Z32 Differential swap time

[BlueC]

Well, after taking my '00 to the track this past weekend, I truly want to swap out the differential now. My times ranged from 10.7 - 10.8 @ 70-71mph (1/8th mile track).

My 60fts were my main problem, best was 2.5 and the worst being 2.6. Its a heavy car, so it needs a shorter final drive to get off the line properly. It really wasnt because of the tires spinning either, quite frankly, i dont think they even spun off the line. All in all, it was still fun racing the Q even though it was slower than expected (my '99 maxima did 10.1 @ 74mph consistantly). Now i have a baseline to compare to.

Now i've found a good handful of Z32 differentials ranging anywheres from $120 shipped to $300 shipped. The problem is installation, I cannot make time to do it myself, so I need to look around for a good shop that would perform a "non-oem" job like this. What would you expect the labor hours to run? My guess so far is around $200-400 (2.5-4hrs).

I've already done a bit of reading up on this swap (I know the main info), but any input would be helpful for my situation.

[BlueC]

I contacted a shop i've used in the past with my old car, they said it'd be 2.1 hrs labor according to their books, and they understand the differential is coming from a different car. The shop manager sounded ok with it, which is what I like to hear.

Anything I should watch out for when shopping around for a used Z32 differential? Specific oil I should use when having the new differential put in (maybe something good for friction and the cold temps around here)?

[FarFetched]

If you want to check my posts about Y33 diff swap (I got diff for 35$) out of 90-91 300ZX. zerothread?id=136080Install time less then 1 hrs. For DIY install 1-2 hrs max. It is the easiest diff swap I've ever done - trust me I've got ~10 yrs of diff repair experience. Also, check 97Q45t web site regarding 4.08 diff swap, I added some very important info when it comes to installation if the diff. Cheers!

[BlueC]

Yea I would do the work myself, but honestly, I would not have the time. Not only that, i'd rather let a shop deal with it incase something were to go wrong with the installation (something breaks not related to the differential in the process).

I actually have a differential from a '90 300ZX on the way, paid around $200 shipped for it, rust free.

Altogether I expect to pay $400-500 total, which in my mind is not that much for a nice improvement in acceleration. Plus im not strapped for cash or anything.

[Q45tech]

The functional equivalent of ~~19-21 lb/ft 10% RW torque more should be interesting saving you 0.2-0.25 secs in the 1/8th.........very soft fast wearing rear tires might do almost the same?

I'm interested in how the 10% higher cruise rpm affects MPG.

[BlueC]

The functional equivalent of ~~19-21 lb/ft 10% RW torque more should be interesting saving you 0.2-0.25 secs in the 1/8th.........very soft fast wearing rear tires might do almost the same?

I'm interested in how the 10% higher cruise rpm affects MPG.

I'm sure even more time could be shaved off. My tires never even spun off the line. Keep in mind, they are 245/45/17 all-season tires, that really do not grip well. My 60ft times like I said were extremely poor, around 2.5-2.6.

With the shorter gear, it will be much quicker off the line, not to mention the midrange will be stronger. I raced a 2003 Lincoln LS (3.9L V8), both him and I were around the same until about 30mph, then he started to crawl away. He kept getting consistant 10.2-10.4, while I never saw anything below 10.7.

With that said, my goal is to hit 10.0 with the new differential, and I think it is EASILY doable. The whole time I knew it was the tall gearing holding back the good ET I wanted. I plan on doing another run right around sept-oct, right after the installation for a direct comparison. Only thing different will be the differential. I did 3 runs last weekend, so with those all being 10.7-10.8, I feel it will be an accurate comparison.

[Q45tech]

Your stock rear torque should be ~~ 220 lb/ft* at tire road interface times gearing, 10% more from new diff gear is 22 lb/ft more = ~ 0.22 seconds in quarter/or 1/8...............you probably cannot finish the quarter in 2nd gear so quarter may not be better due to shift time to 3rd before the lights.

take the cube root of 10% increased gearing [~~2.2%] and decrease 1/8 mile time by this amount 10.7 x 0.978= 10.4646 =~ 10.45 secs.....0.22-----0.25 +- improvement.

Acceleration physics is pretty reliable when small changes [numbers] are involved.

* Dynojet might show a little more due to disparity between Q weight and drum weight and tire friction in direct [3rd gear] however 1/8 will be in 1st and 2nd gear.

If you use a premium synthetic 75-80 weight diff lube you can gain much [maybe 0.1 sec] in launch as the low speed diff friction is high until 10 mph.

Historically you can find the affects of 3.538 > 4.083 on some 94 Q this was a 15.4% increase vs your 10%...........transmission gears are the same for 94-01 Q.

What you really find out is the early Q produced more than rated [published torque] and the 96 and later may have produced a tiny bit less than rating.

I expect that your low 1/8 is primarily from the ethanolized fuel in your AREA, try some real conventional gasoline or racing fuel 100+ octane no lead [no ethanol] high density...........might be worth 0.4 seconds or more.

Current fuel blends are so weak in heat [BTU] that most engines have a very tough time making anywhere close to designed power.

They were designed when with real gasoline in mind. Hard to compare old blends with new lower cost to make versions.

