Where can I find “thinker oil”?… is that some new synthetic infused with nano-brains?…

 

Way to **** up an intelligent thread douchebag.

People run those gears fine with the proper oil weight. You shouldnt use thicker oil to mask the problem. That will eventually just lead to more problems. Sucks, and it might cost you more money but it doesn't sound like the shop did the proper install.

 

lighten up tough guy. It was a lighthearted comment about a typo - no reason to get your panties in a bundle.

by the way genius, you didn’t add anything to the thread that hasn’t already been said - which is total common sense anyway.

 

If the backlash is not set right gears will make some noise. It will not cause problems if it set up a little out of spec. If it is a high pitched whine while you are driving, then its bad. Its probably just your busted diff mount.

 

Nope. Put in the solid diff bushing, same noise as before I replaced it. I'm running 140w oil (Motul) as well BTW.

Doing searches I found this on Google. Based on the noise I would think that it is something to do with the carrier bearings. When I dip below 20mph it goes away. Now that I've driven it for 2000 miles, I can pick out some different noises:

- there is a whirrrr noise under heavy acceleration - I believe that is the gears and the "high strungness" of them making noise which would indicate the lash is just slightly loose (but still within spec). Note, 'tight = more heat' and I track the car so not overly worried about it being on the loose side.

- there is the whumwhumwhum noise which is the most annoying and is on the video. That I believe is the pinon or carrier bearings based on the below. A side note, when the car is on the lift and you take it up to 70mph there is no noise from the diff at all. Only when the car is on the ground and pressure applied to the axles/tires/suspension does the noise manifest itself. That leads me to believe its got something to do with the bearings as they can spin freely without any force pushing on them as they spin.

(http://www.ringpinion.com/FAQ.aspx#38)

What is this whirring noise?

Whirring noise only while decelerating at any or all speeds is most likely caused by bad pinion bearings or loose pinion bearing preload, and almost never by bad ring and pinion gears.

A howl or whine during acceleration over a small or large speed range is usually caused by worn ring and pinion gears or improper gear set up.

Rumbling or whirring at speeds over about 20 mph can be caused by worn carrier bearings. The noise may change while turning.

Regular clunking every few feet may indicate broken ring or pinion gears.

Banging or clunking only on corners can be caused by broken spider gears, lack of sufficient positraction lubrication, or worn positraction clutches.

Rumble while turning may indicate bad wheel bearings.

A steady vibration that increases with the vehicle’s speed can be caused by worn u-joints or an out of balance driveshaft.

Clunking only when starting to move or getting on and off the gas might be loose yokes, bad u-joints or worn transfer case or transmission parts.

I'm really tempted to replace the whole pumpkin and start over but I blew my funds on the first two rebuilds and cash is tight (sucks when that happens). So in the mean time I drive it with the music very, very loud and pretend it isn't there - at some point I'll get frustrated enough and try to fix it myself, for better or worse.

-- friz

 

From previous reading on the google'd results, I saw mention of the fact that overtightening the crush sleeve could damage the pinion bearing. That would coincide with my post above about the bearings being damaged. That's all theory though...

 

well i have had mine in for over 18k miles and not a problem. no metal shavings in my gear oil or on the magnet so I have to say its not my ring and pinion gear.

 

Are there any issues with draining fluid, then taking the back diff cover off while the pumpkin is on the car? Might open up the case when I drain the oil this weekend and look around.

 

Finally got under the car to look at stuff. One thing I noticed, and I don't have the knowledge to say if this is bad or not so someone chime in, is where the driveshaft and pinion meet there is about 1mm of deflection and play when I spin the driveshaft back and forth. I made a quick vid, look in the 10 o'clock position and you can see the play as I spin the drivetrain back and forth with my hand. Car is in neutral with the parking brake off.

http://www.youtube.com/watch?v=JJUMCE89rpw

Thoughts?

 

You're sure it's not the tires? The fact that lifting the car makes it go away would seem to indicate it's either suspension or tire related, not rear diff...

 

Normal, and you'll have that play on the input shafts as well. At least by looking at your vid, it looks normal to me, without measuring it.

Has the whine gotten any louder? Or is it hard to tell? If you want me to drive it again, stop by.

 

It's gotten louder, and now has a clunk to it - I can crank the stereo up all the way and still hear it. Will setup an appt to let you drive it Sharif.

 

That puzzles me too. Don't think its tires or wheels - I've had 2 sets of tires on there, 2 different rims with the same results. Maybe suspension... ?

 

Any good news?

 

Yeah ... I found a place that will sell me a used stock pumpkin, gears, seals, etc for $475 shipped. (lol?)

On a serious note, took it back over to Sharif last week and he drove it. Somethings not right; best thing we can think of is 2 things:

- the front diff aluminum SPL bushings I replaced the stock bushings with push the driveshaft out of alignment. I'm going to go back to stock bushings and see if that fixes anything. Looking under the car, the stock bushings are maybe 1/4" thick. The SPL ones are 1/2" thick (top and bottom) and don't compress like the stock rubber ones do so I've got a 1/2" angle difference. I know people have no problems with the SPL mounts - at this point I'm just trying to figure out what it is and that's a differentiation from other cars without the problem.

- the pumpkin case itself is allowing some movement internally where it shouldn't. I've read of a few other people with this phenomenon via the Google. Maybe I'm special?

So plan is to replace bushings, test drive, then replace pumpkin. BTW - those front diff mounts are F-ing expensive from the dealer; $64 x4 + $12 for the insulators x2 = $280 total.

Will update if/when I get around to it... probably won't be for a couple weeks.

friz

 

god, cant even tell you what an upset this thread is, i was literally abuot to buy these 4.083 gears for my g coupe tomorrow. but it sounds like i have a very high chance of having issues with them. do the 3.9 gears do this as well? does everyone who gets the 4.083 gears get this issue? im not a rich guy so i cant afford to throw more money into fixing things like this.

 

well after selling my dif and putting a used one in the noise is still there in my z. so it appears its just the tires from being out of alignment

 

I wouldn't say you have a high chance of issues - I think a good 95% of people who have done the gear swap, either 3.9, 3.7, or 4.0, haven't had any issues at all. As with any mod, you're redesigning the way the car was engineered and as such any mod has the chance to not work like other cars with the same mod. I'm sure if you look hard enough you'll find a small subset of problems with every mod. I love the gears - car feels so damn good with the extra little bit of power in the butt-dyno - but the headache I have when I get home kinda sucks.

I'd say go for it - you'll probably be just fine.

 

BTW - I changed out the 140w oil and put in some Mobil 1 75w90 last week. When I drained the old oil with ~3100 miles on it it came out black with a good bit of metal on the magnet, if you scrapped it off it would be about a tablespoon full. Was the most metal I've seen on the diff plug in the 4-5 diff oil changes I've done on the car when it was stock.

 

Just a quick update - I ordered a new pumpkin w/ stock everything (used from an 06). I plan to drop the current pumpkin off and then bolt on the used stock pumpkin and see if it magically goes away. If so, I'll disassemble the 4.083 pumpkin and take some pictures. I've got a couple days off this week so am going to attempt it Thurs/Fri.