BigBlue

iTrader: (4)

^good to know about your fd gears. Yeah I like Vivid Racing; got some of my things there. As you know and those that change fd gears will find out, the "Shim" issue can be quite a challenge by itself (If you have a person who is really good at the install), that's why you don't get "any" shims with the new kit. To do it right can take some trial and error until the right combo of shims happens; each car can be different than the next even if it's the same exact year/model. That is why if you look at a good parts list, the shim sizes are many! Key to get it right. I bought all new bearings and only had about 28K on them, but just wanted to take advantage of it and go all new, even though it turned out my used bearings looked new.

chamuko

any 1/4 mile time differences with the 4.08s ?????

harman850t5

iTrader: (8)

My 60fts were terrible and I need to use 5th gear. Driver and possibly the 275/35s. We got rained out before I could get comfortable. I'll find out in 2 weeks if they really helped me out.

Mr_Smith

Read the first 15 and last 5 pages but didn't see it answered, are these gears good for other events like drifting or auto x? Got an 03 base. Sorry if its obvious but I dot know much about gearing but it seem a lot of you are liking the acc from those 4.08

Doc_Z

I'd like to know exactly what all do most guys replace when changing out the diff? Which are the critical parts to definitley change out?

I see 2 installation kits offered by companies like z1 but what exactly is in these kits? I'm trying to decid if kit 2 is absolutely necessary, but its hard to judge without knowing what's all inside. Would prefer to see a complete list and possibly part numbers.

bmyles

This thread is not about a differential swap, just the gears. The install kit options only depend on the year your car was built. You own a 2008, so you get the later one. That's all there is to it.

Doc_Z

Yeah sorry I meant Final Drive not Diff.

Ok thanks.

RiujinZero

Just got my z today and after driving many a sporty car in my lifetime I have to say that the Z is probably the most over geared car for it's power I have ever driven, lol.

Definitely doing the FD as one of my first performance mods. Everything else can wait.

A-Town-Z

iTrader: (4)

Anyone have any before and after vids? I'm sure its quite the difference

harman850t5

iTrader: (8)

http://youtu.be/b_xTtVapMMY

A-Town-Z

iTrader: (4)

Thanks.. wasn't the best video ever... ha but a video nonetheless!! Bump for more vids!

Dr Pepper

I'm halfway through my breakin miles on the 4.08's and can already feel a more aggressive Z comin my way! I can't wait... Went ahead and did the Quaife while I had the diff open. Another needed mod for my 08 base open diff lol. Any questions about the install just pm me. I don't mind helping with what I can. Did the install myself this weekend. Everything went smooth. Very pleased. Y'all have a great day!!

sr20drag

Anyone with tech knowledge please chime in. ONLY

I have a 2000 model q45 3.69 vlsd diff in my 95 s14 drag car. i am running out of gear at 156mph in the 1/4 and my car has more. Its 5.3L lsx turbo and a powerglide.

I have two gear options but i prefer the 3.35 auto trans gear from the g35/350z. The other option is 2003-2005 q45 rear gear which is 3.13 but open diff.

My question: Does the ring and pinion gear from the 350z/g35 interchange into my 2000 model q45 differential? I have heard that the 4.08 gear from the 240sx r200's is thinner than the newer gear sets??? Can anyone confirm???

One way or the other I will have a 3.35 gear or a 3.13 gear(with shorter drag tire) in my 240 for next season. I dont want to have to cut up my subframe to fit a 359z/g35 diff in my 240 but i will if i have to. I would rather swap the FD gears from an auto tranny diff into my 2000 q45 diff and be done.

Anyone have some 3.35 gears they want to sell me for cheap that has swapped there auto gear sets? I can NOT use manual tranny gear sets because the 3.54 is not tall enough to reach my goals.

ian99rt

iTrader: (12)

Measure the ring gear bolt hole pattern for a rough maybe this will fit. Something tells me a q45 diff is going to be bigger and heavier duty than diff for a 3400 lbs sports car.

In your car I would suggest looking at domestic powertrain options for a diff. Mustang Cobra IRS, C4 vette diffs, viper dana 44 (actually pretty cheap option).

Or go solid axle since your drag racing.

Toneloc

Not to beat a dead horse...after reading most of these pages and reading (you only gain faster acceleration in 1st gear) Why doesn't someone post a video of two bone stock z's (one with 4.08s in it) with same weight and what not and do a roll race in each gear and see what the difference is in reality instead of actual physics. I've seen few people gain almost 1/2 a sec in the 1/4mile with these gears....Obviously it does increase something. I may have not been in a z with 4.08's but I have been in a ws6 with 410's before and after and it is night and day.

