Sub frame alignment?

[jlwdvm]

Any good tricks out there to get the front sub on a 1st gen f-body squared up with the rear, setting wheel base, etc?

[paulk68]

this guy makes it look pretty easy


https://www.youtube.com/watch?v=bmrrNXEbPKg

[Spiffav8]

this guy makes it look pretty easy


https://www.youtube.com/watch?v=bmrrNXEbPKg

So easy your WIFE can do it! Yeah....that isn't happening. lol

[Sieg]

Good system........as long as the rear differential is square in the car. :thumbsup:

The pinch weld is the most accurate reference on these cars and it's not exactly a fine line. :)

[jlwdvm]

I took about a week of measuring and tweeking the sub and rear end placement before I welded on my rear end tabs for my Ride Tech 4-link...everything was perfect. Then I decided to drop the front sub to pull the motor to install a Improved Racing oil pan baffle insert, and a few other things that were easier with the sub out. Everything is back together now and it is time to start tweeking again!

[Ron in SoCal]

Good system........as long as the rear differential is square in the car. :thumbsup:

The pinch weld is the most accurate reference on these cars and it's not exactly a fine line. :)

Not sure I'd trust the pinch weld Sieg, but your first point is key as a place to start. Measure the car twelve ways from Sunday and get that rear end centered as perfectly as possible. Then when placing the subframe underneath you get a reference point for a good X dimension from the front lower ball joints to a common reference point in the rear. If using rear shock mounts - or any other location on both sides such as axle tube ends - make sure they're square / centered as well!

The downside to this method is the the car may not be square to begin with, but it should track straight even if the body is a little off kilter.

There's more, but that's a good start.

EDIT: even after all that, I think mine was off by 3/16". Not sure if it was due to the subframe not being square (?), but that was as close as it would get.

[paulk68]

I took about a week of measuring and tweeking the sub and rear end placement before I welded on my rear end tabs for my Ride Tech 4-link...everything was perfect. Then I decided to drop the front sub to pull the motor to install a Improved Racing oil pan baffle insert, and a few other things that were easier with the sub out. Everything is back together now and it is time to start tweeking again!

So I am in the same boat. I have the front sub out of the car to paint and install the ridetech suspension and I have not even touched the rear ridetech bolt in 4 link heck i dont even have my rear end yet to weld the bracket too. Wich one should I put in first the rear or get the front as close as i can then do the rear?

[jlwdvm]

I squared the front up using measuring holes in the sub and the rear frame rails. After I got the front sub squared to the rear frame rails I squared the rear end to the front and set my wheel base as well. I have my car on a 2-post lift, so it is easy to take lots of measurements!

[GregWeld]

This is the reason for a frame table!! LOL


I'd set the car on leveled jack stands (you can use some thicknesses of steel sheet etc) - get it level fore and aft and across... I like a 6' level -- and use some lengths of steel tubing to bridge the gaps... (borrow these if you need to). Or get yourself a laser level so you have a fixed point to measure from - these have become quite inexpensive and can be used for lots of things.

Set the car down on them at the same points of contact side to side and front and back... See if the car sits level or does it rock etc. Then I'd drop some plumb lines down to tape on the floor. See if these points are "square"... same distance ACROSS in an X pattern (like squaring up anything)... and that they're the same width and distance front and back... if you can find that square.... Then connect the dots! From there you can pull a tape for take off measurements.... again using a plumb bob to a point on the floor.... The sub should be square to the other square plus or minus a 1/16th...

Using the taped points on the floor - you can pull repeatable measurements and you can reposition various parts (such as the sub) by simply realigning your floor points and the plumb bob...

Make sure you don't set up your jack stands in a place that will interfere with bolt holes etc that you'll need to access. Use tape to mark the floor where they sit so you can move them or sit them back in place if you need to reposition for some reason.

Remember that these bodies were done on an assembly line and the tolerances "then" weren't so great! Don't be surprised to find you body "off" - wheel openings side to side at different heights - or ground to various points off... These cars are designed with rubber bushings at the suspension points - and the subframe was on rubber bushings - and the body mount positions are "close enough"...

Your alignment is designed to be able to make adjustments... but you still want to start off with everything as tight of a spec as possible.

[GregWeld]

Good system........as long as the rear differential is square in the car. :thumbsup:

The pinch weld is the most accurate reference on these cars and it's not exactly a fine line. :)



I would agree with this point -- but most of these pinch welds have suffered some serious abuse over the years -- so it's not always a reliable point of reference. I'm seen some pretty jacked up pinch welds (literally!)

