Broken sipder gear, take apart diff advice? (1 Viewer)

[TDonkey]

I have a '97 T100 4x4. For as long as I've had it, the rear end's been growling a little. I noticed the backlash seems pretty extreme. So, many years ago I "proactively" got a rear diff from a Tacoma and stuck it in the basement. And drove the truck 25000 more miles.

Last year the growling got worse, now I'm getting frightened. So today, I brought the spare diff into the garage to check it out. It looks great, everything looks like it is in spec except I have some damage to a tooth on one of the spider gears.

The damaged gear is one of the ones that sit on the shaft inside the diff case. It's not one of the side gears. My question is, will I have to press bearings off the side gears to R&R the shaft and other two gears?

 

[Jetboy]

Can you post a pic of the damage?

The answer is no - you shouldn't have to press any bearings off to get the spider gears out.

You could install a lockrite/ezlocker to replace.

If the damage is minor, I'd just run it. I've ground significant amounts of a few teeth off ring gears on my landcruiser with no adverse effects. (5.29 gears = thick ring gear = grinding required to get thrust pin in).

 

[TDonkey]

Jetboy, thanks for the optimism. I got a couple of photos of the broken gear.

I never studied gears before and this is my first time looking at an axle drive. But I suspect that the broken tooth on this straight cut gear might be a bigger "issue" than removed material from a helical gear. Also it looks like this damage was caused by some kind of unkind impact which may leave it in danger of breaking more. Not knowing either point I think I oughta not use the broken gear.

So the stealer will sell me 1 spider gear for about $60, if I take the pinion off it adds about $30 for the crush tube and seal.

The part number of the gear (and diff itself) is different "substituted" now so I will compare them for differences when I get the part.

Unfortunately I don't know the mileage of the donor truck. It would be nice to clean the parts and look at the bearings and make sure the ring gear bolts are threadlocked well.

I tried to check the gear pattern with white grease, it looked like it was hitting the center to me, but I found ZUK's page and found I need to check it with real gear paint. He also seems to like to shim up the sides a little if the parts are broken in.

I am led to believe that I can take the diff apart and reassemble it and it will more or less set up exactly the same. Could I be lazy and skip removing the pinion?

 

[Jetboy]

There's enough damage there I would probably replace it. You could grind it down and make it work, but I'd just throw in a new one.

Two things.

First, $60 for a spider gear is rape. You shouldn't pay $60 for a full complete ready to run 8" third member. $50 is more or less the going rate. I've thrown away lots of spider gears. You should be able to use one off your old diff. No reason to buy a used one when you have 4 used ones from your old diff. If not, call a local offroad shop that installs lockers in toyotas and ask for one. They might give it to you for free or a case of beer.

Second, you don't need a crush sleeve. You don't need to mess with any of the ring and pinion setup. The "pinion" you need to remove is NOT the pinion with a gear cut on the end that drives the ring gear. I think it's confusing as some of the repair manuals call spider gear shaft a pinion also. Two different parts. There is a 1" ish size pin that goes through the center of the 3rd member center section. It's what the spider gears rotate on. That pin can be removed without affecting the ring and pinon at all. Look at the end of the pin and on one side of rotating internal carrier there will be a machine screw or bolt to remove that will allow that pin to slide out. You just remove the pin, work the spider gear out. Put the new one in, put the pin back in, and use it.

 

[TDonkey]

I wish I had the usual "8 inch" third because it's a lot less expensive than the T100/Taco/Tundra diff I am working with. I can't find many of these in junkyards, and parts cost a lot more, for instance most of the bearings can only come from the dealer; Timken's DRK355 overhaul kit seems to cost over $500 because they are buying all but one of the bearings from the parts counter.

Also the parts database doesn't show that these specific gears are used on another diff.

I'll call around to the beach buggy shops to see if any of those guys have some pieces laying about that I can pick a spider gear from. I wish my situtation would allow me to keep the truck up on stands with axles removed overnight, but I have to R&R the third in one afternoon.

If I take the nut off to replace the oil seal, I should probably reset the drive pinion preload, which is why I had the crush tube on my list. If I don't use it I can give it back.

It looks like the minimum I have to do to get the spider gear shaft out, is remove the bearing cap, pull the diff case out and drop the ring gear. Looks like I can get the shaft retaining pin out without undoing the bearing cap even, but the ring gear would be in the way of the spider gear shaft.

 

[Tigerstripe40]

Why not pull the corresponding gear from the diff currently in your T100 ?

Which bearings are you looking for?

Cruiser outfitters has a master kit that has carrier and pinion bearings for $177.75
the 8" V6 diff bearing set is $153. $24 doesn't seem to be that much more...
http://cruiseroutfitters.com/lockers.html

 

[jynx]

I can't remember exactly how the Tacoma diffs are set up, but if that is the only damage then this is my suggestion.

