Just bought my first Foxbody, I think I screwed up big time.

[MileHighDart]

So, I've been shopping locally for a nice fox body stang for a couple months. After seen lots of highly modified cars, convertibles, and cars that have been beat to crap, I finally found a nice looking 89 LX , with 5.0 and a 5-speed.
Transmission has supposedly been "rebuilt"
Has centerforce clutch/flywheel
Has 3:73 gears
Subframe connectors
Cold air kit.
Aftermarket cat-back exhaust system.
Clean car with just a few mods, great this is just what I was looking for.

We drove the car around town for about 15 minutes, ran great, sounded good, steering, brakes, all good. Tranny shifed good 1 through 4, but we never got above 50mph or so.
So we go back to the guys house, I hand over the cash, he hands me the title, we sign everything, and I head for home.

As soon as I got on the highway and dropped it into 5th gear I knew I had made a big mistake. How could I be so stupid as to not insist that we take it out on the highway.
Anyway, as soon as I go to 5th there is a very nasty vibration in the driveline. Its worse at certain speeds, like 58-63, then it smooths out a little, and starts up again as I approach 70mph. The vibration is high speed and makes the whole car vibrate and makes kind of a droneing sound from the driveline, or rear end, or maybe its just vibrating the whole car. Very annoying, but its my own stupid fault for not going for a "proper" test drive be handing over the cash. If I drop it back into 4th its much smoother,, then back to 5th and its vibrating and loud.

Any ideas on what could be causing this vibration ? Anyone had simular problems ?
Dont know where to start, buy a reman tranny and swap it out, or take it to a tranny shop and see if they can diagnose it to see that might be wrong. ?

I dont dare take the wife for a ride in it, she'd be like "you bought this piece of crap ?"

Where do I start ?

 

[Jason 302]

So 58-63 mph in 4th gear it doesn't do this, but in 5th it does?

I had some vibration issues until I had my driveshaft balanced. Sometimes a gear swap can cause balance issues.

I've also heard of people rotating the driveshaft on the pinion and solving their issue.

 

[MileHighDart]

Correct, much smoother in 4th, then shift to 5th, vibration starts.

 

[foxbodymike87]

mabye your tanny mount is loose. the faster you go the more the tanny wiggles around

 

[Febreezeit50]

I'd take it to a transmission shop and have them figure it out. If you have the extra cash of course. That way they have a mild warranty on whatever they do. Especially since it seems youre convinced it only happens in 5th

 

[ID89GT]

Check u joints as well, could be something simple

 

[bonestock87]

Just call the guy that sold it to you and ask if he knows what needs replaced. He probably does and you don't have to keep guessing. At least make him feel bad for keeping the problem hidden.

 

[1991notchbackLX]

Drivetrain vibrations are common on these cars, don't consider it a deal breaker. It's usually because some jackwagon with a 10 piece Sears tool set thinks he's smarter than Ford design engineers and starts stripping off parts and throwing them into the dumpster. Check to see if the "dogbone" was removed to save weight. That "dogbone" is actually a vibration dampener. Also check your universal joints and driveshaft, as mentioned above. Even if it's in the transmission (and it's probably not), you're looking at a relatively cheap rebuild in the long run.

 

[foxbodymike87]

In massachussetts at least.. The law is if you find a problem the owner didn't tell you about within 7 days he HAS to fix it.

 

[fivespeedsteed]

Will be a relatively cheap fix no matter what it is, you'll invest a little more than the cost of the car but it will be worth it in the end

Sent from my DROID3 using Tapatalk

 

[wythors]

It's usually because some jackwagon with a 10 piece Sears tool set thinks he's smarter than Ford design engineers and starts stripping off parts and throwing them into the dumpster.

That's the root cause of most problems I read about on all Mustang forums.

 

[Bullitt347]

4th gear is the only gear where the power flow through the transmission is straight through the mainshaft of the transmission, and therefore has the least deflection and path of least resistance. All other gears the power goes through the counter shaft before it gets back to the tailshaft.. 5th and reverse are on the backside of the transmission and use the same idler gear (countershaft gear) and do not use the main countershaft that 1st 2nd and 3rd gears use. If you pull the tailshaft housing off of the trans, you will see only 5th and reverse gears. The rest of the gears in the trans are in the main case. You could just have a tailshaft housing bushing worn out, or the 5th gear clearance could be out of spec. If the vibration is only gear related and not speed related, then you can count on the driveshaft/rear diff or wheels/tires as not being the problem.

 

[MileHighDart]

Thanks for the ideas on what to check for.

Where is this "dogbone" so I can check to see if its there or been removed. (remember it's my first fox and just got it yesterday).

 

[RycheGT]

Youll have to go under the car to see if the dog bone is still there. It will be attached to the bottom of the rear end with two bolts. Look at the bottom of the rear at the pinion, and you should see a large piece of steel. Looks like a weight shaped like a dog bone. You cant miss it.

Only picture I could find. It doesnt show location, and its from the side, but it gives you an idea of what to look for.

 

[bentley429isBAC]

I'd say its the driveshaft. If not I doubt its anything serious.

 

[fivespeedsteed]

does it want to bog down in lower gears at low rpms? 4th to 5th is a big gap, i usually wait till 50 to shift to 5th because if i shift to 5th at 40, my rpms are just above 1000, and they should be in cruising speed above 1500. is it more of a vibration or a missing stuttering causing a vibration

 

[wythors]

Thanks for the ideas on what to check for.

Where is this "dogbone" so I can check to see if its there or been removed. (remember it's my first fox and just got it yesterday).

The rust colored part.

 

[MileHighDart]

Wythors,,, thanks for posting that pic, makes sence now what I'm looking for. And from crawling under the car I can tell you for sure that I do not have a dogbone on my car.

I actually had to go back to the sellers house today to pick up some extra parts that went with the car. He had removed all the A/C parts from under the hood, but they were stored at his buddy's house. Anyway, I got all that stuff, plus the original shocks/struts that he took off. He replaced them with some kind of fancy adjustable shocks. He said if I wanted to swap them back that I could probably sell the fancy shocks and get some of my initial investment back.

But anyway I had a long talk with him about the vibration issue. I think he actually felt pretty bad about it. I told him that if we had test driven it on the highway that would not have bought the car. Also, he owned this car for a few years, then sold it to his buddy out of state, and then just recently he bought the car back from his buddy. I think he hasn't actually driven the car himself in quite some time cause its just been sitting since he got it back from his bud. So he was quite surprised when I brought up the issue with the vibration, I dont really think he knew there was a problem.

Anyhow, he seems like a really nice guy and he wants me to be happy with the car, so he actually offered to help me figure out what the problem is. He's had several fox bodies and seems to know them pretty well. I've read a lot online in the last 24 hours about vibration issues and about a lot of guys going to the aluminum drive shaft to try to cure vibration. I happened to mention this to him when we were talking, and turns out he has an aluminum driveshaft thats not being used (from one of his other cars) and he's willing to let me swap it out and see if it helps. He even said I could bring the car down next weekend and we could swap it out to see if it helps. He also has an extra harmonic balancer for the engine cause he thinks the one on the car is bad, so we'll be swapping that out as well.

I'll keep you guys posted,

 

[Febreezeit50]

Good luck man, once its fixed you will be happy!

 

[strattoc]

If it was the harmonic balancer you would feel it in every gear since the engine revs in every gear. Whats funny about that is my car is an AOD but at 55-65 I have a very noticeable vibration which was bad until I lowered the car a bit and changed the u-joints, but I still have a steel driveshaft. Mine is very bad at 120 mph, but who drives that fast anyways.