Seems my front differential assembly is bad.

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Fudd
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Joined: Sun Feb 18, 2018 10:01 pm
My tercel:: 87 4wd wagon

Seems my front differential assembly is bad.

Post by Fudd » Sun Mar 11, 2018 7:32 pm

I changed out the calipers and rotors on my brakes today, using MR2 and 93 Tercel parts. It all went pretty smooth and fabricating the spacers was no problem. There’s still some air in the lines, but I’ll get that out when I replace the booster and master cylinder later.

My big problem now seems to be the front differential. I was hoping I’d be lucky and swap out the brakes and the grinding would go away, and some of it did. However it’s now plain that the bulk of it is either coming from the differential or the transmission. I’m suspicious of the differential, because 1 the gears are mismatched,(3.73 in front 4.10 in back), and 2 the grinding is equal in all gears and it seems to shift smoothly.

I’m wondering what kind of damage I’d be looking at if I were to pull the front diff assembly and then take it to a transmission shop, or should I look around for a used one?

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Petros
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My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Seems my front differential assembly is bad.

Post by Petros » Sun Mar 11, 2018 10:09 pm

verify it is from the front diff first. I would advise against driving it until you know the cause, if it is the diff or the trans, it still might be fixable. sending metal particles throughout the trans while it is being driven will also most certainly turn it all in to scrap metal soon enough.

Grinding noices can also come from a wheel bearing, that should have been easy to verify when you did the brake replacement by turning the front wheel bearing by hand and feeling if it is smooth turning or rough.

if not the wheel bearings you should pull the front diff cover (drain the gear oil first of course) and inspect the inside of the diff. if you see damage to the gear faces, or the bearings are coming apart, best bet would be to find another front diff assembly and swap it out. That would include the whole bell housing, front diff housing and everything in it. if you do not disturb the relationship between the ring and pinion gears there should be no need to adjust or make changes to the internal parts. that means you must find the matching ratio to your rear diff ratio, but that should not be that big of a problem.

I would advise against trying to rebuild the front diff, or changing the internal parts. If you can find the parts it would likely cost you a lot more than just replacing the whole assembly.

good luck.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

Fudd
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Joined: Sun Feb 18, 2018 10:01 pm
My tercel:: 87 4wd wagon

Re: Seems my front differential assembly is bad.

Post by Fudd » Mon Mar 12, 2018 12:35 am

Pretty sure it’s not the wheel bearings. While I was doing the brakes I ran it with a wheel up in the air after doing each side to try and figure out where the sound was coming from. Same grinding sound regardless of which wheel I had spinning.

I’ll check out the ring gear and differential next.

Fudd
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Posts: 13
Joined: Sun Feb 18, 2018 10:01 pm
My tercel:: 87 4wd wagon

Re: Seems my front differential assembly is bad.

Post by Fudd » Tue Mar 27, 2018 6:40 pm

So I got the car jacked up today and pulled the differential cover off and everything inside looked good. No metal chunks or shavings that I could see. I put it in neutral and rotated the front wheels so that I could observe all of the teeth on the ring gear and inspect the spider gears more closely. I then got out my inspection scope and stuck it way back in there so I could see the pinion gear. I rotated the wheels again while watching each tooth on the pinion gear and they all looked good. It all looked great.

So I guess that’s one thing I don’t have to worry about fixing...yet. Since the gears are mismatched, eventually I will have to do something.

Now I’m just wondering where the hell that grinding noise is coming from and how to isolate it.

Fudd
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Posts: 13
Joined: Sun Feb 18, 2018 10:01 pm
My tercel:: 87 4wd wagon

Re: Seems my front differential assembly is bad.

Post by Fudd » Tue Mar 27, 2018 8:49 pm

So now I’m starting to think it’s both front wheel bearings. The passenger bearing is definitely bad, as I can hear a high pitched squeel coming from it. The grinding however is just about impossible to pinpoint based on sound. When it’s up on jacks 80% of the noise goes away and trying to locate exactly where it’s emanating from over the motor noise is impossible.

So since I need at least one new bearing anyway, I figure I may as well start there and see if it fixes things. I did this once before on a RAV4 and it wasn’t much fun.

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xirdneh
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My tercel:: 87 tercel 4x4 wagon w/reringed engine, 83 tercel 4x4 wagon w/salvaged engine and 4.1 Diff's
Location: seabeck, washington, USA

Re: Seems my front differential assembly is bad.

Post by xirdneh » Tue Mar 27, 2018 11:46 pm

unless the bearing was extremely bad its hard to tell if the bearing is bad while the axle is still connected to it.
so when you checked them during the brake job with axles attached you would not be able to tell by rotating the hub
growling noise while driving is the usual sign of bearings going bad
noise usually changes or gets louder when turning
Love those Tercell 4x4 wagons but they sure suffer from road noise.

Fudd
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Joined: Sun Feb 18, 2018 10:01 pm
My tercel:: 87 4wd wagon

Re: Seems my front differential assembly is bad.

Post by Fudd » Wed Mar 28, 2018 12:07 am

I think I’m just going to go ahead and change them both out. Bearings are cheap and it needs at least one anyway and hopefully that will turn out to be the culprit and I can start driving this car around.

And thanks for the help so far. I’ve had a whole lot going on lately and it seems like this cars been on a back burner.

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