Lowering my dually?

[Super_Dave]

Does anyone know of an easy way to take 2" out of the bed height on my 2006 Ram dually? Would it create a domino effect to other suspension system changes?

[Super_Dave]

Total drop was 1.5". It did require me to adjust my mud flap height as I could tell it would probably drag under load.

[Bedlam]

I agree there will not be a problem if you stay within operating limits of the joints. Go too much extreme either direction is when you see problems which will first show up under load.

[mkirsch]

Bedlam wrote:
Changing axle height changes the drive shaft angle between the transfer case or transmission and the axle. This anle will be exaggerated even more once the rear loaded down. The OEM accounts for loaded and unload ride heights when designing the drive line angle if you go too far out of specification, it will cause joint issues. if you look at some suspension lift kits made for trucks, they will actually have a wedge that is inserted between the axle and springs to lessen the joint angle after adding the lift. You can argue that this is more of an issue in the front to due to a shorter run, but it also happens in the rear.

Read up on proper pinion angles and drive line vibration before dismissing what happens when you change ride height.

But in this case, it's STILL within the OEM range so no problem.

[twodownzero]

wnjj wrote:
Driveline angle doesn’t matter, it’s the angle of the pinion that needs to match the angle of the transfer case output shaft. If the suspension is lowered In a way that keeps the rear axle unrotated compared to its original location it should be fine. Changing the hanger length on one end of a leaf spring can cause issues. Removing blocks between the axle and springs should not.

Driveline angle kinda matters, as the steeper the tube slope, the faster the u joints will wear. I agree with the remainder here, lowering the truck in this manner should not make a difference.

[Super_Dave]

Stopped by a suspension shop today and they will do it and replace the Ubolts with larger diameter bolts, new dowel pins for $275.

[wnjj]

Grit dog wrote:

wnjj wrote:
Driveline angle doesn’t matter, it’s the angle of the pinion that needs to match the angle of the transfer case output shaft. If the suspension is lowered In a way that keeps the rear axle unrotated compared to its original location it should be fine. Changing the hanger length on one end of a leaf spring can cause issues. Removing blocks between the axle and springs should not.

This is also a consideration, but not typically with "small" adjustments such as this, like you pointed out.

My point was the angle between the front and rear yokes is all that matters, with the exception of extreme lifts that have the driveline at absurd angles. U-joints are designed to accept angles. The vibration comes when the angle at the front and rear yoke are not matched. This is because a driveline running at an angle actually speeds up and slows down with each revolution if the driven yoke is at any angle. Matching the rear yoke angle cancels that out so that the rear pinion doesn’t see those surges.

[bucky]

Moving blocks or spacers will certainly lower bed spacing on the frame. Remember all of those 99 and 2000 F250 and 350 4WD Fords that looked like they got hit in the butt?
Ford had a TSB for RV towing to flip the block or replace a 4 inch with a 2 inch. I had to do it to mine.
You will have to adjust the hitch some to level the 5er but you will gain bed clearance.

[Me_Again]

There was 10 years ago or something like that a guy that had a RAM web site and this mod was documented on it.

here is a quote regarding doing this mod.


"I took the spacers out last Saturday took me just over 2hrs. Moved the spacers from under the spring to above the spring reused the old u bolts and spring center pins. Dropped the rear bumper about 1 1/2 inches"

NO one back then complained about drive line vibrations after the mod. Chris

[Grit_dog]

wnjj wrote:
Driveline angle doesn’t matter, it’s the angle of the pinion that needs to match the angle of the transfer case output shaft. If the suspension is lowered In a way that keeps the rear axle unrotated compared to its original location it should be fine. Changing the hanger length on one end of a leaf spring can cause issues. Removing blocks between the axle and springs should not.

This is also a consideration, but not typically with "small" adjustments such as this, like you pointed out.

[Grit_dog]

twodownzero wrote:

Bedlam wrote:
It will change your drive line angle. If you are getting considerable squat from your load plus lowering axle height you may find u-joints failing under heavy load or joints binding during spring compression. Lowering the rear too much without adjusting the front may make the truck nose high when loaded - This will affect your steering and lighting.

