I recently bought my car and am trying to work through all the little problems. My first major problem was a high speed shake which I've determined to be due to mismatched tires on the front. The accelerating shake still happened even with all 4 tires from my friends car on mine. However, I still have a shake or bounce feeling from the rear while accelerating but not decelerating or cruising. It feels like the wheels are bouncing a little. The previous owner claims new shocks all around, but I have no proof other than that they appear to be quite clean.

Has anybody else experienced this? What would you check first?

As I mentioned, the car is fairly new to me so I'm unfamiliar with a lot of it. I did notice when I was swapping wheels that the passenger rear axle's universal joint had a bit of slop in it. Not sure if that is normal or if it could be the cause of my problem. I'm also suspecting engine mounts or the shocks.

What do you guys think?

Thanks,
Ultimoblaze

The front brakes may be hung up. Mine did the exact same thing until I overhauled the brakes. From sitting it seemed like the fronts would keep holding until up to speed then they would break free or something.

I've heard of some shaking that was caused by sloppy motor mounts. Seeing as they're quite cheap and easily replaced, I'd suggest doing a visual inspection and if they look anything like mine were, just go ahead and replace them. If it doesn't fix the problem, at least you've eliminated them from the possibilities. If you have any oil leaks at the front of the motor, chances are some of that oil ended up pooling in your lower mount and has deteriorated the rubber. The dogbone bushings cost as little as $10, it's easy to see if they are worn, and about a 15 minute job to replace. Mine I think were about 32 years old, which is pretty amazing in a 27 year old car

Is it that easy to replace the dogbone bushings? I looked at them and didn't see any cracks like in your pictures. When I was under the car I noticed dimples in the oil pan where somebody must have put a jack and it appears that the oil pan gasket has leaked (grime all around the oil pan from the gasket down). I never got a good view of any of the mounts, but If they aren't terribly hard to replace I was considering doing them anyway.

And it's definitely not a stuck brake. When I put my wheels back on today and kicked the blocks out the car started rolling away on me on a very shallow incline. Luckily I had just fixed the parking brake and was able to run around and grab it to stop the car from running in to the shed. And no, the back brakes weren't locking up either, I was easily able to turn the hubs by hand when I was adjusting the parking brake.

To replace the dog bone bushings, remove the strut by taking the nuts/bolts off the 2 ends of the strut (There's a small triangular plastic cover hiding the right rear nut, it just pops right off). Once you have the dogbone out, you can punch out the metal sleeves and then either punch or cut out the rubber bushings. If they're as bad as mine, they'll pop right out, but I've known that some have had to cut through the rubber with a hacksaw before they came out. When you go to replace it, best to put the front nut/bolt in first, then grab the back rocker cover and pull the engine toward you until the rear of the strut lines up with the frame mount holes. It's easier than it may sound.

The right/front motor mount is pretty easy as well, and best done while the dogbone is out. Remove the nuts holding the motor mount and then jack the engine up about 4" (Put a 2x4 under the oil pan and you can put the jack on the wood, you won't dent your pan). Once the engine is raised you can either leave the jack there or put a short piece of 2x4 between the vibrational dampener and the cradle. Re & Re the mount, lower the engine, replace and torque the nuts and you're good to go. One thing I did find is the quality of the mounts I received weren't the best and the bolts in the mount don't line up perfectly with the holes in the cradle. I ended up using a dremel to ream the lower front hole out about 1/16" to make it fit.

If your oil pan gasket needs to be replaced, sorry to say but that's a bit of a job. You need to jack up the engine, remove the starter and bell housing dust cover, and swing the upper motor mount support out of the way to get enough room to get the pan off. Not the worst job in the world, but plan on an afternoon to complete.

If your car has had suspension mods that could be a place to check out. If it's stock then the following would not apply. My car had a vibration from a standing start or low speed acceleration. The vibration would not happen at light throttle or while cruising. It felt a bit like a pinion angle vibration (found only on rear wheel drive cars). My rear suspenion has coil overs and seemed to sit very low. I raised the ride height and the vibration went away. The low ride height must have been causing an axle shaft bind or excess axle angle. Not sure which, but the car no longer has that condition. Again, if your car has a stock rear suspension this is unlikely to be your condition.

