66 w/T5 vibration (bad)

[427sohc]

Would appreciate any suggestion on where to look to fix the following problem:

Slight vibration at about 40mph. this vibration can be felt just about anywhere in the car. Severe (really) vibration starting at 80-85mph. It is independent of engine rpm as the vibration continues if I take it out of gear at this speed. This vibration seems to be less noticeable in the steering wheel compared to anywhere else in the car. The shifter is really bad. I am afraid to take it up to higher speeds as it feels like the car wants to shake apart.

I have so far balanced the drive shaft and the wheels. Also tried a second set of new wheels. No difference. The guy balancing the shaft said he saw nothing wrong with the U-joints. Also can't feel any play where the drive shaft enters the tail housing.

Setup: 66 hardtop with a strong 289 (carb, intake, heads, cam, headers, etc.). T5 tranny installed. I am told the rear end is a 4.11 setup. Don't know this for sure as I just bought the car.

Suggestions?

 

[Loup-garou]

Try putting the rear axle on jackstands and running the car in gear. Have someone give it some throttle and run it up through the gears while you watch the drivetrain for obvious ocillation or shaking.

The problem might not be obvious without "loading" the drivetrain, but it's worth a shot.

 

[MustangMatt1966]

ya never know though, u take a car that is 35 years plus old...they all feel like they are going to fall apart over 80 mph i know mine does lol

 

[Mr_siv]

try rotating the tires, see if you can feal the vibration in the front end than. if so, you have an out of ballence tire/rim

- Jason

 

[STSFCTN67]

When I did my swap I had the EXACT same problem. After doing all the obvious, I added two thick washers to each bolt to the bottom of the transmission mount and the crossmember. That fixed the problem.

 

[VictorII]

Might be a bad tail housing busing in the trans. Or one of the u-joints. But if you had the drive shaft balanced the shop probably checked the joints. Also, is the joint centered in the rear end? Sounds like the trans if the shifter is that bad though.

 

[one2gamble]

thick washers? Like the trans mount was lose or were you trying to correct the drive train angle?

 

[Ronstang]

It could be a drivetrain angle problem. When you use a commercial crossmember to install a T-5 you end up at about 6 degrees and stock is 3 degrees.

 

[mustangprodude]

I had a vibe issue when I had my C4 rebuilt on my former 64.5 . Turns out that the driveshaft was not exactly centered in the pinion flange. Simply loosened the u-bolts, lines it the center and retightened the bolt. Solved my vibes.

 

[BobV]

It could be a drivetrain angle problem. When you use a commercial crossmember to install a T-5 you end up at about 6 degrees and stock is 3 degrees.

I agree that it COULD be a drivetrain angle issue. (and should be checked)

I disagree that a commercial crossmember WILL give you a 6* angle with a T5. My Ron Morris X-member came in at 3.5*. I think the 6* is what some swappers were reporting with the Darkhorse TREMEC x-member.

 

[Glen's 1965 5.0]

Mine is...

My T5 angle is 7 degrees and the SOSR is a penny's thickness away from the upper support rib. My crossmember is a NPD one. Corrected the angle on the rear axlew and the vibration is gone.

 

[one2gamble]

how do you measure the angle ?

 

[427sohc]

Thanks for the quick replies....

Loup-garou: I admit I am a little hesitant to do that. Sounds a little dangerous to me.

Mr_siv: Tried that. Pretty sure it's not the wheels

STSFCTN67: Do you mean adding height between the crossmember and the tranny? In other words, raising the tail housing? Do you recall how much you raised it?

VictorII: How do I check for a bad tail housing bushing?

one2gamble, Ronstang, BobV, Glen's 1965 5.0: In one way or another you all talk about the drive train angle. Sorry for my ignorance, but what exactly is the drive train angle? And, like one2gamble, I would like to learn how to measue it.

mustangprodude: I will check that, thanks.

To summarize:
1. I try to check on whether the u-joint is centered at the pinion
2. Should I try to raise the tranny on the crossmember?
3. Drivetrain: I would appreciate more details from you guys on what exactly it is I should be looking for.

Thanks again. Help like this is not easy to come by here in Germany

 

[Glen's 1965 5.0]

Check out this link http://www.drivetrain.com/driveline_angle_problem.html and do a search in Google on Pinion Angle for allot of info. My car has 7 degrees of positive pinion angle on the rear axle contrary to what is stated in the articles but it works great for me.

 

[TT670]

My car suffered the exact same problem, I was ready to pull the engine and tell the guy who balanced it to stick it up his a$$ when I found the transmission was touching the tunnel in the shifter area. Make 100% sure there is no contact anywhere.. After some trimming on the hole in the tunnel the vibration is no more..

 

[VictorII]

VictorII: How do I check for a bad tail housing bushing?

The way I do it is to disconnect the rear of the shaft and then sort of wiggle the yoke while it is in the tailshaft. I don't know the exact spec. but it should be free, however not too free. If it wobbles all over the place, it is likely bad. Hope this helps.......

 

[STSFCTN67]

It is not the driveshaft angle it is the fact that when you tightened the C4 tranny mount to the new crossmember the bolt bottoms out without torquing the two parts together enough. Add about two regular hardware washers and let me know if that works.

Thanks for the quick replies....

Loup-garou: I admit I am a little hesitant to do that. Sounds a little dangerous to me.

Mr_siv: Tried that. Pretty sure it's not the wheels

STSFCTN67: Do you mean adding height between the crossmember and the tranny? YES undefinedIn other words, raising the tail housing? Do you recall how much you raised it?

VictorII: How do I check for a bad tail housing bushing?

one2gamble, Ronstang, BobV, Glen's 1965 5.0: In one way or another you all talk about the drive train angle. Sorry for my ignorance, but what exactly is the drive train angle? And, like one2gamble, I would like to learn how to measue it.

mustangprodude: I will check that, thanks.

To summarize:
1. I try to check on whether the u-joint is centered at the pinion
2. Should I try to raise the tranny on the crossmember?
3. Drivetrain: I would appreciate more details from you guys on what exactly it is I should be looking for.

Thanks again. Help like this is not easy to come by here in Germany