ISO: Front and/or Rear Differential

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Sabrarain97
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My tercel:: 1985 Tercel dlx 4WD Wagon Automatic
Location: 97540

ISO: Front and/or Rear Differential

Post by Sabrarain97 »

Hello all! My name is Sabra, I recently bought a 1985 Toyota Tercel 4wd automatic wagon. I Bought her knowing there was a couple repairs needed and was surprised by a few more repairs than expected.

ISO/BUYING:
Terry (the Tercel) needs a rear differential (gear ratio 3.909) before I can get her back on the road. I am also looking for a front differential as well, though it is less immediate of a need. So if anyone has these parts for sale or knows someone else that might please DM me!

Thank you all for your help, it is appreciated!
I hope for Terry to be on the road of recovery soon!
Last edited by Sabrarain97 on Mon Nov 08, 2021 12:04 pm, edited 1 time in total.
~Sabra w/ a 1985 Toyota Tercel 4WD/FWD Automatic DLX (Terry)
ISO: Working Stock Carb for 3AC Engine
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NWMO
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Re: ISO: Front and/or Rear Differential

Post by NWMO »

Sabra,

The automatic trans cars are not nearly as common and include different gear ratios than the M/T cars. I think the earliest A/T cars may have had a 3.73 gear ratio, but by 85' you should be running 3.909 I believe. If you have a little space, it would be easiest and most economical to purchase an A/T parts car to get your diffs.
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain
Sabrarain97
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Posts: 19
Joined: Sat Nov 06, 2021 8:11 pm
My tercel:: 1985 Tercel dlx 4WD Wagon Automatic
Location: 97540

Re: ISO: Front and/or Rear Differential

Post by Sabrarain97 »

Thanks for the advice, NWMO. We have definitely been looking for a parts car, but seems pretty rare for an A/T. While I have you, this is slightly off topic, but do you know if the front and rear differential gear ratios are the same, or are they different?

Thanks a lot!
~Sabra w/ a 1985 Toyota Tercel 4WD/FWD Automatic DLX (Terry)
ISO: Working Stock Carb for 3AC Engine
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NWMO
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Re: ISO: Front and/or Rear Differential

Post by NWMO »

While I'm no expert on the automatic cars, I'm certain the gear ratio will be the same front and rear (unless a previous owner swapped a different ratio in, not uncommon on the M/T cars).

Chris
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain
Sabrarain97
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Posts: 19
Joined: Sat Nov 06, 2021 8:11 pm
My tercel:: 1985 Tercel dlx 4WD Wagon Automatic
Location: 97540

Re: ISO: Front and/or Rear Differential

Post by Sabrarain97 »

Okay thank you for sharing your knowledge!
~Sabra w/ a 1985 Toyota Tercel 4WD/FWD Automatic DLX (Terry)
ISO: Working Stock Carb for 3AC Engine
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NWMO
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Re: ISO: Front and/or Rear Differential

Post by NWMO »

If you visit the similar, but not related, Facebook page, you might message jhanek szypulski or timothy thomas. Both are in Washington with multiple cars, a lot of connections and are pretty cool dudes.

Chris
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain
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rer233
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Re: ISO: Front and/or Rear Differential

Post by rer233 »

Unfortunately you're about 8 1/2 years late- when I converted my '87 4WD A/T to manual, I posted the rear "punkin" and transaxle here, but no one was interested (for good reason IMO) so I scrapped 'em with the donor vehicle shell. Was a shame too- they only had about 150,000 miles on them and worked fine. Sorry...
if it aint there, there's a good chance it won't break!
83 SR5 Silver/Blue (Snowmobile/work beater)-totaled but drivable
85 SR5 Blue
88 SR5 White (the 'good' one)-not anymore-totaled
87 fwd silver wagon a/t
87 4wd dx Cream (a/t- not anymore- now m/t)
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Petros
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Re: ISO: Front and/or Rear Differential

Post by Petros »

if the earlier AT cars used the 3.73:1 ratio (yes, the front and rear diffs are always the same ratio), it might be possible to replace both the front and rear diffs with matching ratios out of a manual trans into your car so you can get it back on the road. if you can not find the correct ratio.

it may even be a reasonable thing to install the 4.1:1 front and rear ratios, but that means your top speed with the auto trans would be a high rpm at fwy speeds, going the other way, to the 3.73:1 ratio, would be better.

