Y33 only had a 5 bolt half shaft. Thanks for the idea of swaping half shafts, but from what I have heard....that swap in not as easy as it sounds or it is such a pain in the a$$ to do that it more cost effective to have a new spacer custom made so that the original G50 diff can hold a 4.08 gear.

Glad to hear you like your new found performance mod. I have the installed the yellow box that Q45tech recommended in future hopes of getting a 4.08 eventually re-installed. It works perfectly and installation was very easy...cost was $100, but if and when I get another 4.08 installed at least my speedo will be correct. The car seemed to act a little funny with the speedo not reading correctly, but I only had a 4.08 in my car for less than 10 days so I really can't say one way or the other.

http://www.blackrobotics.com/yb_home.htm

[FarFetched]

I've found a nice write up for 240SX, it shows some insight on R200V differential!Now I am looking for on for my Old Lady!Quote »Thanks to 97Q45t I am now on a new quest for perfection![/quote]I thought I will not be spending on performance mods - Yeah right I won't as much as I spent on my Jeep - definitely more

[Falkdesigns]

That is awesome Duy!!!! What a find you made, and got yourself. Something for me to add to my list of mods I still want to do.

Did you install your springs yet? I'm in the process of sourcing the KYB New SR Specials I have on my Q and should have set pricing on them soon. A cheaper alternative to OE shocks/struts and a performance gas shock made by the OE mfg designed to work with lowered springs.

[97Q45t]

Thanks Kevin,I haven't install the Tein springs yet. I was trying to focus on the differential swap project first, plus the idea of reusing the "not so old but factory spec inserts and struts" doesn't make me feel good. I think I'll just wait for a while for the SR Special from you.

[3Q Jay]

great job, Duy--and an awesome discovery, too! i bet you have to modulate the gas just a bit to maintian traction with TCS off!

Now, Rob alluded to a custom spacer---is the carrier not the same on G50 vs.FY33 [half shaft bolt pattern difference acknowledged]. I'm wondering if a simple ring and pinion from z32 into g50 is an option?

[3Q Jay]

also, Duy--I use redline 75w-90 in me fy33 diff.

[rsiwicki]

From personal experience and much research *see search results on 4.08*.....building a 4.08 for a G50 is about damn near impossible even by some of the most experienced driveline shops. Yes there is some sort of custom spacer that needs to be made in order to run a 4.08 ring pinion, but there are other tricks that I am not fully knowledgeable of that need to be completed. I could only wish there was a much more simple less costly solution. If you do get a 4.08.....trust me you will like it a lot.

I have seriously thought about having custom half-shaft adapter plates made to bolt inbetween the Z32 differential half shafts (Z32 differential is more narrower so it would possible work) and the Q half shafts due to different bolt patterns or have custom made half shafts altogether at the proper length to accomodate for a Z32 differential. The cost of the half shaft bolt pattern adapters (from 5 bolt to a 6 bolt pattern) or entire custom make half shafts should not cost more than the pain of trying to get a custom 4.08 built.

The 4.08 would move my 3-4 shift from about 135mph to about 120mph which would probably make for a very quick car that runs 0-120mph.....I need to keep the speeds down as I really enjoy my 3-4 shift as WOT around 135mph because one day the police are going to catch me. Then again....what logic is there in me not going to 135mph still after my 3-4 shift with a 4.08 installed.
Modified by rsiwicki at 10:23 AM 6/1/2005

[elwesso]

I think if you wanted to put the 4.08 in the g50 that is the best option.. HOwever, i discussed this with someone else and we agreed that the 5 bolt ones arent made for as much power... I think if you were staying NA, this would be fine..... However, running FI and the smaller halfshafts would not be ideal IMHO. Then again, with FI you wouldnt need/want the 4.08!

Id like to see someone do the halfshaft to a NA 4.08 and see what it does!

[FarFetched]

For G50 engine you would need TT Z32 diff with bigger ring gear R230V diff to be exact because of more available power at hte wheels!Trust me I have seen blown ring pinions.

[97Q45t]

Article on the swap is about 40% done on http://fgy33.tripod.com, under "Modifications". I will add pictures when my DSL goes back up. Currently surfing the internet through slower-than-dialup T-mobile wireless.

[97Q45t]

A little update on the swap:

After about 150 - 200 miles, there's no problem with the differential so far. In the first 100 miles, it was hardly to tell the difference in accelerations before and after the swap. Now I feel it everytime the car leaves the stop lights.

I did a few WOTs at the stop lights tonight. Ambient temperature was 82 degrees F. With the TCS off, the rear tires were spinning (more like 2 fast chirps). With the TCS on, power transferred to the rear wheels was cut for about 0.5 - 1 second. The car was definitely faster with TCS off. Note that my car has 275/40/18 rear tires. Before the swap, even with stock 205/65/16 (or 215/60/16?) the wheels didn't spin at all at WOT, with TCS off or on.

I haven't had a change to test the ABS yet but since the TCS worked I'd assume the the ABS would work be cause the ABS sensors worked.

Stay tune for mileage update with the 4.083 diff.

Duy

[BadQ45t]

You running a staggered tire setup? Any rubbing with 275's on the back? What size you running up front? I just bought a set of 19x8.5 rims and want to put in the most meat I can on my 97.