Vibration!!!

[moltman]

New guy to NICO, new guy to the 300Z! I recently purchased an '86 2door coupe with ~116K miles on it. Body's in great shape, interiors in great shape, a couple nit noid issues but one possible biggie! At highway speeds of 60-85mph I get this real bad vibration that seems to be coming from the rear diff area. Just so you know...theres brand new tires with balancing, wheels are NOT bent, 4 wheel alignment just done yesterday and camber was out very minimally. However, none of those things have gotten rid of the vibration. I'd heard that the older Z's sometimes suffered from rear end issues but what are the causes? I've looked at the CV boots for breakage to see if contaminants may have gotten to the CV joints but everything is rock solid and no leaks or wholes...can anyone help me out? evildky...you seem to be everywhere in this forum and appear to be very knowledgable...got any clues for this first time Z owner?

[evildky]

how are the U-joints in the driveshaft? could also be a balance issue with the driveshaft, but I'd start with the mounts, the front diff mount (pinion mount) is more prone to failure than the rear mount

[moltman]

The Ujoints "seem" solid/sound but now that you mention it I have notice a slight squeak in first gear that increases as speed increases but does go away after the revs get up...could be. I've already ruled out the rear wheel bearings as there is no play at the hub with the wheel on and under no load...I think I'll start with the Ujoints and go from there. Thanks for the input!

[moltman]

evildky:I've been doing some reading on the drive shaft/u-joints type work and came across a statement in Chiltons that states that 1975 and later models u-joints can NOT be replaced and that if the u-joints are bad, the entire drive shaft has to be replaced? Is that right?

[evildky]

actually it applies to all 70-78's. they are press fit, a good driveshaft shop or machine shop cna still replace them but it's very labor intensive and likely cheaper to replace the driveshaft

[moltman]

Delayed revisit to this post...I've had my car checked out (professionally) by a couple different shops and they all tell me the rear wheel bearings are good, drive shaft/ujoints are good and balanced, etc. I've had the wheels and tires (tires are new with very little weight) balanced 2x and the wheels independently spun without tires to look for bent wheels...nothing bent. Oh yah, I had a 4 wheel adjustment done as well and the rear wheels are within camber allowances. I'm at a loss here as I honestly cant figure out what may be going on. I've changed all the fluids to fully synthetic as well and cleaned the diff and transmission of any and all metal shavings (there was very little) with no affect. I dont get any vibration in my feet or in the gear shift. The vibration is most notable in 5th gear when speed is =or> 70mph. However, I have also noticed that there is a slight vibration in 3rd gear around 2500-3200 rpm. The car has 120k on it but it really drives like its near new and I would like it to be at its best, e.g. more than just a daily driver.

evildky...do you have any, any ideas? For that matter, has anyone else out there run into this type of problem? Any and all possibilities considered so please feel to respond!

[evildky]

front and rear diff mount might let the diff set at an off angle causing vibration? rear crossmsmber bushings can allow the whole rear to move whihc could cause vibration, it everyhing is solid and balanced then I guess the next items to check would be the trans outut shaft bearing, diff input and output bearings

[moltman]

OK...sounds like some further investigation is needed.

I see you're in KY...have you heard of any "good" Z31 shops in the Denver, CO, area? The Nissan dealers here are ok...but getting rich on my $$!

[evildky]

lol, sorry, closest I an think of would be Ultimate Z in IL, have you check with your local Z club? (zcca.org) I must say I don nto recomend dealers for older cars, chances are the tech working on your car has never worked on one before, any good import chop will be as good or better than the dealer

[Pharaohabq]

okay, I've really got no idea what would do it, have you looked at your shocks? The Struts could be worn perhaps allowing for wheel hop at higher speed. I dunno just a guess. Are there any problems with your half shafts or hubs? Perhaps they one time lost a wheel and hit the hub hard enough to bend it. Again just a guess.

EvilDKY probably has the best guess in the Diff mount, or driveshaft out of balance.

Phar Btw, I've got Maroon 86 300zx parts, 68K mi... Just saying.