Clutch or engine issues could too. I bought a Lumina minivan a number of years ago that started and ran fine. soon as i got on a freeway and hit 65-70 mph it started shuddering all over. I thought the transmission was bad and banging in and out of gear. Turned out it had a defective coil pack. Ran perfect for years after that.

The suspension is stock as far as I can tell. Not sure how do identify a pinion angle vibration though.

The car accelerates hard like it should it just shakes under acceleration. High speeds it is fine. It feels like the wheels are out of round or something if you can imagine what that would feel like. Or if you've ever seen truck pulls before how sometimes the rear tires will bounce when they're pulling? That's what it feels like to me although not as extreme.

Pinion angle is the relationship between a driveshaft and the center line of the pinion gear/shaft. Doesn't apply to Fieros ... was just using the condition to relate to what I felt with my car. Your condition does seem like it could be driveline related. When determining which of multiple repairs might correct a conditon I always go for the easiest and less expensive ones first (IE: overheating - start with a thermostat ... not a head gasket). The dog bones, engine/trans mounts and engien cradle mounts are the easiest to see/access. Start with that and hopefully you'll find the issue before having to go too far.

Ok, that's my preferred method of diagnostics too. Can I just get mounts from Autozone or something? As for replacing, I can use a board and jack from the oil pan after removing all the nuts on the mounts right? Is that with the dogbone on or off? I'll have to read the repair manuals to see what they say about changing the mounts.

You can get mounts from a variety of parts stores, but always keep the Fiero parts vendors in mind when making purchases. We'd have less sources for parts if too many of these guys shut down. As far as jacking up the engine I'd never recommend using a board under the oil pan. I doubt that the factory service manual makes that recommendation ... check it out and see what the factory recommends. You should probably let others who know your engine (I've got something different) contribute their thoughts.

I think the 'preferred' method of raising the engine is to lift it from the top, but that requires some equipment that not everybody has access to. I combed the forum and found quite a few folks that have used the board under the oil pan method, so I gave it a shot and didn't have any issues. The oil pan is a lot stronger than it looks. Should be done after all the nuts/bolts on the mounts have been removed, and the dogbone off.

Just a note though, a lot of folks have done an engine swap by lifting the car up by the trunk latch, but I wouldn't want to be caught dead (literally) trying that method.

I don't have any equipment but 2 jack stands and a jack. My oil pan already has dents in it and is leaking around the seal from a previous owner jacking directly on the pan. Does anybody have a preferred source for the mounts?

I always jacked my my engines up by placing a wood block that covered the bottom of the pan on the floor jack. I never dented one. It transfers all the load to the vertical sides of the pan.

You can get the mounts at pretty much any auto parts store, NAPA, Autozone etc. Watch for 'Made in India' ones, I got a couple and they were crap, wouldn't even line up with the holes and had to wait a couple of days to get that I could get to fit.

Finally got the mounts done. The transmission mounts that came out were completely trashed. When pulling the front one out the top bracket pulled apart from the rest of the mount. So after replacing the engine and transmission mounts I still feel the shake, but it's not nearly as bad as before. I didn't do the dogbone, but when I had it off I saw that that needs to be done too. Do you guys recommend the Ultimate Dogbone or should I just get the new rubber for it? Does the Ultimate transmit a lot more engine vibration into the car?

I'm thinking the problem is the CV joint. If that is the case though, I won't get a chance to take them off until next spring. What do you guys think?

You should be able to test the CV joints and output bearings just by grabbing the axle and pushing and pulling in different directions. Don't be gentle about it...

What am I looking for? How much movement is acceptable?

When it was new there was no movement at all. If you can move the axle as it comes out of the transmission, the bearing is bad. Usually there is some leaking going on too. The CV joints may not be quite as tight and still function fine.

I just checked it and I can twist it just a bit. I can pull up and down a bit, maybe a 1/4". The passenger side does appear to have a slight leak as I have wiped gear oil off it a few times now.

quote Originally posted by gtoformula: If your car has had suspension mods that could be a place to check out. If it's stock then the following would not apply. My car had a vibration from a standing start or low speed acceleration. The vibration would not happen at light throttle or while cruising. It felt a bit like a pinion angle vibration (found only on rear wheel drive cars). My rear suspenion has coil overs and seemed to sit very low. I raised the ride height and the vibration went away. The low ride height must have been causing an axle shaft bind or excess axle angle. Not sure which, but the car no longer has that condition. Again, if your car has a stock rear suspension this is unlikely to be your condition.

