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.