Rear Axle Alignment

tt400 · #1 (**permalink**) 06-13-2011, 07:06 PM

I am putting to gether my cobra with a 9" rear axle and coilover suspension. The rear axle is 1/2" offset farther to the passenger side of the car. I also measured the distance between the front spindles and the center of the rear axles. It is 1/2 shorter on the passenger side. Is this correct? Am I doing something wrong here?
Thanks

Wbulk · #2 (**permalink**) 06-13-2011, 08:22 PM

I would be glad to help if you can give the following information.

1. is your body on
2. do you have heim joints for the rear four link arms
3. do you have front tubular A arms with the 4" wide K member
4. what year is your car.

If you give me this we can figure this out.

Wayne

tt400 · #3 (**permalink**) 06-13-2011, 09:00 PM

The body is not on. Its a 2004 car.
I do have the tubular front A arms
I am measuring the out of alignment of the axle off the frame.

tt400 · #4 (**permalink**) 06-13-2011, 09:06 PM

The body is not on. Its a 2004 car.
I do have the tubular front A arms
I am measuring the out of alignment of the axle off the frame.

Wbulk · #5 (**permalink**) 06-14-2011, 01:03 AM

Do you have the heim joints on the four link arms? These allow you to center the axle and set the pinion angle at ride height.

The goal is to get your body centered to the frame and get the fender lips at reasonably the same height front left to right and rear left to right. Then you want to get the rear axle centered to the rear fender lips. With the centering process, (with an axle with heim joints), the pinion angle needs to be set at ride height and the axle at the correct wheel base and centered left to right. Then you can adjust the heim joints so they so they bolt up.

With your body on was the body centered to the frame front and rear, (fender lips to the frame). It is normal for them to be off a little. The originals were off but you want to get it as close as possible. If you look at the lower edge between the wheel wells with the body on you have a little play to move the body before it hits the sides of the frame. If the front is considerably off you may want to cut the front support off that mounts to the front of the hood opening. I cut the welds, centered the body, and made sure the lips were level with the frame and then rewelded it.

It is very hard to measure the wheel base accuratly from the spindles. Notice the bar that is clamped to the K member below. The center of the K member is the center of your spindles. Hold you tape over the bar equal to 1/2 the thicknes of the K member and then measure back 90" for the center of the axles to see where you are. There is a machined edge you may want to measure to after doing the math deductions. It's easier to measure to than trying the eyeball the center of the axle flange. Also in my gallery is a picture of my four link with heim joints.

When I did all this on mine I started with leveling the frame front to back and side to side with blocks and shims. It is sad to see a car that a guy has put a lot of money into and body or axle is cocked on the frame. Call me and we can discuss it in far more detail.

Wayne

tt400 · #6 (**permalink**) 06-14-2011, 04:04 PM

Thank you for the reply's. I have the four link arms. They are not adjustable that I can see. Right I am not as concerned on how they line up on the body as the rear axle is not straight in the car. I cannot tell if the axle B&B sent me is bent or if something else is off. The car will not go straight down the road as it now sets.

Tim Brewer · #7 (**permalink**) 06-14-2011, 09:20 PM

So, are you sure you don't have adjustment on your four-link bars? I kinda think you must have. Also your axel should adjust side to side with a panhard bar. Can you take a picture?

Wbulk · #8 (**permalink**) 06-14-2011, 09:25 PM

It sounds like your four link brackets on the frame or the axle may be off. Mine were off and even with the heim joints it would not work. I had to have them redo the brackets. Without the heim joints you are at the mercy of the welder and the accuracy of his jig.

I would get the frame level like I said. I would then get the axle on jack stands centered left and right with the frame and level. The ride height is just a little over and inch from the bump stops to the axle. Cut some blocks about 1 1/4" and set them on the axle under the bump stops. Shim the axle up until they both touch. Then you need to set the pinion angle so the nose is up just about 2 degrees. Install the lower arms only and then check your wheel base. If it's off check the arm lengths and the welded brackets on the frame. If it's good see if the upper arms will fit. You may have to have new brackets made and welded on.

The bottom line is you will have to find out were the exact problem is. I feel your pain. I have been there.

Wayne

treblig · #9 (**permalink**) 06-15-2011, 02:14 PM

Quote:

Originally Posted by tt400

I am putting to gether my cobra with a 9" rear axle and coilover suspension. The rear axle is 1/2" offset farther to the passenger side of the car. I also measured the distance between the front spindles and the center of the rear axles. It is 1/2 shorter on the passenger side. Is this correct? Am I doing something wrong here?
Thanks

If your measuring the center of the pinion to the center of the frame that is wrong. The pinion should be .500 off center to the out put shaft on the trany on the passager side.
In order for the u-joints to work properly, your pinion needs to be offset and your angle of your pinion and trany needs to equal 180 degrees.

Wbulk · #10 (**permalink**) 06-15-2011, 03:44 PM

tt400, the reason I say the pinion angle should be about 2 degrees up is that's what Barry Mcgill who built your frame told me he made them. The engine frame mounts vary in height depending on what engine was going in and sometime you need to shim the rear trans cross member down on the B&B depending on what you have.

Slow Dawg · #11 (**permalink**) 06-18-2011, 12:56 PM

Ok, first off, loosen all 8 bolts on all 4 control arms. Unbolt shocks. raise the axle to ride height (lower control arms are level). Retighten all 8 bolts. Sometimes that's all it takes to center it. When I install the body, I measure to center it off the axle, not the frame. Don't measure off the spindle. They move. If you loosen one of the upper control arm bolts and move the arm or turn the steering wheel 10 degrees either way, your measurements will go crazy. Wayne was correct by measureing off the k-member. I use a 6 foot long, 3/4 inch angle iron (perfectly straight) across the back of the k-member. Between the frame and front lower control arm. That should be roughly 88".
If this doesn't work, give me or Bryan a call at the shop.