I have a 1989 Mustang Convertible GT with 90,000 miles on it.  While the car is cold and I'm driving at low speeds, I feel a shake/vibration coming from the front end.  When I increase my speed and the engine gets warmer, the shake/vibration reduces.  I have changed the rod ends, balanced the tires and had the car aligned. 

  Additionally, I have a 1985 convertible with 75,000 miles on it that has the same problem but not as bad.  Do you think it is motor mounts or ball joints?

Chuck 

Are you feeling this vibration in the seat of the car or are you feeling it from the steering wheel? If its in the steering wheel, i'd say you need to have your tires/wheels road force balanced. Mustangs are sometimes sensitive to tires that are slightly out of round and typical spin balancing machine isnt going to show this. You will need to find a store that has a road force spin balancer so they can measure the run out to see if everything is running true.

If you are feeling it in the seat of the car, the same could be said for your rear tires/wheels. Its possible your u-joints or an out of balance driveshaft could be causing it but Id be inclined to think that the severity of the vibration would intensify as you go faster with those problems, not the opposite as in this case.  Since the intensity lessens as you speed up, I am still thinking the problem is your tire/wheel combo. You might also consider having them re-checked on a different machine as a balancing machine out of calibration can cause vib's too. I dont think a tired motor mount would create your symptoms either but its hard to say without actually driving the car myself. Start with the easiest thing to check and have those tires/wheels re-checked. I'd be willing to bet thats your problem. 

Thanks for the advice, I will try another wheel shop to balance my tires.  I think the Fire Stone I've been taking my cars to are having problems with their balancer.  I truly hope you are correct and this eliminate the problems.  There is nothing like small things that make it so you can't fully enjoy your ride. 

 I'll let you know the results as soon as I return to the states.  I'm in the AF serving overseas for a few more months.

Chuck

hello,

Having similar issues, I have a 92 vert.  NEW Springs, shocks, struts, Maximum steering shaft, new rack, new Motorsport control arms with the "better ball joints", Kenne Brown Caster Camber plates. Its only lowered 7/8" When i turn about 3/4 of the turn radius i hear a click as if the wheels were loose on the spindles. And oh yeah , new tie rod ends of course.it vibrates at about 30 to 60. then get stable. but ive noticed lately it seems losser. this all started cause i heard a click, and figured what the hell, UPGRADE..  Oh and installed drilled rotors and new bearings and new calipers with the stainless sleeves, And braided lines. I measured the spindle diameter and ther were in spec.

What do you guys torque your front bearings too?

i am a fairly good wrench, but i admit, i am stumped. Everything was torqued to what the chilton book said. but i am open for suggestions.

I appreciate any and all help

Are you feeling the vib's in the seat or the steering wheel? Really the only way to find that popping noise is to do a once over and make sure everything is tight. If your not running spring isolators, that  could cause a little noise but its hard to say without looking at the car. I will also say this sounds like a tire that needs to be road force balanced. You might benefit best by just taking it to a front end expert and having them check it all out for you.

So, even after making all the front end modifications, you still have the vibration?  I was planning on rebuilding my front end and changing the lowering springs, but if you have not seen any benefit I will wait.  Please let me know if the balancing helps or if the front end shop provides some sound advice.

Chuck