Rear Axle Play??

[UMDSmith]

I have an 89 hatch 5 speed. I do need alignment and balancing and some new nitto's on the back, but all that aside, when I am driving and decide to accelerate up around 80 mph, a nasty almost knocking noise reverberates through the car, and I can feel it in my feet, almost as if associated with the drive shaft.

I started looking for loose parts and when doing work on the front left tire, it actually had a little play horizontally (I could pull it toward me and away about 1/4" of an inch). After tightening that down sop that it had no more play, the sound did not go away.

Recently, when going up small driveways and parking lot ramps, if I am making a right into them, once the back tire hits the ramp, I hear a nasty knock.

I have since jacked up the rearend to look for something loose, and to see if my driveshaft had some play. I found that my right rear tire can be pulled toward me and pushed in about 1/4" to 3/8" as well, while the left is tight and has 0 play. The lugs are all tight, and the entire drum assembly moves as well.

Is this a c-clip issue, and how dangerous is this situation?? I do plan on swapping up to 5-lug the expensive way, with new axles, new gear ratio, alum driveshaft, etc. but am not quite ready for that cost. Any advice/suggestions would be welcome.

-Joe

 

[Gearbanger 101]

I have an 89 hatch 5 speed. I do need alignment and balancing and some new nitto's on the back, but all that aside, when I am driving and decide to accelerate up around 80 mph, a nasty almost knocking noise reverberates through the car, and I can feel it in my feet, almost as if associated with the drive shaft.

Could be bad U-joints....could also be your pinion angle. If the U-joints check out OK, check the buschings in you upper control arms.

Recently, when going up small driveways and parking lot ramps, if I am making a right into them, once the back tire hits the ramp, I hear a nasty knock.

You initially said you though you felt it under your feet? Mustangs are notorious for bad ball joints, you may want to check them out?

I have since jacked up the rearend to look for something loose, and to see if my driveshaft had some play. I found that my right rear tire can be pulled toward me and pushed in about 1/4" to 3/8" as well, while the left is tight and has 0 play. The lugs are all tight, and the entire drum assembly moves as well.

The rear axles are suppose to have a little play (float). Have you checked your tranmission mount?

 

[UMDSmith]

wow, looks like I have quite a list of things to check. I have to wait till I can get it up to my dads place where he has a lift, I don't even have a garage in my apartment.

A little play in the rear axle wouldn't arouse my suspision(sp?), but the fact that the right has a good deal, while the left has none caught my attention.

So the list of things to check.

ball-joints
bushings (I do have a lot of wheel hop so the control arms will eventually be replaced, although wouldnt they cause vibration throughout entire speed range?)
tranny mounts
c-clips (Possibility still)
pinion angle?

Now, for some reason this vibration only really happens at 80 mph and is slight, worse when I accelerate, and even worse around turns at 80mph. Once I hit 90-100 it does smooth back out a bit, but the car still needs an alignment.

I am still in the learning process on the ford, I love this car, but am a novice when it comes to anything other then basic engine work. (this forum helps a ton).

-Joe

 

[sublime29]

Make sure that your driveshaft is not hitting anything.I don't think you should have any play in your rear axle shaft.If you can move it with your arms imagine what the weight of your car and the g's when turn would do to the axle.I would think that is your problem and very dangerous.I broke a axle shaft right off the line and the whole thing wait flying.I would hate to see that doing 60 or more.Get it to a shop asap.

 

[UMDSmith]

Yeah, once I discovered that was a potential issue, I haven't driven it. It will not slide all the way out, but it definatly has some movement.

The car itself is phenominal, just a few little problems to work out before I can start building it up even more. I am using the rule that anything that breaks will be replaced with something of higher quality.

-Joe

 

[Gearbanger 101]

So the list of things to check.

ball-joints
bushings (I do have a lot of wheel hop so the control arms will eventually be replaced, although wouldnt they cause vibration throughout entire speed range?)
tranny mounts
c-clips (Possibility still)
pinion angle?

Now, for some reason this vibration only really happens at 80 mph and is slight, worse when I accelerate, and even worse around turns at 80mph. Once I hit 90-100 it does smooth back out a bit, but the car still needs an alignment.

What I got from your initial post was that the vibration you were getting was from hard acceleration, which can be one of several things. More often than not, it's from bad U-Joints, but it can be related to a number of other things

Ball Joints - Were my first guess because you stated that you felt it underneath your feet and when you turned the wheel. But if you're positive that it's not coming from the front end, the I wouldn't worry.

Bushings - There are several throughout the entire rear end. A worn upper control arm bushing will cause excess deflection a cause the pinion angle to change dramatically under hard acceleration. Doing this throws off the geometry in relation to your transmission, drive shaft and rear end.

Tranny Mount - If the tranny mount is damaged it could also throw off the drive train geometry with a similar effect to what a bad U-joint would produce. It's also a good idea to replace engine mounts if they're fairly old. They may not be damaged, but the stock rubber mounts have a tendency to "settle" over time and as such has an effect on driveshaft geometry as well.

C-Clips - Doubt it's the cause of your vibration, but as I said before, some endplay with your axles is normal. It's nothing to check it out, so go ahead and do so.

Pinion Angle - As stated above. A couple of degree's of positive angle seems to work best with street use, but you'll have to get yourself a set of adjustable upper control arms in order to alter that.

You're wheel hop is likely worn out quad shocks. If you're not planning to replace the control arms right away, changing the quad shocks should cure your wheel hop woes.

Now aside from all that, there's also wheel balance to consider as well as the possibility of a bent axle....soooo many variables, it's best to start going down the list with the most common (and least expensive) in hopes of finding the right one.

 

[cmozez]

Side to side play in the axel is normal. Up and down plat is worn bearings.

 

[UMDSmith]

Thanks a ton guys, I have quite a few things to check.

The thing that keeps throwing me off is, under WOT, until at least 80 mph, it has zippy vibration except for some initial wheelhop, it is only at that 80mph mark that the vibration truly starts, then it smooths out again at 90mph, relatively so.

Although it could definately be anything listed. Since it only happens when Im driving at 80, and it is so hard to tell where the vibration is ocming from, since I feel it through my feet on the floorpanels, I just have to check it all.

 

[odingalt]

What did you find out?

 

[UMDSmith]

Well, finally got it diagnosed, turns out it was a misbalanced driveshaft. I have a new aluminum driveshaft on order from summit racing right now. Lets hope that fixes all the problems.