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Old 08-09-2010, 04:32 PM   #1 (permalink)
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Building a FE D-Series trans for my CRX VX

I'm planning on building a transmission for my CRX this winter when I swap in the D15Z1 I picked up last week.

I made an Excel spreadsheet that shows Vehicle Speed versus RPM for a stock HF transmission (49 State with 2.954 Final Drive). This is essentially what is in my car right now:



I've read some people talk about putting Si 1-3 gears in a HF trans, but I want even shorter 1-3 gears. The JDM DOHC "ZC" transmission has a 1.944:1 2nd gear, a 1.346:1 3rd gear, and a 1.033:1 4th gear. The 1.033:1 4th is too tall, but the DX/Si has a 0.937:1 4th gear.

Below is a graph with a Stock 1st (All D-Series transmission have the same 1st), ZC 2nd and 3rd, DX/Si 4th, HF 5th, and stock HF final drive.



This really tightens up 1-3 and the DX 4th is a nice bridge between the ZC 3rd and HF 5th. This should liven up the car a little on acceleration but still retain the superior cruising fuel economy.

Thoughts?

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Old 08-09-2010, 04:46 PM   #2 (permalink)
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Looks like the HF tranny has similar (same?) gear ratios as the VX tranny... Never did like the 'huge' leap between 2nd & 3rd. I'd be interested curious how the build goes and what the result are like.
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Old 08-09-2010, 04:56 PM   #3 (permalink)
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Quote:
Originally Posted by D-Series.org
1st gear:
3.250 39/12 all

2nd gear:
1.650 33/20 hf/std (88-91)
1.762 37/21 cx/dx/lx/vx (92-95)
1.782 41/23 cx/dx/lx/hx (96-00)
1.894 36/19 dx/si (88-91)
1.900 38/20 ex/si (92-95)
1.909 42/22 ex/sol si (96-00)
1.944 35/18 dohc zc (88-91)

3rd gear:
1.033 31/30 hf/std (88-91)
1.066 32/30 cx/vx (92-95)
1.172 34/29 dx/lx/hx (92-00) *also in 96-00 cx
1.250 35/28 ex/si (92-00)
1.259 34/27 dx/si (88-91)
1.346 35/26 dohc zc (88-91)

4th gear:
0.823 28/34 hf/std (88-91)
0.853 29/34 cx/vx (92-95)
0.909 30/33 dx/lx/hx/ex/si (92-95) *also in 96-00 cx
0.937 30/32 dx/si (88-91)
1.033 31/30 dohc zc (88-91) *can also be a flipped hf/std 3rd gear
1.066 32/30 cx/vx (92-95) *not really a 4th gear, but it can be used as 4th

5th gear:
0.694 36/25 hf (88-91)
0.702 37/26 all non si (92-00)
0.750 36/27 sol si (93-95)
0.771 35/27 dx/si (88-91)
0.878 29/33 dohc zc (88-91)
1.000 29/29 mfactory (aftermarket)

Final drives (cable = 88-91, hydro = 92-00):
2.954 65/22 some HFs (88-91)
3.250 65/20 cx/vx/HF (88-95) cable form in some HFs, hydro from in 92-95 cx/vx
3.722 67/18 hx/cx*/dx* (88, 96-00) found in 1988 dx, hx, 96-00 hatchback
3.888 70/18 dx/std/zc (88-91) 89-91 dx, 4spd std, zc
4.058 69/17 dx/lx/ex? (88-00) found in all hydro dx/lx, cable form in 88-91 ex sedan?
4.250 68/16 ex/si (88-00) found in all d-series si's, and hydro EX's
4.437 71/16 zxi/aerodeck (88-00**) found in cable zxi, believed to exist in hydro from in euro aerodeck wagon
The VX and HF are similar, but not exactly the same.

Personally I hate the drop between 1-2 the most in this car, it really is a dead spot when driving at low speeds.

All D-series gears are interchangeable, so just finding the parts is the only trouble. I've had these transmissions apart before, so it shouldn't be that big of a deal.

A ZC trans can be had for $150 plus shipping, and I'm sure I can find a DX trans for that 4th gear pretty easily. We shall see...
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Old 08-09-2010, 11:10 PM   #4 (permalink)
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Thanks for posting that! So I can replace the 0.771 in a Civic Wagon with the 0.702 37/26 all non si (92-00)? That should be easier to find than the HF 5th gear!
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Old 08-09-2010, 11:34 PM   #5 (permalink)
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I am going to say yes, but it may not be a 100% drop in swap, the gear may need minor machining to fit. The reason is because it is a hydro 5th going into a cable case. Some hydro gears need machine work to fit. I would do some searching on d-series.org to find out for sure.

I know the swap I have planned will work because all parts are from cable transmissions.
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Old 09-09-2010, 11:15 PM   #6 (permalink)
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With that tall hf final drive It almost makes all the gear swapping not worth it. I understand your desire to liven up the low end, however with such a tall final drive you are doing alot of work to still have a slow car with tall gears.
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Old 09-09-2010, 11:37 PM   #7 (permalink)
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Keep in mind swapping gears is not that simple. There are several main shaft and counter shaft parts that need to be addressed, which are not likely to be interchangeable.
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Old 09-10-2010, 08:36 PM   #8 (permalink)
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I believe that the D-series gears are pretty interchangeable, as long as you use a 1st gear for 1st, a 2nd for 2nd, etc. One of the D transmission gurus (Mista Bone on lots of Honda forums) tells us that we can swap the HF 5th into our Si transmission, or swap a later D-series 5th (0.702 ratio?) instead, and others I know have swapped Si and JDM (yo!) ZC gearing around. With an HF 5th, as I recall!

-soD
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Old 09-14-2010, 09:55 AM   #9 (permalink)
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Quote:
Originally Posted by bengry View Post
With that tall hf final drive It almost makes all the gear swapping not worth it. I understand your desire to liven up the low end, however with such a tall final drive you are doing alot of work to still have a slow car with tall gears.
Changing the final drive simply isn't an option, I won't sacrifice the cruising fuel economy of this car. However, anyone who has driven an HF can attest to how terrible the RPM drop between 1-2 and 2-3 gears are.

Honestly, it is not a whole lot of work to swap out the gears, I've pulled apart these transmissions before. A complete ZC trans can be had for $150, which will have all the required parts for second and third gear. People practically give away DX transmissions which is where I will find my 4th.

Quote:
Originally Posted by slipstreampilot View Post
Keep in mind swapping gears is not that simple. There are several main shaft and counter shaft parts that need to be addressed, which are not likely to be interchangeable.
As stated above, most D-Series parts are interchangeable. Nearly all are when using parts from 88-91 cable clutch transmissions into other cable clutch transmissions. It starts getting a little more hokey when putting parts from the later hydro clutch transmissions into the cable clutch boxes and vice versa. I mean, the guys building close ratio D boxes for racing use HF 3rd gears as their 4th gears.
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Old 09-16-2010, 02:44 PM   #10 (permalink)
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The sad part is that you cannot swap the drive and driven gears, so you cannot "invert" the gear ratios. You'd have a really amazing range of ratios available if you could do that.

Oh well. I guess we have to make do with what's actually out there.

-soD

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