Vibrations on first test drive 95 mustang

[fivemustangs]

I have a vibration while driving down the road in my 95 mustang gt, but not at idle. I have done a T5 swap into my mustang and used a world class t5 from a 96 mustang 3.8 (which I drove before) I switch the bellhousing, put in a pilot bearing. But I did not swap out the drive shaft when I did the swap, was wondering if this would cause the problem. I think I might still have the t5 yolk in the garage and was wondering if swaping that out might help, or do I need to swap the whole shaft? maybe a loose mounting bolt? The engine is rebuilt with a machine balanced rotating assembly, gt40 heads, exhaust........ect. When the dyno guy took it for a ride he said it had a slight vibration and also on the dyno whn it is slowing down in netural you can see the engine shaking a little. just looking for the facts so I can fix it asap when I get it back. its been WAY to long.
Thanks!

 

[Chythar]

Driveshaft is the same on 94-95 Mustangs, whether it be V6. Gt, Cobra, auto or manual. However, if your driveshaft is out of balance and you don't match it up with the rear axle the same way, you can get vibration.

Does the vibration match up with anything? Engine RPM? Overall speed? Does it go away when you push in the clutch? Where did you get the flywheel from? I presume you got a 50oz flywheel? When the engine was rebuilt, did you have the rotating assembly balanced?

 

[icemetalstang]

I put a new clutch in my car. I get the same vibration . However in neutral it will not vibrate.(Car reved to 4500 RPM) When in gear and clutch pushed in mine vibrates. (Car reved to 4500RPM). It will also vibrate in gear but only above 4000 RPM. I put in a cheap advance clutch. It seems to me the clutch is cheap and not well balanced. Needless to say Im ripping it out and not being cheap this time.

 

[fivemustangs]

There is not a vibration with the clutch in or when the car is in netural, just when you are driving down the road and the driveshaft and rearend in turning. The fly wheel is a 50oz and was in a previous car of mine for about 2000 miles and the rotating assembly was fully machine balanced within 5 grams. The engine was build this winter by me, it was my third 302 I have built but nothing out of the odinary, crank, pistons, rods torque eveything down, main girdle gt40 heads trick flow cam and intakes......so on. I have not changed the gears but drained the fluid out and replaced it with new lube and added friction mod. to it. I have heard that the driveshafts on the manuel and auto's are different, I have owned both and they do look different. The t5 drive shaft has a damper on the end with the tranny and the auto does not. But when you buy a aluminum drive shaft they are universal for both t5 and auto?

 

[Chythar]

OK, that helps to narrow it down. The vibration does not match up with the engine revs, whether the clutch is in or out. that rules out the engine and clutch. If the vibrations get worse the faster you go (ex: vibration at 25mph, more at 35mph, even more at 45mph, etc), and you're using the same driveshaft as before, then the driveshaft is out of phase with the differential. Remember, there are 4 bolts holding the driveshaft on, which means there are 4 diferent ways you can bolt the driveshaft in place. Usually when removing the driveshaft you mark a spot on both the differential and driveshaft so you can match them up again. Since you didn't and you have vibration, you'll have to find that spot again. Basically, remove the driveshaft bolts; keep the pinion from moving but rotate the driveshaft 1/4 turn; then bolt everything back together. The vibration should change. If it's still there, repeat until you've tried all 4 positions. One of them should eliminate the vibration.

94-95 driveshafts are identical - I had a driveshaft from a V6 (auto) and a Cobra (manual), and they were identical, even down to the part numbers on the driveshafts.

 

[fivemustangs]

I never unbolted the driveshaft from the diff. I only pulled it from the tranny I am supposed to get the car back tomorrow and the dyno guy says that its only pushin 190 WRHP and that is less then it should be with my mods. I was wondering if it could be the clutch or flywheel? Because I am missing about 80HP. Any other ideas?