TheGrendel
Active Member
Is it me or does it seem he’s getting too much pinion rotation on acceleration?
Got an interesting one… 🤔
- Thread starter Physicistkev
- Start date
Physicistkev
Member
When I rewatch the longer videos, it’s disturbing how poor the pinion angle looks and how much movement there is.
But remember, the fisheye lens exaggerates movement up close and gives linear things a horizontal curve when there isn’t one. That’s just how the optics work. I’m going to do a shot with my phone today. I’ll post that and see if there is a significant difference between a fisheye and non-fisheye lens.
I think there will be, but there’s no proof like empirical proof.
But remember, the fisheye lens exaggerates movement up close and gives linear things a horizontal curve when there isn’t one. That’s just how the optics work. I’m going to do a shot with my phone today. I’ll post that and see if there is a significant difference between a fisheye and non-fisheye lens.
I think there will be, but there’s no proof like empirical proof.
Physicistkev
Member
Here is the video from this morning. Using an iPhone mounted on the rock slider. I couldn't mount it in the same place as the GoPro from the last video as it was too close to the differential. Also, the focus is on the driver side, rear, lower control arm mounting bracket, so the driveshaft is a bit out of focus. Anywho, I think the deflection looks A LOT less severe, which I would chalk up to the fisheye lens on the GoPro. Also, I think the pinion angle looks more appropriate in this video. My thoughts, but I'll let you all weigh in.
I still think the pinion angle needs to come down as it's at -1 degrees and I want to see -2 degrees, as noted earlier in the thread.
I still think the pinion angle needs to come down as it's at -1 degrees and I want to see -2 degrees, as noted earlier in the thread.
Mike Pierson
Hooked
The rear OEM driveshaft, since it’s so long and has the rzeppa joint, can be off a bit and it doesn’t cause issues. If the boot is damaged and it’s slung all the grease, it can stop it from sliding which can put pressure on the pinion and bearings when you articulate, which could cause them to fail. Also, check the boots at the joints.
CalSgt
Hooked
If your pinion bearings are starting to fail the pinion snout should get super hot.
When I set up a differential I use an IR thermometer to check temps on the pinion snout and diff cover during break in.
New bearings and gears will produce more heat than broken in ones but still shouldn’t get much over 250 degrees while broken in ones don’t typically get over 200. If preload is set wrong or the bearings are failing they start to cook themselves.
Take it out and run at highway speed for a while and get differential temperatures.
If your bearings are going bad it will be catastrophic (expensive) once they’ve had enough and give out. Far cheaper to repair now than it will be to replace the carrier/locker.
If you have any friends with the same Jeep you could probably swap rear drive shafts for troubleshooting whether it’s the Rzepa or something else. Drive shafts usually are catastrophic when they fail on the highway too, they can shatter transmission and transfer case housings and beat the shit out of everything else.
When I set up a differential I use an IR thermometer to check temps on the pinion snout and diff cover during break in.
New bearings and gears will produce more heat than broken in ones but still shouldn’t get much over 250 degrees while broken in ones don’t typically get over 200. If preload is set wrong or the bearings are failing they start to cook themselves.
Take it out and run at highway speed for a while and get differential temperatures.
If your bearings are going bad it will be catastrophic (expensive) once they’ve had enough and give out. Far cheaper to repair now than it will be to replace the carrier/locker.
If you have any friends with the same Jeep you could probably swap rear drive shafts for troubleshooting whether it’s the Rzepa or something else. Drive shafts usually are catastrophic when they fail on the highway too, they can shatter transmission and transfer case housings and beat the shit out of everything else.
Physicistkev
Member
How long is “a while”? I did 70 for about 15 minutes and the rear differential cover was 197. The snout was 201. Is that enough time to allow the heat to build up?
CalSgt
Hooked
Yeah, I would think that is plenty enough time and speed to check the temps and you’re right in the ballpark of normal temperature wise.
Physicistkev
Member
I’ve had it up several times and did a lot of rotations when I installed the new axles. The chirp only comes after the driveline is hot.
I think the next test is to get the driveline hot enough to chirp and then measure the temp of the diff. That should tell me the answer to diff or drive shaft.
Likely still replace bearings in diff and just replace the drive shaft with an aftermarket one.
Physicistkev
Member
Good morning everyone. I've had a busy and fruitful morning of testing.
Frist thing I want to say is this. Thank you to everyone that has commented and made suggestions. I wouldn't have understood how to test or monitor various things without all of you. While I understand the laws of physics very well, it's hard to tie that to specific testing scenarios and to understand what is normal or abnormal. On to the mornings findings.
First, my IR thermometer was using very low batteries, so I have had to throw out the temps I got yesterday during my test. I did a much more thorough set of tests this morning and got the consistency I would look for in a well run experiment.
Second, I went out this morning and drove around for about 45 minutes. First 25 minutes was just 60-70 on freeways and large roads. I took temps at 10, 20 and 25 minutes. I took temperature at 4 different places on the diff, just to make sure I wasn't missing a hot spot. Top of the rear diff cover, bottom of the rear diff cover, top of the neck facing the drive shaft and bottom of the neck facing the drive shaft. This should get me accurate readings of right around the pinion bearing and what the fluid cooled portions of the diff were at vs the non-fluid cooled or less fluid cooled areas.
10 min: Top of cover 157, bottom of cover 155, bottom of neck 160, top of the neck 160
20 min: Top of cover 158, bottom of cover 156, bottom of neck 161, top of the neck 161
25 min: Top of cover 157, bottom of cover 155, bottom of neck 160, top of the neck 161
I had no chirp during any of this time.
