Toyota Tercel taller gearing (Corolla too)

[Daox]

I've mentioned it several times, but I'll be working on my 1993 Tercel in the not horribly distant future. Thus, I've been thinking about all the different mods I'd like to do and making a to-do list for myself.

One of those things is swap in some taller gearing. The stock 4 speed (aka C141) isn't absolutely horrible, but its far from ideal for mileage. Here is a screen shot from a calcultor I've made and used over the years. As you can see, at 45 mph (my main commuting speed) the engine is spinning at almost 2100 rpm. At 65 mph its right around 3000 rpm.




The easiest swap is a 5 speed from a 95+ Tercel (aka C151). This has a taller 5th gear, but a higher ratio differential. Here are the gear ratios of the Tercels & Paseos (they both use interchangeable transmissions). Using this trans would get me down to 1800 rpm at 45 mph, 2600 at 65 mph. Still not really amazing. If I'm going to pull an engine and trans out, I'm going to want a bit more.





The best option I have then is to take that C151 5 speed, and put my C141 differential gearing in it. I'm not 100% sure that it would physically all fit up, but I assume so. Doing so would give me 1700 rpm at 45, and 2450 at 65 mph.


So, I thought that was the best I could do for quite a while, until I started digging around even more. Dummy me, I had completely forgotten about the other transmissions that were available in the Tercels and Paseos. Their accursed names won't be mentioned here, but they start with an A and end with an utomatic. Yes, I'm no fan of automatics.

As it turns out, the 4 speed auto transmissions (only put in Paseos and some 95+ Tercels, the rest had 3 speeds) have a 2.821 differential ratio. Bingo, or Yahtzee if you prefer. Throwing a 2.821 differential ratio into my extra Paseo 5 speed (C150) would give me a very nice 1525 rpm at 45 mph, and 2200 at 65 mph. However, I don't have an automatic transmission laying around, so I enlisted some help over on TercelOnline, a forum for Tercels and Paseos that I've been on for ages.

[MetroMPG]

So you're investigating to see if the diff gears from the automatic will fit in the C151 5-speed box?

[dirtydave]

That should be an easy trade I would think. Most people on specific model forums are all about power and higher RPM's. I tried to go to a KIA website and got laughed out when I said I got 45MPG. They didn't believe me

Those are some low RPM's Should be a good mod!

[MetroMPG]

You'd think there would be a natural match between "go fast" forums and ecomodders for gearing swaps.

[Daox]

Originally Posted by MetroMPG

So you're investigating to see if the diff gears from the automatic will fit in the C151 5-speed box?

Mostly, yes.

I don't have a C151 on hand. I do have a spare C150 from a Paseo. The difference being a .815 5th gear vs .725. That translates to a ~170 rpm (1350 rpm) drop at 45 mph, so perhaps worth finding one if I really want to go all out.

[Daox]

Originally Posted by dirtydave

That should be an easy trade I would think. Most people on specific model forums are all about power and higher RPM's. I tried to go to a KIA website and got laughed out when I said I got 45MPG. They didn't believe me

Those are some low RPM's Should be a good mod!

There are enough people with parts cars out there that I'd probably just buy the gearing off them.

The Tercel forum guys know me from my Paseo build I did a few years back (best tank of 72 mpg), so they get it.

[Daox]

Alright, special thanks to tercelonline user Aysia. She tore into her 4 speed auto from her parts Paseo to get me some pictures of the 4 speed auto diff parts.

It looks like the A244 (4 speed auto trans from the Paseo) uses a C5x differential. This is the differential from a Corolla's manual transmission, not a Tercel/Paseo trans. Therefore, the gearing from the A244 won't fit into a C15x 5 speed. However, it will fit into a C5x (duh). Thankfully, I have a C52 laying around, and it will bolt up to the Tercel engine using the Tercel bellhousing and some drilling and tapping for the Tercel engine mount. So, now its my turn to crack open a trans and measure up its guts to make sure everything will in fact transfer over.













Here is an pic that compares the C151 differential to a C52 diff. Notice the 6 bolt vs 8 bolt pattern.

[MetroMPG]

Too many A's and C's to follow, but it sounds promising!

[Daox]

Haha, yeah it is a bit much to take in. Once you get it its pretty simple though:

C15x = Tercel / Paseo manual transmission
C5x = Corolla / Matrix / Yaris transmission (will fit a Tercel with minor modification)

A24x = Tercel / Paseo automatic transmission

I'm just trying to figure out what bits fit in what transmissions to get the ratios I want.

[cosmick]

Curious what reference you're using, if any, to indicate you're not dropping the RPM more than ideal? Or is this, like me, just trying to get a new baseline to work from?