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Discussion Starter · #1 · (Edited)
I have a very mild rod-knock, so I'm going to replace the rod bearings and oil pump in-situ and see how it goes. I'm not sure if this procedure will work on a non-ZR2 as there may be less clearance between the oil pan and the dropped-down front axle. It's pretty tight, but there is JUST enough room! For instance, when I first tried it, I put the castle nuts back on the Pitman arm and idler arm and there wasn't enough room! The extra 5 mm made the difference.

2WD may be similar, or a million times easier. I did this on a ZR2 Blazer today. The front wheels do not need to be removed and the CV axles do not need to be removed. steering components are not disconnected in a way that would require an alignment.
  1. Lift the front of the vehicle about a foot to make room for working underneath. I used ramps.
  2. Remove the engine rock-shield (4 bolts).
  3. Turn the steering to left lock
  4. Loosen the pitman arm and idler arm castle nuts to flush with the end of the threads, but do not remove them. (21mm for mine)
  5. Use a pickle fork to separate the pitman arm. There was enough room to swing a sledge hammer without removing the left wheel even with 31s.
  6. Turn the steering to right lock
  7. Use a pickle fork to separate the idler arm. Again, there was enough room to swing a sledge hammer without removing the right wheel
  8. Turn the steering wheel back to center and then turn right about 1/4 of a steering wheel turn (to move the pitman arm over a little bit)
  9. Disconnect the steering damper (13mm nut & bolt if equipped) on the frame end and collapse it. You can leave the centerlink end attached or remove the damper completely.
  10. Remove the castle nuts from the pitman arm and idler arm and drop down the center link (still completely attached to the tie rods so no alignment needed). Check that the pitman arm and idler arm are stiff.
  11. Remove the four 11mm bolts holding the front driveshaft to the front diff. Set them and the straps aside (do not put them back in the yoke - you need the space). Separate the driveshaft from the diff input yoke. I used a crowbar. Tape the u-joint caps to prevent them from falling off. Check the u-joint for smoothness.
  12. Push the centerlink forward above the cross-frame member with force as this will move the tires a bit. The steering damper will tuck in just above the frame.
  13. There are two nuts and bolts holding the left side of the front diff to the frame. Completely remove the lower 18mm nut and bolt.
  14. The upper bolt requires an 18mm deep socket on a 4" extension inserted into the frame from the left side to hold the nut. Apply penetrating oil to the nut via the hole in the bottom of the frame. My frame has some mild corrosion, so I had to file the side hole a little to make it large enough to accept my socket. Undo the upper nut until it is undone and then rethread it a turn. Remove the ratchet leaving the extension in the frame. Carefully manipulate the extension with the nut on it to remove the nut and then move it to the hole at the bottom of the frame right below it and drop the nut out of the bottom of the frame. Do NOT attempt to remove the nut from the hole that you inserted the socket into as the hole is not big enough to remove the nut and then you'll have to try to rescue it from inside the boxed frame.
  15. Remove the upper of the two nuts & bolts holding up the right side of the front diff. Loosen the lower of the two bolts so that the nut is flush with the end of the bolt.
  16. Lift up on the diff pumpkin to relieve pressure on the upper left side bolt and remove the bolt. Allow the right side of the diff to lower. The CV axle will land on the a-arm and hold up the diff (it's light).
  17. Lift up on the right side of the diff and remove the loose nut and bolt holding the diff to the frame and lower the left side of the diff to rest the CV axle on the a-arm.
  18. With the diff fully dropped down, push it forward. The exact location is not that important right now.
  19. Drain the oil and lift up the oil dipstick about four inches (10 cm) so that it doesn't get bent when you remove the pan (the oil pan will hit it if you don't)
  20. Disconnect the battery (do not skip this step or you'll short it when you pull the starter)
  21. Remove two 14mm bolts holding the starter to the block and push the starter aside. No need to remove the wires.
  22. Remove two 10mm bolts and the metal shield that closes off the starter hole to the torque converter.
  23. Disconnect the trans cooler lines from the oil pan on the right side by removing two 10mm nuts and a stud.
  24. Disconnect the bracket (10 mm bolt) holding the forward end of the remote oil cooler lines
  25. Remove the two bolts holding the remote oil cooler housing to the block (2 x 13mm bolts) and push the housing to the left a little bit.
  26. Remove the three bellhousing bolts (14 mm) between the transmission and the oil pan.
  27. Remove the two large rubber grommets at the bottom rear of the oil pan. I did this by shooting some WD40 on them, then grasping them with vice grips and then twisting them until they turned, then pulling down on them. I could not accomplish this by hand!
  28. Use a long extension and a 13mm deep socket to remove the two nuts directly above the rubber grommets. If you drop them, you will be able to get them easily after removing the oil pan.
  29. Remove ten (10) 13mm bolts that hold the oil pan to the block.
  30. Remove the oil pan to the rear
    1. Lower the oil pan down onto the diff with the back lower than the front.
    2. Push the transmission cooler lines to the right to allow the pan to clear
    3. Manipulate the front diff, the cooler lines, and the oil pan to remove the pan. It's quite tight, but it does come out.
    4. Pull down the oil pan gasket that's probably stuck to the bottom of the block with RTV.
Re-installation is the reverse, except after getting the oil pan up, put one bolt in on each side of the pan snug but not tight. Next put the two nuts on at the back of pan. If you drop a nut and need to extract it from the bellhousing, you'll have less work to undo with only two bolts in the pan.
 

