Front center limit strap

[kmas0n]

I've got a project jeep I'm working on and I'm converting the front suspension from leaf springs to a 3 link. I'm measuring for my coil overs and the everything is playing well together except the driveshaft. All full droop the driveshaft binds at about 10.5 - 11" of shock travel. Everything else can accommodate 12" of shock travel. So, I'm thinking center limit strap, so I can run 12" coil over shocks and don't loose any flex, but the DS is protected at full droop.

Where is the best place to put the strap?
Center of frame, center of axle?
Center of frame, top of pumpkin
top of pumpkin and frame directly above it?
2 straps equidistant from center to top of pumpkin?

Or just 10" travel coil over shocks.

 

[jjvw]

If the rear center limit strap on mine is any indication, for the purposes of protecting the driveshaft my instinct would be to put the limit strap over the driveshaft.

From your description, this is not a TJ. Mine has 12" shocks up front split 50/50 without the need to protect the driveshaft. This makes me wonder what differences there are between setups.

 

[srimes]

Since it's the driveshaft you're protecting, ideally it should be on the pumpkin in-line with the driveshaft.

To reduce stress on the strap the upper mount should be straight up. But this isn't critical and some angle won't matter.

 

[jjvw]

Since it's the driveshaft you're protecting, ideally it should be on the pumpkin in-line with the driveshaft.

To reduce stress on the strap the upper mount should be straight up. But this isn't critical and some angle won't matter.

Stress would be a non-issue because the speed at which the strap would reach full tightness is a slow event due to the shocks doing what they do. All the strap and boots mounts need to withstand is a small momentary dynamic load slightly more than the weight of the axle assembly. This event would be very rare because the axle needs to be near fully unloaded before the limit strap comes into affect.

 

[kmas0n]

If the rear center limit strap on mine is any indication, for the purposes of protecting the driveshaft my instinct would be to put the limit strap over the driveshaft.

From your description, this is not a TJ. Mine has 12" shocks up front split 50/50 without the need to protect the driveshaft. This makes me wonder what differences there are between setups.

I believe most 3 links will be similar The biggest difference would be size, The axle is narrow, the frame is wide and the driveshaft is short (about 22"). The control arms are about 24 inches, so the change in wheelbase and axle plunge are greater. I've been able to address most of that stuff. driveshaft bind seems to be the only hang up.

And the differential is on the wrong side.

 

[kmas0n]

Since it's the driveshaft you're protecting, ideally it should be on the pumpkin in-line with the driveshaft.

To reduce stress on the strap the upper mount should be straight up. But this isn't critical and some angle won't matter.

My concern here is on the rare situation that both front shocks travel to full extension if only one side is limited by a strap (by nearly two inches) it might cause an unexpected bounce or throw the body sideways. I'm not sure, maybe it would make no difference.

 

[jjvw]

... and the driveshaft is short (about 22"). ..

That about answers it. That leaves shock travel and bias as the only remaining things to consider.

 

[kmas0n]

That about answers it. That leaves shock travel and bias as the only remaining things to consider.

oh yeah ,12 inch. 6/6

 

[jjvw]

My concern here is on the rare situation that both front shocks travel to full extension if only one side is limited by a strap (by nearly two inches) it might cause an unexpected bounce or throw the body sideways. I'm not sure, maybe it would make no difference.

The two occasions the strap reaches full tightness is either when you jump the Jeep or when you turtle it and hang the front axle. Only event has unexpected movements can result in a violent disaster.

 

[PNW_LJ]

I believe most 3 links will be similar The biggest difference would be size, The axle is narrow, the frame is wide and the driveshaft is short (about 22"). The control arms are about 24 inches, so the change in wheelbase and axle plunge are greater. I've been able to address most of that stuff. driveshaft bind seems to be the only hang up.

View attachment 536727
And the differential is on the wrong side.

What front axle is that?

 

[kmas0n]

The two occasions the strap reaches full tightness is either when you jump the Jeep or when you turtle it and hang the front axle. Only event has unexpected movements can result in a violent disaster.

But at least I could salvage the drive shaft

 

[kmas0n]

What front axle is that?

The mighty Dana 25

 

[jjvw]

But at least I could salvage the drive shaft

Either one warrants protecting the driveshaft. Or even simply satisfying your sensibility that the driveshaft shouldn't be allowed to go into bind even if the circumstances never actually occur. That is why mine has a rear center strap.

 

[kmas0n]

I've been thinking about this all afternoon. When passenger side is at full drop and driver is a full stuff, the driveshaft is far enough inboard that it's not in bind, as the driver side extends, there is bind at some point before full extension. Find that point and add a center strap.

 

[jjvw]

I've been thinking about this all afternoon. When passenger side is at full drop and driver is a full stuff, the driveshaft is far enough inboard that it's not in bind, as the driver side extends, there is bind at some point before full extension. Find that point and add a center strap.

When I was working out my rear strap, I was raising and lowering the axle while spinning a tire with the tcase in neutral. The parasidic draw was enough to spin the shaft and stop when the bind began. Then I built the upper and lower mounts to stop the axle some fraction of an inch above that early bind point to account for strap stretch.

In my case, the strap hangs the axle about 3/4" before full shock extension on either side. From there, the axle can pivot the last little bit, should that movement somehow be useful in the rare occasions the strap is being used.