TomCat39

Can stock gear sets be reversed?

By that I mean switch them around on the shafts? i.e. 92-95 SI 2nd gear is 38:20, can they be changed on the shafts to be 20:38 to be used as say 5th?

*Creative thinking* don't know feasibility.

JRCivic1

First of all, the mainshaft side of second gear is a machined part of the shaft itself and the partner gear is the selectable portion on the countershaft. So first and second gear are definitely out in your exercise. This leaves third, fourth and fifth. Unfortunately, this wouldn't be a drop in affair either since only one gear of the matched pair has the dog engagement teeth for the synchro and hub slider to engage in order to select the gear in question. You must also realize that the fixed gears on the countershaft are machined to be pressed onto the countershaft itself and are spaced in such a way in order to to accommodate the space occupied by the hub/slider, selector rod and synchro brass on the corresponding portion of the mainshaft. In short... there is no easy way to do what you have asked or considered.

Now, fortunately enough for you, the factory has already essentially done what you are asking about. If you examine the shape of the gear stacks on the main and counter shafts, you will see that from bottom to top, the mainshaft gears get LARGER in diameter and the countershaft gears get SMALLER in diameter. The pairs numerically reverse from bottom to top. So, the more simplistic answer to your question is actually what gear pair from XXX transmission fits into my Si box and makes the chosen gear ratio taller or shorter ??? If this is a solution you would consider... I can give you a few hints to help you research what you need.

TomCat39

Thank you for the detailed reply! I highly appreciate it!

I was starting on the path you describe towards the end of your post. And it appeared there was a decent possibility for the Taller 4th gear in the SI box. The struggle seemed to be 5th gear.

Hints would be greatly welcomed. I suspect I won't be able to get to my ideal result, but closer is better.

Ideal result was a 4th gear ratio of 0.868421053 or 33:38 teeth and a 5th gear ratio of 0.538461538 or 21:39 teeth.

My research so far has only been with 92-95 civic boxes. I have next to no knowledge with Del Sol boxes or pre 92 boxes.

TomCat39

These gear sets are taller for the 88-91 HF. May not get to the same ratio as I want, but anything in that direction is better for my purposes.

I don't know if all D series gear boxes are equal and will accept any D-series gear sets though.

And I think there are might even older D series transmissions for the 1.2 and 1.3 Liters maybe? I really am not familiar with the really old Honda's like the CVCC.

Just how far can we go back for gear sets that will work with the 5th and 6th gen gear boxes @JRCivic1, @94EG8, @Aquafina?

94EG8

'88 - '91 may work. I never really dealt with them and I kind of forget what swaps. Hydro DOHC has weird ratios (I can't remember what they are, just that they're special) as well.

Aquafina

iTrader: (3)

88-00. 1/2 cannot be swapped between cable and hydro. .5xx 5th would be useless.

TomCat39

Thanks for the info about 1 and 2 issues between cable and hydro @Aquafina.

I am not sure why you say a .5xx 5th would be useless.

Mathematically speaking it works out to be the same as a VX 5th in a VX tranny.

I always thought the torque requirements were set on the complete system not just one ratio?

VX in 5th Gear -> 0.702 * 3.25 = 2.2815:1 Engine rotations to wheel rotation.

SI in Custom 5th Gear -> 0.538461538 * 4.25 = 2.28846:1 Engine rotations to wheel rotation.

Is there more than just what the math indicates?

Aquafina

iTrader: (3)

VX trans is fine if you have a VX engine and ECU and don't care about very slow acceleration.

If you don't have the VX engine and ECU you will get worse gas mileage. VX's can't even get out of their own way. Non lean-burn Honda's like to sit at a higher RPM while cruising. 1.0005th/4.058 FD in my car (2,400lb, Z6) netted me upper 40's MPG.

TomCat39

My 5th gen Hatchback has never hit the 40 MPG even with the DX transmission. I believe it might be the ethanol mixed gas maybe.

With the non-vtec 1.5L 16 valve motor and the manual DX transmission I would cruise on the highway about 2500 RPM in 5th and my avg MPG was 33.83 MPG.

I've now swapped in the vtec 1.6 liter motor and the Coupe SI manual transmission and started fresh tracking MPG since the swap. Cruising on the highway is now 3000-3200 RPM and my avg MPG has fallen to 31.xx.

I think understand the point you are making about what the motor likes for cruising so maybe a slightly taller 5th might be the good compromise. I was looking to drop the cruising RPM closer to the 2500 I'm used to.

I will have to play with eccomodders calculator to see if the HF 5th gear would make it too tall or if that is the best compromise for the 4.25 Final Drive.

I've read, the D16Z6 has better lower end torque than the 6th gen 1.6 liters vtec motor so thought the lower RPM should actually help the fuel efficiency on the highway.

Thank you for the insight.