Z ELIMINATOR

iTrader: (3)

Email me at
novakracing@cogeco.ca
and i will send you my 1/4 mile run all motor with the 4.08 gears
it shows the tack and the spedo.
Its a 7 AT 370z all moter
it a 12.42 pass

thanks

Z

The_Assassin

Dropped off 4.083 gears today and a spare diff I bought. He will call me tomorrow to let me know if I need new bearings or not. I got an 07 350z cant wait to test these out. Am guessing I have to break them in for the first 500 miles right?

bjr

YES.
From what I remember don't drive over 50mph the first 100 miles or so and don't stay at any one speed for a long time - vary it. Also the first drive should only be a test drive for 10 miles around the neighborhood at the most then let it cool for an hour before a second drive. A lot of heat is generated on the first drive if it is shimmed correctly. Google it and you will eventually find the good advice. This is the internet so remember that you will find tons of people that don't know what they are doing and don't know they have done something wrong until 50,000 miles later when they have problems. Don't take advice from someone that says I didn't break them in and my car is fine after x,000 miles - especially someone that just did it only a month ago!

You will be wearing the gearset into each other the first time you drive it and causing more heat than normal and will want to change the fluid after 1000 miles to get out the break in particles from the top surface of the gears. Do some research when you are waiting for your guy to finish and have fun!

The only discrepency between break in I found compared to the owners manual of break in for the entire car is that a fluid drain is not necessary from a factory fresh car on the rear end but I would still do it if I were you. Most serious gearheads would be draining so they could take the cover off to check visually for any problems and some of them even clean the gears off and repaint them with pattern marking compound and check how they are meshing but that is not easy on our car since the cover has a mounting stud in it and cannot just simply take the cover off in 5 minutes like on a full size truck or an old muscle car with live axles.

Once you find the information you'll see you don't have to baby it for 1000 miles, only just at first so don't let the break in make it seem like you will be having no fun in the near future and that you just can't bear to make it through break in and decide to skip it. Good luck. Hope you found a good mechanic!

The_Assassin

Thanks for your response. Damn that's going to be difficult not to go over 50. I go to school and have to drive on the high way. I will try my best to let it sit for an hour after the first 10 miles. The shop is a good distance from my house. A lot of places around my area said no or they wanted $500 just for the install plus shop fees for oil, shims and all that other stuff. Just don't think that this should be $600. Oh ok I will be sure to change the oil after 1000 miles or so. I definitely will have to read up on how to do it first lol. I hope hes good a shop that couldn't do it recommended him.

bjr

I see. In your case, talk to the guy one more time and tell him you have questions about proper break in. If he laughs it off maybe he isn't the right guy? But also you can ask him if he is planning on doing a test drive (a competent mechanic on this work would) and he will be doing you a favor too. Let him do the first small drive and let it cool before you ever pick it up.
When I did mine I went about 5 miles out into the surrounding neighborhoods and came back. 30-60 minutes later I drove around town for awhile (read into this putting a few dozen miles on it <50mph). Next day was out on the highway and drove 70+ for over an hour. Once the initial gear wearing starts there is no more danger of heat build up.
Point is you can go to school or all the way back home same day if he does the crucial part of break in for you. The first two drives are critical then you can drive normal. Or have a plan like you are thinking to go someplace nearby for 30-60 minutes once you pick it up - store, friend, MickeyD's .
If you understood how much work is involved to do it right and that shims cost $30 a piece, etc. and how many special tools you would have to buy on your own it wouldn't seem like so much. Be prepared if you need bearings the price will probably go up 50%.
Here is a simple and typical break in procedure some guy got from his shop on a Camaro rear end. Just ignore the specifics about the type of gear oil to use and it sounds like most advice I found. Really simple!


Ring and pinion sets require a break-in period to prevent damage from overheating. Overloading or overheating will cause the lubrication to fail resulting in damage to the ring and pinion. In order to maximize the life of you differential, please follow this break-in procedure.

1. After installation, fill the differential with only premium national brand 80w90 or 85w140 GL-5 gear oil. Also add 4-8 ounces of Dane Spicer friction modifier to the oil if your differential contains a limited-slip or posi unit. Alert: Verify that the drain and fill plugs are properly secured.

2. Drive your vehicle easy for 30 minutes or approximately 20 miles. Avoid aggressive starts, hard stops and long distances at a steady speed.

3. Let the differential cool for at least 45 minutes.

4. Repeat steps 2 and 3 once.

5. It is not recommended to tow during the first 500 miles. Also avoid wide-open throttle acceleration for the first 300 miles.

6. When towing for the first time, drive easy for 20 miles let the differential cool for 45 minutes.

7. It is recommended to change the differential fluid between 2,500 and 5,000 miles. Use the lubricant specified in step 1. Subsequent oil changes should be performed every 20,000-30,000 miles.

Many differentials have been damaged by overheating, overloading, inadequate or improper lubrication. The above procedures may be a minor inconvenience, but if followed, your differential should prove to be one of the most dependable devices in your vehicles.