Flipping Stock Center Trailing Arm Crossmember

[TudorJeff]

Has anyone every flipped the stock cross member that holds the trailing arms in place? I was staring at one of my chassis' the other day and it sure looks like it might correct some of the pinion angle added in by lowering the rear of the truck.

in other words, flipping the cross member looks like it would effectively raise the front of the trailing arm mounting location. That would raise the snout of the rear end, taking out some of the extra pinion angle that is put in when the lowering springs are added.

I did a search and didn't come up with anything. Just looking for thoughts or real life experiences with it. Thanks.

[kieth]

That is exactly what I am going to do on my 65 chevy after I lower it. Drill out the 2 trailing arm mounts , flip them over and you should be good to go. I do not know why others spend money on those fancy crossmembers, other that having the exhaust run through it. I actually did a experiment on my 66gmc and modified the stock center crossmember by cutting out some material on both sides, to allow the exhaust to flow through the crossmember instead of under it. I think it is going to work just fine....here are pictures.

Kieth

http://kieth.smugmug.com/Trucks/66-G...87058874_6EYgj

[TudorJeff]

Ah yes, so you plan to just flip the actual mounts and leave the cross member itself in place in the frame. I was thinking to leave the mounts on the cross member and flip the whole thing (removing it from the frame when i get it blasted). Sounds like the same positive end result though.

[trustyrusty65]

I may not be following correctly (and admittedly this is only my second post), but I think you would actually want the snout on the rearend to tilt DOWN toward the transmission yoke if your truck is lowered. Tilting it up on a lowered truck, which has the rearend raised in relation to the transmission compared to stock will actually increase the pinion angle at the rearend, which of course you do not want. You want the rear yoke to point back down at the front one. I had this debate at my old job (Truck Stop Accessories in Reno) when I lowered a 2005 F@rd dually with spring hangers and blocks. When I finished, the boss saw the pinion shims "turned 180 degrees" and made me turn them around. After I did it, you could just see the u-joint angle looked terrible. I insist that his way (with the fat part of the pinion shim at the front, so the rearend pointed UP) corrected the angle for the rearend being lowered in relation to the trans yoke (happens with a suspension lift). After some debate, I got to put the shims back the original way. I must have been right; I never saw that truck again at work, but I did see it on the road a few weeks ago.

I'm also not sure how much of effect moving the trailing arm pivots up would actually change the angle in the back. The pinion angle is somewhat determined by the bend in the arm itself, and effected by the geometry between the springs and pivots; if you move the pivots, the springs might just compress funny and make up some of the difference you got by moving the brackets.

--Just my two cents (looks more like four cents doesn't it?), maybe somebody has done it, but I've never heard of this.

Nice truck, by the way, I wish mine was in such shape, or as assembled.

[fleetsidelarry]

trustyrusty, most people are using shorter springs (or bags) to lower the trailing arms set-ups rather than blocks. Shorter springs cause the axel to rotate around the front pivot points and actually points the pinion more downward. Raising the front pivot points would then correct the angle. So would shims with the "fat" part forward. Different with lowering blocks.

[kieth]

what did you think about the exhaust cutouts in the crossmember ? We really did not remove any strength, left the 90 degree angle just took a little meat out. The only thing in my way is the emergency brake cables.....they could be moved up....??

http://kieth.smugmug.com/Trucks/66-G...87058246_uVKng

[fleetsidelarry]

I liked it! I don't see where it would compromise integrity. and the idea about flipping the mounts. or the entire crossmember if it was coming out, either works. guys that are bagging should be checking this out. haven't given any thought to e-brake since it's not an issue for me at the present (I suppose it ought to be, since I don't have one)

[SCOTI]

Flipping the T/A mounts is an easy way to place the pinion angle closer to stock on mild to extreme drops. It raises the C/L of the bolt about 3.25".

[Hottrucks]

theres a few posts on for us 67-72 guys..my truck has flipped T/A with 1" blocks and is bagged...Oh and I cut the V out of the X memeber to make it round so my exhaust goes though it nicely..Just can't figure out how to over the rear axle with out cutting out the foor but I have an Idea for that too

Nice to see you guys thinking outside the box like I do its not all about the $$$$ its Ole Skool

[Slow Build]

Originally Posted by kieth

what did you think about the exhaust cutouts in the crossmember ? We really did not remove any strength, left the 90 degree angle just took a little meat out.

I'm no expert but it seems like you took out alot more than you needed to. Are you sure you aren't losing strength there?

[SCOTI]

Originally Posted by Slow Build

I'm no expert but it seems like you took out alot more than you needed to. Are you sure you aren't losing strength there?

He could alway run some steel plate perpendicular to those holes for reinforcement while not impacting the exhaust. I'd do 2pc per hole (kind of boxing in the exhaust hole).

[Dble Hump]

I just removed my trailing arm brackets last night. I am wonder if anyone sells a new bracket that would move the bolt C/L location more than 3.25" upward?

[SCOTI]

Originally Posted by Dble Hump

I just removed my trailing arm brackets last night. I am wonder if anyone sells a new bracket that would move the bolt C/L location more than 3.25" upward?

Much more than that, & the T/A's will start hitting the frame depending on ride height. You'll also start getting real close to the front bed panel/floor (might/might-not interfere).

[chad64chevy]

i was think about flipping the bracket 2 myself! save some money and learn something, can't hurt right!!

[63sbssbbw]

Flipping the whole crossmember creates interference with bottom of the cab,minor mods are required for it to clear.
IMO flipping just the mounts would be the more efficient way to go.
T

[Str8axle]

I'd flip the brackets. A lot easier to change back if you don't like the end result.

Ray

[PGSigns]

I did not move the brackets on mine and after bagging it the pinion angle is fine. I have almost a straight line all the way through. I think if you wanted to lay the frame this would be a requirement but for a simple bagged setup with a frame notch it is not needed.
Jimmy

[VWBeamer]

This will also help with traction. It's hard to explain, but if the trailing arm front is lower than than the rear, the axle tries to drive OVER the arms, this lifts the wheel up and causes wheel hop.

If the trailing arm front is higher than rear axle, the wheels try to drive under the arms. This causes the weight of the truck to transfer to the wheels and plants the truck.

The idea is explained here for a four link, of course it's a little different, but the first part applies.

http://www.jimmyjudd.com/jimmy/4link.htm

[forestb]

at what point would you all recommend using shims or flipping the brackets? Meaning how low does my truck need to be in order for me to start worrying about this? Also I have seen shims in catalogs and herd people talking about them but where on the suspension do you put them? Does anybody have any photos?

[kieth]

Originally Posted by Slow Build

I'm no expert but it seems like you took out alot more than you needed to. Are you sure you aren't losing strength there?

I left the flange (90 degree part) that is where the strength is would not have done it if I thought it would compromise strength......

I have been in the truck body business for 25 years, cut a few thousand trucks in half and put them back together. Not my first rodeo .....but the thought is appreciated. Kieth

[kieth]

I just took a look at some of the more expensive after market crossmembers and said I think I can do that just as well and for a whole lot less money. I have not needed to flip the brackets yet but will do so if needed. Kieth

[Frizzle Fry]

2 reasons NOT to flip the T/A brackets FWIW:
1) Raising the front of the T/A will cause it to hit the frame with less drop.
2) If you plan to run your exhaust through the xmember you can run the pipes up/over the T/A's if they are not raised at the front. If you do flip the brackets a nice tucked exhaust routing gets more complicated.

[SCOTI]

Keep in mind the aftermarket units are all .250" plate min thickness (the OE unit is less). Not a big difference, but a difference.

[kieth]

You will know if you have the problem, it will sound like the tailshaft bearing in your transmission is going out. On air ride over the road tractors it happens all the time, all you do is re adjust the ride height control valve to the proper height and all is well. Here we changed the angularity of the driveline and have to re engineer it so the drive lines are in the proper angle (when we lowered it we put the u joints in a bind) 15 degrees is the critical angle for a std u joint when that is exceeded it howls like a banshee because it is bound up because of the pinion angle. when we change the brackets at the front of the crossmember up higher we also change the angle of the nose of the rear end so it has the proper angularity. It is now within its 15 degree limit and does not bind up. Kieth

[oldtrux]

those so called "fancy crossmembers"are like 200 bucks.raised hoop,exhaust holes,e brake slots,grade 8 hardware,and powder coated!just my thoughts,oh ya,also gives you 2 1/2 inches of ground clearance in the centre of truck where you need it!