Trans gears.
 

I asked my uncle about custom cut gears yesterday, and he didn't seem too enthusiastic. Pretty much because his tooling has too much slop (thousanths) in his opinion, and getting HSS, straight cutting a gear, and having it heat treated may be a waste of time and cash if it's too sloppy. I'll try to measure some gears on the next manual trans I take apart to determine slop, but I was thinking, what if engineers designed a pretty decent level of flexibility in the trans already? If, for instance, the input and output shafts are both the same size/design, and there's enough room in the trans case, why not just pull a 1.75 2nd or 2 3rd, flip it, and have a nice low OD gear? Does anyone have any experience w/ this? Maybe it'll work w/ a little machining? :)

For hondas it is a very common practice to use my hf third gear as a fourth gear. So, it is very common to swap gears around willy nilly like this. There is a lot of wiggle room with these transmissions, you can even swap betweem hydro and cable clutched trannies because they kept the design the same when they messed with the clutch (though I do think the finals are not swappable between the two types).

Sweet! Are you talking about a swap and flip to get an inverse ratio, or just moving gears around?

Just switching, I don't think the flip will work, as I've never heard of it being done.

I'm hoping it does. And since most swaps seem to be acceleration oriented, I don't think many would've tried it yet since we can't accelerate quickly by taking a 2:1 2nd gear combo, flipping it, and using it as an OD w/ a .5:1 ratio. Even it's not a lego situation, I bet machining 'em to fit would be easier than cutting gears. Hopefully... :D

Gear Mods
 

Here is a link to a gear mod from a friend I have been in contact with for some time. Lots of good pics. His machinist used wire Electrical Discharge Machining to modify the gears. I decided on grinding for my parts, mainly for local shop capability and cost. A lot of work for a .545 vs .770 fifth gear but lowers my engine RPM by 30%.

https://mypeoplepc.com/members/tleone/gears/

P.S. omg, please reply to my PM sent you earlier this week.

Custom gear making is VERY expensive.

Do a google search on "gear hobbing" - this is the method of manufacture. Flat out milling a gear with involute teeth - yikes, that would be a nightmare.

The problem with most transmission gears is that the teeth are helical. This actually SOLVES a problem of teeth wearing down (I can further delve in to the dynamics of gear trains if you'd like :)) and noise. The reverse gear in most transmissions has straight cut teeth, and we all know how that sounds. Imagine if all your gears sounded like that (whiiiiiiiiiiiiiiiiiiiiine!).

Custom racing transmissions sometimes use straight cut gears with dog engagement instead of helical gears with synchro engagement.

CO - you're having this done to your car?

As for cost, the guy who did the custom aero-modded XFi machined his own 5th gear ratio. He was quoted $2500 to have a shop do it.

Modified Metro XFi: throwing convention to the wind

https://metrompg.com/posts/photos/198...ar-trimmed.jpg

Switching gears would be awesome. Not sure about toyota's transmissions, but vw's transmissions have separate gears, so I just need to figure how to get the synchros working. Thanks for the help everyone!

Gear Mods
 

I have the 7% O/D 5th gear only in the car right now(since Monday).

No $2500 jobs for me. My cost for the gearset pictured: $200 for precision grinding + $55 for junk transmission. Almost finished. The gears are ground and pressed together.

Sending gears to my brother in IL to do the welding. He is a certified pipefitter and does the quality welding you see in the pictures.

After welding, I will hone the gear bores myself and assemble the rest. My good neighbor will give me a hand installing the trans.

Can't wait to see 1850 RPM at 56 MPH. Will be 33.05 rpm per 1 mph vs. 43.63 rpm per 1 mph with original gears.

Gear Mods
 

Dear CO ZX2,

zpiloto has just replied to a thread you have subscribed to entitled - Trans
gears. - in the General Tech forum of GasSavers.

This thread is located at:
https://www.gassavers.org/showthread....4&goto=newpost

Here is the message that has just been posted:
***************

---Quote (Originally by CO ZX2)---
Here is a link to a gear mod from a friend I have been in contact with for some
time. Lots of good pics. His machinist used wire Electrical Discharge Machining
to modify the gears. I decided on grinding for my parts, mainly for local shop
capability and cost. A lot of work for a .545 vs .770 fifth gear but lowers my
engine RPM by 30%.

https://mypeoplepc.com/members/tleone/gears/

P.S. omg, please reply to my PM sent you earlier this week.
---End Quote---


zpiloto: Was this your car that was modified?


CO ZX2:

No, it was not my car. That car belongs to the author of the site in the link.

But I am preparing a similar gearset now. Should be done soon. See above reply to MetroMPG.

cheeper to try taller tires than to change gears

Ah. I never thought of doing it that way. Wire EDM is cool stuff, we do quite a bit of wire and sinker electrode EDM processes at my work. Beautiful welds on the gears BTW. Were they heat treated after welding?

Interesting :) I don't think I would want to change my current gear ratios, but would like another gear of 0.5:1 overdrive or something :). My current gears are quite good for hypermiling anyway; 5th is 50mph / 1900rpm or something like that.