Hybrid Transmission: Anything I'm missing before I start?

I currently have a 1989 Honda CRX HF (1839 lbs) with a JDM D15B Vtec (128 hp). At the time of the swap (a few months ago) I was unable to obtain a Si tranny. Just last week I started to hear the whirring and chattering of bearings going out (Input Shaft bearing and probably a few others) Time for a new transmission as the HF tranny isn't worth the $200-$300 worth of new bearings and seals.

This weekend I purchased a ZC tranny (20 spline = 1989-91) which has the closest gearing of any D-Series transmission. I personally don't wish to use the equal-length axles that are required by the ZC transmission... So I'll be swapping in my HF's differential so that I may continue to use the stock axles. (the HF, DX and Si Differential are all the same right? Minus the Ring Gear and bearing sizes)

While I have the new tranny broken down, I'll install the HF 5th gear (including the corrosponding counter gear) so that I may keep my highway speed RPM's down (making my long drives much more pleasant)

Just thought I'd share my plans with everyone and see if I'm missing anything that needs to be done in order to carry my plans out.

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Running 185/60/14 (22.74 Inch) Tire/Wheel Combo

My Hybrid Transmission

ZC 1-4 (1st: 3.250; 2nd: 1.944; 3rd: 1.346; 4th: 1.033)
HF 5 (5th: 0.694)
ZC Final Drive (Final: 3.88 )

Data shown with redlining @ 7200rpm

GEAR MPH RANGE (RPM SHIFT RANGE)
1st: 0 - 38.64 (idle - 7200)
2nd: 38.64 - 64.60 (4306 - 7200)
3rd: 64.60 - 93.31 (4985 - 7200)
4th: 93.31 - 121.58 (5526 - 7200)
5th: 121.58 - 180.96 (4837 - 7200)

5th @ 80mph: 3183 rpm
ZC 5th Gear @ 80mph would be 4027 rpm!

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Things to do:

--Replace all bearings and seals
-There's a difference in the bearing sizes
Countershaft bearing (30x47x21 = HF; 30x55x21 = Si)
Mainshaft bearing (6205UC/26 = HF; 6305SPL = Si)
Differential Oil Seal (35x56x8 = HF; 40x56x8 = Si)
Speedometer Drive Gears have different part numbers between HF and Si
The transmission cases are of course different part numbers because the bearings are different sizes.

Since the only sizing that is different is one dimension, can I use either size bearings on the HF differential?
If I can use either size bearing on the HF Differential and ZC Main/Countershafts then I can use either case (ZC or HF) I want right? Just pick the bearings that match the casing?

--Swap in HF 5th gear and counter gear

--Swap in the HF Differential
-I am required to re-shim the differential upon bearing replacement right?
-Since I'm using the ZC Countershaft (part of Final Drive) I need to swap on the ZC ring gear onto the HF Differential correct? Is that all that the "final gear" consists of?

I've been searching every Honda/Acura website I can find as well as Google etc to gather as much info as I can. The above questions still remained somewhat unanswered to me from what I've found.

Thanks you for any help you may give.
John (BlueCrxNC)
[email protected]

You seem pretty damn knowledgeable about trannys so i got a question or two:

First off, are ALL d series gear interchangeable? As in you could mix and match between dx, hf, and si gearing?

Are there non-aftermarket LSD d series transmissions?

Lastly, are gears from different transmissions (trims) different strengths?

Thanks! btw-where are you in NC...Im johnston county...yee haw....

From Jerry Isner:
John,
Sounds to me like you have a good grasp on the basics. The bearings that
are on each side of the differential where they fit into the case are
smaller outside diameter on the HF than on the Si. If you want to use your
HF case with the HF axles, yes, you can just use the Si countershaft and
swap the Si ring gear onto the HF differential (ring gear bolts are left
hand thread). Or conversely, you could swap the HF bearings onto the Si
differential. Use the ZC input shaft with ZC gears on it and swap the HF
5th onto it. You need to use the ZC input shaft as 2nd gear is part of the
shaft and is not removeable. (Luckily you don't have 21 spline 88
transmission or you would also need to change the clutch.) Swap the ZC 2
thru 4 gears onto the Si countershaft and the HF 5th. All of this would
give you a ZC/Si hybrid.

If you want to use all ZC gears, just swap the ZC ring gear onto the HF
differential (with the HF bearings to use the HF case or the ZC bearings to
use the ZC case), use both ZC main and counter shafts with ZC gears and swap
on the HF 5th. There are lots of possibilities, depending on what parts you
have and what you want to end up with. If you need more help, just let me
know.
Jerry

That's all I needed to hear! Thanks Jerry

PunkAlex,
I would only see myself as a good researcher :) Now with computers I'm very knowledgeable and everything that I know about computers is self-learned (Even the hard way [ie. When I was 12-13 yrs old I literally opened up a hard drive to see what was inside... I had no idea that doing so would render the drive useless:loser:])

I do believe that all D-series gears are interchangeable (unless it goes by the clutch type; cable vs hydro), allowing you to do as I am; Making the best from what the factory has to offer.

Your chances of finding the elusive D-series LSD tranny are worse than slim to none. It'd be like winning the lottery :) There are LSD ZC's and then there are LSD trannies from the JDM D15B Vtec (the motor I have; but they are hydro, if that makes any difference)

Oh, and I'm located in Greensboro, NC (Guilford County) but travel to Charlotte often (soon to move to Charlotte) When I get my transmission done, maybe I work something out so we can meet up. [email protected] -> John Strickland