[moltman]

tks for the feedback. The shocks are new and I've had the tires pulled off the wheels and had the wheels spun to see if they're bent...no bent wheels. Hubs are in great shape...no scuff marks anywhere on the circumference of the hub's either. All 4 tires are new and each wheel/tire took less than 1.5 ounces to balance them. I did get lucky today though. One of the Nissan dealers here in Denver that I hadnt ever done business with actually has an older technician in their shop that was on a local race team that ran 300z's. He went on a test drive with me today and told me that he needed to get it on the lift, but thought I had a combination of a driveshaft/ujoint issue and a bearing issue in the diff. We'll see...I have an appointment with them and we'll go from there. I also found out today, through evildky's link to the zcca.org website that the local Z club still has racing events here in Denver. They have an arrangement with the Colorado State Patrol to use their training track for club members to race on. Not sure I'd put my girl through it, but it might be worth exploring!

[bigred240sx]

my car was doin the same thing and i found out the bolts holding driveshaft to the diff were loose and missing

[evildky]

awesome, your local clubs are a great resource for parts, information and socializing, I'm going bowling with my local club this weekend

[Perrenial Badass]

I have that same vibration in my car. I say the problem is in the diff. Because I broke whatever is causing the vibration when I was drag racing. I launched really hard, and I could feel the diff getting pissy behind me. After that run, I had the vibration. Strongest for me in 3rd and 5th gears for some reason... I didn't get above 3rd though (1/8th mile tack).

I haven't bothered to take everything out to try fixing it since I'm planning to get a drivetrain from a Shiro and swap it all out. But when that happens, if you still are having the problems, I'll take the diff apart to see if I can figure out what I broke.

[moltman]

sorry for the delayed response...was out of town for the 4th weekend!

Its funny you mention 3rd and 5th gears...thats exactly when I notice the vibration is worse or at least more noticeable! However, I was just tooling down the interstate when it all started.

bigred240sx...tks for the input...all bolts are there and tightness is to spec (torque setting). I pulled the rear hubs/wheel bearings this weekend...thats a job!...races, bearings, and grease were all in great shape.

Does anyone out there have a service manual for the 86 Coupe (na)? I would be interested in knowing if there were any such problems noted "back-in-the-day"...that they wouldnt mind looking for any related problems?

[evildky]

3rd and 5th gear vibration is most ikely in the trans, they share a shaft and bearing

[moltman]

All,

Turns out the vibration was happening as a result of a bent driveshaft. I finally got the car on a lift and they spun her up in speed while up in the air. Shaft was visibly non-concentric in its rev's! I guess I need to buy and build my own lift...

So, I managed to get a new "steel" shaft with replaceable and serviceable u-joints for $219.00, shipping included...from wholesaleimportparts.com. Of course Nissan had an OEM for $685! (There are only two left in the entire Nissan inventory for an 86 Coupe N/A). The shaft weighs in at 12lbs...which is really light for steel, shaving approximately 17lbs from the original. Thats actual as I weighed it once it was pulled)! You can definitely tell the difference as the car seems to get speed much easier...an has no vibration whatsoever!

Thanks to all for the ideas and help...especially evildky...your knowledge is obvious!

[evildky]

gald you got it worked out, I've sufferend abotu every known failure, so I know lots of places to look

[moltman]

Vibration saga continues...the vibration is back...new driveshaft/u-joints reduced it somewhat for a while but I now have vibration in all gears, typically around 2500-3200rpm...vibration at highway speed (65-75mph) is most notable, and is in the same rpm band. Had the car on a lift again - with a transmission person this time - and with the transmission/drive shaft turning at the rpm's noted above both the tech and I felt ZERO vibration from the transmission (put metal pry rod on transmission housing-not extension, put rod on diff and felt ZERO vibration, put pry rod on extension and FELT VIBRATION! Turned car off, and using pry rod you could see notable movement at the end of the extension housing when pushing on the drive shaft. Tech said that its the "extension housing "Bushing". This is an 86 Coupe N/A so I believe I have the FS5W71C transmission-right? Anyway, from what I can see in the Chiltons/Haynes manuals all I can see there is an oil seal and dust cover and I have to believe that whats gone bad is something internally like the main output shaft...what do you think? I've found a used transmission with extension housing for $698...that comes with a 3yr unlimited mileage warranty and 1yr labor warranty if I use an ASE certified shop to put it in. Of cours the install is another $xxx! I'm thinking that if the estimate (I get it tomorrow) is much more than that to repair it, I'm just going to stick the new/used unit in their and keep the extra for parts...assuming there is something worth keeping. What do you think?

