What to change - driveshaft, center bearing, motor-mounts, bushings?

[JedCoop]

Yes, my '92 shares the dreaded driveshaft (propeller) vibration problem. If is definitely NOT the tires. But I am not convinced of the best way forward. (If I can avoid buying a $500 part, I will! I am not trying to getmy '92 into factory condition. My attention is mostly on my '94)

Yes, my '92 shares the dreaded driveshaft (propeller) vibration problem. If is definitely NOT the tires. But I am not convinced of the best way forward. (If I can avoid buying a $500 part, I will! I am not trying to get my '92 into factory condition. My attention is mostly on my '94)

The car has 190K on it. I replaced the transmission mount 50K miles ago. I put the car on blocks - supported by the springs with rear wheels off. Vibration is worse on blocks than when driving. It starts at 30 MPH, gets better above 40 MPH. On the road the vibration doesn't feel too bad at 50 - 60, gets worse at 70. I feel vibration through the seat and the steering wheel. Similar to what others have described.

In park I feel vibrations through the wheel and seat as I rev the engine up slowly. These are not strong vibrations, but they do not occur on my '94.

When I changed the transmission mount I was wondering about the driveline geometry. I made a picture to explain. It is really important that the centerline of the shaft with the flex coupling is parallel to the shaft going into the rear differential. That is because if the two ends of the shaft with u-joints isn't parallel, there will always be some shaking forces in the transmission of power.

My first transmission mount had collapsed, dropping about 1/2-3/4 of an inch. This would change a lot of angles. I worry that if I change the drive shaft, there will still be stresses on the flex plate and vibration in the shaft forces due to the fact that all the elements are not just right. I drew up the diagram below to help explain what I am worrying about.

You figure while running the engine all of these pieces need to move a little in any case.

I know what I need to do to make it very right - replace all the parts. I am hoping to find a good enough solution that is cheaper.

My motor mounts have never been changed - and my vibration in park suggests they need replacing. Do I need to? Even if I do change the drive shaft?

What if I just change the center bearing and lubricate the u-joints?

And my rear subframe bushings look OK, but my visual inspection does not assure me they are OK. Is it worth replacing them?

I am assuming I can't DIY replace the flex plate... and the local driveline shop won't touch a Q driveshaft.

Thanks for any help!

(p.s. I'll probably use an OEM shaft if I do replace it).

[texasoil]

the 'height' of the center support bearing is CRITICAL to smooth operation. Engine mounts MUST be replaced (surely gone by now and significantly tilt the engine when under load). Center bearing rubber surround is available and should be replaced. Flex the u-joints and see if they are 'notchy' and then hit smartly on them to loosen up the stuck roolers and recheck. If the flex plate shows significant (any more than slight/few minor cracks) cracking--its gonna cause vibrations.

[JedCoop]

the 'height' of the center support bearing is CRITICAL to smooth operation. Engine mounts MUST be replaced...

I had always worried that just changing the trans mount but not the engine mount might cause more wear and tear on the driveshaft.

I reread some threads, including this one: zerothread?id=1963

Without specifically cecking the motor mounts I know I get too much vibration into the steering wheel from the engine. Seems to be a strong sign that motor mounts need replacing. I don't thik it makes sense to replace the driveshaft and not change the engine mounts, so I'll start there. for DIY motor mounts are cheaper to replace than the driveshaft, but it is a much bigger job.

It looks like disconnecting the driveshaft makes that job easier, so I'll check the u-joints and change the center bearing surround as you suggest. Thanks for the advice. When I get home tonight I'll check the flex disk before I order parts, though.

I'd love to rent an instrument to quantify the vibration before and after the change. I'll call around, but I doubt I'll find anything. I have an oscilliscope, but need some kind of sensor and a way to calibrate it.

[gloucester Q]

thanks jedcoop. i can't help you any, but i'm getting ready to attempt tackling this problem too. if i hadn't come across your thread i was going to start at the driveshaft, but now i believe i'll start with the mounts like you and work my way back. based on that last thread there is no way in hell i'm doing the mounts myself. think i'll bite the bullet and see what the local dealer wants for it. keep me posted, and i'll do likewise. i've noticed that my vibration is independent of engine speed, and happens most strongly at around 35 mph. 25 is good (well, good, not great) and 55-85 is not bad either. anyway, hopefully i'll get those mounts changed out within 2 weeks and post an update, and then keep working my way back as time and money allow.

