Notes about the JDM L3 transmission
AKA, the "ZC tranny"

slightly revised/updated 10/31/02

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Are your differential carrier bearings totally worn out causing the ring gear to eat into the tranny case?
Here's a link to wasted differential carrier bearing removal

*updated 8/24/00*
LSD noise
axle information
MPG with the new .702 5th gear

*update 1/24/02*
new gearing

The JDM L3 5-speed transmission is identical to the USDM L3 Si 5-speed. The only difference is the optional LSD, gearing, and the axle seals.

Some JDM L3's came with an optional Limited Slip Differential. You can identify these by simply looking through the final drive of the transmission. If you can see a large pin bisecting the bore of the final drive, then it is equipped with a standard open-type differential. If you can see clean through the bore of the differential with no obstruction, then you have found a rare LSD equipped ZC tranny.
Originally, the LSD equipped transmissions had "LSD" stamped in ink on the outside housing. However, given the age of these transmissions, don't rely on this method of ID. Serial numbers are no indication of year or gearing.

*note* The LSD's in these transmissions make strange noises when making slow tight turns. You can also feel the noise. According to several others polled on this subject, the noise is normal? On one reccomendation, I replaced my Valvoline 5w-30 transmission oil with Honda Manual Transmission Fluid. The Honda MTF does indeed quiet down the LSD mechanism. After putting some miles on the Honda oil, the feel and noise is substantially reduced.

Gear Ratios
Gear Ratios

Because the JDM L3 "ZC" tranny was paired with a 1.6l DOHC powerplant, it was designed to use the larger "Integra sized" inner CV joints with the 40mm splined shafts. The bore in the transmission casings is the same as the USDM L3 transmissions, so the outside diameter of the seals is the same. However, because of the larger caliber splined axle shafts, you will need the larger inner diameter seals.

Here are the part numbers for the seals. Your local Honda dealer can order them.


DO NOT use 86-89 Integra axles. I guarantee that the shafts will pop out of the inner joint within 30 feet of the installaton location (your garage, the shop, etc.).

You can use 90-93 Integra axles. They have longer inner joints which keep the axle shaft from popping out.
On the passengers side, I built a hybrid axle using the OE Civic short axle and outer joint mated to a 90-93 Integra RIGHT side axle inner joint. The short Civic axle appears to be longer than the 90-93 Integra axle by almost an inch. The length of the inner joints is virtually the same. I'll be looking into doing something simlar to the drivers side using a 90-93 Integra LEFT inner joint and an OE Civic short axle.....

A popular thing to do with these close ratio ZC tranny's is to replace the 3.888 final drive with the USDM Si final drive - 4.250. This lowers the overall gearing of the transmission while retaing the close ratio - perfect for drag racing, but not the highway.

I have experimented with taking this idea one step further to get the best of both worlds by replacing the 5th gear as well. There are a number of 5th gear ratios to choose from:
.694 = 88-91 CRX HF
.702 = 92-95 Civic
.750 = 92-95 Civic Si
.771 = 88-91 Civic/CRX Si
.878 = ZC L3, made over a number of years found in the Japanese market and Europe.

*8/12/00 In the past 2.5 years with the supercharger, the best highway gas mileage had been 30 MPG with a stock ECU and injectors with lots of fuel pressure at sea level. That mileage slipped to 27 MPG with 450cc injectors and the ZDYNE gold ECU in the mile high city.
My efforts to get better fuel economy with the .702 5th gear were in vain. After swapping in the ZC 1-4/LSD/.702 5th gear tranny in preparation of a 2000 mile road trip and keeping close track of the MPG, there was no significant gain. In addition, I also found that the spread between 4th and 5th was too big.

*MPG figures from the 2000 mile road trip*
The entire trip average (a little over 2000 miles) turned out to be 29.83 MPG. This was with the cruise set at 85 MPH with occasional legs (2 lane highways) requiring acceleration to 100+ to pass.
The best leg (North Platte, NE to Grand Island, NE) was 33.31 MPG - 137.4 miles using 4.125 gallons of fuel.
The worst leg (Denver, CO to North Plate, NE) was 28.41 MPG - 269.3 miles using 9.479 gallons of fuel. This was consistant with the return home (North Platte to Denver leg) of 28.84 MPG.

So, the .702 5th turned out to be not so great. The gap from 4th to 5th was huge. There was no improvement in MPG. The acceleration was terrible compared to the .771. The only benefit was lower highway cruising RPM.
Over the winter of '01-'02, I've tried something else. A lower 5th gear and taller FD. I like the close 1-4, but the new motor rips through those gears too fast. I think I'm giving up real acceleration for short speedy bursts.
Here's the contents of the new tranny configuration:
ZC 1-4 gears
.771 Si 5th
EF sedan final drive - 4.058
ZC LSD - it still works
-Update 10/28/02- The new gearing is great! Enough said....ok, maybe not. Here's the verdict I typed out to a curious enthusiast in email:

"I'd honestly have to drive the car back to back with the 4.25 and the 4.058 to really tell the difference. I can tell you that in 5th gear there is only a few hundred RPM difference between the 4.058/.771 5th and the 4.250/.771. When I had the 4.25 FD in it, the ZC 1-4 almost seemed too short. You get this blast of quick revving acceleration, but it's over too quickly and you've got to shift. Of course the biggest bummer with my old setup was the .702 5th. I could have lived with the 4.25 FD if it wasn't for the tall 5th. So, since I'm not fond of tearing apart transmissions, I thought I'd kill two birds...put the Si .771 5th back in it, and widen out the ZC 1-4 with the 4.058. The 4.058 also brings down the RPM in 5th with the .771 so it wasn't like going back to the original .771 RPM in 5th. I actually haven't driven the car since early July. I had two catastrophic JR belt tensioner failures which also took out the SC belt within 1 month. Both nearly left me stranded - so I swapped the insurance over to the yellow CRX and drove it until it started snowing (this week). With all the gravel they put down here, I don't drive the SC Civic or the yellow CRX in the winter. That's what the 88 DX beater is for.

So anyway, back to the point - if you can get ahold of ZC1-4, that gearing, or the spread between the gears is definately WAY better than a regular Si box. Each gear accelerates like the one before it. The Si 1-4 is fine in 1st, 2nd, but the shift to third is a bit more gappy and 3rd is too long. I wouldn't put the 4.058 with the Si gearing. If you know anyone with a 5 speed 88-91 sedan - drive it, that's what it would be like. Not quite as bad as the DX (3.888 FD). So, bottom line after typing all this out, yes, the 4.058 was worth it, but not absolutely necessary. If you haven't got the parts available to build that combo, maybe just try putting the ZC 1-4 in with the Si 5th and 4.25 FD. I just think that with FI (the torquey supercharger kind) that the equally spaced slightly wider gearing takes advantage of the torque. I did take the Civic for a quick jaunt to blow it out a few weeks ago - damn impressive acceleration compared to the B16A powered CRX."