[evildky]

wow well tahts a enw one, IIRC the only bearing osn the output shaft would be at the center plate, but my thought is if driveshaft is balanced it still shouldn't move, you sure about the balance of taht shaft before you go throught eh trouble of swapping transmissions?

[moltman]

Shaft is brand new...I guess I could have it checked too, but given that the problem was there before the new driveshaft AND the fact that its now obvious in all gears at the same rpm range I was ruling out the shaft. I did talk to the previous owner and he told me he had recently put in a new/used rear diff mount. I've also been under her belly and looked at the many bushings...while they look 22yrs olds they all appear to be sound. I'm starting to feel like taking her completely apart and rebuilding her over the winter...only problem is time and is an 86 n/a worth the $$ to do it?

[evildky]

it's a car not an investment, if you care enough about the car and need it a certain way to enjoy it hae at, I have way more $$ in my S30 that it's worth, it's just my love of the marquee thats keeps me putting money into it, that being said, the hyperflex kits while nto complete do replace most of the bushings and at a bragain considering, and they will firm up the cars handling a bit, by taking out the slop thefactory parts allow for

[moltman]

hyperflex kit?...are these the poly bushings?

If you have a link I'd appreciate your sharing it with me. I too love the marquee...would love to have a TT but ...

I got the estimate from the shop today...$1082 to "fix this problem". They automatically put in a new bearing kit at a minimum. However, I can get a new/used transmission w/extension housing for $698 and get a 3yr unlimited mileage warranty with it. They also warrant any installation costs if the unit is installed by an ASE certified shop. I could do the install but the shop will do it for $400. So for $1098 I get a gone through, guarunteed transmission with a warranty! The only issue is is that I am not convinced the shops diagnosis is accurate. Like you said, the only bushing is at the plate so the shaft should still spin right.

I think you idea of starting with bushings is the way to go...I honestly believe in starting with the least expensive repairs and working up! If they dont fix the problem, it definitely wont hurt to have replaced them. The only thing I'm out is the effort of doing it. That being said, time is the issue...the wife just deployed to Iraq (yah, we're military) so I'm holding down the fort w/3 kids yaddah, yaddah, yaddah! I guess I know where my "spare" time will be spent for the next few weeks! Anyone got a cold beer?

[evildky]

here si the masterkit form courtesyparts.com, http://www.courtesyparts.com/M...8105Gnot sure how their price compares to others but I kow they sell them, and here si a guy taht sells a lot of specialty bits for the Z31http://www.z31parts.com/polyparts.html

[moltman]

checked courtesy...master kit is for 90-96 z32, mine is an 86.

checked z31parts...no complet kits and he's out of stock on many. looks like its huntin time!

Thanks for the assist though!

[moltman]

evildky

Do you or anyone else out there know if Jason at Z31parts.com is doing business or not? I've sent him an email asking about parts, the rear diff mount and transmission mount in particular and I'm not getting any response.

[Perrenial Badass]

Yes, he's still doing business. He does have a life outside of the internet though, selling the parts is more like a hobby as he does have a full time job. I don't know him personally, but have bought from him before. It takes him a bit to respond to emails, but the transactions are flawless and he is a good person to do business with. Plus, he's the only person who sells those parts, their entire existance is thanks to the work of him and a few other members of the Z31 community.

Give him a few days, then send him another email.

As for the bushings, you will want the master bushing kit from MSA.http://www.thezstore.com/page/...100ZX

[moltman]

PB: thanks for the feedback. I was just wondering as he had mentioned in one of his posts' that he was moving, changing jobs, or something like that...good to hear he's still in business. I'm starting a transmission/rear diff rebuild and wanted to get the transmission mount and rear diff mount in while I'm at it. Hopefully he'll see the email before I get it done.

Also...thanks for the link to MSA!

[Perrenial Badass]

Well, you could try giving him a call. I don't remember if his number is ont he page, and you guessed it - I'm too lazy to look. But failing the number is on the page, you could PM someone in the local area and see if they could either give you his number or contact him for you. I think Racinjitter and he talk some, although I'm too lazy to check that either so I may be wrong.