I have never had a AT transaxle apart, but I think it should be possible if you get a complete front diff/bellhousing assembly you will be able to swap the parts over from your existing front diff/bellhousing so the new front ring and pinion can be swapped into your car. replacing the rear diff is straight forward and should not be a problem (I have change out rear diff assemblies). changing out both front a rear diff assembiles would be a big job, you would have to pull the whole front trans/axle assembly, but it might be a viable option if you can not locate a 3.909:1 rear diff.

how did you destroy a rear diff? they are normally fairly robust. the only time I have seen them damaged was if a seal was allowed to leak all the lube out and it burned up, or I have also seen someone install mismatching front and rear diffs, and than they proceeded to destroy either the rear diff, the trans, the front diff, or all three, because of the stress on the drivetrain when mis-matched front and rear diff ratios are installed.
.

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)
Sabrarain97
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Posts: 19
Joined: Sat Nov 06, 2021 8:11 pm
My tercel:: 1985 Tercel dlx 4WD Wagon Automatic
Location: 97540

Re: ISO: Front and/or Rear Differential

Post by Sabrarain97 »

Thank you Petros and rer233 for the info.

Petros: I would never kill a diff/both diffs like this, I am such an easy going driver. HOWEVER, I bought it like this. It was a stupid younger guy (second owner of the car) that I bought it from that probably drove it for a long time with something in there messed up and ultimately killed it. He was still using it as a daily driver with all this stuff messed up (and more that I have not mentioned), he just seemed pretty careless and ignorant about the whole thing. Had I known it was the diff messed up at the time of purchase, I would not be in this situation *facepalm*. But we changed the diff fluid in the rear and sure enough, lovely little metal sparklies everywhere. Then took it in and learned both diffs are problematic along with a few other things.
~Sabra w/ a 1985 Toyota Tercel 4WD/FWD Automatic DLX (Terry)
ISO: Working Stock Carb for 3AC Engine
Sabrarain97
Newbie
Posts: 19
Joined: Sat Nov 06, 2021 8:11 pm
My tercel:: 1985 Tercel dlx 4WD Wagon Automatic
Location: 97540

Re: ISO: Front and/or Rear Differential

Post by Sabrarain97 »

So anyway, I am trying to focus on just getting the rear diff fixed rn (looking to ship that part and have a shop do the work for me), as i do not have a ton of money and do not have the mechanical know-how or space to do the whole job with myself and my buddies. Basically, I need it to run so I can drive it half way down Oregon (safely) and get it home. Then I will have a garage space to do more work ourselves.
~Sabra w/ a 1985 Toyota Tercel 4WD/FWD Automatic DLX (Terry)
ISO: Working Stock Carb for 3AC Engine
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NWMO
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Re: ISO: Front and/or Rear Differential

Post by NWMO »

A truck & trailer may be cheaper and easier in the long run.
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain
Sabrarain97
Newbie
Posts: 19
Joined: Sat Nov 06, 2021 8:11 pm
My tercel:: 1985 Tercel dlx 4WD Wagon Automatic
Location: 97540

Re: ISO: Front and/or Rear Differential

Post by Sabrarain97 »

NWMO, yea it probably would be, but I do have a space to store it for free and a really good experienced mechanic here in Eugene. So, (IMO) If I am going to have to buy the parts anyway, might as well just do this half of the work here and then be able to drive it down later to finish the other work i our own space out of the weather. Ultimately it is the weather that is keeping us from doing it ourselves (we have the tools/equipment), as Eugene is the wettest place in OR. We have friends/fam up here so it is no trouble really to have to drive back up to grab it after the rear diff is fixed.
~Sabra w/ a 1985 Toyota Tercel 4WD/FWD Automatic DLX (Terry)
ISO: Working Stock Carb for 3AC Engine
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Petros
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Re: ISO: Front and/or Rear Differential

Post by Petros »

you should be able to drive it in front drive only without too much worry about the rear diff. presuming you fill the rear diff with new lube. there is not too much load on the rear diff when in 2wd mode, it drives though the front cv axles in 2wd, and the rear just trails along.