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Discussion Starter · #3 · (Edited)
What did the crank look like when you got the caps off?
I haven't taken the caps off yet. Notably, neither the main caps nor the rod caps are exhibiting any blueing from overheating that I could see (without taking the caps off). There's normal oil browning on the whole assembly. The oil had a tiny bit of the party-glitter in it but most of the metal on the oil drain magnet was super-fine goop. With the engine running and me lying underneath it, I could hear the #1 rod was knocking noticeably and the #2 was making a tiny noise.

The day it started, I drove it 104 miles with no problem or noise. I stopped for some gas and upon startup, it knocked. I drove it about 20 miles straight home and by the time it got home, it wasn't making much noise at all. I started it the next day and it was knocking noticeably again, so I decided to try to replace the pump and bearings. I don't drive it that much, and it's a beater, so I'm not inclined to put a ton of effort into it if I don't have to. Other than the knock, the engine is running great! I expect I wore the pump on the way home with the metal in the oil but hopefully, the oil filter caught the rest before it got into the rest of the bearings.
 

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I have a very mild rod-knock, so I'm going to replace the rod bearings and oil pump in-situ and see how it goes. I'm not sure if this procedure will work on a non-ZR2 as there may be less clearance between the oil pan and the dropped-down front axle. It's pretty tight, but there is JUST enough room! For instance, when I first tried it, I put the castle nuts back on the Pitman arm and idler arm and there wasn't enough room! The extra 5 mm made the difference.

2WD may be similar, or a million times easier. I did this on a ZR2 Blazer today. The front wheels do not need to be removed and the CV axles do not need to be removed. steering components are not disconnected in a way that would require an alignment.
  1. Lift the front of the vehicle about a foot to make room for working underneath. I used ramps.
  2. Remove the engine rock-shield (4 bolts).
  3. Turn the steering to left lock
  4. Loosen the pitman arm and idler arm castle nuts to flush with the end of the threads, but do not remove them. (21mm for mine)
  5. Use a pickle fork to separate the pitman arm. There was enough room to swing a sledge hammer without removing the left wheel even with 31s.
  6. Turn the steering to right lock
  7. Use a pickle fork to separate the idler arm. Again, there was enough room to swing a sledge hammer without removing the right wheel
  8. Turn the steering wheel back to center and then turn right about 1/4 of a steering wheel turn (to move the pitman arm over a little bit)
  9. Disconnect the steering damper (13mm nut & bolt if equipped) on the frame end and collapse it. You can leave the centerlink end attached or remove the damper completely.
  10. Remove the castle nuts from the pitman arm and idler arm and drop down the center link (still completely attached to the tie rods so no alignment needed). Check that the pitman arm and idler arm are stiff.
  11. Remove the four 11mm bolts holding the front driveshaft to the front diff. Set them and the straps aside (do not put them back in the yoke - you need the space). Separate the driveshaft from the diff input yoke. I used a crowbar. Tape the u-joint caps to prevent them from falling off. Check the u-joint for smoothness.
  12. Push the centerlink forward above the cross-frame member with force as this will move the tires a bit. The steering damper will tuck in just above the frame.
  13. There are two nuts and bolts holding the left side of the front diff to the frame. Completely remove the lower 18mm nut and bolt.
  14. The upper bolt requires an 18mm deep socket on a 4" extension inserted into the frame from the left side to hold the nut. Apply penetrating oil to the nut via the hole in the bottom of the frame. My frame has some mild corrosion, so I had to file the side hole a little to make it large enough to accept my socket. Undo the upper nut until it is undone and then rethread it a turn. Remove the ratchet leaving the extension in the frame. Carefully manipulate the extension with the nut on it to remove the nut and then move it to the hole at the bottom of the frame right below it and drop the nut out of the bottom of the frame. Do NOT attempt to remove the nut from the hole that you inserted the socket into as the hole is not big enough to remove the nut and then you'll have to try to rescue it from inside the boxed frame.
  15. Remove the upper of the two nuts & bolts holding up the right side of the front diff. Loosen the lower of the two bolts so that the nut is flush with the end of the bolt.
  16. Lift up on the diff pumpkin to relieve pressure on the upper left side bolt and remove the bolt. Allow the right side of the diff to lower. The CV axle will land on the a-arm and hold up the diff (it's light).
  17. Lift up on the right side of the diff and remove the loose nut and bolt holding the diff to the frame and lower the left side of the diff to rest the CV axle on the a-arm.
  18. With the diff fully dropped down, push it forward. The exact location is not that important right now.
  19. Drain the oil and lift up the oil dipstick about four inches (10 cm) so that it doesn't get bent when you remove the pan (the oil pan will hit it if you don't)
  20. Disconnect the battery (do not skip this step or you'll short it when you pull the starter)
  21. Remove two 14mm bolts holding the starter to the block and push the starter aside. No need to remove the wires.
  22. Remove two 10mm bolts and the metal shield that closes off the starter hole to the torque converter.
  23. Disconnect the trans cooler lines from the oil pan on the right side by removing two 10mm nuts and a stud.
  24. Disconnect the bracket (10 mm bolt) holding the forward end of the remote oil cooler lines
  25. Remove the two bolts holding the remote oil cooler housing to the block (2 x 13mm bolts) and push the housing to the left a little bit.
  26. Remove the three bellhousing bolts (14 mm) between the transmission and the oil pan.
  27. Remove the two large rubber grommets at the bottom of the oil pan. I did this by shooting some WD40 on them, then grasping them with vice grips and then twisting them until they turned, then pulling down on them. I could not accomplish this by hand!
  28. Use a long extension and a 13mm deep socket to remove the two nuts directly above the rubber grommets. If you drop them, you will be able to get them easily after removing the oil pan.
  29. Remove ten (10) 13mm bolts that hold the oil pan to the block.
  30. Remove the oil pan to the rear
    1. Lower the oil pan down onto the diff with the back lower than the front.
    2. Push the transmission cooler lines to the right to allow the pan to clear
    3. Manipulate the front diff, the cooler lines, and the oil pan to remove the pan. It's quite tight, but it does come out.
    4. Pull down the oil pan gasket that's probably stuck to the bottom of the block with RTV.
Re-installation is the reverse, except after getting the oil pan up, put one bolt in on each side of the pan snug but not tight. Next put the two nuts on at the back of pan. If you drop a nut and need to extract it from the bellhousing, you'll have less work to undo with only two bolts in the pan.
[QUOTE="ala_frosty, post: 12262144, member: 103672"
 