[jlwdvm]

If your wheel base is the same on each side, wouldn't the rear end have to be square with the front subframe (since the wheels are attached to it)? The 4 corners made up of the tire patches would be square...right? I have the sub centered side-to-side according the the pinch welds. Currently I have the wheel base within an 1/8" when comparing drivers side to passenger. I am using wheel studs on the rear with the car at ride height and a level placed on 2 studs and then measuring to a stud on the front rotor after doing the same and also making sure the rotor is the same distance from the frame so toe isn't a factor.

[snappytravis]

Ditto on the laser level I measured out the center of my front crossmember under engine. Then I set the level on the crossmember below radiator, shot towards rear of car with it line up on next crossmember back and could see exactly where the rear end was sitting. If this makes sense, I also used a digital tram guage set it up on 2 jack stands one by the front hub and one on the rear axle center line. Then was able to measure wheelbase of both sides.. Same theory as plum bob. Specs call plus or minus 1/4 inch. I would think if you were this close the rest could be adjusted in suspension. I do agree with Weld, How close where these from the factory? I used seat belt bolt holes, Drain plug holes, anything that is stamped from the factory for a reference.. Measure from rear subframe mounting holes across to radiator support mounting holes. Measure, measure, measure. Then cross your fingers and start welding!

[GregWeld]

If your wheel base is the same on each side, wouldn't the rear end have to be square with the front subframe (since the wheels are attached to it)? The 4 corners made up of the tire patches would be square...right? I have the sub centered side-to-side according the the pinch welds. Currently I have the wheel base within an 1/8" when comparing drivers side to passenger. I am using wheel studs on the rear with the car at ride height and a level placed on 2 studs and then measuring to a stud on the front rotor after doing the same and also making sure the rotor is the same distance from the frame so toe isn't a factor.

Sounds like it's in pretty good shape then!! Try to get the wheelbase a little closer if at all possible. If not - it probably didn't leave the factory anywhere near an 1/8th.

Drop a point of measure off all four corners and measure on the diagonal... that's how you check for square. If that checks out - you're golden.

[bsharpe]

I spent a lot of time trying to align the subframe on my firebird. It is not easy with these cars especially on jackstands. I understood that my unibody was not perfect (the pinch welds are destroyed and she has been hit), the ford 9" and 4 link isn't perfect (I didn't measure enough when I installed it) and my subframe has some issues but I didn't expect to run into major problems and spend as much time as I did.

I used a laser level and old vinyl tiles under the jackstands to level the car. I then plumb bobbed from everything that was symmetrical on the car like holes in the frame and the pinch welds. I used a chalk line to find the center line of the car. I then squared the rear axle to the body by taking cross measurements and wheelbase measurements. I then tried to square the subframe to the rear axle. I was unsuccessful and found major issues with my subframe. I am now evaluating my options.

[GregWeld]

I spent a lot of time trying to align the subframe on my firebird. It is not easy with these cars especially on jackstands. I understood that my unibody was not perfect (the pinch welds are destroyed and she has been hit), the ford 9" and 4 link isn't perfect (I didn't measure enough when I installed it) and my subframe has some issues but I didn't expect to run into major problems and spend as much time as I did.

I used a laser level and old vinyl tiles under the jackstands to level the car. I then plumb bobbed from everything that was symmetrical on the car like holes in the frame and the pinch welds. I used a chalk line to find the center line of the car. I then squared the rear axle to the body by taking cross measurements and wheelbase measurements. I then tried to square the subframe to the rear axle. I was unsuccessful and found major issues with my subframe. I am now evaluating my options.



These cars have "issues" -- they're not exactly spring chickens... they've had a rough life... The point is - that you either have to get the body back to where it should be - or you have to modify things to get all of this to line up and be square and the wheelbase to be right. Whatever course that takes is a matter of skill and pocketbook... etc.

When I did my brother in laws Camaro - it had taken a hit on the driver side... so much so that I had to pie cut the area where the steering wheel goes thru the firewall... and I had to make a "spacer" to take up the area under the floor between the floor and the sub mount. We didn't have another way to fix this "alignment" issue. We made it work and the car drives perfectly. And his gaps are perfect. The key is to have accurate measurements so that you can "fix" the issue and know what you're doing. You can fix anything if you know where you need to be when you're finished.

