Gear ratio problem

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JDNightFox
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Posts: 171
Joined: Sun Nov 01, 2015 5:39 pm
My tercel:: toyota
Location: CA

Gear ratio problem

Post by JDNightFox »

My door badge says my car was manufactured April of 1986. The title says it is a 1986 model

From my understanding, it should have the 4.10 gear ratio. But I just finished pulling the rear axle and it has 11 pinion teeth and 41 ring teeth.

I took off the cover from the blown up front end and counted that one too. It also has 11 pinion teeth and 41 ring teeth.

The new rear axle housing that I received from Xirdneh with "3.73" written on it, since I have mismatched ratios, that I was going to swap into the rear to match up my ratios....also has 11 pinion teeth and 41 ring teeth.

The new transmission I bought was from an 85. If I turn the driveshaft 4 turns the front wheels do one complete revolution, which puts my front axle at 4.10, yet my original drivetrain was apparently 3.73 and now I need a 4.10 rear end so that my gear ratios can match again.

Is there any other way to ID the gear ratios? I feel like I'm messing up somewhere because how did this happen
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Petros
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Posts: 11930
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Gear ratio problem

Post by Petros »

someone may have swapped out the original 4.1:1 front and rear and put in an earlier '83-84 front and rear diff because that was available. It is not likely it was an odd production version, but on a car this old anything is possible.

there are a few other differences on 4.1:1 front transaxle, presuming they changed out the whole assembly. there should be three wire connectors on the later one (back up light, 4wd indicator, and EL indicator), the earlier trans has only two, no EL indicator. Internally there are more, the shift forks are all steel on the '83-84, and aluminum on the later transmissions.

you have to get the front and rear to match, if you trashed a diff (either front or rear) that might explain it, they were mismatched. I have a spare 4.1:1 front diff/bellhousing assembly if you can use it, be happy to sell it to you if you can use it.

BTW, I have noticed that on all of the 4.1:1 rear diffs (and I think the front too as I recall) there is the numbers "4.1" stamped into the side of the ring gear. on the 3.73:1 there is no markings. you take a rag and wipe around the outside edge of the ring gear until you can see it.
'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)
JDNightFox
Top Notch Member
Posts: 171
Joined: Sun Nov 01, 2015 5:39 pm
My tercel:: toyota
Location: CA

Re: Gear ratio problem

Post by JDNightFox »

Both of my rears have 37 stamped on their ring gear so I'm assuming that means they are 3.73

My front is already 4.10 so I just need to change out the rear to a 4.10, which is what I was planning on doing yesterday until I pulled the old one out and found it was already a 3.73

My reverse light, 4wd, and EL lights work so I'm assuming it's the correct style transmission
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Petros
Highest Ranking Member
Posts: 11930
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Gear ratio problem

Post by Petros »

three times I bought T4wd cheap, with either bad front or rear diff (or trans) and found they had mismatched front and rear diff ratios. fortunately I had the correct spare in the garage, or one was available at the local picknpull, and was able to fix it. but it is not unusual that someone swaps out the incorrect ratio front or rear diff. If they knew where to look it up, this much heartach and carnage can be prevented. One decent '85 I bought just has a DIY trans swap, only to have it fail within a week, so the owner in frustration just sold it as-is.

I think there is a wrecking yard data base that lists interchangeability on various car parts that says all year T4wd trans/diffs are interchangeable. while it might be true they can be swapped out, but it can not be done without changing out the other diff as well.
'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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