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Discussion Starter · #8 · (Edited)
The reason I would question it is because of the tight clearance, The zr2 has more room to work because of the suspension lift, it sounds like he was barely able to squeeze the oil pan out.
Totally valid question! The ZR2 uses different CV axles because of the ZR2 trucks are wider than the regular truck. However, I don't think that the engine is mounted any higher in the ZR2 models. I am pretty sure that this will work and you won't have to deal with the steering damper, so your centerlink should swing forward a little more. The CV axles pretty much land on the lower control arms which might be 1.5" higher on the non-ZR2, so your concern is going to be the clearance between the diff and the front of the oil pan. Without the steering damper, you may be able to get the axle more forward than I could and have enough room that way.

Worst case scenario, you could pull the left side tire off, disconnect the upper ball joint and pull the left CV axle out of the diff and this would allow the diff to drop any extra space that you needed. I would try it without removing the wheel first and if there really isn't enough room, then pull out that left CV axle from the diff - no need to remove it completely from the hub.

And if you do give it a try, please report back here, and I'll update the OP to confirm that it does work on the non-ZR2 models, or any additional items you encounter. Thanks.
 

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Discussion Starter · #9 ·
What did the crank look like when you got the caps off?
The bearing spun a long while ago the crank journal is smooth and worn almost exactly 0.010 on the "outside" of the journal (furthest from the crank rotational axis) and obviously no longer polished. It's so smooth that I wonder if someone had the crank out and resurfaced this journal for an undersized bearing. The bearings are normally 0.050 in thickness and the spun ones were 0.040, so 0.020 too thin. I'm currently examining options.
  • Ghetto: undersized bearings and send it.
  • Weak sauce: Pull the crank and get the journal machined for a properly undersized bearing.
  • Properly: Replace the crank and worn rod.
Also of note: I attempted to put stock sized rod bearings (Enginetech) into the #2 rod and it locked up the crank. I've measured the bearing thickness and they measure the same as the ones that came out. When I put the old ones back in, they worked. I have a hunch that there's something odd going on with the new bearings but I haven't figured out what that is just yet. I repeated this twice and same result each time. The old bearings have some odd patterns on the outside surfaces, like they were chattering, which prompted me to want to change them. I thought I could hear a bit of a knock on #2 rod, but I couldn't feel any movement in it at all and the only weirdness was those chatter marks.
 

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Discussion Starter · #10 ·
When putting it back together, I had to RTV the top of the oil pan gasket to get it to stay up against the block. I tried, but was unable to get the pan up with the gasket just falling into the groove in the oil pan.

It might be possible to pull the crank with the trans pulled back enough to remove the flexplate. At the point where the crank is coming out, it might be just easier to work on it with the engine completely out of the vehicle. From a work-hours perspective, it's probably a bit of a wash, but pulling the engine makes working on it a lot easier. Maybe not an option for someone without a crane, though.

I ended up putting 0.010 undersized bearings on the #1 rod and replaced the #2 rod bearings with STD size bearings. The latter weren't toast, but they were too thin.
 
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