though I have to tell you if the rear diff gets bundled up you will not even be able to tow it, it will have to be trailered. On one of my rescue tercels I bough sight unseen, it had a number of problems, one of them being a trashed rear diff. It had the wrong transaxle front ratio installed, and they destroyed the rear one trying to drive it in 4wd. The rear axle would not even roll, because the rear diff was bundled up. I replaced the rear diff assembly to the correct ratio for that year, and found it locked up in 4wd. the seller told me they put a "new" transmission in it, and than they buggered up the rear diff, so I was suspicious. I check the ratio, sure enough, they used the incorrect front ratio diff in it, and that buggered the original rear diff. fortunately at the time I also had the correct (different ratio) spare rear diff assembly, so I got to do the job over again. it has a number of other dumb-ass botched repairs, that I also had to fix, but it turned out to be a nice running tercel4wd by the time I was done with it. sold it to another forum member.
'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)
Sabrarain97
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Posts: 19
Joined: Sat Nov 06, 2021 8:11 pm
My tercel:: 1985 Tercel dlx 4WD Wagon Automatic
Location: 97540

Re: ISO: Front and/or Rear Differential

Post by Sabrarain97 »

Petros, could you possibly walk me through how to inspect the diffs so that I can make sure that they are both the same ratios? Or is that something that is easy enough to just ask the mechanic to check? I guess there is always the possibility that I could be going through the same situation as you did. I did put new lube into the rear diff, but it just sounds so bad, I definitely dont want to make matters worse driving it 300 miles at 55/60 mph. The shop strongly recommended that I do not drive it much until getting it repaired.
~Sabra w/ a 1985 Toyota Tercel 4WD/FWD Automatic DLX (Terry)
ISO: Working Stock Carb for 3AC Engine
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Petros
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Re: ISO: Front and/or Rear Differential

Post by Petros »

if the ring and pinion gears have already started disintergraing than I would not drive it at all. it means there are chunks of metal missing from the gear teeth and swilrling around loose in the diff housing.

the simple check is to jack up both front and rear wheels on one side so they are off the ground (block up the other side so it will not move), with the parking brake off and the trans in neutral, you should be able to rotate one of the wheels and see the other one rotating. mark with chaulk and than make ten revoutions, and see if the other wheel move the same. that works on the manual trans, not sure if it will work on an auto trans.

the most sure way is to remove the front cover off the diff (the oil will leak out), and just count the teeth on the ring gear. there should also be the numbers either 4:10, or 3.901 stamped into the edge of the ring gear (you will have to wipe the oil and sludge off of it as you turn to find the numbers). the rear you can just jack up off the ground, and turn the drive shaft by hand and count the number of driveshaft turns it takes to make the rear wheels rotate one revolution. Mark with chaulk, you are looking for the difference between 4.1 revs of the driveshafe vs. 3.9 reves, to rotate the wheels one revolution. Note, both rear wheels have to turn the same, if one brake is draging the spider gears in the diff will mess up your rotations.

the other way to get the ratio from the rear is to remove the third member and count out the number of teeth on the ring gear and the pinion gear to get the ratio. that is a big job, but if it has to come out anyway, you might as well get started on it.

no matter what you end up with the front and rear has to match, exactly the same ratio. I have ran across someone mismatching the front and rear ratio more than once on the Tercel4wd. It has to be corrected before the 4wd can be used. I drove a "rescue" Tercel from Omaha to Seattle that has a number of problems, the seller also claimed it had a "new" transmission. as soon as I got it on the road I gently pulled the lever into 4wd, and instantly heard the gears clash. I drove it back only using the front wheel drive, and than had to change out the rear diff when I got back. the idiot wrecking yard cross reference manual shows all the years rear diffs and front transaxle are interchangeable, that is only true if you change the front and rear diffs across as a set. so someone has an '85 and trashes the trans, they go to a wrecking yard and they sell them an '84 trans (the manual says it should swap over). but they have different diff ratios. so the DIYer, not knowing any better, put in their "new" transmission, and shortly after they get it on the road again they either trash the new trans, front diff, or rear diff.
'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)
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