Check out this "spacer" I had to make for the driver side! I milled it to the .001 of an inch... just because... there was really no reason to get that close other than I just like using some of my tools. HAHAHAHAHAHAHAHA



http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-22.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-22.jpg.html)




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-23.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-23.jpg.html)




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-24.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-24.jpg.html)




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-25.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-25.jpg.html)




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/IMG_0640.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/IMG_0640.jpg.html)





http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-26.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-26.jpg.html)




It worked out just fine!




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/IMG_1141.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/IMG_1141.jpg.html)

[snappytravis]

These cars have "issues" -- they're not exactly spring chickens... they've had a rough life... The point is - that you either have to get the body back to where it should be - or you have to modify things to get all of this to line up and be square and the wheelbase to be right. Whatever course that takes is a matter of skill and pocketbook... etc.

When I did my brother in laws Camaro - it had taken a hit on the driver side... so much so that I had to pie cut the area where the steering wheel goes thru the firewall... and I had to make a "spacer" to take up the area under the floor between the floor and the sub mount. We didn't have another way to fix this "alignment" issue. We made it work and the car drives perfectly. And his gaps are perfect. The key is to have accurate measurements so that you can "fix" the issue and know what you're doing. You can fix anything if you know where you need to be when you're finished.

Check out this "spacer" I had to make for the driver side! I milled it to the .001 of an inch... just because... there was really no reason to get that close other than I just like using some of my tools. HAHAHAHAHAHAHAHA



http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-22.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-22.jpg.html)




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-23.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-23.jpg.html)




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-24.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-24.jpg.html)




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-25.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-25.jpg.html)




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/IMG_0640.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/IMG_0640.jpg.html)





http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/file-26.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/file-26.jpg.html)




It worked out just fine!




http://i919.photobucket.com/albums/ad33/gregweld/Rudys%20Camaro/IMG_1141.jpg (http://s919.photobucket.com/user/gregweld/media/Rudys%20Camaro/IMG_1141.jpg.html)

To much Dukes of Hazards in the old Days!

[bsharpe]

The point is - that you either have to get the body back to where it should be - or you have to modify things to get all of this to line up and be square and the wheelbase to be right. Whatever course that takes is a matter of skill and pocketbook... etc.

That is why I spent so much time measuring. I know now that the Scott Mock subframe is the problem. I wanted it to be the body but the real and major issue is the subframe.

[GregWeld]

That is why I spent so much time measuring. I know now that the Scott Mock subframe is the problem. I wanted it to be the body but the real and major issue is the subframe.



Wow.... never heard that before.... LOL


Sorry. Yeah -- that sub has more than a few issues.

[bsharpe]

Wow.... never heard that before.... LOL


Sorry. Yeah -- that sub has more than a few issues.

I hoped for the best because I have one of his original subframes which was built before he had any issues and everybody loved his subframes but that was before Ron Sutton taught everybody to measure and tune their suspension.

[GregWeld]

I hoped for the best because I have one of his original subframes which was built before he had any issues and everybody loved his subframes but that was before Ron Sutton taught everybody to measure and tune their suspension.



It's such a shame -- I really liked Scott.... and he was a good contributor here. Sometimes - like Jeb Bush said - Stuff happens. For whatever reason his quality control took a giant dump. Sad.

[jlwdvm]

I was able to get my wheel base measurements nearly the same on each side (less than 1/16" difference, and the sub is nearly centered between the pinch welds. I stopped at "nearly" because who knows how accurate the pinch welds are!

[TheJDMan]

That video talks about using pins in the front alignment holes which is good, but it says nothing about using the rear alignment reference holes which are located just forward of the front leaf spring mounts. These rear reference holes are intended be used to cross measure the sub frame for square much more precisely than the pinch weld. Using the rear reference points in conjunction with the front alignment holes, I was able to square my sub to within 1/64" front to rear and side to side.

[Black93GT]

That video talks about using pins in the front alignment holes which is good, but it says nothing about using the rear alignment reference holes which are located just forward of the front leaf spring mounts. These rear reference holes are intended be used to cross measure the sub frame for square much more precisely than the pinch weld. Using the rear reference points in conjunction with the front alignment holes, I was able to square my sub to within 1/64" front to rear and side to side.
:idea: Now that's the tidbit of info I'm looking for. Thanks!