I have an '85 Trans Am convertible conversion. It has 14,500 original miles on it. When I got it, it still had the original tires which were bad so I put on new tires. I thought this was for sure the problem. It was still there. I have two 85's so did a swap because both have new tires. Still the same. The other one is as smooth as can be, so I know the tires and wheels aren't the problem.


I have a shake starting at about 40 mph to about 50 mph or around that. It seems like the body just rocks. I just installed a new idler arm since I know the factory ones were not good. It was bad for sure and the rest of the front end is good. I drove off and it still has the problem. This car has an "X" member across the bottom, door bracing, etc. I am wondering if the body could be flexing at this speed? I don't know what else to look for since my experience is limited and trial and error is costly. When I got it, again, I figured the tires were just bad. What else could cause it to do a little dance at this speed? Shocks? Someone said maybe it has bad rotors. Rotors wouldn't do anything unless you were putting on the brakes would they? When I am at cruising speed around 70 mph it is good to go. Start to slow back down and when it hits this range, it starts to wobble. Any suggestions would be appreciated.

 

I was gonna say rotors.. but u didnt mention braking ..
U put new tires.. so the wheel is balanced..
done right I hope.. wheels arnt damaged ..
check the suspension (tie rods, ball joints..)
Is the alignment good?

After 50 mph, no more shaking?
Double check what was installed..

Good luck

 

Yeah sounds like its in the front susp., don't forget to check strut mounts.

 

get the tires rebalanced, could just be out of balence

 

I have two 85 Transams. I took both at the same time and had new tires put on them. I saw that the car had a shake so thought maybe it was the wheels. I swapped from the other T/A and still had the shake. The other one was fine with both sets. As smooth as can be.

I thought about rotors, but it shakes without hitting the brakes. Would it shake anyway?

I think the strut mount might be possible. I had thought about struts. This baffles me. Thanks for the suggestions. I appreciate all the help I can get. This stuff gets expensive from trial and error.

 

I've been chasing one down as well, I've replaced everything except the strut mounts so I just recieved my alloy specialties mounts in the mail today, they will go in soon!

 

I had a ford probe one time that gave me a fit. I finally put in a new front rack, just to find out it was still the same wobbly problem. I finally took the car back to ford and they discovered the strut mounts they had put on earlier were screwed up. Problem solved. Their bad work cost me lots of money and I would have never thought about strut mounts. I will have to check on this right away. Like tomorrow!

 

Did you replace the mounts yet? I'm having a similar problem with my vert and have replaced the ball joints, outer rod ends, idler arm and tires. I've had the tires rebalanced at another tire shop and still get the shake.

 

I am going to check into it. I just drove it last night on a longer trip to see how the idle arm helped it. It did help for sure but the shake is still there. It starts right around 40 mph and smooths out at around 50 mph or a little less. Really weird. I checked the "X" bracing underneath the car and it seems tight. I need to get it on a rack and check closer though.

 

X bracing? Is the bracing on your vert different from the ASC conversions? Also, you say your shake smooths out at about 50 mph. Does it start coming back at about 70 mph and get stronger with more speed? The reason I ask is I think I may have multiple problems, like a combo of an out of balance driveshaft and bad strut mounts.