Lift problems
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dueselfabrication
- Posts: 64
- Joined: Sun Jan 06, 2013 4:17 pm
- Location: Falls Church, Virginia
Re: Lift problems
About the spring height, might they need some breaking in because they're new? Springs usually settle a bit, in my experience. Not sure if that will center them very much.
-Jeff
2006 LJ - spacers, 33's, pocket flairs, dents, and too much courage
1973 Wagoneer - still not sure why, but since it's here it's going to be cool.
2006 LJ - spacers, 33's, pocket flairs, dents, and too much courage
1973 Wagoneer - still not sure why, but since it's here it's going to be cool.
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mineral co
Topic author - Posts: 229
- Joined: Tue Jul 09, 2013 1:20 pm
- Location: Mineral County, Colorado
Re: Lift problems
As the stomach churns. . .
I put 2* shims in the rear to bring the rear pinion down the last two necessary degrees over the weekend. A quick drive out on the highway shows a marked improvement at higher speeds.
However, yesterday, I was driving the truck around in town, and the speeds are, obviously, much lower. While the vibration is pretty much zero at higher speeds, I now how a noticeable vibration at lower speeds (15 - 20 mph). The board needs a smiley face showing me holding a gun pointed at my own head.
So, here's the numbers.
Sitting in my back driveway, which has a bit of a downward slope, the transfer case is pointing down at 7*. The axle pinion is pointing up at 6*. In theory, under a bit of a load, the pinion will climb a little bit and be very close to pointing up at 7*, and the world will be all happy.
However, I think I may be at the limit of what the stock driveshaft can do. After having rotated the pinion down that 2 additional degrees, the driveshaft has had to get longer again and, now, I can see the end of the splines at the sliding joint. That means it's time to check the angles through the u-joints. So, this morning, I pulled everything apart again, and the angle at the TC and rear pinion were as previously stated at TC = 7* down and pinion = 6* up. I reinstalled the driveshaft and it is at 17* up, or down, depending on which end you are referencing.
So, that means there is a 10* angle through the upper joint and 11* angle through the lower joint with the truck just sitting. In theory, the lower joint's angle would decrease to 10* under load. To me, these numbers are at the extreme upper limit of what a normal u-joint can be operated at if it is to be "vibration free" under all conditions. In practice, these numbers may be beyond the upper limit. I was also suspicious that the sliding joint may be worn and, with the further reduced engagement, could be rotating "out of round". However, I can't feel any slop in it when pushing the sliding joint sideways.
Last night I was thinking that I was looking at a new, longer driveshaft but after measuring all this out, I'm no longer satisfied that a longer driveshaft will be sufficient to rectify the problem. Now I'm wondering if the only viable, proper solution is to replace the driveshaft with a double Cardon unit and rotating the pinion up. I'm working on a 14-bolt replacement rear axle and the pinion will stick out even further than on the current axle (AMC-20) and that will make the angles even more pronounced if I stick with a single joint driveshaft.
Am I just overly frustrated with all this BS, or am I really at the limits of what the stock driveshaft will accomodate?
I literally just got my test adaptor plates to put the AAM disc brakes on the 14-bolt, so I'm going to go play with that for a while.
I put 2* shims in the rear to bring the rear pinion down the last two necessary degrees over the weekend. A quick drive out on the highway shows a marked improvement at higher speeds.
However, yesterday, I was driving the truck around in town, and the speeds are, obviously, much lower. While the vibration is pretty much zero at higher speeds, I now how a noticeable vibration at lower speeds (15 - 20 mph). The board needs a smiley face showing me holding a gun pointed at my own head.
So, here's the numbers.
Sitting in my back driveway, which has a bit of a downward slope, the transfer case is pointing down at 7*. The axle pinion is pointing up at 6*. In theory, under a bit of a load, the pinion will climb a little bit and be very close to pointing up at 7*, and the world will be all happy.
However, I think I may be at the limit of what the stock driveshaft can do. After having rotated the pinion down that 2 additional degrees, the driveshaft has had to get longer again and, now, I can see the end of the splines at the sliding joint. That means it's time to check the angles through the u-joints. So, this morning, I pulled everything apart again, and the angle at the TC and rear pinion were as previously stated at TC = 7* down and pinion = 6* up. I reinstalled the driveshaft and it is at 17* up, or down, depending on which end you are referencing.
So, that means there is a 10* angle through the upper joint and 11* angle through the lower joint with the truck just sitting. In theory, the lower joint's angle would decrease to 10* under load. To me, these numbers are at the extreme upper limit of what a normal u-joint can be operated at if it is to be "vibration free" under all conditions. In practice, these numbers may be beyond the upper limit. I was also suspicious that the sliding joint may be worn and, with the further reduced engagement, could be rotating "out of round". However, I can't feel any slop in it when pushing the sliding joint sideways.
Last night I was thinking that I was looking at a new, longer driveshaft but after measuring all this out, I'm no longer satisfied that a longer driveshaft will be sufficient to rectify the problem. Now I'm wondering if the only viable, proper solution is to replace the driveshaft with a double Cardon unit and rotating the pinion up. I'm working on a 14-bolt replacement rear axle and the pinion will stick out even further than on the current axle (AMC-20) and that will make the angles even more pronounced if I stick with a single joint driveshaft.
Am I just overly frustrated with all this BS, or am I really at the limits of what the stock driveshaft will accomodate?
I literally just got my test adaptor plates to put the AAM disc brakes on the 14-bolt, so I'm going to go play with that for a while.
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'84 GW, returning to service.
360, 727, Selec-Trac 229, TFI, Hydro-Boost, 4" all-spring BDS lift (what a PITA!), BFG/AT 31x10.5x15, 5125 Bilstiens
360, 727, Selec-Trac 229, TFI, Hydro-Boost, 4" all-spring BDS lift (what a PITA!), BFG/AT 31x10.5x15, 5125 Bilstiens
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BigJ200
- Posts: 228
- Joined: Tue Jan 17, 2012 1:36 pm
- Location: Kuna, Idaho
- Contact:
Re: Lift problems
It would really help if you could post some photos of the angles. BTW, when you checked for slop in your driveline, I assume you had it in neutral to relieve the pressure. And yes, it is clearly over extended. It must be lengthened.
U-joint operating angles of 10 and 11 degrees can definitely cause vibrations. It depends on the tube diameter, wall thickness, length, all at a given RPM. 3 degrees is the "normal" recommended operating angle for standard Spicer u-joints. It's difficult to maintain that when lifts become part of the picture.
MB
U-joint operating angles of 10 and 11 degrees can definitely cause vibrations. It depends on the tube diameter, wall thickness, length, all at a given RPM. 3 degrees is the "normal" recommended operating angle for standard Spicer u-joints. It's difficult to maintain that when lifts become part of the picture.
MB