Sudden back end trouble!

[joney]

This morning I started my Ex after not driving for a couple days. Pulled out and its rear end started shuddering, rumbling noise and felt like I was driving over boulders like bowling balls! That went away within the next 2 blocks. There was maybe 1/3" inch of snow, not sure if it was the 4WD trying to kick in, but it really wasn't a slick road. So no idea why. Maybe related or not, last week I was doing Fluid Film on the underside, my front U-joint looked weird to me, trying to get a pic of it to post. Also noticed the pumpkin in back was wet along its seam on bottom (no rain or snow at that time or before) Last March I asked a mechanic to check all the fluids including the differential he said they were OK (of course I have no proof he actually did. How do I check this out? I noticed that after the shuddering stopped this morning, the truck rode rougher, like there were actually more potholes than there already were.

 

[Rick]

Check both U-joints for looseness. While checking look for looseness in the pinion yoke as well.

There is a plug on driver side of the differential housing. Remove the plug and make sure there is gear lube up to the bottom of the hole. While you have the rear end jacked up rotate the wheels to check for any roughness.

 

[joney]

Check both U-joints for looseness. While checking look for looseness in the pinion yoke as well.

There is a plug on driver side of the differential housing. Remove the plug and make sure there is gear lube up to the bottom of the hole. While you have the rear end jacked up rotate the wheels to check for any roughness.

Thanks for the answer! The last few months I've been able to feel a vibration under the truck at idle, haven't noticed it at other times. I believe I could check the u joints front and back with a screwdriver or pry bar with the truck sitting on the ground? Trying to look up how to check the pinion yoke, no luck so far.. With 30 degree temps and snow here, really wondering what else to check, as it's likely I'd have to have a shop do what actual work it may need? Don't want to drop a driveshaft (2 of them in a 4WD as I understand it), or get unnecessary charges from a shop, retired on a low budget. Further advice always appreciated! Gotta love this forum!

 

[Josh P]

The wet seam on the differential, is it only along the seam where the cover is or along the underside from the pinion seal back?

 

[joney]

The wet seam on the differential, is it only along the seam where the cover is or along the underside from the pinion seal back?

Thanks for the input, I'll have to check! It is along the bottom most 1/3 of the seam where the (rear) differential has bolts all around it, the pinion seal must be directly in front of the back differential I assume (quite unfamiliar with suspension stuff at present, LOL).

 

[C420sailor]

I wonder if you had snow/ice on the wheels that slung off, and this leak is coincidental. Ice frozen to wheels makes them WAY out of balance and the truck will shudder

That said, these trucks are getting to the mileage where the pinion bearings are wearing out. I just had to rebuild my rear diff recently, as my pinion bearings were half toast. It would be okay around town, but on the Highway the fluid would get hot, thin out, get past the pinion seal, and coat the bottom of the differential. Near the end, I noticed oil spots on the BACK OF THE HATCH. It got so hot and thin that droplets would be carried up into the low pressure area behind the truck and stick to the body lol.

I didn’t realize how noisy the diff was until I rebuilt it and could now hear all the other **** that needed fixing lol

 

[joney]

I wonder if you had snow/ice on the wheels that slung off, and this leak is coincidental. Ice frozen to wheels makes them WAY out of balance and the truck will shudder

That said, these trucks are getting to the mileage where the pinion bearings are wearing out. I just had to rebuild my rear diff recently, as my pinion bearings were half toast. It would be okay around town, but on the Highway the fluid would get hot, thin out, get past the pinion seal, and coat the bottom of the differential. Near the end, I noticed oil spots on the BACK OF THE HATCH. It got so hot and thin that droplets would be carried up into the low pressure area behind the truck and stick to the body lol.

I didn’t realize how noisy the diff was until I rebuilt it and could now hear all the other shi* that needed fixing lol

Thanks for your answer! No ice/snow on the wheels, very little on the ground. The service records from previous owners don't show any differential/pinion service. Still looking up how to check the pinions, should have one on front and back for 4x4 I think. Not sure if I should be driving short trips even, although this is the one and only instance of this happening, I've noticed a driveline -seeming vibration at idle for a couple of months. The stuff that makes non-mechanics go hmmm. I dnn't do a ton of hwy driving though.

 

[Rick]

Thanks for the answer! The last few months I've been able to feel a vibration under the truck at idle, haven't noticed it at other times. I believe I could check the u joints front and back with a screwdriver or pry bar with the truck sitting on the ground? Trying to look up how to check the pinion yoke, no luck so far.. With 30 degree temps and snow here, really wondering what else to check, as it's likely I'd have to have a shop do what actual work it may need? Don't want to drop a driveshaft (2 of them in a 4WD as I understand it), or get unnecessary charges from a shop, retired on a low budget. Further advice always appreciated! Gotta love this forum!

