Car shakes when taking off help???

[STANKYstangs]

Good afternoon friends! New here and I apologize if I bring up a topic that’s already been discussed. I did a brief search and I didn’t notice anything that was as specific as my issue. And google wasn’t much help either.

I have an 03 GT 5 speed convertible. Mainly stock with the exception of a few bolt ones. I bought the car to put an engine in it. After that was all done, I noticed the car had a very aggressive shake when taking off in first gear. But not so much reverse. (Although, taking off in reverse is usually never as aggressive) at first it would shake so much the whole car felt like it was jumping around from left to right and it would wobble the stick in the car.

The problem is, I already replaced most of what I would consider the primary culprits of this condition. It has a brand new fly wheel, brand new clutch, pressure plate and both bearings and recently I replaced both engine mounts and trans mount.

After replacing all the mounts, the shake got a LOT better but is still there from time to time. The only other thing I can think of is drive shaft but I have never trouble shot a drive shaft before. (To be honest, it KINDA feels like wheel hop now) I’m assuming you just grab it and yank it around and see if there’s any play in the u-joints? Problem I have with the drive shaft is if that’s bad, then why doesn’t it vibrate all the time? Once the clutch is all the way out this car drives like a dream!

Is there something else I should look into? Any suspension issues I should look at? I have been under the car quite a bit and I noticed all the shocks are aftermarket and I shook down all 4 wheels and they are solid.

What in the actual H E double hockey stick am I missing here??

 

[Mcmahst]

Still sounds like a clutch engagement issue. Unfortunately, new doesn’t mean good anymore. I will wait to see what others think before investigating the clutch and flywheel, but that is a typical alignment and clatter symptom. Good luck.

 

[Noobz347]

Check the U-Joints.

Does your car have a one-piece or two-piece driveshaft? If two, check that too.

 

[squeak93]

03 should be 1 piece shaft -unless some weird custom job. I tend to agree that a u joint "Should" show its ugly face at higher speeds, and this seems more of a clutch engagement issue. Any bearing related stuff would tend to progressively get worse at speed/rpm.

Do you know anyone with a lift that could get it in the air (with rear suspended but on its own weight/ride height) so you can view under it while someone engages 1st gear to see if anything shows bent or visibly wrong?

Any issues at speed shifting gears etc? Clutch engagement good (top of pedal but no slipping etc.)?

If only first gear it could be a transmission related issue to 1st only which would add up if no other gears have issues or no shifting problems in later gears etc.

 

[STANKYstangs]

Check the U-Joints.

Does your car have a one-piece or two-piece driveshaft? If two, check that too.

Still sounds like a clutch engagement issue. Unfortunately, new doesn’t mean good anymore. I will wait to see what others think before investigating the clutch and flywheel, but that is a typical alignment and clatter symptom. Good luck.

So I have never come across that before. And I’m having a hard time understanding this. Is there an incorrect way to install the clutch or pressure plate? It goes into all gears just fine and I just can’t understand how it’s ONLY a problem when taking off from a dead start. Also, it doesn’t make any noise, it just shakes.

A LITTLE more info, I bought the car to flip. Had a bad engine. Never drove it before I put another engine in it so unfortunately il never know if it was already doing this…

 

[STANKYstangs]

03 should be 1 piece shaft -unless some weird custom job. I tend to agree that a u joint "Should" show its ugly face at higher speeds, and this seems more of a clutch engagement issue. Any bearing related stuff would tend to progressively get worse at speed/rpm.

Do you know anyone with a lift that could get it in the air (with rear suspended but on its own weight/ride height) so you can view under it while someone engages 1st gear to see if anything shows bent or visibly wrong?

Any issues at speed shifting gears etc? Clutch engagement good (top of pedal but no slipping etc.)?

If only first gear it could be a transmission related issue to 1st only which would add up if no other gears have issues or no shifting problems in later gears etc.