[gloucester Q]

minor update: local q dealer wants $1134 (parts, labor, the whole deal) to change the 2 motor mounts and transmission mount. having read the thread you ref'd above, i'm leaning towards having them doing it. then taking care of the rest, systematically, by myself + parts from scottsdale. how are you making out?

[JedCoop]

The size of the motor mount task seems somewhat daunting, so I can understand getting the dealer to do it. I had the car up on blocks and was thinking about how to approach the whole egning hoisting versus subframe dropping thing. Big job, and then I got very busy with the rest of my life. I have hardly looked at NICO in the last couple of weeks, for that matter.

I am now justifying my delay (it makes me feel better) The '92 is mostly for my son. When he is done with exams in three weeks or so we'll start on it again, meanwhile we're not driving the car as much. Maybe my son will absorb some of the knuckle-busting instead of me

Hope yours comes back driving smoothly. Let us know.

[John Nordling]

Thought I would revive this thread because I just finished replacing my driveshaft (new, from Joe) and the vibration problem didn't completely go away.

Here's the background. This is a '90 q45t with just under 92,000 miles. The motor and transmission mounts are all new. The exhaust hangers are all new too. Both rear axels are out as well. That's how I determined most of the vibration was the driveshaft.

When I pulled the old driveshaft it was easy to tell that both u-joints were bad. I put the new one in and fired it up tonight. I was disappointed to still feel some vibration from about 40mph on up, although I didn't go above 70mph. Just for the heck of it, I tried going 60mph in third; the vibration was noticably less. I even tried second and found the same to be true.

So, my guess is something in the transmission. The engine is turning higher revs in the lower gears, so I thought it might be the harmonic damper/front pulledy, but that is new as well.

I think I am just going to have to live with this, but if anyone has any suggestions or can corroborate my guess, please let me know.

You guys are just great. I just couldn't couldn't have gotten so much done without the continued support of NICO when I run into a problem..................John

[maxnix]

New rotors and pads, too?

[gloucester Q]

ay carumba! just what i didn't want to hear... how are the wheels/tires? that and any subframe bushings (like i even know which ones...) are the last possible things i can think of. i'm about where you are, not as far along. got new mtr/transmission mnts, helped about 50%. still haven't tried the d-shaft though. will report soon when i do. 1st plan is to knock the u joints, second to replace with a 94+. so, the dshaft you got from joe came with a new centerbearing and all? randy

[John Nordling]

The brakes are about 1/3 to 1/2 worn, so I haven't replaced them yet. I am upgrading to '97-'01 Q 16" wheels, so when I do the brakes I might have room for something bigger.

But, the test I am running now is without the rear axels in place - no axels, no brakes, no wheels or tires. Just the engine, trans, driveline, and diff. That's why I'm worried about the trans.

[John Nordling]

At under 92,000 miles, I didn't think I would need rear sub-frame bushings. When I had the car aligned the shop said they checked for any play and didn't find anything. I had already replaced the rear sway bar bushings and the diff bushings before the alignment. The rear shocks were fairly new Tokiko Blues according to the previous owner, but I did pull them and replace all of the related rubber parts.

I am putting new tires on, but right now the axels are not in the car so that woludn't affect the vibration. The driveshaft I got from Joe came with everything you need, including the upgraded center support bearing and the redesigned bracket. It's a heavier duty design. I also replaced the trans seal while was at it. Cheap and easy to do!

Let me know what you find out as you go along. I think I will have to live with a certain level of vibration because I simply can't afford to swap out the transmission just to find out...............John in Seattle

[maxnix]

But, the test I am running now is without the rear axels in place - no axels, no brakes, no wheels or tires. Just the engine, trans, driveline, and diff. That's why I'm worried about the trans.

Maybe that is your problem. You have no flywheel effect from the lack of rotational mass of the rotors in particular.

Have you checked your pinion bearing for play?

[John Nordling]

No, but I'll look into it Friday. Am I correct in assuming the rotational mass you're referring to would react differently at higher engine speeds (smoother in 2nd gear at 60mph) than lower engine speeds (noticable vibration in 4th gear at 60mph) because that was what I encountered?

