Regearing a tranny - Toyota Tercel
 

Alright, the time is comming near when I'm going to need to pickup a tranny for my Tercel. Now, I really want to get the rpms down on the highway under 2000. With the stock tranny I plan on picking up for it I can get the rpms down to roughly 2600 @ 65 mph. This is faaaar from ideal. So, I've been thinking of different ways of dropping that down a bit further. I've heard of swapping 5th gears out and was wondering about swapping in another 2nd gear set into the 5th gear position, but in reverse. With an original ratio of 1.904 this would give a nice low .525. At this ratio my rpms @ 65mph would be a much better 1875 rpm.

Does anyone have any experience with this sort of thing? Yeah, I did read the article about the Escort and I'm hoping my situation is different. I also realize I may need to have some machining work done to get it to all fit up. Thats not a real big deal.

I'm at that point right now too! :confused:
Here is my thinking-
My first steps are:
1- Track down all info on compatible (direct swap in or limited modification) transaxle's gear ratios and final drive ratios first. R&R the complete trans if one has the desired ratio.
if this is not acceptable...go to the next step
2- Track down all compatible trans gears or final drive differentials that can be swapped into the trans from 'related' transaxles.
if this is not acceptable...go to the next step
3- Research some racing or machine shops that could 'make' a gear set for you (I was quoted about $700-800 for this when I called around).
if this is not acceptable...go to the next step
4- Pull out hair and scream loudly.
if this is not acceptable...go to the next step
5- Run large diameter tires and keep your speed down.
if this is not acceptable...go to the next step
6- Join EcoModder and search for answers in previous threads.
if this is not acceptable...go to the next step
7- Post New thread titled 'Regearing a tranny' and hope someone has some experience with this sort of thing!:o

Just to clarify - do you call the Paseo a Tercel?

I wish I could offer more advice than XFi already has (I had a laugh when I got to steps 6 & 7).

No, I have a 1993 Toyota Tercel that is undergoing surgery atm. The Paseo is my daily driver.

I guess I'll let you guys know how the tranny stuff goes. Some one has to dive in!

You're the first Tercel-owning hypermiler/ecomodder I've met. Although there was a another Paseo owner that posted a few times @ GS a long time ago.

All of which is to say: you'll have to be the pioneer!

XFi -

Here's one I noticed on GS :

Congrats to COZX2 on the 100+ MPG fill!
http://www.gassavers.org/showthread.php?p=62366
Which led me here (good and bad news I'm afraid) :

Modifying Gears for Taller Overdrive
http://sites.google.com/site/diyoverdrive/
However, I was under the impression that the $200 was a lower cost because they were friends. But, I may be wrong, I never asked CO ZX2.

Question : Does your Escort have the same tranny as CO ZX2's Escort?

EDIT : Whoops, are you trying to re-gear the Escort or the Hyundai?

CarloSW2

Sorry Daox...didn't mean to 'jack your thread! :o

CarloSW2, Daox is modding his tercel, I am modding my escort.
Hyundai's trans isn't getting modded until it is out of warranty.;)

I didn't see the update on that gear mod (the demise of the gear), thanks.
To answer your question...No, the ZX2 trans is different than the Sdn/Wgn Trans.

I did purchase a 'Pony/Fuel Saver' Trans at a yard but still have to tear it down and compare it to my trans.

Well, since I need to get moving on this I've collected enough info to make a descision. I'll be shopping for two Corolla transmissions. The 2nd gear will be taken out of one of them and modified into a new 5th gear for the other. 1875 rpms here I come.

Do you know yet how extensively you need to modify things?

I just looked at the escort site again and noticed that there was a whole page dedicated to the failure. I'll have to talk this over with some of the guys at work. Its nice to have experts around. :)

The actual modification hopefully won't be too horrible. I'll have to bore out both of the 2nd gears, turn the teeth off of the 5th gears, and then press them together. Pretty much exactly what they did in the escort article. Luckily I work at a gear manufacturer and I can get access to machinery, or find someone to do it for me (more likely). I also have access to liquid nitrogen and heating equipment to press them together with a tighter interference fit. I don't know yet if any welding will be done, however I would like to stay away from it mainly due to the heat treating of the gears. I also got some tips from our FEA guy at work on how to get better interference fits with more evenly distributed stress so the fit won't fail as quickly.

I just talked with the warranty guy here about the failure on the escort. He is sure it was due to misalignment. Most likely this happened when they welded it, but it could have also been machined improperly. He gave me a few tips and thinks that if I can get it machined accurately, and avoid welding it I should be good.

"Luckily I work at a gear manufacturer and I can get access to machinery, or find someone to do it for me (more likely)."

Lucky dog. Nice to get that expert opinion on the possible cause of the Escort failure.

