the_tool_man
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- June 6, 2002
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- City, State
- Spartanburg, SC
- Year, Model & Trim Level
- '01 Sport 4x4
'01 Sport rear differential rebuild worklog & questions (long)
Hi all:
Background:
Several months ago, I bought a used '01 Sport with 37k miles on it (just out of warranty). It ran and drove fine at the time, and checked out with my mechanic. It also had a clean Carfax history, which I thought was good at the time, but that I have since learned is meaningless. Over the course of several months, I've noticed an increase in noise from the rear, which could best be described as a low frequency whump-whump type sound. I tried rotating tires and other easy things, but to no effect. Then, last week, I noticed a new noise, a definite gear noise coming from the rear at low speeds becoming more pronounced as the vehicle came to a stop. It was worse on left turns than right, and louder under power or severe braking than at coast. I took it to my mechanic, and here's what we found:
Day 1:
6/19/04 10:00am
Raised the rear of the vehicle and did a visual inspection. Found that the driveshaft had been removed and re-installed with the U-joints misphased. Also found a standard hose clamp had been used instead of the balanced wire clamp on the driveshaft spline boot. Suspecting this might be contributing to the noise, I dissassembled the driveshaft, relubed the spline, and reassembled in phase. Left the hose clamp off, as there was sufficient friction between the boot and shaft to keep it from moving (the original wire clamp was still in place on the other end of the boot). Test drove - no difference in pattern of noise.
6/19/04 12:30pm
Raised the rear of the vehicle and removed the differential cover. The lubricant contained numerous metal filings, and in fact, looked like metallic paint. There was a small pile of metal filings in the bottom of the case, and the magnetic fill plug was covered in filings. The ring gear, carrier, and carrier bearing caps appeared undamaged, though there was more backlash in the spider gears than expected for a 40k mile vehicle. Removed rear wheels and rear brake calipers. Removed carrier cross pin retaining bolt and cross pin. Upon inspection, the cross pin had severe wear areas corresponding to the contact points for the spider gears. The spider gears came out, and appeared undamaged. Pulled C-clips and axles. Inspected rear wheel bearing lands on axles, no apparent damage. Removed carrier bearing caps and pulled carrier. Found no visible damage on pinion teeth. Passenger side carrier bearing was fine, but driver side was severely pitted. Outer race had very large areas of metal missing over about 20% area, and bearing rollers were scarred and showed signs of overheating. Side gears showed no damage. Carrier bearing shims were badly grooved.
6/19/04 2:00pm
Removed carrier bearings from carrier - required heating, and eventually an air chisel to remove them. Removed pinion shaft and bearings from the housing. Pinion bearings showed very minor pitting but no discoloration or other damage. Spent the rest of the day (5:00pm until 7:30pm) washing rear axle and differential housing to remove metal filings. It was especially difficult to clean out the grooves where the axle tubes press into the differential housing.
Conclusions:
There are two points of damage. The driver side carrier bearing is definately toast, and the carrier pin (that the spider gears spin on) has some unusual wear on it. Here's my prevailing theory. The carrier pin was not sufficiently hardened from the manufacturer. Since the hardened spider gears run directly on it with no bearings, the rotation of the spider gears wore the pin. When new, the pin has 4 flats machined into it (2 on each end) to allow oil to move between the spider gears and the pin. On both ends, the area of the pin adjacent to one flat was worn away, creating a ramp from the flat to the OD of the pin. We measured the spider gears and found no measurable wear or damage of any kind. I suspect that the metal particles that wore from the carrier pin caused the destruction of the carrier bearing. In fact, all of the bearings were pitted, so they all eventually would have gone. The gear teeth are completely undamaged, so the metal particles weren't sufficiently hard or large to damage them. Either the carrier pin was not properly hardened, or it was starved of lubricant. I've seen pins with over 100k miles on them with no visible wear at all, so the wear we saw is definately not normal. There seemed to be enough oil in the differential when we removed the cover, so I suspect the pin was bad.
