Ford Mustang Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
75 Posts
Discussion Starter #1
I’ve searched the corral and google with no luck. I have a fox body that I drive 50 miles to work on occasion and cruise in around town. It doesn’t see the drag strip often. It’s mildly modded with a good bit of suspension parts thrown at it. The rear is team z relocated uppers, team z lowers (polyurethane bushing set). Cruising 75 -80 on the highway gives me a vibration. Letting off the gas at that speed gives a nice vibration also. I’m putting in an aluminum driveshaft today and currently checking pinion angle and it is 2.2. For a daily driver, would you want a pinion angle closer to zero for cruising? Thanks in advance.
 

·
Registered
Joined
·
907 Posts

·
Registered
Joined
·
3,045 Posts
Just went through this on the race car, and had some guidance. I'll pass it along.

Pull the car into the shop/garage/concrete. It needs to be somewhat level AND at normal ride height. IF you have a helper, tell them to sit in the driver's seat for a while to simulate a driver. The closer to your weight the better, but this step is not 100% critical (unless you're picky like me).

Remove the drive shaft. Haul it to the next county. Seriously, forget about it. This "can" be done with the shaft in the car but it's a LOT easier to just take it out and you'll understand why once you do it. Also you can check your U-joints while it's out ;)

Grab your angle gauge, digital ones work great for this (I use an angle cube and it is wonderful for doing shaft angles and chassis work). Bought it from...Tim McAmis.

Measure the angle of the transmission output shaft. This can be measured either on the shaft itself or against the seal. Record it's angle, and which way it's angled (down, up etc).

then go to the pinion flange. Measure it. Record it, and record whether it's up, down or otherwise.

---------------
Now then, here is the interesting part. If the transmission is angled DOWN (most of them are), you want the pinion to angle up so that they are "roughly" the same (2° down at the transmission, so you would want 2° UP at the pinion--this would give you zero angle). In this example, you ideally would like to see it at zero under a load. BUT you will have some bushing flex, so you will want to know what kind of bushings you have. Spherical, poly, or rubber. If spherical, you can get by with less than poly, and poly less than rubber.

I know, it makes zero sense whatsoever but it WORKS. Why? Because the 2 u-joints need to be close to the same angle to cancel each other's angular velocity change during rotation.

My 93 has a vibration too that I can't find, and I know it's in the driveline somewhere. All stock replacement stuff except the OE 4 cylinder drive shaft. I've got to have this addressed soon cause it's eating at me. Nothing major but if I kick it in neutral at 60 I can feel it in the shifter. This started after replacing the U-joints last month so maybe just needs balancing. Dunno. Probably pull it and carry it to the drive shaft shop down the road and see what he says.
 

·
Premium Member
Joined
·
3,076 Posts
All Mustang OEM driveshafts have a vibration damper inside them. If this comes detached from the driveshaft, no amount of balancing will work and the driveline is going to vibrate not matter what.

As pointed out in this thread already, pinion angle is 100% meaningless. Place a floor jack under the k-member and raise the front of the car 45". Your pinion angle may now be 45 degrees, but there still may not be any vibration. The only thing that matters are the operating angles of the u-joints.
 
1 - 6 of 6 Posts
Top