Posted this in the Nissan Mechanic Forum with no responses yet:

OK, at the point of frustration with my project car. It is a 1993 Convertible 240SX. I have done the 5spd manual swap, and swapped in an SR20DET. It has a full BRM exhaust. I have upgraded to the 300ZX TT Brakes. The car is sitting on GAB adjustable struts, and RSR springs. I have changed out the tension control rod inserts with poly kit, as well as upgraded front and rear sway bars to the Godspeed sway bars. I think that's all the relevant things to my problem.

The problem is this: Between 58 and 67MPH (as indicated on the digital speedo and verified by GPS), the entire front half of the car shakes. It is noticeable and unpleasant to say the least. The car was sitting on Rota Subzero wheels with Avon Z rated tires. Thinking that it was a wheel fitment/balance issue I have swapped out to a set of Enkei RP05 wheels wrapped in Kuhmo Solas tires. Tire size is 215-45-17 (don't know if that has any bearing on it, but thought I would mention it too). It does not do this at any other speed, and if accelerating very quickly, then it is not nearly as bad.

I know many will say, simply drive much faster than that and don't worry about it, but unfortunately in both morning and afternoon rush hour, that's about the best I can hope for.

Any thoughts, advice, or ideas as to what to do would be very appreciated.

Thanks,
Donald

Normal progress check on shake:

Tire pressure
Tire balance
Tie rod ends
Bushings
Alignment

Biggie,

Thanks for the response.

1. Tire pressure at 36psi on all four corners. That has been the same on both sets of wheels.
2. Both sets of all 4 wheels have been speed balanced.
3. Haven't replaced tie rod ends yet. Could this cause the shake only at the specific speed?
4. Bushings - haven't attacked yet.
5. Alignment was next on the list at the end of the week after new springs.

Had not considered the tie rod ends or the bushings.

I would try rotating the tires and see if that makes a difference as well

RJ - Tried rotating tires first before swapping sets. It's a puzzler. Going to swap outer tie rod ends tonight. I have a set I was planning to put on the car anyway, so just a reason to do it more quickly.

I see you have the same taillights I do from your signature. Do you ever feel they aren't bright enough?

ok. changed out the outer tie rod ends. Also tightened everything I could find underneath. Same problem, but speed range of shaking changed a little. Other thoughts or suggestions?

Driveshaft out of balance? Would think that would cause it at multitude of speeds.

Puzzling.

Have you checked to see if the tire is punctured?
I had this exact problem when the inside belt of the tire snapped and I didn't notice after hitting freeway/highway speed that the wheel started to shake like a girl shaking her big booty.

I have not checked that, but I have swapped a completely different set of wheels and tires onto the car. I think that would eliminate the possibility of a tire problem.

There has also been the suggestion of a bent spindle. I don't know at this point, just scratching my head.

Is it at certain speeds or certain RPM range? Could it be the motor shaking/vibrating?

How are the rotors, it could be warped rotors also

USC Justice wrote: I see you have the same taillights I do from your signature. Do you ever feel they aren't bright enough?

I think its bright enough

Ok.. Just my 2 cents, do the wheels FIT the hub exactly? Many times aftermarket wheels are made to fit a variety of cars. If you have a wheel off and no lugs nuts on, put the wheel on the hub, then see if you can move the wheel up and down. If you can then the rims need hub centering rings (they're really cheap 10-20 bucks for set), but will cause vibration. Lug nut torque is around 87 ft lbs. If everything is good with fitment, you could check wheel bearings (forget what torque is, but might be next step). I would also check ball joints, inner and outer tie rods. I hope it's something cheap and easy. Good luck - keep us posted.

Ok. Latest on the project and problem.

Biggie: it is only at 58 to 67MPH. It doesn't matter what gear. RPM makes no difference.the car has brand new transmission mount, and I have now checked the motor mounts too.

RJ: The rotors have a total of 300 miles on them.

GoinTopless: I have hub centering rings on the wheels. Lower ballpoint are good. Just replaced the outer tie rod ends to no effect. Tension control rods have new bushings in them.

Talked to a tech at the local dealer flag. Apparently it is common for the Driveshaft to lose weights that balance it. Driveline specialties here in town will rebalance and replace the joints for 150. That is the plan for Monday. If Lucky on Wednesday I can get time to put it back in.

Updates to follow...

Just a thought along the lines of the driveshaft. Are you still using a two-piece driveshaft? If so the carrier bearing for the front half of the driveshaft will also cause noise (vibration in floor or seat and roar). Just a thought while you have it all tore down. Good luck and keep us posted.

I had/have the SAME EXACT PROBLEM. Slightly different speed range though as mine is somewhere between 50-58.

I have coilovers, Z-brakes, big wheels/tires all balanced with hub-centric rings, upgraded sway bars, adjustable rear control arms, all new poly-bushings, ball joints, tie rod ends. I know it's out of alignment because I haven't finished messing with the suspension yet. Still on the two piece driveshaft. I'm fairly confident it's a problem in the front of the car. It's more than just a vibration from an imbalance I suspect.

I haven't had time to drive the car, let alone work on it the last few years. I was only able to take it on a single trip this past summer after I did the bushings and ball joints. It still had the shakes. I wish I had an answer for you, but I still haven't been able to figure it out. My vert is going down for a long time here pretty soon, so I wont be much help. Keep us posted.

OK, something of an update today. Life got a bit crazy to say the least. Had the car in the air today and pulled out the drive shaft. Oddly enough, the bollts on the front of the driveshaft (where the splines go into the transmission, had some grooves on them from making contact with the dust cap area at the end of the transmission. Very odd to say the least. had the thought that perhaps this was causing my issue. Actually trimmed down the very end of the transmission (the aforementioned dust cap area). Reassembled things and took for a test drive. Still the exact same issue.