This is going to be very interesting!

I just came across this thread, but before seeing this I was talking with minic6 over at GS about changing my metro 5th gear. I wanted to mod 5th gear because I thought it could be changed without pulling the trans.
Here's what I suggested to minic6.
Then he suggested reusing the inner diameters of the original 5th gear gears and fitting them to the bored out 2nd gear gears to retain the splines and correct shaft diameters etc.


So it sounds like we are on similar paths Daox :) (and I thought I had an original idea :o)

I think the 2nd gear to 5th gear trick is what this ZX2 owner did (bored out, with the 5th gear centers welded in):

Story of a custom 5th gear for a '98 Ford Escort ZX2: +6% MPG

Unfortunately it looks like his web site (linked in the forum post) is no longer active.

I remember COZX2 talking about doing gear work on his trans a while back. If I would have paid more attention, or had a better memory, I would have seen that he did the same stuff. Oh well, just started thinking about it recently and was just throwing ideas around with minic6. Neat to see it actually being done.

Yeah, thats where I got most of the info from.

I still haven't gone ahead with any of this yet though. Too stinkin busy atm plus the focus has shifted to the Matrix. However, I do have to get the Tercel back on the road.

I also agree with the suggestion that a .525 overdrive gear might be to deep. I would run the engine at the target RPM in the current OD gear and see how it responds at that RPM and find a small slope to approximate the increased aero drag from the higher speed you will see at that RPM with the deeper OD gear.

What makes you think .525 is too deep?

1) Because oriental cars are not known for thier low RPM torque.
2) Other than the T56 speed in a V8 camaro & Corvette or a V10 Viper, none of the manufacturers ever go that deep with their OD gears (maybe a reason).

It costs you nothing to run my simple test.

#1 is a valid concern and I have already looked into this as it was a concern of mine too. At 1875 rpm I have roughly 23 horsepower (65 ft/lbs) avaliable to me. That'll set me at about 70% load (@ 65 mph) which is pretty close to ideal for most engines. The only detriment will most likely be the low rpms since peak BSFC occurs at higher rpms in most naturally aspirated engines. If I need more power I simply have to downshift.

#2 really isn't much of a concern. On all the high mileage versions of cars I've seen they always gear them lower. Examples would be the Honda VX, Honda Insight, Geo Metro XFI, and even the new Chevy models that are getting better mileage like the Malibu LTZ and Cobalt XFE.

The real benefits will have to be seen. It all depends on how the BSFC map is for the engine once I'm done with it. If it has long horizontal sections like the Metro map below I'll be in great shape. If its like the Saturn map I won't see as much benefit. Since the torque output of the engine is very flat I'm guessing its more like the Geo map. The red dot is how its geared now, the purple is after modification.

Geo 1L BSFC map
http://www.tercelreference.com/downl...eo_1l_bsfc.jpg


Saturn DOHC BSFC map
http://www.tercelreference.com/downl..._dohc_bsfc.jpg

The Corvette and Viper get away with the huge 0.5:1 overdrive because of their enormous low-end torque. The T-56 would be perfect for a diesel down to 3.0 liters or so.

Nice use of the BSFC maps, Daox.

I would only be concerned about running extremely low gear ratios if you were required to increase low-end torque. I wouldn't be concerned due to the complexity of that task, but rather that you will be putting immense loads through the transmission when geared so low.

I have no idea how over-engineered Japanese transmissions tend to be, but stripped gears seem to be a real possibility...especially if they are of the self-manufactured variety. :p

- LostCause

I have no Idea on the Tercel transmission, but the W58 is 200% over engineered, the R-154 is 300% over engineered and the Getrag is about 250% over engineered IMHO
I know that the 5sfe Camry 5 speed will do 200 Whp no problems as well (don't know transmission code)

Yeah, the Tercel tranny is beefier than need be and I'm sure would hold up just fine. However, I won't be using a Tercel transmission in the car. It'll be swapped out for a Corolla trans to get the ratios I want along with a LSD since I am supercharging it. The Corolla trans is even beefier and proven to take over 300 hp.

I think I'm in the minority when I believe a transmission being 300% stronger is a bad thing. I understand why they do it, but efficiency-wise, that thing is 3x over-engineered (aka, heavy).

Good luck, though.

- LostCause

All depends on the application in my opinion. In an efficient daily driver, Yes absolutely However in something that's going to be relentlessly pounded, and hot roded, No.

There have been a few isolated incidents of guys doing drag racing with drag radials and eventually snapping differential parts. Going with the Corolla trans ensures me that this will not happen. I'd also agree with dremd's comment.

Why not go with changing the final drive? I drive a 92 paseo with a MT and think that the whole transmission is a little short in the ratio domain....