Rotate the carrier until the end of the cross-shaft is visible, there should be a bolt visible that looks like it bolts into the cross-shaft, if not visible, rotate the carrier around 180* to find said bolt. Back that bolt out and with a drift of some sort you should be able to pop the pin out. The offending gears should be able to be removed and inspected without disturbing the carrier. I agree that you should be able to find a used gear relatively inexpensively. I would call up a local 4wd drive shop to ask if they have any laying around. Most 4wd shops or the like just chunk them when they do lunch-box locker installs, so call around. I think I gave $10 or $20 for a pair.

It should go back together in the reverse order. Before you go messing with the carrier bearings, I would make sure you have a dial indicator and a base to keep up with the backlash settings. I got mine from Harbor freight for a decent price.

As far as the pinion bearing preload, if you are going to pull the seal, you can go two ways. The quick and easy way is to mark the nut, back it off, replace the seal, reinstall the nut and tighten it slightly past the original staked location. The more better way would be to get a new nut and a solid sleeve, remove the nut, flange, outer bearing and crush sleeve. measure the crush sleeve and see where to start your pinion preload shim stack at. Install the sleeve, shims and outer bearing, tighten it down and check preload (it is in IN-LBS, so you will need a different torque wrench for that), adjust the shims until you hit the preload number, then remove the flange, install the new seal and put the flange on with the new nut and put about 100 ft-lbs on it with some loc-tite and stake the new nut.

All this sounds terrible, but it really isn't as bad as it sounds, just make sure you have the right tools and take your time. Unless you have a press and really want to get into it deep, you are not going to be able to adjust the pinion depth since that requires messing with the shim stack on the head of the pinion. But the pattern is probably good, you may just need to tighten the carrier bearings to put a little preload on them.

ZUK's page is an excellent resource and is where I learned what I have and where I gathered confidence to start fiddling with them myself. I did pretty much what I just mentioned above to a diff that I replaced in my 90 pickup and have put nearly 100k miles on that used diff. I just got my own press and a bearing splitter, so I don't plan to pay anyone to do diff work anymore. I have fixed to many that were "professionally" done.

Also, unless there is visual damage to a bearing or you feel a "flat spot" when you roll them around then I wouldn't worry with replacing them. Just a new seal and a solid spacer along with the new spider gears and you will probably be good.

Good luck.

 

[TDonkey]

The bearings do feel ok, maybe I shouldn't take the drive pinion out.

It hadn't dawned on me that these open diff cases get tossed aside for locker installs. I'll see if any shops have one laying around.

Grr, some of the ring bolts had backed out so I have to get new ones. All the threaded bores are ok. I did not measure any runout on the ring gear so I'm still going to try it. I think the same thing may have happened on the 3rd currently in the truck. It's like there is no thread lock at all on these bolts.

This is the diff that zuk and some catalogs call the "8.4" it's a little different than the other 8" diffs, this one has 12 bolts on the ring gear and uses shims, not threaded adjusters on the sides. The spider gear spindle is held in with a roll pin. It's possible to remove the retaining pin without removing the bearing cap, but the ring gear teeth will interfere with removal of the spindle pin.

When I change out this 3rd, I have to have the wheels back on the truck and brakes bled before sundown. I think I have to be more sure of my diff building skills before I try putting one together, setting it up and installing it during this timeframe. I have a tranny jack & am sure I can get the old one out and apart in under 2 hours. Maybe I can play with the donor diff enough to build confidence.

I do need to get an in/lb wrench. Thanks for this reminder, and all the other great advice. Yall make me think there's "really nothing to it."

 

[TDonkey]

Because I am a noob I am going to use real gear marking compound. I tried with some grease I had and don't think I got useful results.

I visited a few Ford and GM parts counters before one of them had it, but many didn't know that this is available to them. It's ACDelco # 1052351. I found it at the biggest Chevy dealer in my area, which has a commercial truck and fleet dept.

Once I figure out how to get a good print, I can take it apart. I think the little torque wrench might be for sale at a bicycle shop.

 

[Jetboy]

I wish I could find a good youtube video. This is as close as I think I can find http://www.youtube.com/watch?feature=player_detailpage&v=WTKnGRNzigA#t=245

I think you're going to a lot more work than you need to. You don't have to pull any bearings to replace the spider gears. You shouldn't need any ring and pinion adjustment. Just pull the pin as shown in the above video, pull the bad spider, put the new one in, and you're done.

Maybe I'm a bad mechanic, but I'd pull all the ring gear bolts one at a time. Locktite them back in and the proper torque and leave the rest as is. In the proper torque patter of course. I think that could reliably be done with a very low probability of any movement of the ring gear and result in a good reliable diff.

 

[jynx]

I am with jetboy on this. I`m all about doing it right, but in this case, based on what you have told us, it soiunds like other than the bad spider gear you have a very good dif to start with. I would remove the cross shaft, replace the bad spider gear, clean and reinstall the ring gear bolts, check the pinion preload and then swap that puppy out one afternoon. Then have a frosty beverage while looking for a complete 8" rearend to swap in.