The steering rack seems to be loose as well. When the front of the car is in the air, you can grab one wheel and shake left to right, and there is a lot of slack or slop if you will. far more than my SE-R Altima or Pathfinder (put them in the air as well to compare). A friend of mine riding with as we were testing things seems to think that it is a bad steering rack rather than driveshaft. His reasoning for that is that the vibration and shake is all coming from the front end of the car, and through the steering wheel. He seems to think that the driveshaft out of balance would be felt in the middle and rear of the car.

Could a worn out steering rack create all this havoc?

Going to swap out the springs in the next day or two (going from RSR to Tein springs and new strut mounts). After that going to see if I can get a professional opinion about it.

The only bushings I have not replaced are the steering rack bushings. I remember trying to do a similar test with my car in the air - to see if anything was loose. I don't remember having slop or being able to shake anything. I do feel and see a lot of the vibration transferred to the steering wheel though, as you have stated.

Maybe the inner tie rods are bad? Maybe the bushings that hold the rack to the subframe are blown? Maybe the rack and pinion itself is worn out or worn down? I'm not intimately familiar with the steering rack. I know someone who is though. Maybe he would have some insight. I'll see if he can post in the tech section.

Ok. Lets see if we cant sort this out.

First things first, fix what is loose. Loose chassis and front end parts can cause all sorts of goofy issues, but often times, they will also accentuate other issues. You say the steering rack seems loose, but I would find it more likely that the inner tie rod is loose. There is a second ball and socket joint, similar to the outer tie rod. The inner is inside the bellows boot, and can be replaced. S chassis steering racks are relatively beefy for the weight of the car, and the stress put on them, I have yet to see one worn out. The rack lash does occasionally need to be adjusted. I would suggest trying to support the front wheels by the control arms, so as to load the suspension. Now shake it side to side. If the looseness is minimized, or gone entirely, then the rack lash is out of speck. This allows the rack piston to move up and down. If there is no change, loaded/unloaded, then most likely its the tie rod. You could also pull the clamp off the bellows and slide it down, you should be able to physically see what is loose when you shake it. The tie rod will move in/out, where as the rack piston would move up/down.



^^ Here you can see the rack outside the car. The drivers side has a bellows boot on it, and on the passenger side you can see the inner tie rod. You can also see the poly rack bushings.

Which side did you notice to be loose? Typically the steering rack itself will only show looseness on the left side, because the lash adjuster is at the base of the steering column. The right side has such a long run that it wont show looseness until things are really sloppy.

Another thing I would suggest checking, would be the front lower control arm bushings. If they are worn out, combined with the bad alignment, the front wheels could be walking in and out. It just takes a certain level of stress before it exhibits the problem, IE speed.

Then, you need to have the car aligned, and before it is aligned, make sure that a qualified tech checks over the suspension for any other loose parts. If an alignment is bad enough, it can also cause all sorts of issues, all though shaking isn't often one of them, unless its really really back.

Either way, fix the loose, get it straighened out, then you will have a better platform to diag the issue.

OK, latest update.

I have swapped out the springs and struts all the way around. I also went with new strut mounts, and bushings all the way around. KYB and Tein for struts and springs, and Moog for all strut mounts and bushings. This removed probably 90% of the shakes. I then took it for a complete alignment. Front aligned perfectly. The rear we couldn't get enough adjustment out of the bolts, so the camber is 1.9 and 2.1 (left and right respectively), There is still some steering wheel shake between 58 and 62, but it is not nearly as pronounced as it was before. While it was on the alignment machine, they checked the inner tie rods and said everything was good there. I'm definitely ok with the car now, but I would love to sort out and get rid of the last bit of shake.

It does appear that the looseness and shake was coming from the front drivers corner. HOw does one adjust rack lash? Something I can do, or back to the shop that did the alignment?

On a slightly different note, worry about the rear camber or not? I have been told RUCA's are the only way to solve that, but the amount mine is off isn't really worth worrying about.

After this and adjusting the boost some, I think I'm nearly finished with the car mechanically. then it is time for the paint and body fun. Someday I may get finished with her.

Steering rack bushings been replaced?

Rear camber isn't too different, but are you wanting less camber? That would be the reason to get the RUCAs.

OK, the problem has finally been completely sorted.

Biggie, in answer to your question, yes the steering rack bushings have been swapped out. The big reason I was asking about the RUCA's is just because I don't want to wear tires out more quickly than necessary. Didn't know if the amount of camber in the rear was enough to wear out tires.

The car went back up on the rack late Friday. The steering rack lash was checked and tweaked some (can't tell you how far in which direction, just that it was adjusted). Put the car back on the ground, and bingo. Problem solved.

I'm very pleased with the ride and lack of squeaks throughout the car now. Also doesn't hurt that pretty much every bushing, nut, bolt, etc. attached to the suspension of the car have now been swapped out. Nearly done mechanically speaking. Manual boost controller, and cleaning up a little bit of the wiring in the engine bay, and then it's time to move on to the paint and body work.

Thanks to everyone for all the help. It was making me crazy to say the least.

Glad to hear you got things solved.

Sounds like I'll need to adjust the lash in my rack when it comes out soon. Thanks for the tip Ian!

So was it just your steering wheels shaking or the entire front end?
at the moment the entire front end of my car shakes from about 55-62mph and im completely lost as to what it might be.

Foxyshazam wrote:So was it just your steering wheels shaking or the entire front end?
at the moment the entire front end of my car shakes from about 55-62mph and im completely lost as to what it might be.

Everything. I have not yet taken the time to adjust the lash in my steering rack, but I'm confident that will resolve this issue. Thanks to USC Justice and FlatBlackIan for their contributions on this thread.

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