The mis-assembled drive shaft has me thinking that a previous owner took it to a mechanic (an incompatent one) at some point. Right now it is unclear if that might have been related. There was no evidence that the differential cover had ever been removed, as it still had the factory tag and sealant in place.
This would seem to be a good time to consider installing a trak-lok, but I'm leaving town in a few days on vacation, and don't have time to wait for the parts. Thankfully, my mechanic had a good quality rebuild kit in his shop so I've got everything I need. Also, I'm not sure having a LS rear end in a short wheelbase Explorer would really be such a good idea, as it might be easer to break the rear end loose in snow and spin around. My '93 had a LS rear, and I know they were available on some explorers with the towing package, but I don't know if they were ever a factory option on Sports. Does anybody know? Anyway, the plan is to reassemble what I have with new bearings and synthetic oil. If I decide to switch to a trak-lok, it won't be that hard to do. Anybody care to weigh in on my decision? What about my diagnosis? What else should I be checking into?
Day 2:
6/21/04 1:30pm
Drilled and tapped bottom of differential housing for magnetic drain plug. Used dry compressed air to blow any remaining metal chips out of the axle, working from the axle ends inward. Installed new pinion bearing outer races. Assembled pinion shaft, bearings, crush sleeve, flange and nut (not the easiest nut to tighten). Set bearing preload on pinion shaft. Called it a day.
Day 3:
6/22/04 7:00pm
Cleaned carrier, ring gear, side gears and shims. Pressed on new carrier bearings. Lapped carrier bearing shims to remove scoring. Reassembled carrier with a used, but perfectly good, cross pin. During assembly, we tried to duplicate the original thickness of the carrier bearing shims by adding to them with shims from the rebuild kit, but they wouldn't fit. Apparently, the new Timkin carrier bearings are about 0.005" thicker than the Koyo bearings that were in it. Checked gear pattern. They printed a little farther out on the end of the teeth than you would want with a new set, but it was in exactly the same place as the existing wear pattern. We decided to leave well enough alone, as changing the pattern now would probably make them noisy. Backlash was within tolerance, so no further adjustment was needed. Cleaned axles. Checked axles and wheel bearings again for contaminants or damage and found none. Reinstalled axles and C-clips. Reinstalled rear cover. It was 10:30pm, so we stopped.
Day 4:
6/23/04 5:00pm
Filled differential with Red Line synthetic gear lube. Installed new magnetic fill plug (we used the original as a drain plug). Reinstalled brakes & wheels. Went for a short test drive. Ran quiet under acceleration, coast and engine braking. Tried a number of sharp turns at low speed in the parking lot of our favorite Mexican restaurant and listened, but no noises from the gears or bearings could be heard. Ate dinner at Mexican restaurant. Drove back to shop and topped off gear lube in differential (it takes a while for the lube to drain into the axle tubes, so you have to go back and top it off). Changed fluid in transfer case to Red Line synthetic. Reinstalled spare and cleaned up. Went home at 9:00.
Conclusions:
I had never rebuilt a differential before, so this was a great experience for me. My mechanic was recovering from a back injury, so he basically watched me do it and told me what steps to take. This was not intended to be instructions for rebuilding, as I left out a lot of information, but you can get an idea of the steps involved. Also, since we were re-using the ring and pinon, we didn't have to set pinion depth, which saved a lot of work.
I drove the explorer to work this morning (6/24), about 30 miles of combined city and highway miles. Ran more quietly than when I bought it. I didn't realize how much noise the differential had been making. I had assumed it was tire noise from the crappy Goodyear tires on it. Now I realize the previous owner had to have known something was wrong, because it was making some of the differential noise when I bought it from him.
I saved the old cross pin, because I'm going to have it harness tested to see if it was defective. I plan to post pictures of the damaged parts, but I didn't take very many during the rebuild process because it just takes too long to clean my hands and get the camera out in the middle of things. I'll post a link to them when they're up.