I'm having the exact same problem that you had, I have a (87 GT ) Does anyone know what the angle degrees the axles are supposed to set. Had the car in the shop yesterday on a drive on rack (not the one where the wheels hang down) and the axles look to be on about a 30-35 degrees angle. I'm using lowering springs with about a 1 1/2 drop.How much did you have to raise the car to get rid of the vibration?

quote Originally posted by gtoformula: Pinion angle is the relationship between a driveshaft and the center line of the pinion gear/shaft. Doesn't apply to Fieros ... was just using the condition to relate to what I felt with my car. Your condition does seem like it could be driveline related. When determining which of multiple repairs might correct a conditon I always go for the easiest and less expensive ones first (IE: overheating - start with a thermostat ... not a head gasket). The dog bones, engine/trans mounts and engien cradle mounts are the easiest to see/access. Start with that and hopefully you'll find the issue before having to go too far.

It's the same principle though if you forgo the occupational specifics. My car is lowered about 2" and about an hour ago I heard a crackling sound under load heading up hill echoing off the houses as I passed them. It sounded like a bad outboard CV joint only not as intense. Prior to that, a couple of days earlier the rear end made what felt like a strange twist during a moderate launch from a stop, almost as if one side of the car squatted about an inch or two lower than the other. At this point it's obvious there is a joint problem that raising the car an inch may quiet but will not fix as I'm certain the damage is already done.

Initially upon lowering the car there was a slight wobble like sensation under load that dissipated with time but never completely went away. It was probably a wear-in process. On a stock ride height automatic Fiero I had an inboard joint suffer from dislocated needle bearings secondary to rust contamination and raising the car which allowed a couple of bearings to work their way out of the roller. The result was the wobble described here under load.

[This message has been edited by Joseph Upson (edited 10-16-2012).]

Well my car is on stock suspension components so that can't be my problem. I do suspect CVs though. Anybody have any other suggestions?

I've heard that I could take them off and flip them around and use the other side and it could help.

What's the process for removing them? Approximate time? Special tools? Tips?

quote Originally posted by ultimoblaze: Well my car is on stock suspension components so that can't be my problem. I do suspect CVs though. Anybody have any other suggestions? I've heard that I could take them off and flip them around and use the other side and it could help. What's the process for removing them? Approximate time? Special tools? Tips?

Then you probably have a bad inboard joint. I diagnosed mine by supporting the lower control arms on blocks, after taking the wheels off and putting the tranny in gear, then noticing the passenger side inboard half of the axle having about a 5/16" runout that was only a problem under acceleration. If for whatever reason someone worked on the axle area of the suspension and disconnected the strut or whatever allowing the outboard joint to hang down far enough, it can semi pop an inboard roller over the retainer allowing some of the needle bearings to come out before the roller is forced back on by restoring the axle back to its proper position. Over time more come out until you start to experience the side effects.

[This message has been edited by Joseph Upson (edited 10-16-2012).]

So you ran the car while it was sitting on blocks and were able to see/measure runout on the passenger wheel?

It feels to me to be from the rear passenger side. I was told by the previous owner that the shocks and struts were replaced in the car.

The culprit was the joint on the passenger side of the transaxle? Can anybody provide details for replace/repair? Or point me to the page in the service manual?

[This message has been edited by ultimoblaze (edited 10-16-2012).]

quote Originally posted by ultimoblaze: So you ran the car while it was sitting on blocks and were able to see/measure runout on the passenger wheel? It feels to me to be from the rear passenger side. The culprit was the joint on the passenger side of the transaxle? Can anybody provide details for replace/repair? Or point me to the page in the service manual?

You'll be able to see 5/16" runout in a CV axle from the "Grocery store". That's a lot and even without auto knowledge it would look wrong. The control arms need to be on a solid (as in safe) support all the way out to the ball joints so that they are unlikely to move downward at all before putting the tranny in gear. You should also have a third support at center aft cradle. The car should not move even if you shake or push on it.