It's best to check the u-joints with the weight off the wheels and the vehicle in neutral so there is no bind in the driveline.

 

[joney]

It's best to check the u-joints with the weight off the wheels and the vehicle in neutral so there is no bind in the driveline.

End in the air, or all 4 off the ground?

 

[Josh P]

End in the air, or all 4 off the ground?

You can do each end separately in the air. When was the transmission serviced last?

 

[BKennedy]

All 4 wheels off the ground. Put trans in neutral. Crawl under there with a big screwdriver or small pry bar. Give all the u-joints a wiggle. Check pinyon output shaft. Check for play in the axle bearings by turning the wheels while your hands are in contact with the tires feeling for anything not smooth. Grab the tires and shake them as hard as you can up and down, and side to side. Should be very little play in those axle bearings.

Don't wait too long because the cost of repairs go way up after components fail, versus replacing them when worn.

From what you said, I am thinking you have a bad u-joint(s). It's stuck when you first start moving, then the rotation of the drive shaft forces it free. That needs to be addressed as soon as possible. The vibration will cause other parts to fail.

 

[Turdle]

Please try to get pictures of both u joint areas, and highest area of wet on differential
Also, colder wet weather can cause the park brake shoes and mechanism to hang up. Check this also once you get the rear wheels up and free spinning.

 

[joney]

Please try to get pictures of both u joint areas, and highest area of wet on differential
Also, colder wet weather can cause the park brake shoes and mechanism to hang up. Check this also once you get the rear wheels up and free spinning.

Which wheel is connected to the parking brake? I've never used it, for fear it will lock up (Rust Belt again) and understand it's some kind of drum mechanism?
When these froze up on my 70s cars we had to cut the cable going to it.

Will probably have a shop do any necessary work, guess I'd just like to see for myself what's a problem and what isn't. Reading here and elsewhere about mechanic shops just saying they did the work - and really didn't. No paranoia, but aware of how some will assume an old lady wouldn't know the difference, LOL

Glad you reminded me about the pics! Going out to get them. Thanks to you and everyone for the advice!

 

[XLTrunner]

I've lived by that same credo regarding emergency brake usage as well having lived in the Rust Belt my entire life. As a result, I never use mine, either. And, since there are no safety inspections in MN and never having to worry about parking on hilly terrain, I've gotten along just fine without them over the decades while taking extra precautions when needed while working on it. So, it begs the question...if they are never used, can it be assumed that the pads don't wear out and require replacement?
.

 

[joney]

This morning I started my Ex after not driving for a couple days. Pulled out and its rear end started shuddering, rumbling noise and felt like I was driving over boulders like bowling balls! That went away within the next 2 blocks. There was maybe 1/3" inch of snow, not sure if it was the 4WD trying to kick in, but it really wasn't a slick road. So no idea why. Maybe related or not, last week I was doing Fluid Film on the underside, my front U-joint looked weird to me, trying to get a pic of it to post. Also noticed the pumpkin in back was wet along its seam on bottom (no rain or snow at that time or before) Last March I asked a mechanic to check all the fluids including the differential he said they were OK (of course I have no proof he actually did. How do I check this out? I noticed that after the shuddering stopped this morning, the truck rode rougher, like there were actually more potholes than there already were.

This morning I started my Ex after not driving for a couple days. Pulled out and its rear end started shuddering, rumbling noise and felt like I was driving over boulders like bowling balls! That went away within the next 2 blocks. There was maybe 1/3" inch of snow, not sure if it was the 4WD trying to kick in, but it really wasn't a slick road. So no idea why. Maybe related or not, last week I was doing Fluid Film on the underside, my front U-joint looked weird to me, trying to get a pic of it to post. Also noticed the pumpkin in back was wet along its seam on bottom (no rain or snow at that time or before) Last March I asked a mechanic to check all the fluids including the differential he said they were OK (of course I have no proof he actually did. How do I check this out? I noticed that after the shuddering stopped this morning, the truck rode rougher, like there were actually more potholes than there already were.

 

[joney]

View attachment 436668 View attachment 436669

 

[joney]

seeson't know if anything is useful to see here as there is Fluid Film on it. The reddish color is not really there

 

[Rick]

Which wheel is connected to the parking brake? I've never used it, for fear it will lock up (Rust Belt again) and understand it's some kind of drum mechanism?

Both rear wheels have parking brakes. It uses a small "drum" within the rear rotors and also separate brake shoes.