Squeak, for starters I think I replied to the other messages wrong… it looks like I replied to 2 at once so sorry if I made the post confusing. Yes it’s a one piece shaft and I have not checked that yet. I do have access to some lifts. One is a shop I used to work at so availability is limited and the other is privately owned but he’s hard to catch on free time. As for shifting, it’s smooth as butter. Goes into every gear no problem and clutch engagement is smooth and fantastic. Hell I can get it back into first pretty easy when slowing down. Most experience I have with manuals you have to damn near be stopped to get back into 1st

I can’t remember if I have said this yet but, now that I put all new mounts in, the shake got a LOT better. Sometimes it doesn’t even do it if I’m careful. Before the mounts it was pretty aggressive every time now it’s a lot more mild and only sometimes. It almost feels like wheel hop now.

 

[STANKYstangs]

Sorry for the long delay friends. I got back from vacation Saturday, worked all day Sunday and recovered all day Monday.

Today I got under the car and checked the u-joints. They are super duper uber solid on both ends. Used a pry bar and everything. HOWEVER. now I’m suspecting this garbagio rock auto trans mount is the issue. I grabbed the drive shaft right behind the yoke, (trans side) and very easy up and down movements would move the whole rail end of the transmission up and down. I’d say at least 1/16”. Now I’m no mount specialist and I know they are designed to give a little under load but I don’t feel like that’s normal.

I ordered an ac liquid line that shows up at advanced tomorrow and while I’m out il grab another trans mount. They are cheap and easy enough to try out.

I know this is an odd question but can anyone tell me if play like that is normal in the trans mount? Sadly the engine mounts are also from rock auto but after I changed them the vibration got SOO much better.

Il be back sometime tomorrow or the next day with test drive results. I appreciate all of your inputs!

 

[Mcmahst]

I don’t think 125 thousands of an inch play is the cause of the vibration. And I think that amount of play is within the tolerance of the mount.

Before the flywheel and clutch assembly was installed, was the flatness of the flywheel measured? A new clutch plate will somewhat hide a flywheel that is not completely parallel to the clutch plate, for a while.

 

[squeak93]

I've not gorilla'd my drive shaft or trans in a while like that but I don't recall ANY movement on either of those when tugging on them from under neath. At least not easy movement. Squishy mounts will cause weird issues I suppose. If it's bouncing that easy by hand its certainly moving when applying engine power at takeoff. Now if that's your issue, who knows.

Factory style rubber mounts or a poly setup? any rear end movement when applying the same scientific method to find movement?

 

[Mcmahst]

What did you decide to do?

 

[STANKYstangs]

Hey guy! Sorry I’m slow. So I put another mount on and unfortunately it did the same thing. Had the same up and down movement… as for the read end, I didn’t notice any movement at all down there.

Also, I did not measure the flatness of the new flywheel or pressure plate. I figured brand new parts would just be good out of the box. (Silly me) I’m running out of options here. I just don’t see how it could be the clutch. I have never myself experienced clutch chatter, so I don’t have anything to compare it to. But it doesn’t make any noise, if engages and disengages perfectly fine, shifts smooth as butter and once the clutch is all the way out and your driving it doesn’t shake again. Maybe I’m wrong, but wouldn’t clutch chatter cause an issue any time you engage or disengage the clutch?

 

[Mcmahst]

Take it to a trans shop and have them drive it. It couldn’t hurt.

 

[LILCBRA]

One thing I don't see mentioned, how about the input shaft pilot bushing/bearing in the crankshaft? Unless this is what you referred to here:

The problem is, I already replaced most of what I would consider the primary culprits of this condition. It has a brand new fly wheel, brand new clutch, pressure plate and both bearings and recently I replaced both engine mounts and trans mount.

You said you installed a new engine - there is supposed to be a bushing or bearing in the end of the crankshaft to support the input shaft of the transmission. I'd suspect that if it weren't there that you'd probably end up with all sorts of shaking when attempting to engage the transmission. Crate engines won't come with one installed and if you installed a used engine, if it's from an automatic car, it won't have one either.

https://lmr.com/item/LRS-7600B/96-04-Mustang-Clutch-Pilot-Bearing