Differential, rear suspension question ***BDR specific***

[Gatorac]

I have 181 up on the lift now and I have noticed something that seems odd. The trans output shaft is centered in the frame rails perfectly. The differential is not. It apears the entire rear suspension sub frame is offset to the right by 1/4" and turned slightly. This makes the driveshaft offset to the right by 3/4" It also makes the differential input at an angle on the horizontal axis.

I understand that the drive shaft shouldn't be straight from the trans to the diff in the vertical.

Anyone have any input on this? Is your BDR like this?

[Gatorac]

Here's a pic for reference

[Cashburn]

Normal. That's why it has u-joints. Otherwise you could run direct drive.

[madmaxx]

Looks like it has been torqued and schooled by a Roush!!!! Just joking as Cashburn said normal.

[Gatorac]

Originally Posted by Cashburn

Normal. That's why it has u-joints. Otherwise you could run direct drive.

It has U-joints for the up and down misalignment. Side to side is something different. You can't run direct drive just by being misaligned in one axis. This is not including the diff drive flange not being square. It would explain why my left half shaft has plenty of plunge and the right has none. It's tight. You can't move it back and forth at all. I've been chasing a major drive line vibration since the car was new. From 55-62 mph it shakes so bad from side to side that your teeth will chatter. At higher speeds you can feel the pulsing vibration that is indicative of a drive line issue. The thunder of a V8 tends to make it less of an issue at higher speeds.

My steering rack was off 3/4" from the factory. This was a known issue. I got tired of the 4 point turns in the parking lot. I made some custom brackets to relocate it to the correct position. I was just contemplating that maybe the misalignment was a little deeper then just the rack.

[IMLost]

I didn't measure it but unfortunately I had to pull everything out today. I noticed that it was not completly straight. I think it was moved over a bit to get a little more room for the yoke.I don't know about the newer models (#178) but ours are about the same.

[madmaxx]

My spf driveshaft has the same orientation as the picture above. U-joints need misalignment or they will wear out. Obviously there are economies of scale. I have one of the few cobras in the world with no vibration at any speed or any road with bfg t/a's and my driveshaft is as above so I doubt that is you vibration issue.

I had a couple BDR's and I would feel a slight driveline vibration but it was very very little and never thought twice about it.

[Cashburn]

How is up and down misalignment different than left to right when you are talking about a u-joint?

[Gatorac]

Originally Posted by Cashburn

How is up and down misalignment different than left to right when you are talking about a u-joint?

It's normal, got it.

[Hitch]

Yep normal, equal but opposite keeps the u-joints happy...

Dave

[67JET]

I don't have a BDR (wish i did) but just for referance my rearend looked alittle out of wack and i decided to pull some measurments. You should be able to measure from frame out to face of hub and then measure from corner to corner of car by using the ball joints up front and center line on the rear hub. Also measure front to back each side using the ball joints and center line of rear hub. When i did this it showed me that not only was my rear in one sided it was out of square too. So the next thing i did was to take the rear completely out and cut off the chunk mounts and shock mounts (jag rear) and clean up everything to install new mounts. My chunk is now centered in the car and square but the yoke is still to one side. Your trans centerline and rearend centerline should be parallel to each other no matter if the offset is up-down or side-side or even both. This keeps the angle at each end the same.