Is my front driveshaft too long?

rasband said:
I'm trying to picture anything at droop beyond either still being attached or separating from the splines.
Click to expand...
Not sure I follow. The arc of the control arms pull the axle back faster than the arc of the driveshaft, so at the far end of droop, the splines bottom out and the driveshaft is under compression between the axle and the front output of the t case, holding the axle up from reaching full droop, against the weight of the axle and whatever spring pressure is pushing it down. There's probably not enough force to break the case in a static scenario, but if you dropped the driver tire and the splines bottomed out hard, the impact couldn't be good.
 
freedom_in_4low said:
I did. Or, more accurately, I got one from Tom Wood that was an inch shorter (and X spline so it has more than enough travel in the slip joint).

It works, but in hindsight I would have gotten the dust cap instead of the boot. The boot is stretched a bit longer than it's natural length when the rig is at ride height, which makes it a PITA to install.
Click to expand...
Get the seal and keep it greased.
 
freedom_in_4low said:
Not sure I follow. The arc of the control arms pull the axle back faster than the arc of the driveshaft, so at the far end of droop, the splines bottom out and the driveshaft is under compression between the axle and the front output of the t case, holding the axle up from reaching full droop, against the weight of the axle and whatever spring pressure is pushing it down. There's probably not enough force to break the case in a static scenario, but if you dropped the driver tire and the splines bottomed out hard, the impact couldn't be good.
Click to expand...
Why didn't the shock slow it down?
 
  • Like
Reactions: jjvw
mrblaine said:
Why didn't the shock slow it down?
Click to expand...

It could slow it down plenty and still leave it moving fast enough to apply multiples more force than a human could with a 3 pound hammer, and I don't usually see that action defended when made against a gearbox shaft and a bearing.

If there's no risk to the transfer case then why do you have them shortened?

mrblaine said:
We run into that all the time. We check every front with the axle at full droop and the straps off of the caps. Reach in with a prybar and see if we can move the yoke back on the splines. If we can't, shaft is too long and we get it shortened.
Click to expand...
 
freedom_in_4low said:
It could slow it down plenty and still leave it moving fast enough to apply multiples more force than a human could with a 3 pound hammer, and I don't usually see that action defended when made against a gearbox shaft and a bearing.

If there's no risk to the transfer case then why do you have them shortened?
Click to expand...
You don't actually know the case is at risk. I've never heard or seen one being broken due to that little problem and neither have you. We assume it is an issue, it seems to be an issue and mechanical correctness says we should do it right but that's about it. This thread shows while common, it is rarely discerned, discussed, or remedied.

I run into it very often because I know and have known to check for it. It is more common than not yet we see no pics of blown up cases due to a slightly too long front driveshaft.

The main reason I fix it is I wind up moving the axle further with longer shocks so I check the shaft length as part of doing that. Most don't.
 
I may need a correction here, but other than a full send jump, when does a front axle have a complete droop? Always seems it's articulated and would therefore never create a full droop situation.
 
Oh yeah, that too. Like you said though, I don't think it's happening enough for concern or we'd be reading about it more.
 
mrblaine said:
You don't actually know the case is at risk. I've never heard or seen one being broken due to that little problem and neither have you. We assume it is an issue, it seems to be an issue and mechanical correctness says we should do it right but that's about it.
Click to expand...

That's what's so confusing about what you were trying to accomplish by challenging and then arguing it. If the right thing to do is to address it, why even post? Basic mechanical knowledge and logical thought suggests it could be an issue; we don't know that it's not because there aren't specific examples, but there ARE specific examples of damage to similar types of components caused by less abuse (taking a hammer to a bearing that one plans to use again), so we deal with it because we'd rather drop $100-$300 on the driveshaft than deal with the potential results of not doing it. Because those results suck.
 
freedom_in_4low said:
It could slow it down plenty and still leave it moving fast enough to apply multiples more force than a human could with a 3 pound hammer, and I don't usually see that action defended when made against a gearbox shaft and a bearing.

If there's no risk to the transfer case then why do you have them shortened?
Click to expand...
There is a risk to the tcase but that is secondary to the added wear to the driveshaft itself by putting it into an unnecessary bind which is why I check for it.

A simple rule of thumb if you do not want to do a full travel check is you want your driveshaft collapsed length to be two inches shorter than your ride height length.
 
Blackjack said:
A simple rule of thumb if you do not want to do a full travel check is you want your driveshaft collapsed length to be two inches shorter than your ride height length.
Click to expand...

That's what I should have done. Instead I took the shaft length at full droop and full stuff, and bought it halfway in between those. That's how I ended up with the natural length of the boot wanting to be less than what it is at ride height, so I have the boot working against me trying to install the shaft. I got the boot because I was moving to Oklahoma and knew I'd have more mud to deal with, and don't like the way the cap on my rear DS sprays grease all over the underside of the tub and the side of the exhaust after I grease it.
 
freedom_in_4low said:
That's what's so confusing about what you were trying to accomplish by challenging and then arguing it. If the right thing to do is to address it, why even post?
Click to expand...
Because of the assertion that we risk a broken case, we don't and no one ever has.
freedom_in_4low said:
Basic mechanical knowledge and logical thought suggests it could be an issue; we don't know that it's not because there aren't specific examples, but there ARE specific examples of damage to similar types of components caused by less abuse (taking a hammer to a bearing that one plans to use again), so we deal with it because we'd rather drop $100-$300 on the driveshaft than deal with the potential results of not doing it. Because those results suck.
Click to expand...
We should do it correctly because that is how it should be done, not because we are going to break the right side of the case off.
 
Top Bottom
Back