By your logic, putting weight in the bed will change the driveline angle.

Removing the spring spacers and leaving the bumpstops in the same place does not change the range of the factory suspension. In other words, the "driveline angle" that is created by moving the spacers is the same as putting some weight in the bed and compressing the springs.

The driveline angle necessary to bind the u joints in these trucks is in excess of 30 degrees, perhaps even in excess of 35 degrees. The factory driveline angle is a single digit, probably in the range of 3-5 degrees with the rear suspension completely drooped. Also, moving the rear axle straight up and down by moving those spacers is unlikely to make even a measurable change in the driveline angle at rest.

Don't take my word for it, though. Download an angle finder app on your phone and you can see for yourself.

Where you got the idea that an inch change in ride height was going to cause driveshaft binding is beyond me. Whoever told you that was feeding you nonsense.

The current generations of trucks are way too tall and there are far greater consequences from not lowering them (bedrails getting hit by the trailer, ride height) than from lowering them.

No, for the same given load, the driveline angle WILL change if you change the distance from center of axle to a fixed point (frame).
I neglected to warn what bedlam so astutely thought of, but it is a consideration. Although I'll bet that the greater spring/shim stack of a dually may be about the same as a lower riding truck such as a 2wd 2500 once some height is pulled out of it. And while using the same components (axles, frame, x member, etc) it will very likely still be within "spec" driveline angles.
I've typically only heard of issues with lifts increasing the DL angle too much, but not so much on small reverse levels. If the OP has a 2 piece driveshaft and there is a factory shim above the carrier bearing, it may make sense to remove or reduce that shim height.
Also, considering the drivelines are designed to work within the full factory suspension travel (I hope or assume...), and the OP states that he's not really sacking out the rear suspension in his application, then that is additional factor of safety that the driveline angles will still be acceptable.

[wnjj]

Driveline angle doesn’t matter, it’s the angle of the pinion that needs to match the angle of the transfer case output shaft. If the suspension is lowered In a way that keeps the rear axle unrotated compared to its original location it should be fine. Changing the hanger length on one end of a leaf spring can cause issues. Removing blocks between the axle and springs should not.

[Bedlam]

Changing axle height changes the drive shaft angle between the transfer case or transmission and the axle. This anle will be exaggerated even more once the rear loaded down. The OEM accounts for loaded and unload ride heights when designing the drive line angle if you go too far out of specification, it will cause joint issues. if you look at some suspension lift kits made for trucks, they will actually have a wedge that is inserted between the axle and springs to lessen the joint angle after adding the lift. You can argue that this is more of an issue in the front to due to a shorter run, but it also happens in the rear.

Read up on proper pinion angles and drive line vibration before dismissing what happens when you change ride height.

[twodownzero]

Bedlam wrote:
It will change your drive line angle. If you are getting considerable squat from your load plus lowering axle height you may find u-joints failing under heavy load or joints binding during spring compression. Lowering the rear too much without adjusting the front may make the truck nose high when loaded - This will affect your steering and lighting.

By your logic, putting weight in the bed will change the driveline angle.

Removing the spring spacers and leaving the bumpstops in the same place does not change the range of the factory suspension. In other words, the "driveline angle" that is created by moving the spacers is the same as putting some weight in the bed and compressing the springs.

The driveline angle necessary to bind the u joints in these trucks is in excess of 30 degrees, perhaps even in excess of 35 degrees. The factory driveline angle is a single digit, probably in the range of 3-5 degrees with the rear suspension completely drooped. Also, moving the rear axle straight up and down by moving those spacers is unlikely to make even a measurable change in the driveline angle at rest.

Don't take my word for it, though. Download an angle finder app on your phone and you can see for yourself.

Where you got the idea that an inch change in ride height was going to cause driveshaft binding is beyond me. Whoever told you that was feeding you nonsense.

The current generations of trucks are way too tall and there are far greater consequences from not lowering them (bedrails getting hit by the trailer, ride height) than from lowering them.

[Super_Dave]

Bedlam, how does simply changing the bed gap change the drive line angle? Transmission height and axle height don't change?