Flipping rear trailing arm mounts, raises ride height?

[OJ1988]

I have never heard this mentioned when people talk about flipping the trailing arms, but it makes sense.

If you look at the the trailing arm, due to the location of the coil spring, raising the mounting point isgoing to lower the axle mounting point, in relation to the ground, which will then rais the body of the truck.

I just did this flip on mine, and it raised the truck a good solid 1".

[kieth]

I think the reason they do this on a lowered truck is to keep the angularity of the driveline correct. As you lower a truck you change the relationship of the transmission and driveline, they usually shoot for -3 degrees on the transmission and +3 degrees on the rear end. You can tell you need to do this if your truck starts to act like the rear tires are out of balance at varying throttle positions (versus a constant speed like tire balance) When a vehicle starts out it squats, then as it continues to accelarate the whole vehicle is lifted up. This on throttle raising of the vehicle is where the driveline should be running pretty flat , if the angularity is wrong it will start to bind up the u joints, flipping the trailing arm mounting point helps keep a normal angularity. If you want it lower just let some air out of your bags (if you have them) Kieth

[OJ1988]

I am aware as to 'why' people do this.

I just wanted to add, that this will raise the rear of the truck, which no one ever mentions.

[oldblue1968chevy]

Oj,

Got some pics? Are you flipping the arms or just flipping the mounts?

[OJ1988]

No pics now, but I can get some. Did not flip the arms, just the mounts.

The spring did not change, so the fulcrum is the same.

It's pretty simple.

If you raise the front point, the read point has to go down.
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[SCOTI]

Originally Posted by OJ1988

No pics now, but I can get some. Did not flip the arms, just the mounts.

The spring did not change, so the fulcrum is the same.

It's pretty simple.

If you raise the front point, the read point has to go down.

How much is your truck lowered?

[OJ1988]

5" springs in rear, 3" in front.

Everything is new, super trac bar, shorter shocks all around, poly bshings, etc...

Had it all together with the stock trailing arm mounts, ground off the rivets, fliped mounts, bolted them on, threw in new poly bushings in the trailing arms, bolted them back up, and put the truck back on the ground.

It is a good 1" higher than before.


Just think of a see saw. If you raise one end, the other end will go lower. The springs are the fulcrum.

[fixit-p]

The spring saddle also moves forward about 9/16" - 5/8". I actually have a mock up, the TA and mounts are to scale the only assumption made was the actual angle of the TA before flipping the mount but it illustrates what OJ1988 is saying.

[OJ1988]

Thanks for posting that! I was thinking of making a crud drawing, that thats much better!

[gringoloco]

Raising the dead here... Great info!

I see that the coil mount moves 9/16"--any guesses (or calculations) on just how much the axle itself moves forward when flipping the mounts? Thinking I'll move the center crossmember back an inch or so to compensate and re-center the rear wheels in the arch.

[OJ1988]

If anything it needs to come forward. Lowering it moves the axle back, my axle could come forward a good inch to center in the wheelwell.
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[OJ1988]

Don't forget about your shocks and track bar when moving the rear axle. Also, exhaust clearance may need watched.
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[69gmcc10]

gringo,

Wish I could help. When I converted to trailing arms I flipped the trailing arm mounts, but have no numbers to compare with. I think it stands to reason that it would move a minimum of a 1/2 inch forward. I plan to get the rear bolted in and on the ground this coming weekend and I can take some measurements then and let you know how far off center the axle is in the arch, but I don’t know if that will help. Let me know.

[GEARBOXGARAGE]

Another thing to also consider..... The original angle of the trailing arm vs. the lowered spring/flipped mount angle. If you use a 5" lowering spring and flip the mounts (approx 3" difference in height) that leaves you with only about 2" difference from what stock was. If you use a 3" inch lowering spring and flip the mount, you really wouldn't be changing the angle of the ta, just moving the whole assembly up into the chassis 3". So axle position/angle shouldn't be affected as much as what you may be looking at in the drawing above, because it does not reflect any height change at the spring pocket, only after the drop and changing the mount location......

[69gmcc10]

Good point!

Concidering evem more varables, I am also curious about how lowering blocks and there various heights would affect the numbers?

[gringoloco]

Originally Posted by OJ1988

If anything it needs to come forward. Lowering it moves the axle back, my axle could come forward a good inch to center in the wheelwell.
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I think this is more true on a stepper, as the wheelwells are slightly forward compared to a fleet, I believe...

Originally Posted by 69gmcc10

gringo,

Wish I could help. When I converted to trailing arms I flipped the trailing arm mounts, but have no numbers to compare with. I think it stands to reason that it would move a minimum of a 1/2 inch forward. I plan to get the rear bolted in and on the ground this coming weekend and I can take some measurements then and let you know how far off center the axle is in the arch, but I don’t know if that will help. Let me know.

That would be a great help! If nothing else, it would give us all numbers for comparison.

Originally Posted by GEARBOXGARAGE

Another thing to also consider..... The original angle of the trailing arm vs. the lowered spring/flipped mount angle. If you use a 5" lowering spring and flip the mounts (approx 3" difference in height) that leaves you with only about 2" difference from what stock was. If you use a 3" inch lowering spring and flip the mount, you really wouldn't be changing the angle of the ta, just moving the whole assembly up into the chassis 3". So axle position/angle shouldn't be affected as much as what you may be looking at in the drawing above, because it does not reflect any height change at the spring pocket, only after the drop and changing the mount location......

Very good point. The net effect could be different for each individual combination.

Originally Posted by 69gmcc10

...Concidering even more varables, I am also curious about how lowering blocks and there various heights would affect the numbers?

I think this would depend on the angle of the arms; if the axle mounting pads are fairly level (as with a mild drop), then the axle would just move up. With a more aggressive drop, the mounting pads are at an angle, causing the axle to move forward with the blocks.

I will do a direct, 1:1 comparison soon and report my findings. My truck is currently 6" ECE coils and 1.5" drop blocks. I will take some measurements of fore/aft position and height and see how it differs following the bracket flip...

[gringoloco]

Update: After changing ONLY the front trailing arm mounts, the rear of my truck raised around 3/4". No measureable fore/aft change noted. YMMV...

Before/after pics: