I am subing my 51' GMC pickup. I have the truck pretty much ready to go but I can't find the centerline on that sub. I keep getting different measurements and I don't want to screw this up...

Need help as soon as possible.

Thanks
-Billybob

You need to find two land marks that are the same on both sides on the front and rear of the sub. Usually the body mounts make a good point of reference. Maybe a bolt hole on the rear on both sides. After you find these points, tie a heavy nylon string between the front right and rear left landmarks and the front left and rear right. Stretch the strings very tight and make sure they are not rubbing anything. If they are touching anything but the landmark point your measurements could be off.. The intersection point of the strings is the center of the sub.

Now repeat the process and move the two front or back string attatchment points to two more forward or rearward points. Tie two more strings in the same fashion. This will now give you two intersect points on the centerline of the frame. You can then draw a line through the two points and get a center line.

If you have a problem finding landmarks to use, you could temporarily weld a couple studs to the frame in the exact same point on the frame on each side.

Chris

I would suggest removing the coil springs from the subframe and then slide it up to the frame with wheels and tires on it. Mount the front clip and position the wheels in the wheelwells. A lot of folks end up with the tires in the WRONG place.

Once the wheels are in the correct position you can then measure back to the centerline of the rear axle and square up the front end.

__________________
I went to the school of hard knocks ...
where the tuition is high but the retention is exceptional !

If you find reference points to measure from that you are not sure are correct, there is a way to verify it. Go to a local body shop and ask to see the frame diagram for the donor vehicle. This is a diagram used by the bodyman to straighten the frame after an accident. It will give measurements and reference points that were set-up by the manufacturer.

just finished a camaro sub in my 56 chevy.I used a video from no limit engineering.Best 30 bucks i ever spent. The axle centerline on the camaro sub is the front edge of the upper shock mount hole. Its dead nutz.
good luck.

Great video....it's easy to follow & hard to make a mistake.
Don