Regards,
John.
Hi all:
Background:
Several months ago, I bought a used '01 Sport with 37k miles on it (just out of warranty). It ran and drove fine at the time, and checked out with my mechanic. It also had a clean Carfax history, which I thought was good at the time, but that I have since learned is meaningless. Over the course of several months, I've noticed an increase in noise from the rear, which could best be described as a low frequency whump-whump type sound. I tried rotating tires and other easy things, but to no effect. Then, last week, I noticed a new noise, a definite gear noise coming from the rear at low speeds becoming more pronounced as the vehicle came to a stop. It was worse on left turns than right, and louder under power or severe braking than at coast. I took it to my mechanic, and here's what we found:
Day 1:
6/19/04 10:00am
Raised the rear of the vehicle and did a visual inspection. Found that the driveshaft had been removed and re-installed with the U-joints misphased. Also found a standard hose clamp had been used instead of the balanced wire clamp on the driveshaft spline boot. Suspecting this might be contributing to the noise, I dissassembled the driveshaft, relubed the spline, and reassembled in phase. Left the hose clamp off, as there was sufficient friction between the boot and shaft to keep it from moving (the original wire clamp was still in place on the other end of the boot). Test drove - no difference in pattern of noise.
6/19/04 12:30pm
Raised the rear of the vehicle and removed the differential cover. The lubricant contained numerous metal filings, and in fact, looked like metallic paint. There was a small pile of metal filings in the bottom of the case, and the magnetic fill plug was covered in filings. The ring gear, carrier, and carrier bearing caps appeared undamaged, though there was more backlash in the spider gears than expected for a 40k mile vehicle. Removed rear wheels and rear brake calipers. Removed carrier cross pin retaining bolt and cross pin. Upon inspection, the cross pin had severe wear areas corresponding to the contact points for the spider gears. The spider gears came out, and appeared undamaged. Pulled C-clips and axles. Inspected rear wheel bearing lands on axles, no apparent damage. Removed carrier bearing caps and pulled carrier. Found no visible damage on pinion teeth. Passenger side carrier bearing was fine, but driver side was severely pitted. Outer race had very large areas of metal missing over about 20% area, and bearing rollers were scarred and showed signs of overheating. Side gears showed no damage. Carrier bearing shims were badly grooved.
6/19/04 2:00pm
Removed carrier bearings from carrier - required heating, and eventually an air chisel to remove them. Removed pinion shaft and bearings from the housing. Pinion bearings showed very minor pitting but no discoloration or other damage. Spent the rest of the day (5:00pm until 7:30pm) washing rear axle and differential housing to remove metal filings. It was especially difficult to clean out the grooves where the axle tubes press into the differential housing.
Conclusions:
There are two points of damage. The driver side carrier bearing is definately toast, and the carrier pin (that the spider gears spin on) has some unusual wear on it. Here's my prevailing theory. The carrier pin was not sufficiently hardened from the manufacturer. Since the hardened spider gears run directly on it with no bearings, the rotation of the spider gears wore the pin. When new, the pin has 4 flats machined into it (2 on each end) to allow oil to move between the spider gears and the pin. On both ends, the area of the pin adjacent to one flat was worn away, creating a ramp from the flat to the OD of the pin. We measured the spider gears and found no measurable wear or damage of any kind. I suspect that the metal particles that wore from the carrier pin caused the destruction of the carrier bearing. In fact, all of the bearings were pitted, so they all eventually would have gone. The gear teeth are completely undamaged, so the metal particles weren't sufficiently hard or large to damage them. Either the carrier pin was not properly hardened, or it was starved of lubricant. I've seen pins with over 100k miles on them with no visible wear at all, so the wear we saw is definately not normal. There seemed to be enough oil in the differential when we removed the cover, so I suspect the pin was bad.
