Just finished my OME lift install. Need help diagnosing new vibration
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- Thread starter
- #43
Update: k&h did right by the situation and installed new OEM Toyota u-joints for me yesterday. Cheers to that!
Regarding the driveshaft length bottoming out, tell me if my logic is flawed:
When under load, the rear shackles allow the springs to flatten, effectively lengthening them and pulling the diff away from the transfer case. This in turn, lengthens the driveshaft at the slip joint rather than compressing it. Therefore, the only time that the driveshaft would need to be shorter than when the vehicle is resting on its springs is when the vehicle is up on a lift with axles dangling and the springs shorten, pushing the diff towards the transfer case. By this logic, there really is no need to shorten the shaft as whenever the vehicle is actually being driven, the springs are ether at their resting place under the weight of the vehicle or obsorbing shocks. Maybe this is why nobody seems to notice or find the need to shorten their driveshafts after these standard 2.5-3" OME lifts?
Regarding the driveshaft length bottoming out, tell me if my logic is flawed:
When under load, the rear shackles allow the springs to flatten, effectively lengthening them and pulling the diff away from the transfer case. This in turn, lengthens the driveshaft at the slip joint rather than compressing it. Therefore, the only time that the driveshaft would need to be shorter than when the vehicle is resting on its springs is when the vehicle is up on a lift with axles dangling and the springs shorten, pushing the diff towards the transfer case. By this logic, there really is no need to shorten the shaft as whenever the vehicle is actually being driven, the springs are ether at their resting place under the weight of the vehicle or obsorbing shocks. Maybe this is why nobody seems to notice or find the need to shorten their driveshafts after these standard 2.5-3" OME lifts?
I agree that this shouldn't be a problem with a stock driveshaft. But it sounds like it is . . . anyway.
The new springs should not be allowing the diff to come any closer to the transfer case than the stock ones did. My experience matches yours, I have seen shafts need lengthening after a lift, but never heard of anyone having to shorten one. Maybe it was a pre-existing problem that the new suspension just aggravated (We all have a lot of things we'd like the previous owners to answer for.) I have no idea how much travel the slip joint had from the factory, but I bet it was more than 1/8".
You are dealing with two pivot points: the transfer case yoke, and the front eye of the spring. They will have slightly different arcs, and slightly different effects. The vertical movement of the axle into the same plane as the transfer case is bringing the two closer while the flattening spring is trying to push them apart. The two motions should offset each other somewhat, but not completely. I have no idea which will have a greater effect, but the factory allowed for some travel towards the transfer case, so I assume it is possible for them to get closer together. The only part I am sure of is that I would be very nervous if I only had 1/8" travel between resting and bottoming out.
The new springs should not be allowing the diff to come any closer to the transfer case than the stock ones did. My experience matches yours, I have seen shafts need lengthening after a lift, but never heard of anyone having to shorten one. Maybe it was a pre-existing problem that the new suspension just aggravated (We all have a lot of things we'd like the previous owners to answer for.) I have no idea how much travel the slip joint had from the factory, but I bet it was more than 1/8".
You are dealing with two pivot points: the transfer case yoke, and the front eye of the spring. They will have slightly different arcs, and slightly different effects. The vertical movement of the axle into the same plane as the transfer case is bringing the two closer while the flattening spring is trying to push them apart. The two motions should offset each other somewhat, but not completely. I have no idea which will have a greater effect, but the factory allowed for some travel towards the transfer case, so I assume it is possible for them to get closer together. The only part I am sure of is that I would be very nervous if I only had 1/8" travel between resting and bottoming out.
- Thread starter
- #46
Thanks guys. Consensus has been reached then. Dropping it off to get balanced and shortened 1/2". Sufficient but not to short? Found a shop that will do the whole job for $70. No brainer.
As always, I can't thank all of you enough for helping me think this one through.
As always, I can't thank all of you enough for helping me think this one through.
trying to wrap my head around how things were fine with no lift, but now after a suspension lift, the driveshaft is now too long???
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- Thread starter
- #48
To be honest, I paid no attention to the driveshaft travel before the new suspension. Never had to have any work done to it until the new spring height made the 240k mile old u joints age apparent. And it wasn't until the new spring were attached that the axel was allowed to fall low enough to come forward enough to bind the driveshaft in when the truck was on a lift at a the shop, leading to the mechanics conclusion that my driveshaft is too long for these OME springs.
Quite the puzzle for sure.
Quite the puzzle for sure.