I have a 66 coupe that I performed this swap on. My question is as follows: I had a new driveshaft made with the correct u-joints/new yoke and balanced. The business that performed the work (Pittsburgh driveshaft company) has been in business for 40 years and made the driveshaft 49 1/2" verses the 50" that I told them I needed. Stated that it was better to have it a bit shorter than "stub" it in the rear of the trans. I have about 3 1/4" of total engagement of the splined shaft with yoke. My question is that I have a terrible vibration at 50 mph plus. I have not turned the driveshaft 180 degrees yet to see if vibration goes away but was wondering if this shorter length could have any bearing on this problem?
t5 swap driveshaft length/vibration question
- Thread starter pazcarguy
- Start date
chepsk8
Founding Member
I had one made for myself when I did the swap, but no issues. The length will not be an issue. Did you use the correct flywheel/flexplate for the motor? That is usually where the shake comes from. Also be sure the driveshaft is in solid, there is no play in the trans taillshaft bushings, or the rear universal not seated right.
67coupestang
Founding Member
- May 31, 2002
- 509
- 2
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from what i've read (and it may be incorrect) the early 65-6 stangs have trouble with a t-5 at the right angle. improper joint angles can cause a vibe as well
red65
Member
67coupestang said:
I've got a '95 T-5 in my '65 with a custom aluminum driveshaft and it runs smooth enough (up to 132-ish mph at the track, anyway). The 1/2" shorter shaft shouldn't have any effect.
Check and make sure the shop balanced the driveshaft properly. Ask them if it's possible that the balance isn't right on. Look to make sure that one of the balance weights didn't come loose - they're usually just small plates welded around the circumference of the shaft. Also, before killing yourself looking for driveshaft problems, make sure that it's not something else entirely - an imbalanced wheel/tire would be really common and produces about the same symptoms.
A few trouble shooting tips
If it is driveshaft related it will have the same vibration whether you are in 3rd, 4th or 5th. Try running in each gear at the speed where you get the vibration. You need to be on a flat road cruising. If it changes with the gear it is before the driveshaft. If it remains the same, it is after. If it changes on accel or decel it is either the rear bushing (your yoke should have close to zero vertical movement), or your pinion bearings (pinion yoke should have zero vertical movement).
If it is a pulsing vibration, check your driveline angle in comparison to your pinion angle. Different cross members set the trans at different angles. You want to make sure your pinion angle is within 1/4 degree of your drivetrain angle. Also make sure your drivetrain is parallel with the length of the car.
If the vibration changes when the speed is kept constant and the gear is changed, look at your clutch/flywheel balance, as well as crankshaft play.
Depending on how far the transmission yoke is inserted into the rear of the transmission, a 1/2" difference can make a big difference in play. The first iteration of my driveshaft had almost 2" of the yoke out of the transmission. The newest version (changed for the 8.8" install) has 1.5" at ride height. It works much better.
There is a picture on the brake install page of the web site in my signature that shows the newest version with the 1.5" gap. You can use that as a comparison to yours. If your's is out much further, check it closely for vertical movement. Basically you should just barely (and I mean "barely") be able to feel a light clearance when you try to move the yoke up and down.
HTH,
If it is driveshaft related it will have the same vibration whether you are in 3rd, 4th or 5th. Try running in each gear at the speed where you get the vibration. You need to be on a flat road cruising. If it changes with the gear it is before the driveshaft. If it remains the same, it is after. If it changes on accel or decel it is either the rear bushing (your yoke should have close to zero vertical movement), or your pinion bearings (pinion yoke should have zero vertical movement).
If it is a pulsing vibration, check your driveline angle in comparison to your pinion angle. Different cross members set the trans at different angles. You want to make sure your pinion angle is within 1/4 degree of your drivetrain angle. Also make sure your drivetrain is parallel with the length of the car.
If the vibration changes when the speed is kept constant and the gear is changed, look at your clutch/flywheel balance, as well as crankshaft play.
Depending on how far the transmission yoke is inserted into the rear of the transmission, a 1/2" difference can make a big difference in play. The first iteration of my driveshaft had almost 2" of the yoke out of the transmission. The newest version (changed for the 8.8" install) has 1.5" at ride height. It works much better.
There is a picture on the brake install page of the web site in my signature that shows the newest version with the 1.5" gap. You can use that as a comparison to yours. If your's is out much further, check it closely for vertical movement. Basically you should just barely (and I mean "barely") be able to feel a light clearance when you try to move the yoke up and down.
HTH,
Double check your u-joint to third member connection. Although it looked like it was, mine wasn't properly seated :wall: and gave a transient, hard to find vibration at 65-70MPH in 3rd, 4th and 5th. Vibration seemed worse when in gear, but not accelerating. Pushing in the clutch at speed would make it mostly disappear. Removing and properly re-installing the u-joint to pinion shaft connection helped to smooth out to nearly nothing. I suspect a bit of mine is tire balance, but that was magnified by the u-joint.
Daniel
Daniel
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