Rear Differential Work and 3rd Member Rebuild
- Thread starter 78fj40mg
- Start date
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reddingcruiser
Practicing for retirement
Actually they look like they are in pretty good shape. It's down to checking stuff - clearances, the thrust washers, the condition of the differential shaft (goes through the spacer) and the backlash. Something is worn and out of spec. Adjusting the backlash is a bench top job. If the backlash is in spec you can do everything else with the third member in the housing.
reddingcruiser
Practicing for retirement
Thinking about it, it may be wear on the differential shaft causing the problem.
78fj40mg
TLCA #23510
- Thread starter
- #25
Thanks Dick I appreciate your feedback. Unfortunately, I honestly do not know where to start checking clearances and backlash as I have zero experience with diffs and their associated issues and solutions. Where in the diff do I check clearances?
I'm being summoned to help the wife, be back soon.
I'm being summoned to help the wife, be back soon.
reddingcruiser
Practicing for retirement
Try to pick up a Factory Service Manual (FSM) that covers your year FJ40, or a Haynes manual. It will make it a lot easier to work through these issues.
reddingcruiser
Practicing for retirement
PM Sent
FSMs can be downloaded from here:
https://forum.ih8mud.com/threads/40-50-60-and-80-series-fsm-for-a-hell-of-a-price.610994/
https://forum.ih8mud.com/threads/40-50-60-and-80-series-fsm-for-a-hell-of-a-price.610994/
reddingcruiser
Practicing for retirement
FSM will give you the clearances you need to check. I still think if you pull the differential shaft you'll likely find excess wear that is allowing the gears to slap around. You can do this without pulling the third member.
splitshot
Head cook, Bottle washer, and Peace keeper.
9 times out of 10, these can be refreshed with new thrust washers on both the axle gears and spider gears. If your pinion shaft shows any wear, replace it. Not uncommon for an outer axle bearing to go south (these usually destroy the seal and leak oil all over your backing plate).
Might even consider installing a locker while it is all apart.
Might even consider installing a locker while it is all apart.
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78fj40mg
TLCA #23510
- Thread starter
- #31
I'd like to officially thank Dick @reddingcruiser for helping me today over the phone, I could not have completed this task without his vast knowledge of diffs and his willingness to assist me. 
Removed the pinion shaft and spacer
The pinion shaft spacer appears to be worn since there was a big enough gap between it and the thrust washer for a flat head screw driver to be inserted.
then removed top gear and thrust washer
removed bottom gear and thrust washer. The thrust washer look pretty worn out and need replacing.The spider gears all appear to be in good condition.
removed top gear and thrust washer
removed 'C' clip and left side gear
removed 'C' clip and right side gear
The ring gear has a lot of rotational play, where as the pinion gear is solid with no lateral, vertical or longitudinal play, so I think we're good there. From the looks of things the PO had the diff serviced at some point in time, however, the tolerances were not set properly in accordance with the FSM specifications.
propped up the third member
I removed all bolts and washers, unfortunately I was not able to free the 3rd member from the axle, used some force with a mallet, screw driver, pry bar to no avail.
Do you guys have suggestions on how to separate these two units?
Removed the pinion shaft and spacer
The pinion shaft spacer appears to be worn since there was a big enough gap between it and the thrust washer for a flat head screw driver to be inserted.
then removed top gear and thrust washer
removed bottom gear and thrust washer. The thrust washer look pretty worn out and need replacing.The spider gears all appear to be in good condition.
removed top gear and thrust washer
removed 'C' clip and left side gear
removed 'C' clip and right side gear
The ring gear has a lot of rotational play, where as the pinion gear is solid with no lateral, vertical or longitudinal play, so I think we're good there. From the looks of things the PO had the diff serviced at some point in time, however, the tolerances were not set properly in accordance with the FSM specifications.
propped up the third member
I removed all bolts and washers, unfortunately I was not able to free the 3rd member from the axle, used some force with a mallet, screw driver, pry bar to no avail.
Do you guys have suggestions on how to separate these two units?
spotcruiser
Geezer
Put the truck down on the ground, put one upper nut on loosely (a couple of threads), put a bottle jack under the forward end of the 3rd, jack it up enough to put some decent pressure on the front end of the 3rd, and check it in the morning. Gravity performs some sort of magic overnight.
spotcruiser
Geezer
By the way, you still seem to have one nut installed in that last photo. Just in case you missed that one. 
Stumpalama
Forum Junkie
Yes, upward force with the jack on the flange yoke area. It doesn't need much, just enough to put some upward force on the end. You can also give the 3rd a couple whacks with a 5lb hammer to help jar it loose. I just pulled one yesterday from a CRUSTY FJ62 housing it was less than a minute with pressure to get it to crack loose at the bottom. If it needs more, I use an old 1" wide wood chisel to get in between the 3rd and the axle housing at the bottom with the jack pushing up and that frees it too.
78fj40mg
TLCA #23510
- Thread starter
- #39
I removed the third member today without a glitch with recommendations from @spotcruiser and @Stumpalama .
Moved the third member to bench and attached to the vice and got it ready for some adjustments to tighten the ring and pinion gears in order to minimize the excessive gear noise.
I marked the carrier bearing adjuster rings prior to making any adjustments...
...next I loosened the carrier bearing bolts to free-up the adjusting ring for easier movement while adjusting the Carrier Bearing Pre-Load. Also removed the lock-tab bolt on both sides. I adjusted both side two notches each time until I reached 6 notches on each side and it made hardly any difference. When I rotate the pinion and it makes contact with the ring gear there's a loud clunk. I'm wondering whether or not the pinion is properly adjusted.
I
Here's a vid in which you can hear the clunk while rotating the pinion gear, this was after adjusting the Carrier Bearing Pre-Load.
Moved the third member to bench and attached to the vice and got it ready for some adjustments to tighten the ring and pinion gears in order to minimize the excessive gear noise.
I marked the carrier bearing adjuster rings prior to making any adjustments...
...next I loosened the carrier bearing bolts to free-up the adjusting ring for easier movement while adjusting the Carrier Bearing Pre-Load. Also removed the lock-tab bolt on both sides. I adjusted both side two notches each time until I reached 6 notches on each side and it made hardly any difference. When I rotate the pinion and it makes contact with the ring gear there's a loud clunk. I'm wondering whether or not the pinion is properly adjusted.
Here's a vid in which you can hear the clunk while rotating the pinion gear, this was after adjusting the Carrier Bearing Pre-Load.
spotcruiser
Geezer
Follow the manual. It explains exactly how to set the diff. A lot of pinion backlash only means that you need to move the ring gear closer to the pinion or the pinion needs to move towards the ring gear. Checking gear mesh is what will tell you what you need to change.
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