[FarFetched]

During my short but very enjoyable ownership of Y33 I've learned a few things. One of them was Diff swap is the cheapest ever and very practical for city driving. MPG dropped from staedy 18 to about 16-17 40/60 cty/hwy. I've travelled to BC and Alberta on my (Old Lady) after the diff swap (if memory serves me correct) I was getting 21-22 MPG, of course base on 10% difference. Road to Calgary isn't flat at all, and there are(were) no cops so speed (bursts) ranged from steady 60 to 80 MPH. There is difference in MPG of course.

Cheers!

[BlueC]

I expect that your low 1/8 is primarily from the ethanolized fuel in your AREA, try some real conventional gasoline or racing fuel 100+ octane no lead [no ethanol] high density...........might be worth 0.4 seconds or more.

Current fuel blends are so weak in heat [BTU] that most engines have a very tough time making anywhere close to designed power.

They were designed when with real gasoline in mind. Hard to compare old blends with new lower cost to make versions.

I haven't been using any ethanol blended gas. Been paying $0.10/gallon more for pure premium gas per your suggestion and haven't looked back since. So the car is completly free of ethanol by now.

I do want to try racing fuel, I know that would really help the engine run more efficient since the normal gas still is quite weak like you've said. I'll look into it.

MPG is not a concern for me either. I do mostly city driving on a daily basis, but its a short commute for work. I'm willing to spend a little extra on gas to get some more power off the line.

[BlueC]

Here's my other question. What about the Speedometer being off, will that rack up miles quicker since it is registering a higher speed?

What methods are available for correcting the speedometer on the Y33s?

[Rex]

Here's my other question. What about the Speedometer being off, will that rack up miles quicker since it is registering a higher speed?

Yes, by the speedo error %.

... What methods are available for correcting the speedometer on the Y33s?

My guess is you can change out the "little gear", as discussed in the other currently active 4.08 thread.zerothread/194589

[BlueC]

Yes, by the speedo error %.

My guess is you can change out the "little gear", as discussed in the other currently active 4.08 thread.zerothread/194589

Thanks, I'll have to look into those options.

Looks like the differential will be installed Thursday of next week. The differential arrived last night, but my schedule does not allow it to be installed anytime sooner. I plan to have the diff filled with synthetic oil, any reccomendations on weight that will increase friction, but perform well in the winter?

[greenwar]

BlueC - got a couple of questions for you:

1) Now that I will be a Q owner - can you please let me know where in Minneapolis do you take your car other than the dealer?

2) Where are you finding pure 93 premium gas?

Keep us posted on the diff swap - I am curious to know as well how much more performance you can get out of the 2ton Q.


Modified by greenwar at 7:39 AM 9/5/2006

[96Qowner]

2) Where are you finding pure 93 premium gas?

Check out the marinas. I found a BP station in Detroit Lakes that sells unoxygenated 92 for collector vehicles and off-road use. Haven't seen 93 around here for a few years, though.

[BlueC]

BlueC - got a couple of questions for you:

1) Now that I will be a Q owner - can you please let me know where in Minneapolis do you take your car other than the dealer?

2) Where are you finding pure 93 premium gas?

Keep us posted on the diff swap - I am curious to know as well how much more performance you can get out of the 2ton Q.

Modified by greenwar at 7:39 AM 9/5/2006

1) I'm taking my car to a local shop here in Eden Prairie (Undercar Services). Great people over there, I took my Maxima there for other work I had done and they did a great job.

2) A lot of Mobil stations carry 91 non-oxygenated premium gas, no stations in this state carry pure 93 octane premium gas, not even marinas.

Here's a list http://www.msra.com/NonOxygena...6.pdf

It makes a noticable difference to use non-oxy gas versus the 10% ethanol mixture. Don't let the 91 octane rating fool you either, its plenty for our engines, 93 octane ratings are only there because the ethanol allows that rating to be higher, yet it carries less energy.

[greenwar]

BlueC, Thanks for the detailed answers. I greatly appreciate it. Unfortunately it seems there is no gas station in Eagan, Burnsville area which has non-oxygenated gas. I will probably have to drive to apple valley or Lake Ville.

I will check out the repair shop you mentioned.

Thanks again. Happy cruising..

[BlueC]

A quick update:

It appears that the side flange on the differential I purchased was severly bent. Did not notice it until I brought it in the shop. The shop manager could not locate a replacement part, so he suggested swapping the gears on the cases. They are going to go ahead and do this and I won't have my car back till tomorow. I will let you guys know how it goes.

I'm also going to have a phone call with the place I bought my differential from and see if/how it was insured for shipping.

[BlueC]

Nevermind, I guess it is not possible to swap the gears internally. Looks like the Q won't be getting a differential change now.

I'm actually pretty mad with the company I bought the differential from, they didn't even ship it in a crate, it was bubblewrapped in a cardboard box. Explains the bent flange.

I'm very happy with the shop though, they tried many different things to try and get it to work, plus they shared the same dissapointment with it not working. Very good people over there and i'll be going back there for future services.

[BlueC]

Quick question guys,

Couldn't I technically swap the side flanges from my Q45 differential over to the Z32 differential?

$250 is what it costs for (1) side flange for a 300zx differential directly from nissan.