I'm trying to be very careful and thorough that this is really frustrating. Maybe I should finish up replacing the axels, brakes, wheels & tires and try it again if the pinion bearing play is within specs.

John in Seattle

[maxnix]

Well, rotational mass aside (it should smooth minor vibrations if it is in balance in the plane of rotation), worn driveshafts are known to wear the bearings on the input shaft to the differential. I would look here first. There is a post or two on it. I believe the allowable play is detailed in the FSM.

[RobertsnewQ]

Mine vibrates a tiny bit, but there's a tell-tale grease line around the rear u-joint. Any signs of a bad joint on yours?

[elwesso]

Well, rotational mass aside (it should smooth minor vibrations if it is in balance in the plane of rotation), worn driveshafts are known to wear the bearings on the input shaft to the differential. I would look here first. There is a post or two on it. I believe the allowable play is detailed in the FSM.

As well as tear up the tailshaft on your transmission..... Dont ask how I know!!!

[John Nordling]

Sorry i haven't gotten back; had an infected finger and couldn't do much of anything for about a week.

I got to thinking about the pinion runout, but i don't think that can be the problem. The rear end doesn't 'know' what gear the transmission is in or what rpm the engine is turning. My guess is still that there is something going in the transmission. I seems unlikely that this great engine vibrates more at low speeds than it does at higher speeds, or even that you could notice it in the drive train. So, I'm goping ahead with installing the rear axle shafts, brakes,and wheels.

Anyone ever experienced a vibration coming from the transmission???

[JedCoop]

I haven't done the vib work I was inteding to do. I have been distracted with travel for work and other problems with my '94Q. Since it is my son who drives the '92 mostly now, he needs to help with $$$ to replace the driveshaft.

I just drove the '92 a few hundred miles after not driving it for a about a month. I had fixed an engine vibration problem on it - a bad fuel injector. Now the car seemed decent at most all speeds (including 70+) except around 40 MPH. I don't think it depends on transmission gearing or engine speed, either.

* I get the vibration when driving at 40 MPH * I get the vibration when coasting in neutral at 40 MPH. * I also get the 40 MPH vibration when I set the rear suspension on blocks and take the rear wheels off/bolt the disks on by themselves. * I did check the motor mounts for separation, and they are OK.

After doing all that I decided that motor mounts were not going to solve the problem. The vibration is in the drive train.

But somehow the vibration doesn't seem as bad anymore!? Not bad enough to warrant a $600 part that until now I had thought would probably rid us of the vibration.

[John Nordling]

JedCoop, I'll let you know how it feels when it is all back together. Won't be until next week as we go out of town on Friday and my new tires aren't in yet anyway. I'm expecting a big difference because I could feel the 'set' taken by both u-joints, the one by the differential being the worst.

Idea - You could just unbolt the drive line and check the u-joints to determine how bad they really are. I know, lots of work, but CHEAP!

Back at ya later................John in Seattle

[94q45t]

Sorry to take a side trip on you, but if you're considering new ones, I recommend the 17's from the current body style Q with Goodyear Eagle FS1-DS3's. I know, I know, these are the first domestic brand tires in my life (actually made in Germany, though) but they are unbelievably smooth, and stick like crazy. This didn't completely eliminate vibrations, but they did far more than any Bridgestone or Michelins ever have. Get 'em from the Internet, though. Local dealers are $$$$. Wheels came from ebay.

[texasoil]

any vibration that happens when the car is stopped--is almost always (on the Q45) caused by exhaust system hangers or engine mounts, especially the rear mount (transmission mount). It is very difficult to visually tell its sagged enought to ba the culprit, but if 2200-2400 RPM's are you 'zone', then the transmission mount is suspect No1. Also change the exhaust hanger mounts at the rear of the transmission. They harden with time and cause LOTS of vibration complaints/symptoms.

[maxnix]

any vibration that happens when the car is stopped--is almost always (on the Q45) caused by exhaust system hangers or engine mounts, especially the rear mount (transmission mount). It is very difficult to visually tell its sagged enought to ba the culprit, but if 2200-2400 RPM's are you 'zone', then the transmission mount is suspect No1. Also change the exhaust hanger mounts at the rear of the transmission. They harden with time and cause LOTS of vibration complaints/symptoms.

Always do both together. Incremental labor cost is negligible.