I went to an area where I could do several hard accelerations to see if I could get a higher temp for any of the readings. After several hard accelerations, I took measurements.
Top of cover 159, bottom of cover 157, bottom of neck 162, top of neck 163
Even after doing more pulls, I had the same temp measurement and no chirp. I thought to myself how can I stress the diff more. Well, I went and hooked up our boat and towed it down the road for 10 minutes and had these readings. FYI the boat is just under 3000#'s and the chirp came back after about 1/4 mile with the boat attached.
10 min towing: Top of cover 172, bottom of cover 170, bottom of the neck 175, top of the neck 176
I did some hard pulls towing and I got another 2 degrees higher across the board, but nothing more. The lower temps on the bottom side of things is because the oil is in contact with that part of the diff housing, so I would expect to be a few degrees cooler. For the numbers I was getting yesterday, around 200 after driving at higher speeds, part of that was the higher ambient air temp. It was 20 degrees cooler this morning than when I was testing yesterday, so maybe the batteries weren't that much of an issue? Either way, the consistency of the readings this morning give me a lot of confidence in what I am seeing.
So it's safe to say that the pinion bearing is not an issue. The temps definitely show a healthy set of bearings and gear meshing in the rear differential. Effectively, that forces me to think that the drive shaft is the culprit. I looked over the drive shaft and surrounding area. There are no grease or debris splatters of any kind. Both boots look very good and the plastic cover over the expansion section of the drive shaft is damn near perfect. The rear boot does have some marks or a rough spot, like it was packaged wrong or squashed for an extended period, but there is no hole and certainly no leaking grease.
With regard to the glitter in the diff oil, I am a novice when looking at this stuff. It wouldn't be beyond me to have seen normal wear and think it's more diabolical. I still think I will have the local 4x4 shop that did the regear for me take a look at the diff and maybe just replace the bearings after I install a new rear drive shaft. Or, if they don't kill me on price, I may have them do it. I do have the fancy inch/pound wrench for the pinion tension setting, so I can do it, but it would be nice to have it done by some folks that do this on the regular.
Can anyone find any fault to my logic here?
Frist thing I want to say is this. Thank you to everyone that has commented and made suggestions. I wouldn't have understood how to test or monitor various things without all of you. While I understand the laws of physics very well, it's hard to tie that to specific testing scenarios and to understand what is normal or abnormal. On to the mornings findings.
First, my IR thermometer was using very low batteries, so I have had to throw out the temps I got yesterday during my test. I did a much more thorough set of tests this morning and got the consistency I would look for in a well run experiment.
Second, I went out this morning and drove around for about 45 minutes. First 25 minutes was just 60-70 on freeways and large roads. I took temps at 10, 20 and 25 minutes. I took temperature at 4 different places on the diff, just to make sure I wasn't missing a hot spot. Top of the rear diff cover, bottom of the rear diff cover, top of the neck facing the drive shaft and bottom of the neck facing the drive shaft. This should get me accurate readings of right around the pinion bearing and what the fluid cooled portions of the diff were at vs the non-fluid cooled or less fluid cooled areas.
10 min: Top of cover 157, bottom of cover 155, bottom of neck 160, top of the neck 160
20 min: Top of cover 158, bottom of cover 156, bottom of neck 161, top of the neck 161
25 min: Top of cover 157, bottom of cover 155, bottom of neck 160, top of the neck 161
I had no chirp during any of this time.
I went to an area where I could do several hard accelerations to see if I could get a higher temp for any of the readings. After several hard accelerations, I took measurements.
Top of cover 159, bottom of cover 157, bottom of neck 162, top of neck 163
Even after doing more pulls, I had the same temp measurement and no chirp. I thought to myself how can I stress the diff more. Well, I went and hooked up our boat and towed it down the road for 10 minutes and had these readings. FYI the boat is just under 3000#'s and the chirp came back after about 1/4 mile with the boat attached.
10 min towing: Top of cover 172, bottom of cover 170, bottom of the neck 175, top of the neck 176
I did some hard pulls towing and I got another 2 degrees higher across the board, but nothing more. The lower temps on the bottom side of things is because the oil is in contact with that part of the diff housing, so I would expect to be a few degrees cooler. For the numbers I was getting yesterday, around 200 after driving at higher speeds, part of that was the higher ambient air temp. It was 20 degrees cooler this morning than when I was testing yesterday, so maybe the batteries weren't that much of an issue? Either way, the consistency of the readings this morning give me a lot of confidence in what I am seeing.
So it's safe to say that the pinion bearing is not an issue. The temps definitely show a healthy set of bearings and gear meshing in the rear differential. Effectively, that forces me to think that the drive shaft is the culprit. I looked over the drive shaft and surrounding area. There are no grease or debris splatters of any kind. Both boots look very good and the plastic cover over the expansion section of the drive shaft is damn near perfect. The rear boot does have some marks or a rough spot, like it was packaged wrong or squashed for an extended period, but there is no hole and certainly no leaking grease.
With regard to the glitter in the diff oil, I am a novice when looking at this stuff. It wouldn't be beyond me to have seen normal wear and think it's more diabolical. I still think I will have the local 4x4 shop that did the regear for me take a look at the diff and maybe just replace the bearings after I install a new rear drive shaft. Or, if they don't kill me on price, I may have them do it. I do have the fancy inch/pound wrench for the pinion tension setting, so I can do it, but it would be nice to have it done by some folks that do this on the regular.
Can anyone find any fault to my logic here?