The mis-assembled drive shaft has me thinking that a previous owner took it to a mechanic (an incompatent one) at some point. Right now it is unclear if that might have been related. There was no evidence that the differential cover had ever been removed, as it still had the factory tag and sealant in place.
This would seem to be a good time to consider installing a trak-lok, but I'm leaving town in a few days on vacation, and don't have time to wait for the parts. Thankfully, my mechanic had a good quality rebuild kit in his shop so I've got everything I need. Also, I'm not sure having a LS rear end in a short wheelbase Explorer would really be such a good idea, as it might be easer to break the rear end loose in snow and spin around. My '93 had a LS rear, and I know they were available on some explorers with the towing package, but I don't know if they were ever a factory option on Sports. Does anybody know? Anyway, the plan is to reassemble what I have with new bearings and synthetic oil. If I decide to switch to a trak-lok, it won't be that hard to do. Anybody care to weigh in on my decision? What about my diagnosis? What else should I be checking into?
Day 2:
6/21/04 1:30pm
Drilled and tapped bottom of differential housing for magnetic drain plug. Used dry compressed air to blow any remaining metal chips out of the axle, working from the axle ends inward. Installed new pinion bearing outer races. Assembled pinion shaft, bearings, crush sleeve, flange and nut (not the easiest nut to tighten). Set bearing preload on pinion shaft. Called it a day.
Day 3:
6/22/04 7:00pm
Cleaned carrier, ring gear, side gears and shims. Pressed on new carrier bearings. Lapped carrier bearing shims to remove scoring. Reassembled carrier with a used, but perfectly good, cross pin. During assembly, we tried to duplicate the original thickness of the carrier bearing shims by adding to them with shims from the rebuild kit, but they wouldn't fit. Apparently, the new Timkin carrier bearings are about 0.005" thicker than the Koyo bearings that were in it. Checked gear pattern. They printed a little farther out on the end of the teeth than you would want with a new set, but it was in exactly the same place as the existing wear pattern. We decided to leave well enough alone, as changing the pattern now would probably make them noisy. Backlash was within tolerance, so no further adjustment was needed. Cleaned axles. Checked axles and wheel bearings again for contaminants or damage and found none. Reinstalled axles and C-clips. Reinstalled rear cover. It was 10:30pm, so we stopped.
Day 4:
6/23/04 5:00pm
Filled differential with Red Line synthetic gear lube. Installed new magnetic fill plug (we used the original as a drain plug). Reinstalled brakes & wheels. Went for a short test drive. Ran quiet under acceleration, coast and engine braking. Tried a number of sharp turns at low speed in the parking lot of our favorite Mexican restaurant and listened, but no noises from the gears or bearings could be heard. Ate dinner at Mexican restaurant. Drove back to shop and topped off gear lube in differential (it takes a while for the lube to drain into the axle tubes, so you have to go back and top it off). Changed fluid in transfer case to Red Line synthetic. Reinstalled spare and cleaned up. Went home at 9:00.
Conclusions:
I had never rebuilt a differential before, so this was a great experience for me. My mechanic was recovering from a back injury, so he basically watched me do it and told me what steps to take. This was not intended to be instructions for rebuilding, as I left out a lot of information, but you can get an idea of the steps involved. Also, since we were re-using the ring and pinon, we didn't have to set pinion depth, which saved a lot of work.
I drove the explorer to work this morning (6/24), about 30 miles of combined city and highway miles. Ran more quietly than when I bought it. I didn't realize how much noise the differential had been making. I had assumed it was tire noise from the crappy Goodyear tires on it. Now I realize the previous owner had to have known something was wrong, because it was making some of the differential noise when I bought it from him.
I saved the old cross pin, because I'm going to have it harness tested to see if it was defective. I plan to post pictures of the damaged parts, but I didn't take very many during the rebuild process because it just takes too long to clean my hands and get the camera out in the middle of things. I'll post a link to them when they're up.
Regards,
John.
